From fbb8b7e5e064ea6a467119772097242311e65628 Mon Sep 17 00:00:00 2001
From: John Snow <jsnow@redhat.com>
Date: Fri, 22 Mar 2019 03:22:40 +0100
Subject: [PATCH 073/163] nbd/client: Send NBD_CMD_DISC if open fails after
 connect

RH-Author: John Snow <jsnow@redhat.com>
Message-id: <20190322032241.8111-28-jsnow@redhat.com>
Patchwork-id: 85114
O-Subject: [RHEL-7.7 qemu-kvm-rhev PATCH 27/28] nbd/client: Send NBD_CMD_DISC if open fails after connect
Bugzilla: 1691563
RH-Acked-by: Max Reitz <mreitz@redhat.com>
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>

From: Eric Blake <eblake@redhat.com>

If nbd_client_init() fails after we are already connected,
then the server will spam logs with:

Disconnect client, due to: Unexpected end-of-file before all bytes were read

unless we gracefully disconnect before closing the connection.

Ways to trigger this:

$ opts=driver=nbd,export=foo,server.type=inet,server.host=localhost,server.port=10809
$  qemu-img map --output=json --image-opts $opts,read-only=off
$  qemu-img map --output=json --image-opts $opts,x-dirty-bitmap=nosuch:

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20181130023232.3079982-4-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
(cherry picked from commit c688e6ca7b41a105241054853d250df64addbf8f)
Signed-off-by: John Snow <jsnow@redhat.com>
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 block/nbd-client.c | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/block/nbd-client.c b/block/nbd-client.c
index e6e27da..fc5b7ed 100644
--- a/block/nbd-client.c
+++ b/block/nbd-client.c
@@ -995,12 +995,13 @@ int nbd_client_init(BlockDriverState *bs,
     if (x_dirty_bitmap && !client->info.base_allocation) {
         error_setg(errp, "requested x-dirty-bitmap %s not found",
                    x_dirty_bitmap);
-        return -EINVAL;
+        ret = -EINVAL;
+        goto fail;
     }
     if (client->info.flags & NBD_FLAG_READ_ONLY) {
         ret = bdrv_apply_auto_read_only(bs, "NBD export is read-only", errp);
         if (ret < 0) {
-            return ret;
+            goto fail;
         }
     }
     if (client->info.flags & NBD_FLAG_SEND_FUA) {
@@ -1029,4 +1030,17 @@ int nbd_client_init(BlockDriverState *bs,
 
     logout("Established connection with NBD server\n");
     return 0;
+
+ fail:
+    /*
+     * We have connected, but must fail for other reasons. The
+     * connection is still blocking; send NBD_CMD_DISC as a courtesy
+     * to the server.
+     */
+    {
+        NBDRequest request = { .type = NBD_CMD_DISC };
+
+        nbd_send_request(client->ioc ?: QIO_CHANNEL(sioc), &request);
+        return ret;
+    }
 }
-- 
1.8.3.1