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authormanish.mishra <manish.mishra@nutanix.com>2022-12-20 18:44:18 +0000
committerJuan Quintela <quintela@redhat.com>2023-02-06 19:22:57 +0100
commit6720c2b32725e6ac404f22851a0ecd0a71d0cbe2 (patch)
tree2126e13a6b90d2c3f0725f9db850162c5104b308 /migration/channel.c
parent84615a19ddf2bfb38d7b3a0d487d2397ee55e4f3 (diff)
migration: check magic value for deciding the mapping of channels
Current logic assumes that channel connections on the destination side are always established in the same order as the source and the first one will always be the main channel followed by the multifid or post-copy preemption channel. This may not be always true, as even if a channel has a connection established on the source side it can be in the pending state on the destination side and a newer connection can be established first. Basically causing out of order mapping of channels on the destination side. Currently, all channels except post-copy preempt send a magic number, this patch uses that magic number to decide the type of channel. This logic is applicable only for precopy(multifd) live migration, as mentioned, the post-copy preempt channel does not send any magic number. Also, tls live migrations already does tls handshake before creating other channels, so this issue is not possible with tls, hence this logic is avoided for tls live migrations. This patch uses read peek to check the magic number of channels so that current data/control stream management remains un-effected. Reviewed-by: Peter Xu <peterx@redhat.com> Reviewed-by: Daniel P. Berrange <berrange@redhat.com> Reviewed-by: Juan Quintela <quintela@redhat.com> Suggested-by: Daniel P. Berrange <berrange@redhat.com> Signed-off-by: manish.mishra <manish.mishra@nutanix.com> Signed-off-by: Juan Quintela <quintela@redhat.com>
Diffstat (limited to 'migration/channel.c')
-rw-r--r--migration/channel.c45
1 files changed, 45 insertions, 0 deletions
diff --git a/migration/channel.c b/migration/channel.c
index 1b0815039f..ca3319a309 100644
--- a/migration/channel.c
+++ b/migration/channel.c
@@ -92,3 +92,48 @@ void migration_channel_connect(MigrationState *s,
migrate_fd_connect(s, error);
error_free(error);
}
+
+
+/**
+ * @migration_channel_read_peek - Peek at migration channel, without
+ * actually removing it from channel buffer.
+ *
+ * @ioc: the channel object
+ * @buf: the memory region to read data into
+ * @buflen: the number of bytes to read in @buf
+ * @errp: pointer to a NULL-initialized error object
+ *
+ * Returns 0 if successful, returns -1 and sets @errp if fails.
+ */
+int migration_channel_read_peek(QIOChannel *ioc,
+ const char *buf,
+ const size_t buflen,
+ Error **errp)
+{
+ ssize_t len = 0;
+ struct iovec iov = { .iov_base = (char *)buf, .iov_len = buflen };
+
+ while (true) {
+ len = qio_channel_readv_full(ioc, &iov, 1, NULL, NULL,
+ QIO_CHANNEL_READ_FLAG_MSG_PEEK, errp);
+
+ if (len <= 0 && len != QIO_CHANNEL_ERR_BLOCK) {
+ error_setg(errp,
+ "Failed to peek at channel");
+ return -1;
+ }
+
+ if (len == buflen) {
+ break;
+ }
+
+ /* 1ms sleep. */
+ if (qemu_in_coroutine()) {
+ qemu_co_sleep_ns(QEMU_CLOCK_REALTIME, 1000000);
+ } else {
+ g_usleep(1000);
+ }
+ }
+
+ return 0;
+}