Let SocketClient users write binary data to clients.

This is a dependency for the DNS proxy CLs.

This CL also adds a new socket for the netd process to inherit which
is owned by the inet group.  (so only apps with the INTERNET
permission can use the DNS proxy...)

Change-Id: Ic3475c697913ba85805b4e49801b65e7a1d59289

include/sysutils/SocketClient.h

@@ -28,8 +28,12 @@ public:
     uid_t getUid() const { return mUid; }
     gid_t getGid() const { return mGid; }
 
+    // Send null-terminated C strings:
     int sendMsg(int code, const char *msg, bool addErrno);
     int sendMsg(const char *msg);
+
+    // Sending binary data:
+    int sendData(const void *data, int len);
 };
 
 typedef android::List<SocketClient *> SocketClientCollection;

libsysutils/src/SocketClient.cpp

@@ -50,14 +50,22 @@ int SocketClient::sendMsg(const char *msg) {
     }
 
     // Send the message including null character
+    if (sendData(msg, strlen(msg) + 1) != 0) {
+        SLOGW("Unable to send msg '%s'", msg);
+        return -1;
+    }
+    return 0;
+}
+
+int SocketClient::sendData(const void* data, int len) {
     int rc = 0;
-    const char *p = msg;
-    int brtw = strlen(msg) + 1;
+    const char *p = (const char*) data;
+    int brtw = len;
 
     pthread_mutex_lock(&mWriteMutex);
-    while(brtw) {
-        if ((rc = write(mSocket,p, brtw)) < 0) {
-            SLOGW("Unable to send msg '%s' (%s)", msg, strerror(errno));
+    while (brtw > 0) {
+        if ((rc = write(mSocket, p, brtw)) < 0) {
+            SLOGW("write error (%s)", strerror(errno));
             pthread_mutex_unlock(&mWriteMutex);
             return -1;
         } else if (!rc) {

rootdir/init.rc

@@ -309,6 +309,7 @@ service vold /system/bin/vold
 
 service netd /system/bin/netd
     socket netd stream 0660 root system
+    socket dnsproxyd stream 0660 root inet
 
 service debuggerd /system/bin/debuggerd