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 default 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, this patch
uses MSG_PEEK to check the magic number of channels so that current
data/control stream management remains un-effected.
Signed-off-by: manish.mishra <manish.mishra@nutanix.com>
---
include/io/channel.h | 25 +++++++++++++++++++++++++
io/channel-socket.c | 27 +++++++++++++++++++++++++++
io/channel.c | 39 +++++++++++++++++++++++++++++++++++++++
migration/migration.c | 33 +++++++++++++++++++++------------
migration/multifd.c | 12 ++++--------
migration/multifd.h | 2 +-
migration/postcopy-ram.c | 5 +----
migration/postcopy-ram.h | 2 +-
8 files changed, 119 insertions(+), 26 deletions(-)
diff --git a/include/io/channel.h b/include/io/channel.h
index c680ee7480..74177aeeea 100644
--- a/include/io/channel.h
+++ b/include/io/channel.h
@@ -115,6 +115,10 @@ struct QIOChannelClass {
int **fds,
size_t *nfds,
Error **errp);
+ ssize_t (*io_read_peek)(QIOChannel *ioc,
+ void *buf,
+ size_t nbytes,
+ Error **errp);
int (*io_close)(QIOChannel *ioc,
Error **errp);
GSource * (*io_create_watch)(QIOChannel *ioc,
@@ -475,6 +479,27 @@ int qio_channel_write_all(QIOChannel *ioc,
size_t buflen,
Error **errp);
+/**
+ * qio_channel_read_peek_all:
+ * @ioc: the channel object
+ * @buf: the memory region to read in data
+ * @nbytes: the number of bytes to read
+ * @errp: pointer to a NULL-initialized error object
+ *
+ * Read given @nbytes data from peek of channel into
+ * memory region @buf.
+ *
+ * The function will be blocked until read size is
+ * equal to requested size.
+ *
+ * Returns: 1 if all bytes were read, 0 if end-of-file
+ * occurs without data, or -1 on error
+ */
+int qio_channel_read_peek_all(QIOChannel *ioc,
+ void* buf,
+ size_t nbytes,
+ Error **errp);
+
/**
* qio_channel_set_blocking:
* @ioc: the channel object
diff --git a/io/channel-socket.c b/io/channel-socket.c
index b76dca9cc1..b99f5dfda6 100644
--- a/io/channel-socket.c
+++ b/io/channel-socket.c
@@ -705,6 +705,32 @@ static ssize_t qio_channel_socket_writev(QIOChannel *ioc,
}
#endif /* WIN32 */
+static ssize_t qio_channel_socket_read_peek(QIOChannel *ioc,
+ void *buf,
+ size_t nbytes,
+ Error **errp)
+{
+ QIOChannelSocket *sioc = QIO_CHANNEL_SOCKET(ioc);
+ ssize_t bytes = 0;
+
+retry:
+ bytes = recv(sioc->fd, buf, nbytes, MSG_PEEK);
+
+ if (bytes < 0) {
+ if (errno == EINTR) {
+ goto retry;
+ }
+ if (errno == EAGAIN) {
+ return QIO_CHANNEL_ERR_BLOCK;
+ }
+
+ error_setg_errno(errp, errno,
+ "Unable to read from peek of socket");
+ return -1;
+ }
+
+ return bytes;
+}
#ifdef QEMU_MSG_ZEROCOPY
static int qio_channel_socket_flush(QIOChannel *ioc,
@@ -902,6 +928,7 @@ static void qio_channel_socket_class_init(ObjectClass
*klass,
ioc_klass->io_writev = qio_channel_socket_writev;
ioc_klass->io_readv = qio_channel_socket_readv;
+ ioc_klass->io_read_peek = qio_channel_socket_read_peek;
ioc_klass->io_set_blocking = qio_channel_socket_set_blocking;
ioc_klass->io_close = qio_channel_socket_close;
ioc_klass->io_shutdown = qio_channel_socket_shutdown;
diff --git a/io/channel.c b/io/channel.c
index 0640941ac5..a2d9b96f3f 100644
--- a/io/channel.c
+++ b/io/channel.c
@@ -346,6 +346,45 @@ int qio_channel_write_all(QIOChannel *ioc,
return qio_channel_writev_all(ioc, &iov, 1, errp);
}
+int qio_channel_read_peek_all(QIOChannel *ioc,
+ void* buf,
+ size_t nbytes,
+ Error **errp)
+{
+ QIOChannelClass *klass = QIO_CHANNEL_GET_CLASS(ioc);
+ ssize_t bytes = 0;
+
+ if (!klass->io_read_peek) {
+ error_setg(errp, "Channel does not support read peek");
+ return -1;
+ }
diff --git a/migration/migration.c b/migration/migration.c
index 739bb683f3..f4b6f278a9 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -733,31 +733,40 @@ void migration_ioc_process_incoming(QIOChannel *ioc,
Error **errp)
{
MigrationIncomingState *mis = migration_incoming_get_current();
Error *local_err = NULL;
- bool start_migration;
QEMUFile *f;
+ bool default_channel = true;
+ uint32_t channel_magic = 0;
+ int ret = 0;
- if (!mis->from_src_file) {
- /* The first connection (multifd may have multiple) */
+ if (migrate_use_multifd() && !migration_in_postcopy()) {
+ ret = qio_channel_read_peek_all(ioc, (void *)&channel_magic,
+ sizeof(channel_magic), &local_err);
+
+ if (ret != 1) {
+ error_propagate(errp, local_err);
+ return;
+ }