With 749439bfac "fix udpv6 sendmsg crash caused by too small MTU" tunnel dst's that report a MTU less than IPV6_MIN_MTU are broken even for packets that are smaller than IPV6_MIN_MTU.
According to rfc2473#section-7.1 if the original IPv6 packet is equal or smaller than the IPv6 minimum link MTU, the tunnel entry-point node encapsulates the original packet, and subsequently fragments the resulting IPv6 tunnel packet into IPv6 fragments that do not exceed the Path MTU to the tunnel exit-point. This patch drops the MTU check for tunnel destinations. Signed-off-by: Ashwanth Goli <ashwa...@codeaurora.org> --- net/ipv6/ip6_output.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c index 2e891d2..c4c3313 100644 --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -1235,7 +1235,7 @@ static int ip6_setup_cork(struct sock *sk, struct inet_cork_full *cork, if (np->frag_size) mtu = np->frag_size; } - if (mtu < IPV6_MIN_MTU) + if (!(rt->dst.flags & DST_XFRM_TUNNEL) && mtu < IPV6_MIN_MTU) return -EINVAL; cork->base.fragsize = mtu; if (dst_allfrag(xfrm_dst_path(&rt->dst))) -- 1.9.1