nbd: Don't kill server when client requests unknown option

nbd-server.c currently fails to handle unsupported options properly.
If during option haggling the client sends an unknown request, the
server kills the connection instead of letting the client try to
fall back to something older.  This is precisely what advertising
NBD_FLAG_FIXED_NEWSTYLE was supposed to fix.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1459982918-32229-1-git-send-email-eblake@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/nbd/server.c b/nbd/server.c
index 6d9c15a0b04ad1a9401088bf7aa2837c803f303f..2a4dd10f52c6e058b339f6ee397a683a40c7b03d 100644 (file)
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -483,9 +483,12 @@ static int nbd_negotiate_options(NBDClient *client)
                 return -EINVAL;
             default:
                 TRACE("Unsupported option 0x%x", clientflags);
+                if (nbd_negotiate_drop_sync(client->ioc, length) != length) {
+                    return -EIO;
+                }
                 nbd_negotiate_send_rep(client->ioc, NBD_REP_ERR_UNSUP,
                                        clientflags);
-                return -EINVAL;
+                break;
             }
         } else {
             /*