migration: Transmit initial package through the multifd channels

Signed-off-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>

--

Be network agnostic.
Add error checking for all values.

migration/ram.c

@@ -52,6 +52,8 @@
 #include "qemu/rcu_queue.h"
 #include "migration/colo.h"
 #include "migration/block.h"
+#include "sysemu/sysemu.h"
+#include "qemu/uuid.h"
 
 /***********************************************************/
 /* ram save/restore */
@@ -433,6 +435,16 @@ exit:
 
 /* Multiple fd's */
 
+#define MULTIFD_MAGIC 0x11223344U
+#define MULTIFD_VERSION 1
+
+typedef struct {
+    uint32_t magic;
+    uint32_t version;
+    unsigned char uuid[16]; /* QemuUUID */
+    uint8_t id;
+} __attribute__((packed)) MultiFDInit_t;
+
 struct MultiFDSendParams {
     uint8_t id;
     char *name;
@@ -445,6 +457,68 @@ struct MultiFDSendParams {
 };
 typedef struct MultiFDSendParams MultiFDSendParams;
 
+static int multifd_send_initial_packet(MultiFDSendParams *p, Error **errp)
+{
+    MultiFDInit_t msg;
+    int ret;
+
+    msg.magic = cpu_to_be32(MULTIFD_MAGIC);
+    msg.version = cpu_to_be32(MULTIFD_VERSION);
+    msg.id = p->id;
+    memcpy(msg.uuid, &qemu_uuid.data, sizeof(msg.uuid));
+
+    ret = qio_channel_write_all(p->c, (char *)&msg, sizeof(msg), errp);
+    if (ret != 0) {
+        return -1;
+    }
+    return 0;
+}
+
+static int multifd_recv_initial_packet(QIOChannel *c, Error **errp)
+{
+    MultiFDInit_t msg;
+    int ret;
+
+    ret = qio_channel_read_all(c, (char *)&msg, sizeof(msg), errp);
+    if (ret != 0) {
+        return -1;
+    }
+
+    be32_to_cpus(&msg.magic);
+    be32_to_cpus(&msg.version);
+
+    if (msg.magic != MULTIFD_MAGIC) {
+        error_setg(errp, "multifd: received packet magic %x "
+                   "expected %x", msg.magic, MULTIFD_MAGIC);
+        return -1;
+    }
+
+    if (msg.version != MULTIFD_VERSION) {
+        error_setg(errp, "multifd: received packet version %d "
+                   "expected %d", msg.version, MULTIFD_VERSION);
+        return -1;
+    }
+
+    if (memcmp(msg.uuid, &qemu_uuid, sizeof(qemu_uuid))) {
+        char *uuid = qemu_uuid_unparse_strdup(&qemu_uuid);
+        char *msg_uuid = qemu_uuid_unparse_strdup((const QemuUUID *)msg.uuid);
+
+        error_setg(errp, "multifd: received uuid '%s' and expected "
+                   "uuid '%s' for channel %hhd", msg_uuid, uuid, msg.id);
+        g_free(uuid);
+        g_free(msg_uuid);
+        return -1;
+    }
+
+    if (msg.id > migrate_multifd_channels()) {
+        error_setg(errp, "multifd: received channel version %d "
+                   "expected %d", msg.version, MULTIFD_VERSION);
+        return -1;
+    }
+
+    return msg.id;
+}
+
 struct {
     MultiFDSendParams *params;
     /* number of created threads */
@@ -509,6 +583,11 @@ int multifd_save_cleanup(Error **errp)
 static void *multifd_send_thread(void *opaque)
 {
     MultiFDSendParams *p = opaque;
+    Error *local_err = NULL;
+
+    if (multifd_send_initial_packet(p, &local_err) < 0) {
+        goto out;
+    }
 
     while (true) {
         qemu_mutex_lock(&p->mutex);
@@ -520,6 +599,11 @@ static void *multifd_send_thread(void *opaque)
         qemu_sem_wait(&p->sem);
     }
 
+out:
+    if (local_err) {
+        multifd_send_terminate_threads(local_err);
+    }
+
     qemu_mutex_lock(&p->mutex);
     p->running = false;
     qemu_mutex_unlock(&p->mutex);
@@ -704,12 +788,22 @@ bool multifd_recv_all_channels_created(void)
 void multifd_recv_new_channel(QIOChannel *ioc)
 {
     MultiFDRecvParams *p;
-    /* we need to invent channels id's until we transmit */
-    /* we will remove this on a later patch */
-    static int i;
+    Error *local_err = NULL;
+    int id;
 
-    p = &multifd_recv_state->params[i];
-    i++;
+    id = multifd_recv_initial_packet(ioc, &local_err);
+    if (id < 0) {
+        multifd_recv_terminate_threads(local_err);
+        return;
+    }
+
+    p = &multifd_recv_state->params[id];
+    if (p->c != NULL) {
+        error_setg(&local_err, "multifd: received id '%d' already setup'",
+                   id);
+        multifd_recv_terminate_threads(local_err);
+        return;
+    }
     p->c = ioc;
     object_ref(OBJECT(ioc));