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.klass...@secunet.com>
---
 net/ipv6/ip6_vti.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/net/ipv6/ip6_vti.c b/net/ipv6/ip6_vti.c
index d82042c..9156d6b 100644
--- a/net/ipv6/ip6_vti.c
+++ b/net/ipv6/ip6_vti.c
@@ -484,11 +484,15 @@ static bool vti6_state_check(const struct xfrm_state *x,
        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;
        }
-- 
1.9.1

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