On 05/10/2018 09:48 AM, Ashwanth Goli wrote:
> With 749439bfac "fix udpv6 sendmsg crash caused by too small MTU"
> ipsec tunnels 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.
>
> Dropping the MTU check for ipsec tunnel destinations.
>
> Signed-off-by: Ashwanth Goli <[email protected]>
> ---
> 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)))
>
Given that the (mtu < IPV6_MIN_MTU) condition is unlikely, I would reorder to :
if (mtu < IPV6_MIN_MTU && !(rt->dst.flags & DST_XFRM_TUNNEL))
return -EINVAL;
The fast path should not look at dst.flags
