vti6: Don't report path MTU below IPV6_MIN_MTU.

[ Upstream commit e3dc847a5f85b43ee2bfc8eae407a7e383483228 ]

In vti6_xmit(), the check for IPV6_MIN_MTU before we
send a ICMPV6_PKT_TOOBIG message is missing. So we might
report a PMTU below 1280. Fix this by adding the required
check.

Fixes: ccd740cbc6e ("vti6: Add pmtu handling to vti6_xmit.")
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/ipv6/ip6_vti.c b/net/ipv6/ip6_vti.c
index 67e882d4919512f640e641e7c63e0b76fcbfed3d..912333586de6150e7b9fb5ab4d01490d555d4da9 100644 (file)
--- a/net/ipv6/ip6_vti.c
+++ b/net/ipv6/ip6_vti.c
@@ -485,11 +485,15 @@ vti6_xmit(struct sk_buff *skb, struct net_device *dev, struct flowi *fl)
        if (!skb->ignore_df && skb->len > mtu) {
                skb_dst(skb)->ops->update_pmtu(dst, NULL, skb, mtu);
 
-               if (skb->protocol == htons(ETH_P_IPV6))
+               if (skb->protocol == htons(ETH_P_IPV6)) {
+                       if (mtu < IPV6_MIN_MTU)
+                               mtu = IPV6_MIN_MTU;
+
                        icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);
-               else
+               } else {
                        icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
                                  htonl(mtu));
+               }
 
                return -EMSGSIZE;
        }