diff --git a/adb/Android.bp b/adb/Android.bp
index 12d9a1409..6386a78ed 100644
--- a/adb/Android.bp
+++ b/adb/Android.bp
@@ -470,6 +470,7 @@ cc_library {
         "libadbd_core",
         "libbrotli",
         "libdiagnose_usb",
+        "liblz4",
     ],
 
     shared_libs: [
@@ -571,6 +572,7 @@ cc_library {
         "libbrotli",
         "libcutils_sockets",
         "libdiagnose_usb",
+        "liblz4",
         "libmdnssd",
     ],
 
@@ -605,6 +607,7 @@ cc_binary {
         "libadbd_services",
         "libasyncio",
         "libcap",
+        "liblz4",
         "libminijail",
         "libssl",
     ],
diff --git a/adb/client/adb_install.cpp b/adb/client/adb_install.cpp
index 092a86684..da3154e4a 100644
--- a/adb/client/adb_install.cpp
+++ b/adb/client/adb_install.cpp
@@ -290,7 +290,7 @@ static int install_app_legacy(int argc, const char** argv, bool use_fastdeploy)
         }
     }
 
-    if (do_sync_push(apk_file, apk_dest.c_str(), false, true)) {
+    if (do_sync_push(apk_file, apk_dest.c_str(), false, CompressionType::Any, false)) {
         result = pm_command(argc, argv);
         delete_device_file(apk_dest);
     }
diff --git a/adb/client/bugreport.cpp b/adb/client/bugreport.cpp
index ab93f7d87..e162aaad1 100644
--- a/adb/client/bugreport.cpp
+++ b/adb/client/bugreport.cpp
@@ -282,5 +282,5 @@ int Bugreport::SendShellCommand(const std::string& command, bool disable_shell_p
 
 bool Bugreport::DoSyncPull(const std::vector<const char*>& srcs, const char* dst, bool copy_attrs,
                            const char* name) {
-    return do_sync_pull(srcs, dst, copy_attrs, false, name);
+    return do_sync_pull(srcs, dst, copy_attrs, CompressionType::None, name);
 }
diff --git a/adb/client/commandline.cpp b/adb/client/commandline.cpp
index 04b250df2..ceb21d595 100644
--- a/adb/client/commandline.cpp
+++ b/adb/client/commandline.cpp
@@ -129,20 +129,22 @@ static void help() {
         " reverse --remove-all     remove all reverse socket connections from device\n"
         "\n"
         "file transfer:\n"
-        " push [--sync] [-zZ] LOCAL... REMOTE\n"
+        " push [--sync] [-z ALGORITHM] [-Z] LOCAL... REMOTE\n"
         "     copy local files/directories to device\n"
         "     --sync: only push files that are newer on the host than the device\n"
-        "     -z: enable compression\n"
+        "     -n: dry run: push files to device without storing to the filesystem\n"
+        "     -z: enable compression with a specified algorithm (any, none, brotli)\n"
         "     -Z: disable compression\n"
-        " pull [-azZ] REMOTE... LOCAL\n"
+        " pull [-a] [-z ALGORITHM] [-Z] REMOTE... LOCAL\n"
         "     copy files/dirs from device\n"
         "     -a: preserve file timestamp and mode\n"
-        "     -z: enable compression\n"
+        "     -z: enable compression with a specified algorithm (any, none, brotli)\n"
         "     -Z: disable compression\n"
-        " sync [-lzZ] [all|data|odm|oem|product|system|system_ext|vendor]\n"
+        " sync [-l] [-z ALGORITHM] [-Z] [all|data|odm|oem|product|system|system_ext|vendor]\n"
         "     sync a local build from $ANDROID_PRODUCT_OUT to the device (default all)\n"
+        "     -n: dry run: push files to device without storing to the filesystem\n"
         "     -l: list files that would be copied, but don't copy them\n"
-        "     -z: enable compression\n"
+        "     -z: enable compression with a specified algorithm (any, none, brotli)\n"
         "     -Z: disable compression\n"
         "\n"
         "shell:\n"
@@ -1314,12 +1316,36 @@ static int restore(int argc, const char** argv) {
     return 0;
 }
 
+static CompressionType parse_compression_type(const std::string& str, bool allow_numbers) {
+    if (allow_numbers) {
+        if (str == "0") {
+            return CompressionType::None;
+        } else if (str == "1") {
+            return CompressionType::Any;
+        }
+    }
+
+    if (str == "any") {
+        return CompressionType::Any;
+    } else if (str == "none") {
+        return CompressionType::None;
+    }
+
+    if (str == "brotli") {
+        return CompressionType::Brotli;
+    } else if (str == "lz4") {
+        return CompressionType::LZ4;
+    }
+
+    error_exit("unexpected compression type %s", str.c_str());
+}
+
 static void parse_push_pull_args(const char** arg, int narg, std::vector<const char*>* srcs,
-                                 const char** dst, bool* copy_attrs, bool* sync, bool* compressed) {
+                                 const char** dst, bool* copy_attrs, bool* sync,
+                                 CompressionType* compression, bool* dry_run) {
     *copy_attrs = false;
-    const char* adb_compression = getenv("ADB_COMPRESSION");
-    if (adb_compression && strcmp(adb_compression, "0") == 0) {
-        *compressed = false;
+    if (const char* adb_compression = getenv("ADB_COMPRESSION")) {
+        *compression = parse_compression_type(adb_compression, true);
     }
 
     srcs->clear();
@@ -1333,13 +1359,15 @@ static void parse_push_pull_args(const char** arg, int narg, std::vector<const c
             } else if (!strcmp(*arg, "-a")) {
                 *copy_attrs = true;
             } else if (!strcmp(*arg, "-z")) {
-                if (compressed != nullptr) {
-                    *compressed = true;
+                if (narg < 2) {
+                    error_exit("-z requires an argument");
                 }
+                *compression = parse_compression_type(*++arg, false);
+                --narg;
             } else if (!strcmp(*arg, "-Z")) {
-                if (compressed != nullptr) {
-                    *compressed = false;
-                }
+                *compression = CompressionType::None;
+            } else if (dry_run && !strcmp(*arg, "-n")) {
+                *dry_run = true;
             } else if (!strcmp(*arg, "--sync")) {
                 if (sync != nullptr) {
                     *sync = true;
@@ -1894,22 +1922,25 @@ int adb_commandline(int argc, const char** argv) {
     } else if (!strcmp(argv[0], "push")) {
         bool copy_attrs = false;
         bool sync = false;
-        bool compressed = true;
+        bool dry_run = false;
+        CompressionType compression = CompressionType::Any;
         std::vector<const char*> srcs;
         const char* dst = nullptr;
 
-        parse_push_pull_args(&argv[1], argc - 1, &srcs, &dst, &copy_attrs, &sync, &compressed);
+        parse_push_pull_args(&argv[1], argc - 1, &srcs, &dst, &copy_attrs, &sync, &compression,
+                             &dry_run);
         if (srcs.empty() || !dst) error_exit("push requires an argument");
-        return do_sync_push(srcs, dst, sync, compressed) ? 0 : 1;
+        return do_sync_push(srcs, dst, sync, compression, dry_run) ? 0 : 1;
     } else if (!strcmp(argv[0], "pull")) {
         bool copy_attrs = false;
-        bool compressed = true;
+        CompressionType compression = CompressionType::Any;
         std::vector<const char*> srcs;
         const char* dst = ".";
 
-        parse_push_pull_args(&argv[1], argc - 1, &srcs, &dst, &copy_attrs, nullptr, &compressed);
+        parse_push_pull_args(&argv[1], argc - 1, &srcs, &dst, &copy_attrs, nullptr, &compression,
+                             nullptr);
         if (srcs.empty()) error_exit("pull requires an argument");
-        return do_sync_pull(srcs, dst, copy_attrs, compressed) ? 0 : 1;
+        return do_sync_pull(srcs, dst, copy_attrs, compression) ? 0 : 1;
     } else if (!strcmp(argv[0], "install")) {
         if (argc < 2) error_exit("install requires an argument");
         return install_app(argc, argv);
@@ -1925,27 +1956,30 @@ int adb_commandline(int argc, const char** argv) {
     } else if (!strcmp(argv[0], "sync")) {
         std::string src;
         bool list_only = false;
-        bool compressed = true;
+        bool dry_run = false;
+        CompressionType compression = CompressionType::Any;
 
-        const char* adb_compression = getenv("ADB_COMPRESSION");
-        if (adb_compression && strcmp(adb_compression, "0") == 0) {
-            compressed = false;
+        if (const char* adb_compression = getenv("ADB_COMPRESSION"); adb_compression) {
+            compression = parse_compression_type(adb_compression, true);
         }
 
         int opt;
-        while ((opt = getopt(argc, const_cast<char**>(argv), "lzZ")) != -1) {
+        while ((opt = getopt(argc, const_cast<char**>(argv), "lnz:Z")) != -1) {
             switch (opt) {
                 case 'l':
                     list_only = true;
                     break;
+                case 'n':
+                    dry_run = true;
+                    break;
                 case 'z':
-                    compressed = true;
+                    compression = parse_compression_type(optarg, false);
                     break;
                 case 'Z':
-                    compressed = false;
+                    compression = CompressionType::None;
                     break;
                 default:
-                    error_exit("usage: adb sync [-lzZ] [PARTITION]");
+                    error_exit("usage: adb sync [-l] [-n]  [-z ALGORITHM] [-Z] [PARTITION]");
             }
         }
 
@@ -1954,7 +1988,7 @@ int adb_commandline(int argc, const char** argv) {
         } else if (optind + 1 == argc) {
             src = argv[optind];
         } else {
-            error_exit("usage: adb sync [-lzZ] [PARTITION]");
+            error_exit("usage: adb sync [-l] [-n] [-z ALGORITHM] [-Z] [PARTITION]");
         }
 
         std::vector<std::string> partitions{"data",   "odm",        "oem",   "product",
@@ -1965,7 +1999,9 @@ int adb_commandline(int argc, const char** argv) {
                 std::string src_dir{product_file(partition)};
                 if (!directory_exists(src_dir)) continue;
                 found = true;
-                if (!do_sync_sync(src_dir, "/" + partition, list_only, compressed)) return 1;
+                if (!do_sync_sync(src_dir, "/" + partition, list_only, compression, dry_run)) {
+                    return 1;
+                }
             }
         }
         if (!found) error_exit("don't know how to sync %s partition", src.c_str());
diff --git a/adb/client/fastdeploy.cpp b/adb/client/fastdeploy.cpp
index de82e14e5..bc4b91bb9 100644
--- a/adb/client/fastdeploy.cpp
+++ b/adb/client/fastdeploy.cpp
@@ -112,7 +112,7 @@ static void push_to_device(const void* data, size_t byte_count, const char* dst,
     // but can't be removed until after the push.
     unix_close(tf.release());
 
-    if (!do_sync_push(srcs, dst, sync, true)) {
+    if (!do_sync_push(srcs, dst, sync, CompressionType::Any, false)) {
         error_exit("Failed to push fastdeploy agent to device.");
     }
 }
diff --git a/adb/client/file_sync_client.cpp b/adb/client/file_sync_client.cpp
index 2ed58b2a3..681673449 100644
--- a/adb/client/file_sync_client.cpp
+++ b/adb/client/file_sync_client.cpp
@@ -34,6 +34,7 @@
 #include <memory>
 #include <sstream>
 #include <string>
+#include <variant>
 #include <vector>
 
 #include "sysdeps.h"
@@ -236,6 +237,8 @@ class SyncConnection {
             have_ls_v2_ = CanUseFeature(features_, kFeatureLs2);
             have_sendrecv_v2_ = CanUseFeature(features_, kFeatureSendRecv2);
             have_sendrecv_v2_brotli_ = CanUseFeature(features_, kFeatureSendRecv2Brotli);
+            have_sendrecv_v2_lz4_ = CanUseFeature(features_, kFeatureSendRecv2LZ4);
+            have_sendrecv_v2_dry_run_send_ = CanUseFeature(features_, kFeatureSendRecv2DryRunSend);
             fd.reset(adb_connect("sync:", &error));
             if (fd < 0) {
                 Error("connect failed: %s", error.c_str());
@@ -261,6 +264,22 @@ class SyncConnection {
 
     bool HaveSendRecv2() const { return have_sendrecv_v2_; }
     bool HaveSendRecv2Brotli() const { return have_sendrecv_v2_brotli_; }
+    bool HaveSendRecv2LZ4() const { return have_sendrecv_v2_lz4_; }
+    bool HaveSendRecv2DryRunSend() const { return have_sendrecv_v2_dry_run_send_; }
+
+    // Resolve a compression type which might be CompressionType::Any to a specific compression
+    // algorithm.
+    CompressionType ResolveCompressionType(CompressionType compression) const {
+        if (compression == CompressionType::Any) {
+            if (HaveSendRecv2LZ4()) {
+                return CompressionType::LZ4;
+            } else if (HaveSendRecv2Brotli()) {
+                return CompressionType::Brotli;
+            }
+            return CompressionType::None;
+        }
+        return compression;
+    }
 
     const FeatureSet& Features() const { return features_; }
 
@@ -323,7 +342,7 @@ class SyncConnection {
         return WriteFdExactly(fd, buf.data(), buf.size());
     }
 
-    bool SendSend2(std::string_view path, mode_t mode, bool compressed) {
+    bool SendSend2(std::string_view path, mode_t mode, CompressionType compression, bool dry_run) {
         if (path.length() > 1024) {
             Error("SendRequest failed: path too long: %zu", path.length());
             errno = ENAMETOOLONG;
@@ -339,7 +358,26 @@ class SyncConnection {
         syncmsg msg;
         msg.send_v2_setup.id = ID_SEND_V2;
         msg.send_v2_setup.mode = mode;
-        msg.send_v2_setup.flags = compressed ? kSyncFlagBrotli : kSyncFlagNone;
+        msg.send_v2_setup.flags = 0;
+        switch (compression) {
+            case CompressionType::None:
+                break;
+
+            case CompressionType::Brotli:
+                msg.send_v2_setup.flags = kSyncFlagBrotli;
+                break;
+
+            case CompressionType::LZ4:
+                msg.send_v2_setup.flags = kSyncFlagLZ4;
+                break;
+
+            case CompressionType::Any:
+                LOG(FATAL) << "unexpected CompressionType::Any";
+        }
+
+        if (dry_run) {
+            msg.send_v2_setup.flags |= kSyncFlagDryRun;
+        }
 
         buf.resize(sizeof(SyncRequest) + path.length() + sizeof(msg.send_v2_setup));
 
@@ -352,7 +390,7 @@ class SyncConnection {
         return WriteFdExactly(fd, buf.data(), buf.size());
     }
 
-    bool SendRecv2(const std::string& path) {
+    bool SendRecv2(const std::string& path, CompressionType compression) {
         if (path.length() > 1024) {
             Error("SendRequest failed: path too long: %zu", path.length());
             errno = ENAMETOOLONG;
@@ -367,7 +405,22 @@ class SyncConnection {
 
         syncmsg msg;
         msg.recv_v2_setup.id = ID_RECV_V2;
-        msg.recv_v2_setup.flags = kSyncFlagBrotli;
+        msg.recv_v2_setup.flags = 0;
+        switch (compression) {
+            case CompressionType::None:
+                break;
+
+            case CompressionType::Brotli:
+                msg.recv_v2_setup.flags |= kSyncFlagBrotli;
+                break;
+
+            case CompressionType::LZ4:
+                msg.recv_v2_setup.flags |= kSyncFlagLZ4;
+                break;
+
+            case CompressionType::Any:
+                LOG(FATAL) << "unexpected CompressionType::Any";
+        }
 
         buf.resize(sizeof(SyncRequest) + path.length() + sizeof(msg.recv_v2_setup));
 
@@ -494,7 +547,12 @@ class SyncConnection {
     // difference to "adb sync" performance.
     bool SendSmallFile(const std::string& path, mode_t mode, const std::string& lpath,
                        const std::string& rpath, unsigned mtime, const char* data,
-                       size_t data_length) {
+                       size_t data_length, bool dry_run) {
+        if (dry_run) {
+            // We need to use send v2 for dry run.
+            return SendLargeFile(path, mode, lpath, rpath, mtime, CompressionType::None, dry_run);
+        }
+
         std::string path_and_mode = android::base::StringPrintf("%s,%d", path.c_str(), mode);
         if (path_and_mode.length() > 1024) {
             Error("SendSmallFile failed: path too long: %zu", path_and_mode.length());
@@ -533,9 +591,21 @@ class SyncConnection {
         return true;
     }
 
-    bool SendLargeFileCompressed(const std::string& path, mode_t mode, const std::string& lpath,
-                                 const std::string& rpath, unsigned mtime) {
-        if (!SendSend2(path, mode, true)) {
+    bool SendLargeFile(const std::string& path, mode_t mode, const std::string& lpath,
+                       const std::string& rpath, unsigned mtime, CompressionType compression,
+                       bool dry_run) {
+        if (dry_run && !HaveSendRecv2DryRunSend()) {
+            Error("dry-run not supported by the device");
+            return false;
+        }
+
+        if (!HaveSendRecv2()) {
+            return SendLargeFileLegacy(path, mode, lpath, rpath, mtime);
+        }
+
+        compression = ResolveCompressionType(compression);
+
+        if (!SendSend2(path, mode, compression, dry_run)) {
             Error("failed to send ID_SEND_V2 message '%s': %s", path.c_str(), strerror(errno));
             return false;
         }
@@ -558,7 +628,25 @@ class SyncConnection {
         syncsendbuf sbuf;
         sbuf.id = ID_DATA;
 
-        BrotliEncoder<SYNC_DATA_MAX> encoder;
+        std::variant<std::monostate, NullEncoder, BrotliEncoder, LZ4Encoder> encoder_storage;
+        Encoder* encoder = nullptr;
+        switch (compression) {
+            case CompressionType::None:
+                encoder = &encoder_storage.emplace<NullEncoder>(SYNC_DATA_MAX);
+                break;
+
+            case CompressionType::Brotli:
+                encoder = &encoder_storage.emplace<BrotliEncoder>(SYNC_DATA_MAX);
+                break;
+
+            case CompressionType::LZ4:
+                encoder = &encoder_storage.emplace<LZ4Encoder>(SYNC_DATA_MAX);
+                break;
+
+            case CompressionType::Any:
+                LOG(FATAL) << "unexpected CompressionType::Any";
+        }
+
         bool sending = true;
         while (sending) {
             Block input(SYNC_DATA_MAX);
@@ -569,10 +657,10 @@ class SyncConnection {
             }
 
             if (r == 0) {
-                encoder.Finish();
+                encoder->Finish();
             } else {
                 input.resize(r);
-                encoder.Append(std::move(input));
+                encoder->Append(std::move(input));
                 RecordBytesTransferred(r);
                 bytes_copied += r;
                 ReportProgress(rpath, bytes_copied, total_size);
@@ -580,7 +668,7 @@ class SyncConnection {
 
             while (true) {
                 Block output;
-                EncodeResult result = encoder.Encode(&output);
+                EncodeResult result = encoder->Encode(&output);
                 if (result == EncodeResult::Error) {
                     Error("compressing '%s' locally failed", lpath.c_str());
                     return false;
@@ -610,12 +698,8 @@ class SyncConnection {
         return WriteOrDie(lpath, rpath, &msg.data, sizeof(msg.data));
     }
 
-    bool SendLargeFile(const std::string& path, mode_t mode, const std::string& lpath,
-                       const std::string& rpath, unsigned mtime, bool compressed) {
-        if (compressed && HaveSendRecv2Brotli()) {
-            return SendLargeFileCompressed(path, mode, lpath, rpath, mtime);
-        }
-
+    bool SendLargeFileLegacy(const std::string& path, mode_t mode, const std::string& lpath,
+                             const std::string& rpath, unsigned mtime) {
         std::string path_and_mode = android::base::StringPrintf("%s,%d", path.c_str(), mode);
         if (!SendRequest(ID_SEND_V1, path_and_mode)) {
             Error("failed to send ID_SEND_V1 message '%s': %s", path_and_mode.c_str(),
@@ -840,6 +924,8 @@ class SyncConnection {
     bool have_ls_v2_;
     bool have_sendrecv_v2_;
     bool have_sendrecv_v2_brotli_;
+    bool have_sendrecv_v2_lz4_;
+    bool have_sendrecv_v2_dry_run_send_;
 
     TransferLedger global_ledger_;
     TransferLedger current_ledger_;
@@ -921,7 +1007,8 @@ static bool sync_stat_fallback(SyncConnection& sc, const std::string& path, stru
 }
 
 static bool sync_send(SyncConnection& sc, const std::string& lpath, const std::string& rpath,
-                      unsigned mtime, mode_t mode, bool sync, bool compressed) {
+                      unsigned mtime, mode_t mode, bool sync, CompressionType compression,
+                      bool dry_run) {
     if (sync) {
         struct stat st;
         if (sync_lstat(sc, rpath, &st)) {
@@ -942,7 +1029,7 @@ static bool sync_send(SyncConnection& sc, const std::string& lpath, const std::s
         }
         buf[data_length++] = '\0';
 
-        if (!sc.SendSmallFile(rpath, mode, lpath, rpath, mtime, buf, data_length)) {
+        if (!sc.SendSmallFile(rpath, mode, lpath, rpath, mtime, buf, data_length, dry_run)) {
             return false;
         }
         return sc.ReadAcknowledgements();
@@ -960,11 +1047,12 @@ static bool sync_send(SyncConnection& sc, const std::string& lpath, const std::s
             sc.Error("failed to read all of '%s': %s", lpath.c_str(), strerror(errno));
             return false;
         }
-        if (!sc.SendSmallFile(rpath, mode, lpath, rpath, mtime, data.data(), data.size())) {
+        if (!sc.SendSmallFile(rpath, mode, lpath, rpath, mtime, data.data(), data.size(),
+                              dry_run)) {
             return false;
         }
     } else {
-        if (!sc.SendLargeFile(rpath, mode, lpath, rpath, mtime, compressed)) {
+        if (!sc.SendLargeFile(rpath, mode, lpath, rpath, mtime, compression, dry_run)) {
             return false;
         }
     }
@@ -1027,8 +1115,10 @@ static bool sync_recv_v1(SyncConnection& sc, const char* rpath, const char* lpat
 }
 
 static bool sync_recv_v2(SyncConnection& sc, const char* rpath, const char* lpath, const char* name,
-                         uint64_t expected_size) {
-    if (!sc.SendRecv2(rpath)) return false;
+                         uint64_t expected_size, CompressionType compression) {
+    compression = sc.ResolveCompressionType(compression);
+
+    if (!sc.SendRecv2(rpath, compression)) return false;
 
     adb_unlink(lpath);
     unique_fd lfd(adb_creat(lpath, 0644));
@@ -1040,9 +1130,28 @@ static bool sync_recv_v2(SyncConnection& sc, const char* rpath, const char* lpat
     uint64_t bytes_copied = 0;
 
     Block buffer(SYNC_DATA_MAX);
-    BrotliDecoder decoder(std::span(buffer.data(), buffer.size()));
-    bool reading = true;
-    while (reading) {
+    std::variant<std::monostate, NullDecoder, BrotliDecoder, LZ4Decoder> decoder_storage;
+    Decoder* decoder = nullptr;
+
+    std::span buffer_span(buffer.data(), buffer.size());
+    switch (compression) {
+        case CompressionType::None:
+            decoder = &decoder_storage.emplace<NullDecoder>(buffer_span);
+            break;
+
+        case CompressionType::Brotli:
+            decoder = &decoder_storage.emplace<BrotliDecoder>(buffer_span);
+            break;
+
+        case CompressionType::LZ4:
+            decoder = &decoder_storage.emplace<LZ4Decoder>(buffer_span);
+            break;
+
+        case CompressionType::Any:
+            LOG(FATAL) << "unexpected CompressionType::Any";
+    }
+
+    while (true) {
         syncmsg msg;
         if (!ReadFdExactly(sc.fd, &msg.data, sizeof(msg.data))) {
             adb_unlink(lpath);
@@ -1050,33 +1159,32 @@ static bool sync_recv_v2(SyncConnection& sc, const char* rpath, const char* lpat
         }
 
         if (msg.data.id == ID_DONE) {
-            adb_unlink(lpath);
-            sc.Error("unexpected ID_DONE");
-            return false;
-        }
-
-        if (msg.data.id != ID_DATA) {
+            if (!decoder->Finish()) {
+                sc.Error("unexpected ID_DONE");
+                return false;
+            }
+        } else if (msg.data.id != ID_DATA) {
             adb_unlink(lpath);
             sc.ReportCopyFailure(rpath, lpath, msg);
             return false;
-        }
+        } else {
+            if (msg.data.size > sc.max) {
+                sc.Error("msg.data.size too large: %u (max %zu)", msg.data.size, sc.max);
+                adb_unlink(lpath);
+                return false;
+            }
 
-        if (msg.data.size > sc.max) {
-            sc.Error("msg.data.size too large: %u (max %zu)", msg.data.size, sc.max);
-            adb_unlink(lpath);
-            return false;
+            Block block(msg.data.size);
+            if (!ReadFdExactly(sc.fd, block.data(), msg.data.size)) {
+                adb_unlink(lpath);
+                return false;
+            }
+            decoder->Append(std::move(block));
         }
 
-        Block block(msg.data.size);
-        if (!ReadFdExactly(sc.fd, block.data(), msg.data.size)) {
-            adb_unlink(lpath);
-            return false;
-        }
-        decoder.Append(std::move(block));
-
         while (true) {
             std::span<char> output;
-            DecodeResult result = decoder.Decode(&output);
+            DecodeResult result = decoder->Decode(&output);
 
             if (result == DecodeResult::Error) {
                 sc.Error("decompress failed");
@@ -1093,8 +1201,7 @@ static bool sync_recv_v2(SyncConnection& sc, const char* rpath, const char* lpat
             }
 
             bytes_copied += output.size();
-
-            sc.RecordBytesTransferred(msg.data.size);
+            sc.RecordBytesTransferred(output.size());
             sc.ReportProgress(name != nullptr ? name : rpath, bytes_copied, expected_size);
 
             if (result == DecodeResult::NeedInput) {
@@ -1102,33 +1209,19 @@ static bool sync_recv_v2(SyncConnection& sc, const char* rpath, const char* lpat
             } else if (result == DecodeResult::MoreOutput) {
                 continue;
             } else if (result == DecodeResult::Done) {
-                reading = false;
-                break;
+                sc.RecordFilesTransferred(1);
+                return true;
             } else {
                 LOG(FATAL) << "invalid DecodeResult: " << static_cast<int>(result);
             }
         }
     }
-
-    syncmsg msg;
-    if (!ReadFdExactly(sc.fd, &msg.data, sizeof(msg.data))) {
-        sc.Error("failed to read ID_DONE");
-        return false;
-    }
-
-    if (msg.data.id != ID_DONE) {
-        sc.Error("unexpected message after transfer: id = %d (expected ID_DONE)", msg.data.id);
-        return false;
-    }
-
-    sc.RecordFilesTransferred(1);
-    return true;
 }
 
 static bool sync_recv(SyncConnection& sc, const char* rpath, const char* lpath, const char* name,
-                      uint64_t expected_size, bool compressed) {
-    if (sc.HaveSendRecv2() && compressed) {
-        return sync_recv_v2(sc, rpath, lpath, name, expected_size);
+                      uint64_t expected_size, CompressionType compression) {
+    if (sc.HaveSendRecv2()) {
+        return sync_recv_v2(sc, rpath, lpath, name, expected_size, compression);
     } else {
         return sync_recv_v1(sc, rpath, lpath, name, expected_size);
     }
@@ -1210,7 +1303,8 @@ static bool is_root_dir(std::string_view path) {
 }
 
 static bool copy_local_dir_remote(SyncConnection& sc, std::string lpath, std::string rpath,
-                                  bool check_timestamps, bool list_only, bool compressed) {
+                                  bool check_timestamps, bool list_only,
+                                  CompressionType compression, bool dry_run) {
     sc.NewTransfer();
 
     // Make sure that both directory paths end in a slash.
@@ -1292,7 +1386,8 @@ static bool copy_local_dir_remote(SyncConnection& sc, std::string lpath, std::st
             if (list_only) {
                 sc.Println("would push: %s -> %s", ci.lpath.c_str(), ci.rpath.c_str());
             } else {
-                if (!sync_send(sc, ci.lpath, ci.rpath, ci.time, ci.mode, false, compressed)) {
+                if (!sync_send(sc, ci.lpath, ci.rpath, ci.time, ci.mode, false, compression,
+                               dry_run)) {
                     return false;
                 }
             }
@@ -1308,7 +1403,7 @@ static bool copy_local_dir_remote(SyncConnection& sc, std::string lpath, std::st
 }
 
 bool do_sync_push(const std::vector<const char*>& srcs, const char* dst, bool sync,
-                  bool compressed) {
+                  CompressionType compression, bool dry_run) {
     SyncConnection sc;
     if (!sc.IsValid()) return false;
 
@@ -1373,7 +1468,8 @@ bool do_sync_push(const std::vector<const char*>& srcs, const char* dst, bool sy
                 dst_dir.append(android::base::Basename(src_path));
             }
 
-            success &= copy_local_dir_remote(sc, src_path, dst_dir, sync, false, compressed);
+            success &=
+                    copy_local_dir_remote(sc, src_path, dst_dir, sync, false, compression, dry_run);
             continue;
         } else if (!should_push_file(st.st_mode)) {
             sc.Warning("skipping special file '%s' (mode = 0o%o)", src_path, st.st_mode);
@@ -1394,7 +1490,8 @@ bool do_sync_push(const std::vector<const char*>& srcs, const char* dst, bool sy
 
         sc.NewTransfer();
         sc.SetExpectedTotalBytes(st.st_size);
-        success &= sync_send(sc, src_path, dst_path, st.st_mtime, st.st_mode, sync, compressed);
+        success &= sync_send(sc, src_path, dst_path, st.st_mtime, st.st_mode, sync, compression,
+                             dry_run);
         sc.ReportTransferRate(src_path, TransferDirection::push);
     }
 
@@ -1480,7 +1577,7 @@ static int set_time_and_mode(const std::string& lpath, time_t time,
 }
 
 static bool copy_remote_dir_local(SyncConnection& sc, std::string rpath, std::string lpath,
-                                  bool copy_attrs, bool compressed) {
+                                  bool copy_attrs, CompressionType compression) {
     sc.NewTransfer();
 
     // Make sure that both directory paths end in a slash.
@@ -1510,7 +1607,7 @@ static bool copy_remote_dir_local(SyncConnection& sc, std::string rpath, std::st
                 continue;
             }
 
-            if (!sync_recv(sc, ci.rpath.c_str(), ci.lpath.c_str(), nullptr, ci.size, compressed)) {
+            if (!sync_recv(sc, ci.rpath.c_str(), ci.lpath.c_str(), nullptr, ci.size, compression)) {
                 return false;
             }
 
@@ -1528,7 +1625,7 @@ static bool copy_remote_dir_local(SyncConnection& sc, std::string rpath, std::st
 }
 
 bool do_sync_pull(const std::vector<const char*>& srcs, const char* dst, bool copy_attrs,
-                  bool compressed, const char* name) {
+                  CompressionType compression, const char* name) {
     SyncConnection sc;
     if (!sc.IsValid()) return false;
 
@@ -1602,7 +1699,7 @@ bool do_sync_pull(const std::vector<const char*>& srcs, const char* dst, bool co
                 dst_dir.append(android::base::Basename(src_path));
             }
 
-            success &= copy_remote_dir_local(sc, src_path, dst_dir, copy_attrs, compressed);
+            success &= copy_remote_dir_local(sc, src_path, dst_dir, copy_attrs, compression);
             continue;
         } else if (!should_pull_file(src_st.st_mode)) {
             sc.Warning("skipping special file '%s' (mode = 0o%o)", src_path, src_st.st_mode);
@@ -1621,7 +1718,7 @@ bool do_sync_pull(const std::vector<const char*>& srcs, const char* dst, bool co
 
         sc.NewTransfer();
         sc.SetExpectedTotalBytes(src_st.st_size);
-        if (!sync_recv(sc, src_path, dst_path, name, src_st.st_size, compressed)) {
+        if (!sync_recv(sc, src_path, dst_path, name, src_st.st_size, compression)) {
             success = false;
             continue;
         }
@@ -1638,11 +1735,11 @@ bool do_sync_pull(const std::vector<const char*>& srcs, const char* dst, bool co
 }
 
 bool do_sync_sync(const std::string& lpath, const std::string& rpath, bool list_only,
-                  bool compressed) {
+                  CompressionType compression, bool dry_run) {
     SyncConnection sc;
     if (!sc.IsValid()) return false;
 
-    bool success = copy_local_dir_remote(sc, lpath, rpath, true, list_only, compressed);
+    bool success = copy_local_dir_remote(sc, lpath, rpath, true, list_only, compression, dry_run);
     if (!list_only) {
         sc.ReportOverallTransferRate(TransferDirection::push);
     }
diff --git a/adb/client/file_sync_client.h b/adb/client/file_sync_client.h
index de3f19245..cb8ca9323 100644
--- a/adb/client/file_sync_client.h
+++ b/adb/client/file_sync_client.h
@@ -19,11 +19,13 @@
 #include <string>
 #include <vector>
 
+#include "file_sync_protocol.h"
+
 bool do_sync_ls(const char* path);
 bool do_sync_push(const std::vector<const char*>& srcs, const char* dst, bool sync,
-                  bool compressed);
+                  CompressionType compression, bool dry_run);
 bool do_sync_pull(const std::vector<const char*>& srcs, const char* dst, bool copy_attrs,
-                  bool compressed, const char* name = nullptr);
+                  CompressionType compression, const char* name = nullptr);
 
 bool do_sync_sync(const std::string& lpath, const std::string& rpath, bool list_only,
-                  bool compressed);
+                  CompressionType compression, bool dry_run);
diff --git a/adb/compression_utils.h b/adb/compression_utils.h
index c445095ca..a0c48a207 100644
--- a/adb/compression_utils.h
+++ b/adb/compression_utils.h
@@ -16,10 +16,15 @@
 
 #pragma once
 
+#include <algorithm>
+#include <memory>
 #include <span>
 
+#include <android-base/logging.h>
+
 #include <brotli/decode.h>
 #include <brotli/encode.h>
+#include <lz4frame.h>
 
 #include "types.h"
 
@@ -37,15 +42,103 @@ enum class EncodeResult {
     MoreOutput,
 };
 
-struct BrotliDecoder {
+struct Decoder {
+    void Append(Block&& block) { input_buffer_.append(std::move(block)); }
+    bool Finish() {
+        bool old = std::exchange(finished_, true);
+        if (old) {
+            LOG(FATAL) << "Decoder::Finish called while already finished?";
+            return false;
+        }
+        return true;
+    }
+
+    virtual DecodeResult Decode(std::span<char>* output) = 0;
+
+  protected:
+    Decoder(std::span<char> output_buffer) : output_buffer_(output_buffer) {}
+    ~Decoder() = default;
+
+    bool finished_ = false;
+    IOVector input_buffer_;
+    std::span<char> output_buffer_;
+};
+
+struct Encoder {
+    void Append(Block input) { input_buffer_.append(std::move(input)); }
+    bool Finish() {
+        bool old = std::exchange(finished_, true);
+        if (old) {
+            LOG(FATAL) << "Decoder::Finish called while already finished?";
+            return false;
+        }
+        return true;
+    }
+
+    virtual EncodeResult Encode(Block* output) = 0;
+
+  protected:
+    explicit Encoder(size_t output_block_size) : output_block_size_(output_block_size) {}
+    ~Encoder() = default;
+
+    const size_t output_block_size_;
+    bool finished_ = false;
+    IOVector input_buffer_;
+};
+
+struct NullDecoder final : public Decoder {
+    explicit NullDecoder(std::span<char> output_buffer) : Decoder(output_buffer) {}
+
+    DecodeResult Decode(std::span<char>* output) final {
+        size_t available_out = output_buffer_.size();
+        void* p = output_buffer_.data();
+        while (available_out > 0 && !input_buffer_.empty()) {
+            size_t len = std::min(available_out, input_buffer_.front_size());
+            p = mempcpy(p, input_buffer_.front_data(), len);
+            available_out -= len;
+            input_buffer_.drop_front(len);
+        }
+        *output = std::span(output_buffer_.data(), static_cast<char*>(p));
+        if (input_buffer_.empty()) {
+            return finished_ ? DecodeResult::Done : DecodeResult::NeedInput;
+        }
+        return DecodeResult::MoreOutput;
+    }
+};
+
+struct NullEncoder final : public Encoder {
+    explicit NullEncoder(size_t output_block_size) : Encoder(output_block_size) {}
+
+    EncodeResult Encode(Block* output) final {
+        output->clear();
+        output->resize(output_block_size_);
+
+        size_t available_out = output->size();
+        void* p = output->data();
+
+        while (available_out > 0 && !input_buffer_.empty()) {
+            size_t len = std::min(available_out, input_buffer_.front_size());
+            p = mempcpy(p, input_buffer_.front_data(), len);
+            available_out -= len;
+            input_buffer_.drop_front(len);
+        }
+
+        output->resize(output->size() - available_out);
+
+        if (input_buffer_.empty()) {
+            return finished_ ? EncodeResult::Done : EncodeResult::NeedInput;
+        }
+        return EncodeResult::MoreOutput;
+    }
+};
+
+struct BrotliDecoder final : public Decoder {
     explicit BrotliDecoder(std::span<char> output_buffer)
-        : output_buffer_(output_buffer),
+        : Decoder(output_buffer),
           decoder_(BrotliDecoderCreateInstance(nullptr, nullptr, nullptr),
                    BrotliDecoderDestroyInstance) {}
 
-    void Append(Block&& block) { input_buffer_.append(std::move(block)); }
-
-    DecodeResult Decode(std::span<char>* output) {
+    DecodeResult Decode(std::span<char>* output) final {
         size_t available_in = input_buffer_.front_size();
         const uint8_t* next_in = reinterpret_cast<const uint8_t*>(input_buffer_.front_data());
 
@@ -63,7 +156,8 @@ struct BrotliDecoder {
 
         switch (r) {
             case BROTLI_DECODER_RESULT_SUCCESS:
-                return DecodeResult::Done;
+                // We need to wait for ID_DONE from the other end.
+                return finished_ ? DecodeResult::Done : DecodeResult::NeedInput;
             case BROTLI_DECODER_RESULT_ERROR:
                 return DecodeResult::Error;
             case BROTLI_DECODER_RESULT_NEEDS_MORE_INPUT:
@@ -77,33 +171,29 @@ struct BrotliDecoder {
     }
 
   private:
-    IOVector input_buffer_;
-    std::span<char> output_buffer_;
     std::unique_ptr<BrotliDecoderState, void (*)(BrotliDecoderState*)> decoder_;
 };
 
-template <size_t OutputBlockSize>
-struct BrotliEncoder {
-    explicit BrotliEncoder()
-        : output_block_(OutputBlockSize),
-          output_bytes_left_(OutputBlockSize),
+struct BrotliEncoder final : public Encoder {
+    explicit BrotliEncoder(size_t output_block_size)
+        : Encoder(output_block_size),
+          output_block_(output_block_size_),
+          output_bytes_left_(output_block_size_),
           encoder_(BrotliEncoderCreateInstance(nullptr, nullptr, nullptr),
                    BrotliEncoderDestroyInstance) {
         BrotliEncoderSetParameter(encoder_.get(), BROTLI_PARAM_QUALITY, 1);
     }
 
-    void Append(Block input) { input_buffer_.append(std::move(input)); }
-    void Finish() { finished_ = true; }
-
-    EncodeResult Encode(Block* output) {
+    EncodeResult Encode(Block* output) final {
         output->clear();
+
         while (true) {
             size_t available_in = input_buffer_.front_size();
             const uint8_t* next_in = reinterpret_cast<const uint8_t*>(input_buffer_.front_data());
 
             size_t available_out = output_bytes_left_;
-            uint8_t* next_out = reinterpret_cast<uint8_t*>(output_block_.data() +
-                                                           (OutputBlockSize - output_bytes_left_));
+            uint8_t* next_out = reinterpret_cast<uint8_t*>(
+                    output_block_.data() + (output_block_size_ - output_bytes_left_));
 
             BrotliEncoderOperation op = BROTLI_OPERATION_PROCESS;
             if (finished_) {
@@ -121,13 +211,13 @@ struct BrotliEncoder {
             output_bytes_left_ = available_out;
 
             if (BrotliEncoderIsFinished(encoder_.get())) {
-                output_block_.resize(OutputBlockSize - output_bytes_left_);
+                output_block_.resize(output_block_size_ - output_bytes_left_);
                 *output = std::move(output_block_);
                 return EncodeResult::Done;
             } else if (output_bytes_left_ == 0) {
                 *output = std::move(output_block_);
-                output_block_.resize(OutputBlockSize);
-                output_bytes_left_ = OutputBlockSize;
+                output_block_.resize(output_block_size_);
+                output_bytes_left_ = output_block_size_;
                 return EncodeResult::MoreOutput;
             } else if (input_buffer_.empty()) {
                 return EncodeResult::NeedInput;
@@ -136,9 +226,158 @@ struct BrotliEncoder {
     }
 
   private:
-    bool finished_ = false;
-    IOVector input_buffer_;
     Block output_block_;
     size_t output_bytes_left_;
     std::unique_ptr<BrotliEncoderState, void (*)(BrotliEncoderState*)> encoder_;
 };
+
+struct LZ4Decoder final : public Decoder {
+    explicit LZ4Decoder(std::span<char> output_buffer)
+        : Decoder(output_buffer), decoder_(nullptr, nullptr) {
+        LZ4F_dctx* dctx;
+        if (LZ4F_createDecompressionContext(&dctx, LZ4F_VERSION) != 0) {
+            LOG(FATAL) << "failed to initialize LZ4 decompression context";
+        }
+        decoder_ = std::unique_ptr<LZ4F_dctx, decltype(&LZ4F_freeDecompressionContext)>(
+                dctx, LZ4F_freeDecompressionContext);
+    }
+
+    DecodeResult Decode(std::span<char>* output) final {
+        size_t available_in = input_buffer_.front_size();
+        const char* next_in = input_buffer_.front_data();
+
+        size_t available_out = output_buffer_.size();
+        char* next_out = output_buffer_.data();
+
+        size_t rc = LZ4F_decompress(decoder_.get(), next_out, &available_out, next_in,
+                                    &available_in, nullptr);
+        if (LZ4F_isError(rc)) {
+            LOG(ERROR) << "LZ4F_decompress failed: " << LZ4F_getErrorName(rc);
+            return DecodeResult::Error;
+        }
+
+        input_buffer_.drop_front(available_in);
+
+        if (rc == 0) {
+            if (!input_buffer_.empty()) {
+                LOG(ERROR) << "LZ4 stream hit end before reading all data";
+                return DecodeResult::Error;
+            }
+            lz4_done_ = true;
+        }
+
+        *output = std::span<char>(output_buffer_.data(), available_out);
+
+        if (finished_) {
+            return input_buffer_.empty() && lz4_done_ ? DecodeResult::Done
+                                                      : DecodeResult::MoreOutput;
+        }
+
+        return DecodeResult::NeedInput;
+    }
+
+  private:
+    bool lz4_done_ = false;
+    std::unique_ptr<LZ4F_dctx, LZ4F_errorCode_t (*)(LZ4F_dctx*)> decoder_;
+};
+
+struct LZ4Encoder final : public Encoder {
+    explicit LZ4Encoder(size_t output_block_size)
+        : Encoder(output_block_size), encoder_(nullptr, nullptr) {
+        LZ4F_cctx* cctx;
+        if (LZ4F_createCompressionContext(&cctx, LZ4F_VERSION) != 0) {
+            LOG(FATAL) << "failed to initialize LZ4 compression context";
+        }
+        encoder_ = std::unique_ptr<LZ4F_cctx, decltype(&LZ4F_freeCompressionContext)>(
+                cctx, LZ4F_freeCompressionContext);
+        Block header(LZ4F_HEADER_SIZE_MAX);
+        size_t rc = LZ4F_compressBegin(encoder_.get(), header.data(), header.size(), nullptr);
+        if (LZ4F_isError(rc)) {
+            LOG(FATAL) << "LZ4F_compressBegin failed: %s", LZ4F_getErrorName(rc);
+        }
+        header.resize(rc);
+        output_buffer_.append(std::move(header));
+    }
+
+    // As an optimization, only emit a block if we have an entire output block ready, or we're done.
+    bool OutputReady() const {
+        return output_buffer_.size() >= output_block_size_ || lz4_finalized_;
+    }
+
+    // TODO: Switch the output type to IOVector to remove a copy?
+    EncodeResult Encode(Block* output) final {
+        size_t available_in = input_buffer_.front_size();
+        const char* next_in = input_buffer_.front_data();
+
+        // LZ4 makes no guarantees about being able to recover from trying to compress with an
+        // insufficiently large output buffer. LZ4F_compressBound tells us how much buffer we
+        // need to compress a given number of bytes, but the smallest value seems to be bigger
+        // than SYNC_DATA_MAX, so we need to buffer ourselves.
+
+        // Input size chosen to be a local maximum for LZ4F_compressBound (i.e. the block size).
+        constexpr size_t max_input_size = 65536;
+        const size_t encode_block_size = LZ4F_compressBound(max_input_size, nullptr);
+
+        if (available_in != 0) {
+            if (lz4_finalized_) {
+                LOG(ERROR) << "LZ4Encoder received data after Finish?";
+                return EncodeResult::Error;
+            }
+
+            available_in = std::min(available_in, max_input_size);
+
+            Block encode_block(encode_block_size);
+            size_t available_out = encode_block.capacity();
+            char* next_out = encode_block.data();
+
+            size_t rc = LZ4F_compressUpdate(encoder_.get(), next_out, available_out, next_in,
+                                            available_in, nullptr);
+            if (LZ4F_isError(rc)) {
+                LOG(ERROR) << "LZ4F_compressUpdate failed: " << LZ4F_getErrorName(rc);
+                return EncodeResult::Error;
+            }
+
+            input_buffer_.drop_front(available_in);
+
+            available_out -= rc;
+            next_out += rc;
+
+            encode_block.resize(encode_block_size - available_out);
+            output_buffer_.append(std::move(encode_block));
+        }
+
+        if (finished_ && !lz4_finalized_) {
+            lz4_finalized_ = true;
+
+            Block final_block(encode_block_size + 4);
+            size_t rc = LZ4F_compressEnd(encoder_.get(), final_block.data(), final_block.size(),
+                                         nullptr);
+            if (LZ4F_isError(rc)) {
+                LOG(ERROR) << "LZ4F_compressEnd failed: " << LZ4F_getErrorName(rc);
+                return EncodeResult::Error;
+            }
+
+            final_block.resize(rc);
+            output_buffer_.append(std::move(final_block));
+        }
+
+        if (OutputReady()) {
+            size_t len = std::min(output_block_size_, output_buffer_.size());
+            *output = output_buffer_.take_front(len).coalesce();
+        } else {
+            output->clear();
+        }
+
+        if (lz4_finalized_ && output_buffer_.empty()) {
+            return EncodeResult::Done;
+        } else if (OutputReady()) {
+            return EncodeResult::MoreOutput;
+        }
+        return EncodeResult::NeedInput;
+    }
+
+  private:
+    bool lz4_finalized_ = false;
+    std::unique_ptr<LZ4F_cctx, LZ4F_errorCode_t (*)(LZ4F_cctx*)> encoder_;
+    IOVector output_buffer_;
+};
diff --git a/adb/daemon/file_sync_service.cpp b/adb/daemon/file_sync_service.cpp
index 5ccddeabf..d58131e5b 100644
--- a/adb/daemon/file_sync_service.cpp
+++ b/adb/daemon/file_sync_service.cpp
@@ -35,6 +35,7 @@
 #include <optional>
 #include <span>
 #include <string>
+#include <variant>
 #include <vector>
 
 #include <android-base/file.h>
@@ -266,37 +267,60 @@ static bool SendSyncFailErrno(borrowed_fd fd, const std::string& reason) {
     return SendSyncFail(fd, StringPrintf("%s: %s", reason.c_str(), strerror(errno)));
 }
 
-static bool handle_send_file_compressed(borrowed_fd s, unique_fd fd, uint32_t* timestamp) {
+static bool handle_send_file_data(borrowed_fd s, unique_fd fd, uint32_t* timestamp,
+                                  CompressionType compression) {
     syncmsg msg;
-    Block decode_buffer(SYNC_DATA_MAX);
-    BrotliDecoder decoder(std::span(decode_buffer.data(), decode_buffer.size()));
+    Block buffer(SYNC_DATA_MAX);
+    std::span<char> buffer_span(buffer.data(), buffer.size());
+    std::variant<std::monostate, NullDecoder, BrotliDecoder, LZ4Decoder> decoder_storage;
+    Decoder* decoder = nullptr;
+
+    switch (compression) {
+        case CompressionType::None:
+            decoder = &decoder_storage.emplace<NullDecoder>(buffer_span);
+            break;
+
+        case CompressionType::Brotli:
+            decoder = &decoder_storage.emplace<BrotliDecoder>(buffer_span);
+            break;
+
+        case CompressionType::LZ4:
+            decoder = &decoder_storage.emplace<LZ4Decoder>(buffer_span);
+            break;
+
+        case CompressionType::Any:
+            LOG(FATAL) << "unexpected CompressionType::Any";
+    }
+
     while (true) {
         if (!ReadFdExactly(s, &msg.data, sizeof(msg.data))) return false;
 
-        if (msg.data.id != ID_DATA) {
-            if (msg.data.id == ID_DONE) {
-                *timestamp = msg.data.size;
-                return true;
-            }
+        if (msg.data.id == ID_DONE) {
+            *timestamp = msg.data.size;
+            decoder->Finish();
+        } else if (msg.data.id == ID_DATA) {
+            Block block(msg.data.size);
+            if (!ReadFdExactly(s, block.data(), msg.data.size)) return false;
+            decoder->Append(std::move(block));
+        } else {
             SendSyncFail(s, "invalid data message");
             return false;
         }
 
-        Block block(msg.data.size);
-        if (!ReadFdExactly(s, block.data(), msg.data.size)) return false;
-        decoder.Append(std::move(block));
-
         while (true) {
             std::span<char> output;
-            DecodeResult result = decoder.Decode(&output);
+            DecodeResult result = decoder->Decode(&output);
             if (result == DecodeResult::Error) {
                 SendSyncFailErrno(s, "decompress failed");
                 return false;
             }
 
-            if (!WriteFdExactly(fd, output.data(), output.size())) {
-                SendSyncFailErrno(s, "write failed");
-                return false;
+            // fd is -1 if the client is pushing with --dry-run.
+            if (fd != -1) {
+                if (!WriteFdExactly(fd, output.data(), output.size())) {
+                    SendSyncFailErrno(s, "write failed");
+                    return false;
+                }
             }
 
             if (result == DecodeResult::NeedInput) {
@@ -304,7 +328,7 @@ static bool handle_send_file_compressed(borrowed_fd s, unique_fd fd, uint32_t* t
             } else if (result == DecodeResult::MoreOutput) {
                 continue;
             } else if (result == DecodeResult::Done) {
-                break;
+                return true;
             } else {
                 LOG(FATAL) << "invalid DecodeResult: " << static_cast<int>(result);
             }
@@ -314,102 +338,67 @@ static bool handle_send_file_compressed(borrowed_fd s, unique_fd fd, uint32_t* t
     __builtin_unreachable();
 }
 
-static bool handle_send_file_uncompressed(borrowed_fd s, unique_fd fd, uint32_t* timestamp,
-                                          std::vector<char>& buffer) {
-    syncmsg msg;
-
-    while (true) {
-        if (!ReadFdExactly(s, &msg.data, sizeof(msg.data))) return false;
-
-        if (msg.data.id != ID_DATA) {
-            if (msg.data.id == ID_DONE) {
-                *timestamp = msg.data.size;
-                return true;
-            }
-            SendSyncFail(s, "invalid data message");
-            return false;
-        }
-
-        if (msg.data.size > buffer.size()) {  // TODO: resize buffer?
-            SendSyncFail(s, "oversize data message");
-            return false;
-        }
-        if (!ReadFdExactly(s, &buffer[0], msg.data.size)) return false;
-        if (!WriteFdExactly(fd, &buffer[0], msg.data.size)) {
-            SendSyncFailErrno(s, "write failed");
-            return false;
-        }
-    }
-}
-
 static bool handle_send_file(borrowed_fd s, const char* path, uint32_t* timestamp, uid_t uid,
-                             gid_t gid, uint64_t capabilities, mode_t mode, bool compressed,
-                             std::vector<char>& buffer, bool do_unlink) {
-    int rc;
+                             gid_t gid, uint64_t capabilities, mode_t mode,
+                             CompressionType compression, bool dry_run, std::vector<char>& buffer,
+                             bool do_unlink) {
     syncmsg msg;
+    unique_fd fd;
 
-    __android_log_security_bswrite(SEC_TAG_ADB_SEND_FILE, path);
-
-    unique_fd fd(adb_open_mode(path, O_WRONLY | O_CREAT | O_EXCL | O_CLOEXEC, mode));
-
-    if (fd < 0 && errno == ENOENT) {
-        if (!secure_mkdirs(Dirname(path))) {
-            SendSyncFailErrno(s, "secure_mkdirs failed");
-            goto fail;
-        }
+    if (!dry_run) {
+        __android_log_security_bswrite(SEC_TAG_ADB_SEND_FILE, path);
         fd.reset(adb_open_mode(path, O_WRONLY | O_CREAT | O_EXCL | O_CLOEXEC, mode));
-    }
-    if (fd < 0 && errno == EEXIST) {
-        fd.reset(adb_open_mode(path, O_WRONLY | O_CLOEXEC, mode));
-    }
-    if (fd < 0) {
-        SendSyncFailErrno(s, "couldn't create file");
-        goto fail;
-    } else {
-        if (fchown(fd.get(), uid, gid) == -1) {
-            SendSyncFailErrno(s, "fchown failed");
-            goto fail;
+
+        if (fd < 0 && errno == ENOENT) {
+            if (!secure_mkdirs(Dirname(path))) {
+                SendSyncFailErrno(s, "secure_mkdirs failed");
+                goto fail;
+            }
+            fd.reset(adb_open_mode(path, O_WRONLY | O_CREAT | O_EXCL | O_CLOEXEC, mode));
         }
+        if (fd < 0 && errno == EEXIST) {
+            fd.reset(adb_open_mode(path, O_WRONLY | O_CLOEXEC, mode));
+        }
+        if (fd < 0) {
+            SendSyncFailErrno(s, "couldn't create file");
+            goto fail;
+        } else {
+            if (fchown(fd.get(), uid, gid) == -1) {
+                SendSyncFailErrno(s, "fchown failed");
+                goto fail;
+            }
 
 #if defined(__ANDROID__)
-        // Not all filesystems support setting SELinux labels. http://b/23530370.
-        selinux_android_restorecon(path, 0);
+            // Not all filesystems support setting SELinux labels. http://b/23530370.
+            selinux_android_restorecon(path, 0);
 #endif
 
-        // fchown clears the setuid bit - restore it if present.
-        // Ignore the result of calling fchmod. It's not supported
-        // by all filesystems, so we don't check for success. b/12441485
-        fchmod(fd.get(), mode);
-    }
+            // fchown clears the setuid bit - restore it if present.
+            // Ignore the result of calling fchmod. It's not supported
+            // by all filesystems, so we don't check for success. b/12441485
+            fchmod(fd.get(), mode);
+        }
 
-    {
-        rc = posix_fadvise(fd.get(), 0, 0,
-                           POSIX_FADV_SEQUENTIAL | POSIX_FADV_NOREUSE | POSIX_FADV_WILLNEED);
+        int rc = posix_fadvise(fd.get(), 0, 0,
+                               POSIX_FADV_SEQUENTIAL | POSIX_FADV_NOREUSE | POSIX_FADV_WILLNEED);
         if (rc != 0) {
             D("[ Failed to fadvise: %s ]", strerror(rc));
         }
-
-        bool result;
-        if (compressed) {
-            result = handle_send_file_compressed(s, std::move(fd), timestamp);
-        } else {
-            result = handle_send_file_uncompressed(s, std::move(fd), timestamp, buffer);
-        }
-
-        if (!result) {
-            goto fail;
-        }
-
-        if (!update_capabilities(path, capabilities)) {
-            SendSyncFailErrno(s, "update_capabilities failed");
-            goto fail;
-        }
-
-        msg.status.id = ID_OKAY;
-        msg.status.msglen = 0;
-        return WriteFdExactly(s, &msg.status, sizeof(msg.status));
     }
 
+    if (!handle_send_file_data(s, std::move(fd), timestamp, compression)) {
+        goto fail;
+    }
+
+    if (!update_capabilities(path, capabilities)) {
+        SendSyncFailErrno(s, "update_capabilities failed");
+        goto fail;
+    }
+
+    msg.status.id = ID_OKAY;
+    msg.status.msglen = 0;
+    return WriteFdExactly(s, &msg.status, sizeof(msg.status));
+
 fail:
     // If there's a problem on the device, we'll send an ID_FAIL message and
     // close the socket. Unfortunately the kernel will sometimes throw that
@@ -448,7 +437,7 @@ extern bool handle_send_link(int s, const std::string& path,
                              uint32_t* timestamp, std::vector<char>& buffer)
         __attribute__((error("no symlinks on Windows")));
 #else
-static bool handle_send_link(int s, const std::string& path, uint32_t* timestamp,
+static bool handle_send_link(int s, const std::string& path, uint32_t* timestamp, bool dry_run,
                              std::vector<char>& buffer) {
     syncmsg msg;
 
@@ -467,19 +456,21 @@ static bool handle_send_link(int s, const std::string& path, uint32_t* timestamp
     if (!ReadFdExactly(s, &buffer[0], len)) return false;
 
     std::string buf_link;
-    if (!android::base::Readlink(path, &buf_link) || (buf_link != &buffer[0])) {
-        adb_unlink(path.c_str());
-        auto ret = symlink(&buffer[0], path.c_str());
-        if (ret && errno == ENOENT) {
-            if (!secure_mkdirs(Dirname(path))) {
-                SendSyncFailErrno(s, "secure_mkdirs failed");
+    if (!dry_run) {
+        if (!android::base::Readlink(path, &buf_link) || (buf_link != &buffer[0])) {
+            adb_unlink(path.c_str());
+            auto ret = symlink(&buffer[0], path.c_str());
+            if (ret && errno == ENOENT) {
+                if (!secure_mkdirs(Dirname(path))) {
+                    SendSyncFailErrno(s, "secure_mkdirs failed");
+                    return false;
+                }
+                ret = symlink(&buffer[0], path.c_str());
+            }
+            if (ret) {
+                SendSyncFailErrno(s, "symlink failed");
                 return false;
             }
-            ret = symlink(&buffer[0], path.c_str());
-        }
-        if (ret) {
-            SendSyncFailErrno(s, "symlink failed");
-            return false;
         }
     }
 
@@ -499,12 +490,15 @@ static bool handle_send_link(int s, const std::string& path, uint32_t* timestamp
 }
 #endif
 
-static bool send_impl(int s, const std::string& path, mode_t mode, bool compressed,
-                      std::vector<char>& buffer) {
+static bool send_impl(int s, const std::string& path, mode_t mode, CompressionType compression,
+                      bool dry_run, std::vector<char>& buffer) {
     // Don't delete files before copying if they are not "regular" or symlinks.
     struct stat st;
-    bool do_unlink = (lstat(path.c_str(), &st) == -1) || S_ISREG(st.st_mode) ||
-                     (S_ISLNK(st.st_mode) && !S_ISLNK(mode));
+    bool do_unlink = false;
+    if (!dry_run) {
+        do_unlink = (lstat(path.c_str(), &st) == -1) || S_ISREG(st.st_mode) ||
+                    (S_ISLNK(st.st_mode) && !S_ISLNK(mode));
+    }
     if (do_unlink) {
         adb_unlink(path.c_str());
     }
@@ -512,7 +506,7 @@ static bool send_impl(int s, const std::string& path, mode_t mode, bool compress
     bool result;
     uint32_t timestamp;
     if (S_ISLNK(mode)) {
-        result = handle_send_link(s, path, &timestamp, buffer);
+        result = handle_send_link(s, path, &timestamp, dry_run, buffer);
     } else {
         // Copy user permission bits to "group" and "other" permissions.
         mode &= 0777;
@@ -522,12 +516,12 @@ static bool send_impl(int s, const std::string& path, mode_t mode, bool compress
         uid_t uid = -1;
         gid_t gid = -1;
         uint64_t capabilities = 0;
-        if (should_use_fs_config(path)) {
+        if (should_use_fs_config(path) && !dry_run) {
             adbd_fs_config(path.c_str(), 0, nullptr, &uid, &gid, &mode, &capabilities);
         }
 
         result = handle_send_file(s, path.c_str(), &timestamp, uid, gid, capabilities, mode,
-                                  compressed, buffer, do_unlink);
+                                  compression, dry_run, buffer, do_unlink);
     }
 
     if (!result) {
@@ -560,7 +554,7 @@ static bool do_send_v1(int s, const std::string& spec, std::vector<char>& buffer
         return false;
     }
 
-    return send_impl(s, path, mode, false, buffer);
+    return send_impl(s, path, mode, CompressionType::None, false, buffer);
 }
 
 static bool do_send_v2(int s, const std::string& path, std::vector<char>& buffer) {
@@ -574,45 +568,80 @@ static bool do_send_v2(int s, const std::string& path, std::vector<char>& buffer
         PLOG(ERROR) << "failed to read send_v2 setup packet";
     }
 
-    bool compressed = false;
+    bool dry_run = false;
+    std::optional<CompressionType> compression;
+
+    uint32_t orig_flags = msg.send_v2_setup.flags;
     if (msg.send_v2_setup.flags & kSyncFlagBrotli) {
         msg.send_v2_setup.flags &= ~kSyncFlagBrotli;
-        compressed = true;
+        if (compression) {
+            SendSyncFail(s, android::base::StringPrintf("multiple compression flags received: %d",
+                                                        orig_flags));
+            return false;
+        }
+        compression = CompressionType::Brotli;
     }
+    if (msg.send_v2_setup.flags & kSyncFlagLZ4) {
+        msg.send_v2_setup.flags &= ~kSyncFlagLZ4;
+        if (compression) {
+            SendSyncFail(s, android::base::StringPrintf("multiple compression flags received: %d",
+                                                        orig_flags));
+            return false;
+        }
+        compression = CompressionType::LZ4;
+    }
+    if (msg.send_v2_setup.flags & kSyncFlagDryRun) {
+        msg.send_v2_setup.flags &= ~kSyncFlagDryRun;
+        dry_run = true;
+    }
+
     if (msg.send_v2_setup.flags) {
         SendSyncFail(s, android::base::StringPrintf("unknown flags: %d", msg.send_v2_setup.flags));
         return false;
     }
 
     errno = 0;
-    return send_impl(s, path, msg.send_v2_setup.mode, compressed, buffer);
+    return send_impl(s, path, msg.send_v2_setup.mode, compression.value_or(CompressionType::None),
+                     dry_run, buffer);
 }
 
-static bool recv_uncompressed(borrowed_fd s, unique_fd fd, std::vector<char>& buffer) {
-    syncmsg msg;
-    msg.data.id = ID_DATA;
-    while (true) {
-        int r = adb_read(fd.get(), &buffer[0], buffer.size() - sizeof(msg.data));
-        if (r <= 0) {
-            if (r == 0) break;
-            SendSyncFailErrno(s, "read failed");
-            return false;
-        }
-        msg.data.size = r;
+static bool recv_impl(borrowed_fd s, const char* path, CompressionType compression,
+                      std::vector<char>& buffer) {
+    __android_log_security_bswrite(SEC_TAG_ADB_RECV_FILE, path);
 
-        if (!WriteFdExactly(s, &msg.data, sizeof(msg.data)) || !WriteFdExactly(s, &buffer[0], r)) {
-            return false;
-        }
+    unique_fd fd(adb_open(path, O_RDONLY | O_CLOEXEC));
+    if (fd < 0) {
+        SendSyncFailErrno(s, "open failed");
+        return false;
     }
 
-    return true;
-}
+    int rc = posix_fadvise(fd.get(), 0, 0, POSIX_FADV_SEQUENTIAL | POSIX_FADV_NOREUSE);
+    if (rc != 0) {
+        D("[ Failed to fadvise: %s ]", strerror(rc));
+    }
 
-static bool recv_compressed(borrowed_fd s, unique_fd fd) {
     syncmsg msg;
     msg.data.id = ID_DATA;
 
-    BrotliEncoder<SYNC_DATA_MAX> encoder;
+    std::variant<std::monostate, NullEncoder, BrotliEncoder, LZ4Encoder> encoder_storage;
+    Encoder* encoder;
+
+    switch (compression) {
+        case CompressionType::None:
+            encoder = &encoder_storage.emplace<NullEncoder>(SYNC_DATA_MAX);
+            break;
+
+        case CompressionType::Brotli:
+            encoder = &encoder_storage.emplace<BrotliEncoder>(SYNC_DATA_MAX);
+            break;
+
+        case CompressionType::LZ4:
+            encoder = &encoder_storage.emplace<LZ4Encoder>(SYNC_DATA_MAX);
+            break;
+
+        case CompressionType::Any:
+            LOG(FATAL) << "unexpected CompressionType::Any";
+    }
 
     bool sending = true;
     while (sending) {
@@ -624,15 +653,15 @@ static bool recv_compressed(borrowed_fd s, unique_fd fd) {
         }
 
         if (r == 0) {
-            encoder.Finish();
+            encoder->Finish();
         } else {
             input.resize(r);
-            encoder.Append(std::move(input));
+            encoder->Append(std::move(input));
         }
 
         while (true) {
             Block output;
-            EncodeResult result = encoder.Encode(&output);
+            EncodeResult result = encoder->Encode(&output);
             if (result == EncodeResult::Error) {
                 SendSyncFailErrno(s, "compress failed");
                 return false;
@@ -657,42 +686,13 @@ static bool recv_compressed(borrowed_fd s, unique_fd fd) {
         }
     }
 
-    return true;
-}
-
-static bool recv_impl(borrowed_fd s, const char* path, bool compressed, std::vector<char>& buffer) {
-    __android_log_security_bswrite(SEC_TAG_ADB_RECV_FILE, path);
-
-    unique_fd fd(adb_open(path, O_RDONLY | O_CLOEXEC));
-    if (fd < 0) {
-        SendSyncFailErrno(s, "open failed");
-        return false;
-    }
-
-    int rc = posix_fadvise(fd.get(), 0, 0, POSIX_FADV_SEQUENTIAL | POSIX_FADV_NOREUSE);
-    if (rc != 0) {
-        D("[ Failed to fadvise: %s ]", strerror(rc));
-    }
-
-    bool result;
-    if (compressed) {
-        result = recv_compressed(s, std::move(fd));
-    } else {
-        result = recv_uncompressed(s, std::move(fd), buffer);
-    }
-
-    if (!result) {
-        return false;
-    }
-
-    syncmsg msg;
     msg.data.id = ID_DONE;
     msg.data.size = 0;
     return WriteFdExactly(s, &msg.data, sizeof(msg.data));
 }
 
 static bool do_recv_v1(borrowed_fd s, const char* path, std::vector<char>& buffer) {
-    return recv_impl(s, path, false, buffer);
+    return recv_impl(s, path, CompressionType::None, buffer);
 }
 
 static bool do_recv_v2(borrowed_fd s, const char* path, std::vector<char>& buffer) {
@@ -706,17 +706,33 @@ static bool do_recv_v2(borrowed_fd s, const char* path, std::vector<char>& buffe
         PLOG(ERROR) << "failed to read recv_v2 setup packet";
     }
 
-    bool compressed = false;
+    std::optional<CompressionType> compression;
+    uint32_t orig_flags = msg.recv_v2_setup.flags;
     if (msg.recv_v2_setup.flags & kSyncFlagBrotli) {
         msg.recv_v2_setup.flags &= ~kSyncFlagBrotli;
-        compressed = true;
+        if (compression) {
+            SendSyncFail(s, android::base::StringPrintf("multiple compression flags received: %d",
+                                                        orig_flags));
+            return false;
+        }
+        compression = CompressionType::Brotli;
     }
+    if (msg.recv_v2_setup.flags & kSyncFlagLZ4) {
+        msg.recv_v2_setup.flags &= ~kSyncFlagLZ4;
+        if (compression) {
+            SendSyncFail(s, android::base::StringPrintf("multiple compression flags received: %d",
+                                                        orig_flags));
+            return false;
+        }
+        compression = CompressionType::LZ4;
+    }
+
     if (msg.recv_v2_setup.flags) {
         SendSyncFail(s, android::base::StringPrintf("unknown flags: %d", msg.recv_v2_setup.flags));
         return false;
     }
 
-    return recv_impl(s, path, compressed, buffer);
+    return recv_impl(s, path, compression.value_or(CompressionType::None), buffer);
 }
 
 static const char* sync_id_to_name(uint32_t id) {
diff --git a/adb/file_sync_protocol.h b/adb/file_sync_protocol.h
index fd9a5169e..8f8f85fa5 100644
--- a/adb/file_sync_protocol.h
+++ b/adb/file_sync_protocol.h
@@ -92,6 +92,15 @@ struct __attribute__((packed)) sync_dent_v2 {
 enum SyncFlag : uint32_t {
     kSyncFlagNone = 0,
     kSyncFlagBrotli = 1,
+    kSyncFlagLZ4 = 2,
+    kSyncFlagDryRun = 0x8000'0000U,
+};
+
+enum class CompressionType {
+    None,
+    Any,
+    Brotli,
+    LZ4,
 };
 
 // send_v1 sent the path in a buffer, followed by a comma and the mode as a string.
diff --git a/adb/test_device.py b/adb/test_device.py
index 6a9ff89ef..f5e4cbb6e 100755
--- a/adb/test_device.py
+++ b/adb/test_device.py
@@ -77,8 +77,7 @@ def requires_non_root(func):
 
 
 class DeviceTest(unittest.TestCase):
-    def setUp(self):
-        self.device = adb.get_device()
+    device = adb.get_device()
 
 
 class AbbTest(DeviceTest):
@@ -753,535 +752,611 @@ def make_random_device_files(device, in_dir, num_files, prefix='device_tmpfile')
     return files
 
 
-class FileOperationsTest(DeviceTest):
-    SCRATCH_DIR = '/data/local/tmp'
-    DEVICE_TEMP_FILE = SCRATCH_DIR + '/adb_test_file'
-    DEVICE_TEMP_DIR = SCRATCH_DIR + '/adb_test_dir'
+class FileOperationsTest:
+    class Base(DeviceTest):
+        SCRATCH_DIR = '/data/local/tmp'
+        DEVICE_TEMP_FILE = SCRATCH_DIR + '/adb_test_file'
+        DEVICE_TEMP_DIR = SCRATCH_DIR + '/adb_test_dir'
 
-    def _verify_remote(self, checksum, remote_path):
-        dev_md5, _ = self.device.shell([get_md5_prog(self.device),
-                                        remote_path])[0].split()
-        self.assertEqual(checksum, dev_md5)
+        def setUp(self):
+            self.previous_env = os.environ.get("ADB_COMPRESSION")
+            os.environ["ADB_COMPRESSION"] = self.compression
 
-    def _verify_local(self, checksum, local_path):
-        with open(local_path, 'rb') as host_file:
-            host_md5 = compute_md5(host_file.read())
-            self.assertEqual(host_md5, checksum)
+        def tearDown(self):
+            if self.previous_env is None:
+                del os.environ["ADB_COMPRESSION"]
+            else:
+                os.environ["ADB_COMPRESSION"] = self.previous_env
 
-    def test_push(self):
-        """Push a randomly generated file to specified device."""
-        kbytes = 512
-        tmp = tempfile.NamedTemporaryFile(mode='wb', delete=False)
-        rand_str = os.urandom(1024 * kbytes)
-        tmp.write(rand_str)
-        tmp.close()
+        def _verify_remote(self, checksum, remote_path):
+            dev_md5, _ = self.device.shell([get_md5_prog(self.device),
+                                            remote_path])[0].split()
+            self.assertEqual(checksum, dev_md5)
 
-        self.device.shell(['rm', '-rf', self.DEVICE_TEMP_FILE])
-        self.device.push(local=tmp.name, remote=self.DEVICE_TEMP_FILE)
+        def _verify_local(self, checksum, local_path):
+            with open(local_path, 'rb') as host_file:
+                host_md5 = compute_md5(host_file.read())
+                self.assertEqual(host_md5, checksum)
 
-        self._verify_remote(compute_md5(rand_str), self.DEVICE_TEMP_FILE)
-        self.device.shell(['rm', '-f', self.DEVICE_TEMP_FILE])
+        def test_push(self):
+            """Push a randomly generated file to specified device."""
+            kbytes = 512
+            tmp = tempfile.NamedTemporaryFile(mode='wb', delete=False)
+            rand_str = os.urandom(1024 * kbytes)
+            tmp.write(rand_str)
+            tmp.close()
 
-        os.remove(tmp.name)
+            self.device.shell(['rm', '-rf', self.DEVICE_TEMP_FILE])
+            self.device.push(local=tmp.name, remote=self.DEVICE_TEMP_FILE)
 
-    def test_push_dir(self):
-        """Push a randomly generated directory of files to the device."""
-        self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
-        self.device.shell(['mkdir', self.DEVICE_TEMP_DIR])
+            self._verify_remote(compute_md5(rand_str), self.DEVICE_TEMP_FILE)
+            self.device.shell(['rm', '-f', self.DEVICE_TEMP_FILE])
 
-        try:
-            host_dir = tempfile.mkdtemp()
+            os.remove(tmp.name)
 
-            # Make sure the temp directory isn't setuid, or else adb will complain.
-            os.chmod(host_dir, 0o700)
-
-            # Create 32 random files.
-            temp_files = make_random_host_files(in_dir=host_dir, num_files=32)
-            self.device.push(host_dir, self.DEVICE_TEMP_DIR)
-
-            for temp_file in temp_files:
-                remote_path = posixpath.join(self.DEVICE_TEMP_DIR,
-                                             os.path.basename(host_dir),
-                                             temp_file.base_name)
-                self._verify_remote(temp_file.checksum, remote_path)
+        def test_push_dir(self):
+            """Push a randomly generated directory of files to the device."""
             self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
-        finally:
-            if host_dir is not None:
-                shutil.rmtree(host_dir)
+            self.device.shell(['mkdir', self.DEVICE_TEMP_DIR])
 
-    def disabled_test_push_empty(self):
-        """Push an empty directory to the device."""
-        self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
-        self.device.shell(['mkdir', self.DEVICE_TEMP_DIR])
+            try:
+                host_dir = tempfile.mkdtemp()
 
-        try:
-            host_dir = tempfile.mkdtemp()
+                # Make sure the temp directory isn't setuid, or else adb will complain.
+                os.chmod(host_dir, 0o700)
 
-            # Make sure the temp directory isn't setuid, or else adb will complain.
-            os.chmod(host_dir, 0o700)
+                # Create 32 random files.
+                temp_files = make_random_host_files(in_dir=host_dir, num_files=32)
+                self.device.push(host_dir, self.DEVICE_TEMP_DIR)
 
-            # Create an empty directory.
-            empty_dir_path = os.path.join(host_dir, 'empty')
-            os.mkdir(empty_dir_path);
+                for temp_file in temp_files:
+                    remote_path = posixpath.join(self.DEVICE_TEMP_DIR,
+                                                 os.path.basename(host_dir),
+                                                 temp_file.base_name)
+                    self._verify_remote(temp_file.checksum, remote_path)
+                self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
+            finally:
+                if host_dir is not None:
+                    shutil.rmtree(host_dir)
 
-            self.device.push(empty_dir_path, self.DEVICE_TEMP_DIR)
-
-            remote_path = os.path.join(self.DEVICE_TEMP_DIR, "empty")
-            test_empty_cmd = ["[", "-d", remote_path, "]"]
-            rc, _, _ = self.device.shell_nocheck(test_empty_cmd)
-
-            self.assertEqual(rc, 0)
+        def disabled_test_push_empty(self):
+            """Push an empty directory to the device."""
             self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
-        finally:
-            if host_dir is not None:
-                shutil.rmtree(host_dir)
+            self.device.shell(['mkdir', self.DEVICE_TEMP_DIR])
 
-    @unittest.skipIf(sys.platform == "win32", "symlinks require elevated privileges on windows")
-    def test_push_symlink(self):
-        """Push a symlink.
+            try:
+                host_dir = tempfile.mkdtemp()
 
-        Bug: http://b/31491920
-        """
-        try:
-            host_dir = tempfile.mkdtemp()
+                # Make sure the temp directory isn't setuid, or else adb will complain.
+                os.chmod(host_dir, 0o700)
 
-            # Make sure the temp directory isn't setuid, or else adb will
-            # complain.
-            os.chmod(host_dir, 0o700)
+                # Create an empty directory.
+                empty_dir_path = os.path.join(host_dir, 'empty')
+                os.mkdir(empty_dir_path);
 
-            with open(os.path.join(host_dir, 'foo'), 'w') as f:
-                f.write('foo')
+                self.device.push(empty_dir_path, self.DEVICE_TEMP_DIR)
 
-            symlink_path = os.path.join(host_dir, 'symlink')
-            os.symlink('foo', symlink_path)
+                remote_path = os.path.join(self.DEVICE_TEMP_DIR, "empty")
+                test_empty_cmd = ["[", "-d", remote_path, "]"]
+                rc, _, _ = self.device.shell_nocheck(test_empty_cmd)
+
+                self.assertEqual(rc, 0)
+                self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
+            finally:
+                if host_dir is not None:
+                    shutil.rmtree(host_dir)
+
+        @unittest.skipIf(sys.platform == "win32", "symlinks require elevated privileges on windows")
+        def test_push_symlink(self):
+            """Push a symlink.
+
+            Bug: http://b/31491920
+            """
+            try:
+                host_dir = tempfile.mkdtemp()
+
+                # Make sure the temp directory isn't setuid, or else adb will
+                # complain.
+                os.chmod(host_dir, 0o700)
+
+                with open(os.path.join(host_dir, 'foo'), 'w') as f:
+                    f.write('foo')
+
+                symlink_path = os.path.join(host_dir, 'symlink')
+                os.symlink('foo', symlink_path)
+
+                self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
+                self.device.shell(['mkdir', self.DEVICE_TEMP_DIR])
+                self.device.push(symlink_path, self.DEVICE_TEMP_DIR)
+                rc, out, _ = self.device.shell_nocheck(
+                    ['cat', posixpath.join(self.DEVICE_TEMP_DIR, 'symlink')])
+                self.assertEqual(0, rc)
+                self.assertEqual(out.strip(), 'foo')
+            finally:
+                if host_dir is not None:
+                    shutil.rmtree(host_dir)
+
+        def test_multiple_push(self):
+            """Push multiple files to the device in one adb push command.
+
+            Bug: http://b/25324823
+            """
 
             self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
             self.device.shell(['mkdir', self.DEVICE_TEMP_DIR])
-            self.device.push(symlink_path, self.DEVICE_TEMP_DIR)
-            rc, out, _ = self.device.shell_nocheck(
-                ['cat', posixpath.join(self.DEVICE_TEMP_DIR, 'symlink')])
-            self.assertEqual(0, rc)
-            self.assertEqual(out.strip(), 'foo')
-        finally:
-            if host_dir is not None:
-                shutil.rmtree(host_dir)
 
-    def test_multiple_push(self):
-        """Push multiple files to the device in one adb push command.
-
-        Bug: http://b/25324823
-        """
-
-        self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
-        self.device.shell(['mkdir', self.DEVICE_TEMP_DIR])
-
-        try:
-            host_dir = tempfile.mkdtemp()
-
-            # Create some random files and a subdirectory containing more files.
-            temp_files = make_random_host_files(in_dir=host_dir, num_files=4)
-
-            subdir = os.path.join(host_dir, 'subdir')
-            os.mkdir(subdir)
-            subdir_temp_files = make_random_host_files(in_dir=subdir,
-                                                       num_files=4)
-
-            paths = [x.full_path for x in temp_files]
-            paths.append(subdir)
-            self.device._simple_call(['push'] + paths + [self.DEVICE_TEMP_DIR])
-
-            for temp_file in temp_files:
-                remote_path = posixpath.join(self.DEVICE_TEMP_DIR,
-                                             temp_file.base_name)
-                self._verify_remote(temp_file.checksum, remote_path)
-
-            for subdir_temp_file in subdir_temp_files:
-                remote_path = posixpath.join(self.DEVICE_TEMP_DIR,
-                                             # BROKEN: http://b/25394682
-                                             # 'subdir';
-                                             temp_file.base_name)
-                self._verify_remote(temp_file.checksum, remote_path)
-
-
-            self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
-        finally:
-            if host_dir is not None:
-                shutil.rmtree(host_dir)
-
-    @requires_non_root
-    def test_push_error_reporting(self):
-        """Make sure that errors that occur while pushing a file get reported
-
-        Bug: http://b/26816782
-        """
-        with tempfile.NamedTemporaryFile() as tmp_file:
-            tmp_file.write(b'\0' * 1024 * 1024)
-            tmp_file.flush()
             try:
-                self.device.push(local=tmp_file.name, remote='/system/')
-                self.fail('push should not have succeeded')
+                host_dir = tempfile.mkdtemp()
+
+                # Create some random files and a subdirectory containing more files.
+                temp_files = make_random_host_files(in_dir=host_dir, num_files=4)
+
+                subdir = os.path.join(host_dir, 'subdir')
+                os.mkdir(subdir)
+                subdir_temp_files = make_random_host_files(in_dir=subdir,
+                                                           num_files=4)
+
+                paths = [x.full_path for x in temp_files]
+                paths.append(subdir)
+                self.device._simple_call(['push'] + paths + [self.DEVICE_TEMP_DIR])
+
+                for temp_file in temp_files:
+                    remote_path = posixpath.join(self.DEVICE_TEMP_DIR,
+                                                 temp_file.base_name)
+                    self._verify_remote(temp_file.checksum, remote_path)
+
+                for subdir_temp_file in subdir_temp_files:
+                    remote_path = posixpath.join(self.DEVICE_TEMP_DIR,
+                                                 # BROKEN: http://b/25394682
+                                                 # 'subdir';
+                                                 temp_file.base_name)
+                    self._verify_remote(temp_file.checksum, remote_path)
+
+
+                self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
+            finally:
+                if host_dir is not None:
+                    shutil.rmtree(host_dir)
+
+        @requires_non_root
+        def test_push_error_reporting(self):
+            """Make sure that errors that occur while pushing a file get reported
+
+            Bug: http://b/26816782
+            """
+            with tempfile.NamedTemporaryFile() as tmp_file:
+                tmp_file.write(b'\0' * 1024 * 1024)
+                tmp_file.flush()
+                try:
+                    self.device.push(local=tmp_file.name, remote='/system/')
+                    self.fail('push should not have succeeded')
+                except subprocess.CalledProcessError as e:
+                    output = e.output
+
+                self.assertTrue(b'Permission denied' in output or
+                                b'Read-only file system' in output)
+
+        @requires_non_root
+        def test_push_directory_creation(self):
+            """Regression test for directory creation.
+
+            Bug: http://b/110953234
+            """
+            with tempfile.NamedTemporaryFile() as tmp_file:
+                tmp_file.write(b'\0' * 1024 * 1024)
+                tmp_file.flush()
+                remote_path = self.DEVICE_TEMP_DIR + '/test_push_directory_creation'
+                self.device.shell(['rm', '-rf', remote_path])
+
+                remote_path += '/filename'
+                self.device.push(local=tmp_file.name, remote=remote_path)
+
+        def disabled_test_push_multiple_slash_root(self):
+            """Regression test for pushing to //data/local/tmp.
+
+            Bug: http://b/141311284
+
+            Disabled because this broken on the adbd side as well: b/141943968
+            """
+            with tempfile.NamedTemporaryFile() as tmp_file:
+                tmp_file.write('\0' * 1024 * 1024)
+                tmp_file.flush()
+                remote_path = '/' + self.DEVICE_TEMP_DIR + '/test_push_multiple_slash_root'
+                self.device.shell(['rm', '-rf', remote_path])
+                self.device.push(local=tmp_file.name, remote=remote_path)
+
+        def _test_pull(self, remote_file, checksum):
+            tmp_write = tempfile.NamedTemporaryFile(mode='wb', delete=False)
+            tmp_write.close()
+            self.device.pull(remote=remote_file, local=tmp_write.name)
+            with open(tmp_write.name, 'rb') as tmp_read:
+                host_contents = tmp_read.read()
+                host_md5 = compute_md5(host_contents)
+            self.assertEqual(checksum, host_md5)
+            os.remove(tmp_write.name)
+
+        @requires_non_root
+        def test_pull_error_reporting(self):
+            self.device.shell(['touch', self.DEVICE_TEMP_FILE])
+            self.device.shell(['chmod', 'a-rwx', self.DEVICE_TEMP_FILE])
+
+            try:
+                output = self.device.pull(remote=self.DEVICE_TEMP_FILE, local='x')
             except subprocess.CalledProcessError as e:
                 output = e.output
 
-            self.assertTrue(b'Permission denied' in output or
-                            b'Read-only file system' in output)
+            self.assertIn(b'Permission denied', output)
 
-    @requires_non_root
-    def test_push_directory_creation(self):
-        """Regression test for directory creation.
+            self.device.shell(['rm', '-f', self.DEVICE_TEMP_FILE])
 
-        Bug: http://b/110953234
-        """
-        with tempfile.NamedTemporaryFile() as tmp_file:
-            tmp_file.write(b'\0' * 1024 * 1024)
-            tmp_file.flush()
-            remote_path = self.DEVICE_TEMP_DIR + '/test_push_directory_creation'
-            self.device.shell(['rm', '-rf', remote_path])
+        def test_pull(self):
+            """Pull a randomly generated file from specified device."""
+            kbytes = 512
+            self.device.shell(['rm', '-rf', self.DEVICE_TEMP_FILE])
+            cmd = ['dd', 'if=/dev/urandom',
+                   'of={}'.format(self.DEVICE_TEMP_FILE), 'bs=1024',
+                   'count={}'.format(kbytes)]
+            self.device.shell(cmd)
+            dev_md5, _ = self.device.shell(
+                [get_md5_prog(self.device), self.DEVICE_TEMP_FILE])[0].split()
+            self._test_pull(self.DEVICE_TEMP_FILE, dev_md5)
+            self.device.shell_nocheck(['rm', self.DEVICE_TEMP_FILE])
 
-            remote_path += '/filename'
-            self.device.push(local=tmp_file.name, remote=remote_path)
+        def test_pull_dir(self):
+            """Pull a randomly generated directory of files from the device."""
+            try:
+                host_dir = tempfile.mkdtemp()
 
-    def disabled_test_push_multiple_slash_root(self):
-        """Regression test for pushing to //data/local/tmp.
+                self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
+                self.device.shell(['mkdir', '-p', self.DEVICE_TEMP_DIR])
 
-        Bug: http://b/141311284
+                # Populate device directory with random files.
+                temp_files = make_random_device_files(
+                    self.device, in_dir=self.DEVICE_TEMP_DIR, num_files=32)
 
-        Disabled because this broken on the adbd side as well: b/141943968
-        """
-        with tempfile.NamedTemporaryFile() as tmp_file:
-            tmp_file.write('\0' * 1024 * 1024)
-            tmp_file.flush()
-            remote_path = '/' + self.DEVICE_TEMP_DIR + '/test_push_multiple_slash_root'
-            self.device.shell(['rm', '-rf', remote_path])
-            self.device.push(local=tmp_file.name, remote=remote_path)
+                self.device.pull(remote=self.DEVICE_TEMP_DIR, local=host_dir)
 
-    def _test_pull(self, remote_file, checksum):
-        tmp_write = tempfile.NamedTemporaryFile(mode='wb', delete=False)
-        tmp_write.close()
-        self.device.pull(remote=remote_file, local=tmp_write.name)
-        with open(tmp_write.name, 'rb') as tmp_read:
-            host_contents = tmp_read.read()
-            host_md5 = compute_md5(host_contents)
-        self.assertEqual(checksum, host_md5)
-        os.remove(tmp_write.name)
+                for temp_file in temp_files:
+                    host_path = os.path.join(
+                        host_dir, posixpath.basename(self.DEVICE_TEMP_DIR),
+                        temp_file.base_name)
+                    self._verify_local(temp_file.checksum, host_path)
 
-    @requires_non_root
-    def test_pull_error_reporting(self):
-        self.device.shell(['touch', self.DEVICE_TEMP_FILE])
-        self.device.shell(['chmod', 'a-rwx', self.DEVICE_TEMP_FILE])
+                self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
+            finally:
+                if host_dir is not None:
+                    shutil.rmtree(host_dir)
 
-        try:
-            output = self.device.pull(remote=self.DEVICE_TEMP_FILE, local='x')
-        except subprocess.CalledProcessError as e:
-            output = e.output
+        def test_pull_dir_symlink(self):
+            """Pull a directory into a symlink to a directory.
 
-        self.assertIn(b'Permission denied', output)
+            Bug: http://b/27362811
+            """
+            if os.name != 'posix':
+                raise unittest.SkipTest('requires POSIX')
 
-        self.device.shell(['rm', '-f', self.DEVICE_TEMP_FILE])
+            try:
+                host_dir = tempfile.mkdtemp()
+                real_dir = os.path.join(host_dir, 'dir')
+                symlink = os.path.join(host_dir, 'symlink')
+                os.mkdir(real_dir)
+                os.symlink(real_dir, symlink)
 
-    def test_pull(self):
-        """Pull a randomly generated file from specified device."""
-        kbytes = 512
-        self.device.shell(['rm', '-rf', self.DEVICE_TEMP_FILE])
-        cmd = ['dd', 'if=/dev/urandom',
-               'of={}'.format(self.DEVICE_TEMP_FILE), 'bs=1024',
-               'count={}'.format(kbytes)]
-        self.device.shell(cmd)
-        dev_md5, _ = self.device.shell(
-            [get_md5_prog(self.device), self.DEVICE_TEMP_FILE])[0].split()
-        self._test_pull(self.DEVICE_TEMP_FILE, dev_md5)
-        self.device.shell_nocheck(['rm', self.DEVICE_TEMP_FILE])
+                self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
+                self.device.shell(['mkdir', '-p', self.DEVICE_TEMP_DIR])
 
-    def test_pull_dir(self):
-        """Pull a randomly generated directory of files from the device."""
-        try:
-            host_dir = tempfile.mkdtemp()
+                # Populate device directory with random files.
+                temp_files = make_random_device_files(
+                    self.device, in_dir=self.DEVICE_TEMP_DIR, num_files=32)
 
-            self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
-            self.device.shell(['mkdir', '-p', self.DEVICE_TEMP_DIR])
+                self.device.pull(remote=self.DEVICE_TEMP_DIR, local=symlink)
 
-            # Populate device directory with random files.
-            temp_files = make_random_device_files(
-                self.device, in_dir=self.DEVICE_TEMP_DIR, num_files=32)
+                for temp_file in temp_files:
+                    host_path = os.path.join(
+                        real_dir, posixpath.basename(self.DEVICE_TEMP_DIR),
+                        temp_file.base_name)
+                    self._verify_local(temp_file.checksum, host_path)
 
-            self.device.pull(remote=self.DEVICE_TEMP_DIR, local=host_dir)
+                self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
+            finally:
+                if host_dir is not None:
+                    shutil.rmtree(host_dir)
 
+        def test_pull_dir_symlink_collision(self):
+            """Pull a directory into a colliding symlink to directory."""
+            if os.name != 'posix':
+                raise unittest.SkipTest('requires POSIX')
+
+            try:
+                host_dir = tempfile.mkdtemp()
+                real_dir = os.path.join(host_dir, 'real')
+                tmp_dirname = os.path.basename(self.DEVICE_TEMP_DIR)
+                symlink = os.path.join(host_dir, tmp_dirname)
+                os.mkdir(real_dir)
+                os.symlink(real_dir, symlink)
+
+                self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
+                self.device.shell(['mkdir', '-p', self.DEVICE_TEMP_DIR])
+
+                # Populate device directory with random files.
+                temp_files = make_random_device_files(
+                    self.device, in_dir=self.DEVICE_TEMP_DIR, num_files=32)
+
+                self.device.pull(remote=self.DEVICE_TEMP_DIR, local=host_dir)
+
+                for temp_file in temp_files:
+                    host_path = os.path.join(real_dir, temp_file.base_name)
+                    self._verify_local(temp_file.checksum, host_path)
+
+                self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
+            finally:
+                if host_dir is not None:
+                    shutil.rmtree(host_dir)
+
+        def test_pull_dir_nonexistent(self):
+            """Pull a directory of files from the device to a nonexistent path."""
+            try:
+                host_dir = tempfile.mkdtemp()
+                dest_dir = os.path.join(host_dir, 'dest')
+
+                self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
+                self.device.shell(['mkdir', '-p', self.DEVICE_TEMP_DIR])
+
+                # Populate device directory with random files.
+                temp_files = make_random_device_files(
+                    self.device, in_dir=self.DEVICE_TEMP_DIR, num_files=32)
+
+                self.device.pull(remote=self.DEVICE_TEMP_DIR, local=dest_dir)
+
+                for temp_file in temp_files:
+                    host_path = os.path.join(dest_dir, temp_file.base_name)
+                    self._verify_local(temp_file.checksum, host_path)
+
+                self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
+            finally:
+                if host_dir is not None:
+                    shutil.rmtree(host_dir)
+
+        # selinux prevents adbd from accessing symlinks on /data/local/tmp.
+        def disabled_test_pull_symlink_dir(self):
+            """Pull a symlink to a directory of symlinks to files."""
+            try:
+                host_dir = tempfile.mkdtemp()
+
+                remote_dir = posixpath.join(self.DEVICE_TEMP_DIR, 'contents')
+                remote_links = posixpath.join(self.DEVICE_TEMP_DIR, 'links')
+                remote_symlink = posixpath.join(self.DEVICE_TEMP_DIR, 'symlink')
+
+                self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
+                self.device.shell(['mkdir', '-p', remote_dir, remote_links])
+                self.device.shell(['ln', '-s', remote_links, remote_symlink])
+
+                # Populate device directory with random files.
+                temp_files = make_random_device_files(
+                    self.device, in_dir=remote_dir, num_files=32)
+
+                for temp_file in temp_files:
+                    self.device.shell(
+                        ['ln', '-s', '../contents/{}'.format(temp_file.base_name),
+                         posixpath.join(remote_links, temp_file.base_name)])
+
+                self.device.pull(remote=remote_symlink, local=host_dir)
+
+                for temp_file in temp_files:
+                    host_path = os.path.join(
+                        host_dir, 'symlink', temp_file.base_name)
+                    self._verify_local(temp_file.checksum, host_path)
+
+                self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
+            finally:
+                if host_dir is not None:
+                    shutil.rmtree(host_dir)
+
+        def test_pull_empty(self):
+            """Pull a directory containing an empty directory from the device."""
+            try:
+                host_dir = tempfile.mkdtemp()
+
+                remote_empty_path = posixpath.join(self.DEVICE_TEMP_DIR, 'empty')
+                self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
+                self.device.shell(['mkdir', '-p', remote_empty_path])
+
+                self.device.pull(remote=remote_empty_path, local=host_dir)
+                self.assertTrue(os.path.isdir(os.path.join(host_dir, 'empty')))
+            finally:
+                if host_dir is not None:
+                    shutil.rmtree(host_dir)
+
+        def test_multiple_pull(self):
+            """Pull a randomly generated directory of files from the device."""
+
+            try:
+                host_dir = tempfile.mkdtemp()
+
+                subdir = posixpath.join(self.DEVICE_TEMP_DIR, 'subdir')
+                self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
+                self.device.shell(['mkdir', '-p', subdir])
+
+                # Create some random files and a subdirectory containing more files.
+                temp_files = make_random_device_files(
+                    self.device, in_dir=self.DEVICE_TEMP_DIR, num_files=4)
+
+                subdir_temp_files = make_random_device_files(
+                    self.device, in_dir=subdir, num_files=4, prefix='subdir_')
+
+                paths = [x.full_path for x in temp_files]
+                paths.append(subdir)
+                self.device._simple_call(['pull'] + paths + [host_dir])
+
+                for temp_file in temp_files:
+                    local_path = os.path.join(host_dir, temp_file.base_name)
+                    self._verify_local(temp_file.checksum, local_path)
+
+                for subdir_temp_file in subdir_temp_files:
+                    local_path = os.path.join(host_dir,
+                                              'subdir',
+                                              subdir_temp_file.base_name)
+                    self._verify_local(subdir_temp_file.checksum, local_path)
+
+                self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
+            finally:
+                if host_dir is not None:
+                    shutil.rmtree(host_dir)
+
+        def verify_sync(self, device, temp_files, device_dir):
+            """Verifies that a list of temp files was synced to the device."""
+            # Confirm that every file on the device mirrors that on the host.
             for temp_file in temp_files:
-                host_path = os.path.join(
-                    host_dir, posixpath.basename(self.DEVICE_TEMP_DIR),
-                    temp_file.base_name)
-                self._verify_local(temp_file.checksum, host_path)
+                device_full_path = posixpath.join(
+                    device_dir, temp_file.base_name)
+                dev_md5, _ = device.shell(
+                    [get_md5_prog(self.device), device_full_path])[0].split()
+                self.assertEqual(temp_file.checksum, dev_md5)
 
-            self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
-        finally:
-            if host_dir is not None:
-                shutil.rmtree(host_dir)
+        def test_sync(self):
+            """Sync a host directory to the data partition."""
 
-    def test_pull_dir_symlink(self):
-        """Pull a directory into a symlink to a directory.
+            try:
+                base_dir = tempfile.mkdtemp()
 
-        Bug: http://b/27362811
-        """
-        if os.name != 'posix':
-            raise unittest.SkipTest('requires POSIX')
+                # Create mirror device directory hierarchy within base_dir.
+                full_dir_path = base_dir + self.DEVICE_TEMP_DIR
+                os.makedirs(full_dir_path)
 
-        try:
-            host_dir = tempfile.mkdtemp()
-            real_dir = os.path.join(host_dir, 'dir')
-            symlink = os.path.join(host_dir, 'symlink')
-            os.mkdir(real_dir)
-            os.symlink(real_dir, symlink)
+                # Create 32 random files within the host mirror.
+                temp_files = make_random_host_files(
+                    in_dir=full_dir_path, num_files=32)
 
-            self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
-            self.device.shell(['mkdir', '-p', self.DEVICE_TEMP_DIR])
+                # Clean up any stale files on the device.
+                device = adb.get_device()  # pylint: disable=no-member
+                device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
 
-            # Populate device directory with random files.
-            temp_files = make_random_device_files(
-                self.device, in_dir=self.DEVICE_TEMP_DIR, num_files=32)
+                old_product_out = os.environ.get('ANDROID_PRODUCT_OUT')
+                os.environ['ANDROID_PRODUCT_OUT'] = base_dir
+                device.sync('data')
+                if old_product_out is None:
+                    del os.environ['ANDROID_PRODUCT_OUT']
+                else:
+                    os.environ['ANDROID_PRODUCT_OUT'] = old_product_out
 
-            self.device.pull(remote=self.DEVICE_TEMP_DIR, local=symlink)
+                self.verify_sync(device, temp_files, self.DEVICE_TEMP_DIR)
 
-            for temp_file in temp_files:
-                host_path = os.path.join(
-                    real_dir, posixpath.basename(self.DEVICE_TEMP_DIR),
-                    temp_file.base_name)
-                self._verify_local(temp_file.checksum, host_path)
+                #self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
+            finally:
+                if base_dir is not None:
+                    shutil.rmtree(base_dir)
 
-            self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
-        finally:
-            if host_dir is not None:
-                shutil.rmtree(host_dir)
+        def test_push_sync(self):
+            """Sync a host directory to a specific path."""
 
-    def test_pull_dir_symlink_collision(self):
-        """Pull a directory into a colliding symlink to directory."""
-        if os.name != 'posix':
-            raise unittest.SkipTest('requires POSIX')
+            try:
+                temp_dir = tempfile.mkdtemp()
+                temp_files = make_random_host_files(in_dir=temp_dir, num_files=32)
 
-        try:
-            host_dir = tempfile.mkdtemp()
-            real_dir = os.path.join(host_dir, 'real')
-            tmp_dirname = os.path.basename(self.DEVICE_TEMP_DIR)
-            symlink = os.path.join(host_dir, tmp_dirname)
-            os.mkdir(real_dir)
-            os.symlink(real_dir, symlink)
+                device_dir = posixpath.join(self.DEVICE_TEMP_DIR, 'sync_src_dst')
 
-            self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
-            self.device.shell(['mkdir', '-p', self.DEVICE_TEMP_DIR])
+                # Clean up any stale files on the device.
+                device = adb.get_device()  # pylint: disable=no-member
+                device.shell(['rm', '-rf', device_dir])
 
-            # Populate device directory with random files.
-            temp_files = make_random_device_files(
-                self.device, in_dir=self.DEVICE_TEMP_DIR, num_files=32)
+                device.push(temp_dir, device_dir, sync=True)
 
-            self.device.pull(remote=self.DEVICE_TEMP_DIR, local=host_dir)
+                self.verify_sync(device, temp_files, device_dir)
 
-            for temp_file in temp_files:
-                host_path = os.path.join(real_dir, temp_file.base_name)
-                self._verify_local(temp_file.checksum, host_path)
+                self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
+            finally:
+                if temp_dir is not None:
+                    shutil.rmtree(temp_dir)
 
-            self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
-        finally:
-            if host_dir is not None:
-                shutil.rmtree(host_dir)
+        def test_push_dry_run_nonexistent_file(self):
+            """Push with dry run."""
 
-    def test_pull_dir_nonexistent(self):
-        """Pull a directory of files from the device to a nonexistent path."""
-        try:
-            host_dir = tempfile.mkdtemp()
-            dest_dir = os.path.join(host_dir, 'dest')
+            for file_size in [8, 1024 * 1024]:
+                try:
+                    device_dir = posixpath.join(self.DEVICE_TEMP_DIR, 'push_dry_run')
+                    device_file = posixpath.join(device_dir, 'file')
 
-            self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
-            self.device.shell(['mkdir', '-p', self.DEVICE_TEMP_DIR])
+                    self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
+                    self.device.shell(['mkdir', '-p', device_dir])
 
-            # Populate device directory with random files.
-            temp_files = make_random_device_files(
-                self.device, in_dir=self.DEVICE_TEMP_DIR, num_files=32)
+                    host_dir = tempfile.mkdtemp()
+                    host_file = posixpath.join(host_dir, 'file')
 
-            self.device.pull(remote=self.DEVICE_TEMP_DIR, local=dest_dir)
+                    with open(host_file, "w") as f:
+                        f.write('x' * file_size)
 
-            for temp_file in temp_files:
-                host_path = os.path.join(dest_dir, temp_file.base_name)
-                self._verify_local(temp_file.checksum, host_path)
+                    self.device._simple_call(['push', '-n', host_file, device_file])
+                    rc, _, _ = self.device.shell_nocheck(['[', '-e', device_file, ']'])
+                    self.assertNotEqual(0, rc)
 
-            self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
-        finally:
-            if host_dir is not None:
-                shutil.rmtree(host_dir)
+                    self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
+                finally:
+                    if host_dir is not None:
+                        shutil.rmtree(host_dir)
 
-    # selinux prevents adbd from accessing symlinks on /data/local/tmp.
-    def disabled_test_pull_symlink_dir(self):
-        """Pull a symlink to a directory of symlinks to files."""
-        try:
-            host_dir = tempfile.mkdtemp()
+        def test_push_dry_run_existent_file(self):
+            """Push with dry run."""
 
-            remote_dir = posixpath.join(self.DEVICE_TEMP_DIR, 'contents')
-            remote_links = posixpath.join(self.DEVICE_TEMP_DIR, 'links')
-            remote_symlink = posixpath.join(self.DEVICE_TEMP_DIR, 'symlink')
+            for file_size in [8, 1024 * 1024]:
+                try:
+                    device_dir = posixpath.join(self.DEVICE_TEMP_DIR, 'push_dry_run')
+                    device_file = posixpath.join(device_dir, 'file')
 
-            self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
-            self.device.shell(['mkdir', '-p', remote_dir, remote_links])
-            self.device.shell(['ln', '-s', remote_links, remote_symlink])
+                    self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
+                    self.device.shell(['mkdir', '-p', device_dir])
+                    self.device.shell(['echo', 'foo', '>', device_file])
 
-            # Populate device directory with random files.
-            temp_files = make_random_device_files(
-                self.device, in_dir=remote_dir, num_files=32)
+                    host_dir = tempfile.mkdtemp()
+                    host_file = posixpath.join(host_dir, 'file')
 
-            for temp_file in temp_files:
-                self.device.shell(
-                    ['ln', '-s', '../contents/{}'.format(temp_file.base_name),
-                     posixpath.join(remote_links, temp_file.base_name)])
+                    with open(host_file, "w") as f:
+                        f.write('x' * file_size)
 
-            self.device.pull(remote=remote_symlink, local=host_dir)
+                    self.device._simple_call(['push', '-n', host_file, device_file])
+                    stdout, stderr = self.device.shell(['cat', device_file])
+                    self.assertEqual(stdout.strip(), "foo")
 
-            for temp_file in temp_files:
-                host_path = os.path.join(
-                    host_dir, 'symlink', temp_file.base_name)
-                self._verify_local(temp_file.checksum, host_path)
+                    self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
+                finally:
+                    if host_dir is not None:
+                        shutil.rmtree(host_dir)
 
-            self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
-        finally:
-            if host_dir is not None:
-                shutil.rmtree(host_dir)
+        def test_unicode_paths(self):
+            """Ensure that we can support non-ASCII paths, even on Windows."""
+            name = u'로보카 폴리'
 
-    def test_pull_empty(self):
-        """Pull a directory containing an empty directory from the device."""
-        try:
-            host_dir = tempfile.mkdtemp()
+            self.device.shell(['rm', '-f', '/data/local/tmp/adb-test-*'])
+            remote_path = u'/data/local/tmp/adb-test-{}'.format(name)
 
-            remote_empty_path = posixpath.join(self.DEVICE_TEMP_DIR, 'empty')
-            self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
-            self.device.shell(['mkdir', '-p', remote_empty_path])
+            ## push.
+            tf = tempfile.NamedTemporaryFile('wb', suffix=name, delete=False)
+            tf.close()
+            self.device.push(tf.name, remote_path)
+            os.remove(tf.name)
+            self.assertFalse(os.path.exists(tf.name))
 
-            self.device.pull(remote=remote_empty_path, local=host_dir)
-            self.assertTrue(os.path.isdir(os.path.join(host_dir, 'empty')))
-        finally:
-            if host_dir is not None:
-                shutil.rmtree(host_dir)
+            # Verify that the device ended up with the expected UTF-8 path
+            output = self.device.shell(
+                    ['ls', '/data/local/tmp/adb-test-*'])[0].strip()
+            self.assertEqual(remote_path, output)
 
-    def test_multiple_pull(self):
-        """Pull a randomly generated directory of files from the device."""
+            # pull.
+            self.device.pull(remote_path, tf.name)
+            self.assertTrue(os.path.exists(tf.name))
+            os.remove(tf.name)
+            self.device.shell(['rm', '-f', '/data/local/tmp/adb-test-*'])
 
-        try:
-            host_dir = tempfile.mkdtemp()
 
-            subdir = posixpath.join(self.DEVICE_TEMP_DIR, 'subdir')
-            self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
-            self.device.shell(['mkdir', '-p', subdir])
+class FileOperationsTestUncompressed(FileOperationsTest.Base):
+    compression = "none"
 
-            # Create some random files and a subdirectory containing more files.
-            temp_files = make_random_device_files(
-                self.device, in_dir=self.DEVICE_TEMP_DIR, num_files=4)
 
-            subdir_temp_files = make_random_device_files(
-                self.device, in_dir=subdir, num_files=4, prefix='subdir_')
+class FileOperationsTestBrotli(FileOperationsTest.Base):
+    compression = "brotli"
 
-            paths = [x.full_path for x in temp_files]
-            paths.append(subdir)
-            self.device._simple_call(['pull'] + paths + [host_dir])
 
-            for temp_file in temp_files:
-                local_path = os.path.join(host_dir, temp_file.base_name)
-                self._verify_local(temp_file.checksum, local_path)
-
-            for subdir_temp_file in subdir_temp_files:
-                local_path = os.path.join(host_dir,
-                                          'subdir',
-                                          subdir_temp_file.base_name)
-                self._verify_local(subdir_temp_file.checksum, local_path)
-
-            self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
-        finally:
-            if host_dir is not None:
-                shutil.rmtree(host_dir)
-
-    def verify_sync(self, device, temp_files, device_dir):
-        """Verifies that a list of temp files was synced to the device."""
-        # Confirm that every file on the device mirrors that on the host.
-        for temp_file in temp_files:
-            device_full_path = posixpath.join(
-                device_dir, temp_file.base_name)
-            dev_md5, _ = device.shell(
-                [get_md5_prog(self.device), device_full_path])[0].split()
-            self.assertEqual(temp_file.checksum, dev_md5)
-
-    def test_sync(self):
-        """Sync a host directory to the data partition."""
-
-        try:
-            base_dir = tempfile.mkdtemp()
-
-            # Create mirror device directory hierarchy within base_dir.
-            full_dir_path = base_dir + self.DEVICE_TEMP_DIR
-            os.makedirs(full_dir_path)
-
-            # Create 32 random files within the host mirror.
-            temp_files = make_random_host_files(
-                in_dir=full_dir_path, num_files=32)
-
-            # Clean up any stale files on the device.
-            device = adb.get_device()  # pylint: disable=no-member
-            device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
-
-            old_product_out = os.environ.get('ANDROID_PRODUCT_OUT')
-            os.environ['ANDROID_PRODUCT_OUT'] = base_dir
-            device.sync('data')
-            if old_product_out is None:
-                del os.environ['ANDROID_PRODUCT_OUT']
-            else:
-                os.environ['ANDROID_PRODUCT_OUT'] = old_product_out
-
-            self.verify_sync(device, temp_files, self.DEVICE_TEMP_DIR)
-
-            #self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
-        finally:
-            if base_dir is not None:
-                shutil.rmtree(base_dir)
-
-    def test_push_sync(self):
-        """Sync a host directory to a specific path."""
-
-        try:
-            temp_dir = tempfile.mkdtemp()
-            temp_files = make_random_host_files(in_dir=temp_dir, num_files=32)
-
-            device_dir = posixpath.join(self.DEVICE_TEMP_DIR, 'sync_src_dst')
-
-            # Clean up any stale files on the device.
-            device = adb.get_device()  # pylint: disable=no-member
-            device.shell(['rm', '-rf', device_dir])
-
-            device.push(temp_dir, device_dir, sync=True)
-
-            self.verify_sync(device, temp_files, device_dir)
-
-            self.device.shell(['rm', '-rf', self.DEVICE_TEMP_DIR])
-        finally:
-            if temp_dir is not None:
-                shutil.rmtree(temp_dir)
-
-    def test_unicode_paths(self):
-        """Ensure that we can support non-ASCII paths, even on Windows."""
-        name = u'로보카 폴리'
-
-        self.device.shell(['rm', '-f', '/data/local/tmp/adb-test-*'])
-        remote_path = u'/data/local/tmp/adb-test-{}'.format(name)
-
-        ## push.
-        tf = tempfile.NamedTemporaryFile('wb', suffix=name, delete=False)
-        tf.close()
-        self.device.push(tf.name, remote_path)
-        os.remove(tf.name)
-        self.assertFalse(os.path.exists(tf.name))
-
-        # Verify that the device ended up with the expected UTF-8 path
-        output = self.device.shell(
-                ['ls', '/data/local/tmp/adb-test-*'])[0].strip()
-        self.assertEqual(remote_path, output)
-
-        # pull.
-        self.device.pull(remote_path, tf.name)
-        self.assertTrue(os.path.exists(tf.name))
-        os.remove(tf.name)
-        self.device.shell(['rm', '-f', '/data/local/tmp/adb-test-*'])
+class FileOperationsTestLZ4(FileOperationsTest.Base):
+    compression = "lz4"
 
 
 class DeviceOfflineTest(DeviceTest):
diff --git a/adb/transport.cpp b/adb/transport.cpp
index e06dbe327..cc2e0e3b1 100644
--- a/adb/transport.cpp
+++ b/adb/transport.cpp
@@ -84,6 +84,8 @@ const char* const kFeatureRemountShell = "remount_shell";
 const char* const kFeatureTrackApp = "track_app";
 const char* const kFeatureSendRecv2 = "sendrecv_v2";
 const char* const kFeatureSendRecv2Brotli = "sendrecv_v2_brotli";
+const char* const kFeatureSendRecv2LZ4 = "sendrecv_v2_lz4";
+const char* const kFeatureSendRecv2DryRunSend = "sendrecv_v2_dry_run_send";
 
 namespace {
 
@@ -1183,6 +1185,8 @@ const FeatureSet& supported_features() {
             kFeatureTrackApp,
             kFeatureSendRecv2,
             kFeatureSendRecv2Brotli,
+            kFeatureSendRecv2LZ4,
+            kFeatureSendRecv2DryRunSend,
             // Increment ADB_SERVER_VERSION when adding a feature that adbd needs
             // to know about. Otherwise, the client can be stuck running an old
             // version of the server even after upgrading their copy of adb.
diff --git a/adb/transport.h b/adb/transport.h
index b1984db30..4b2e00043 100644
--- a/adb/transport.h
+++ b/adb/transport.h
@@ -88,6 +88,10 @@ extern const char* const kFeatureTrackApp;
 extern const char* const kFeatureSendRecv2;
 // adbd supports brotli for send/recv v2.
 extern const char* const kFeatureSendRecv2Brotli;
+// adbd supports LZ4 for send/recv v2.
+extern const char* const kFeatureSendRecv2LZ4;
+// adbd supports dry-run send for send/recv v2.
+extern const char* const kFeatureSendRecv2DryRunSend;
 
 TransportId NextTransportId();
 
diff --git a/adb/types.cpp b/adb/types.cpp
index 26b77ab62..9cdf32b93 100644
--- a/adb/types.cpp
+++ b/adb/types.cpp
@@ -51,7 +51,7 @@ void IOVector::drop_front(IOVector::size_type len) {
     auto dropped = 0u;
     while (dropped < len) {
         const auto next = chain_[start_index_].size() - begin_offset_;
-        if (dropped + next < len) {
+        if (dropped + next <= len) {
             pop_front_block();
             dropped += next;
         } else {
diff --git a/adb/types.h b/adb/types.h
index deca7eafb..620aa8eb7 100644
--- a/adb/types.h
+++ b/adb/types.h
@@ -155,7 +155,7 @@ struct IOVector {
             return nullptr;
         }
 
-        return chain_.front().data() + begin_offset_;
+        return chain_[start_index_].data() + begin_offset_;
     }
 
     size_type front_size() const {
@@ -163,7 +163,7 @@ struct IOVector {
             return 0;
         }
 
-        return chain_.front().size() - begin_offset_;
+        return chain_[start_index_].size() - begin_offset_;
     }
 
     size_type size() const { return chain_length_ - begin_offset_; }
diff --git a/adb/types_test.cpp b/adb/types_test.cpp
index 2c99f9512..41fa1db25 100644
--- a/adb/types_test.cpp
+++ b/adb/types_test.cpp
@@ -117,3 +117,20 @@ TEST(IOVector, misaligned_split) {
     ASSERT_EQ(1ULL, bc.size());
     ASSERT_EQ(create_block("x"), bc.coalesce());
 }
+
+TEST(IOVector, drop_front) {
+    IOVector vec;
+
+    vec.append(create_block('x', 2));
+    vec.append(create_block('y', 1000));
+    ASSERT_EQ(2U, vec.front_size());
+    ASSERT_EQ(1002U, vec.size());
+
+    vec.drop_front(1);
+    ASSERT_EQ(1U, vec.front_size());
+    ASSERT_EQ(1001U, vec.size());
+
+    vec.drop_front(1);
+    ASSERT_EQ(1000U, vec.front_size());
+    ASSERT_EQ(1000U, vec.size());
+}