nbd: make client request fixed new style if advertised

If the server advertises support for the fixed new style
negotiation, the client should in turn enable new style.
This will allow the client to negotiate further NBD
options besides the export name.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Message-Id: <1455129674-17255-10-git-send-email-berrange@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/nbd/client.c b/nbd/client.c
index 5064788bb149a4a0575c6e71863ad16c02f3c517..88f2adab0d76f1669b3853ae721f010bc3ce8f61 100644 (file)
--- a/nbd/client.c
+++ b/nbd/client.c
@@ -76,7 +76,6 @@ int nbd_receive_negotiate(QIOChannel *ioc, const char *name, uint32_t *flags,
 {
     char buf[256];
     uint64_t magic, s;
-    uint16_t tmp;
     int rc;
 
     TRACE("Receiving negotiation.");
@@ -117,19 +116,26 @@ int nbd_receive_negotiate(QIOChannel *ioc, const char *name, uint32_t *flags,
     TRACE("Magic is 0x%" PRIx64, magic);
 
     if (magic == NBD_OPTS_MAGIC) {
-        uint32_t reserved = 0;
+        uint32_t clientflags = 0;
         uint32_t opt;
         uint32_t namesize;
+        uint16_t globalflags;
+        uint16_t exportflags;
 
-        if (read_sync(ioc, &tmp, sizeof(tmp)) != sizeof(tmp)) {
+        if (read_sync(ioc, &globalflags, sizeof(globalflags)) !=
+            sizeof(globalflags)) {
             error_setg(errp, "Failed to read server flags");
             goto fail;
         }
-        *flags = be16_to_cpu(tmp) << 16;
-        /* reserved for future use */
-        if (write_sync(ioc, &reserved, sizeof(reserved)) !=
-            sizeof(reserved)) {
-            error_setg(errp, "Failed to read reserved field");
+        *flags = be16_to_cpu(globalflags) << 16;
+        if (globalflags & NBD_FLAG_FIXED_NEWSTYLE) {
+            TRACE("Server supports fixed new style");
+            clientflags |= NBD_FLAG_C_FIXED_NEWSTYLE;
+        }
+        /* client requested flags */
+        if (write_sync(ioc, &clientflags, sizeof(clientflags)) !=
+            sizeof(clientflags)) {
+            error_setg(errp, "Failed to send clientflags field");
             goto fail;
         }
         /* write the export name */
@@ -165,11 +171,12 @@ int nbd_receive_negotiate(QIOChannel *ioc, const char *name, uint32_t *flags,
         *size = be64_to_cpu(s);
         TRACE("Size is %" PRIu64, *size);
 
-        if (read_sync(ioc, &tmp, sizeof(tmp)) != sizeof(tmp)) {
+        if (read_sync(ioc, &exportflags, sizeof(exportflags)) !=
+            sizeof(exportflags)) {
             error_setg(errp, "Failed to read export flags");
             goto fail;
         }
-        *flags |= be16_to_cpu(tmp);
+        *flags |= be16_to_cpu(exportflags);
     } else if (magic == NBD_CLIENT_MAGIC) {
         if (name) {
             error_setg(errp, "Server does not support export names");