From 4ea3693104c03ac40a6595f5b9bcda58fa18afe7 Mon Sep 17 00:00:00 2001
From: Michal Privoznik <mprivozn@redhat.com>
Date: Thu, 30 Aug 2018 14:11:36 +0200
Subject: [PATCH] virDomainNetDefCheckABIStability: Check for MTU change too
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https://bugzilla.redhat.com/show_bug.cgi?id=1623157

Changing MTU on a running guest is not possible and trying to do
so made us face many problems. That's why we forbid it in
5f44d7e357f61f7. However, there is still one possible path where
users can sneak in change: migration XML.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
---
 src/conf/domain_conf.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index 603a4ad652..c3406cfbe6 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -21901,6 +21901,13 @@ virDomainNetDefCheckABIStability(virDomainNetDefPtr src,
         return false;
     }
 
+    if (src->mtu != dst->mtu) {
+        virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                       _("Target network card MTU %d does not match source %d"),
+                       dst->mtu, src->mtu);
+        return false;
+    }
+
     if (src->virtio && dst->virtio &&
         !virDomainVirtioOptionsCheckABIStability(src->virtio, dst->virtio))
         return false;