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;
+}