bond: Fix segfault sending learning packets with LACP disabled.

It is essentially an invalid configuration to disable LACP but request TCP
balancing: in this configuration, the bond drops all packets.  But
may_send_learning_packets() would still indicate that learning packets
should be sent, so bond_compose_learning_packet() would try to choose an
output slave for those packets, which would be NULL (because all packets
are dropped), which would cause a segfault upon dereference.

This commit fixes the problem by making may_send_learning_packets() no
longer indicate that learning packets should be sent.

I tested this issue by modifying bond_should_send_learning_packets() to
always return true if may_send_learning_packets() returns true, and then
introducing the invalid configuration described above.  Without this comit,
ovs-vswitchd segfaults quickly; with this commit, it does not.

Bug #14090.
Reported-by: Kiran Shanbhog <kiran@vmware.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/lib/bond.c b/lib/bond.c
index b172121b..f6c38e9c 100644
--- a/lib/bond.c
+++ b/lib/bond.c
@@ -488,7 +488,7 @@ static bool
 may_send_learning_packets(const struct bond *bond)
 {
     return bond->lacp_status == LACP_DISABLED
-        && bond->balance != BM_AB
+        && (bond->balance == BM_SLB || bond->balance == BM_STABLE)
         && bond->active_slave;
 }