pinctrl: Explicitly set ICMPv6 code for packet too big.

The ICMPv6 code was set to 1 which is wrong for the packet too big
which is wrong, the code should always remain 0. This resulted in
wrong csum being computed. Set the code to 0 explicitly.

Fixes: 4725ad1 ("controller: Avoid double controller action for ICMP errors.")
Reported-at: https://issues.redhat.com/browse/FDP-763
Acked-by: Dumitru Ceara <dceara@redhat.com>
Signed-off-by: Ales Musil <amusil@redhat.com>
Signed-off-by: Numan Siddique <numans@ovn.org>

controller/pinctrl.c

@@ -1756,6 +1756,7 @@ pinctrl_handle_icmp(struct rconn *swconn, const struct flow *ip_flow,
         if (mtu) {
             put_16aligned_be32(ih->icmp6_data.be32, *mtu);
             ih->icmp6_base.icmp6_type = ICMP6_PACKET_TOO_BIG;
+            ih->icmp6_base.icmp6_code = 0;
         }
 
         void *data = ih + 1;