xfrm: Fix pmtu discovery for local generated packets.

Commit 044a832a777 ("xfrm: Fix local error reporting crash
with interfamily tunnels") moved the setting of skb->protocol
behind the last access of the inner mode family to fix an
interfamily crash. Unfortunately now skb->protocol might not
be set at all, so we fail dispatch to the inner address family.
As a reault, the local error handler is not called and the
mtu value is not reported back to userspace.

We fix this by setting skb->protocol on message size errors
before we call xfrm_local_error.

Fixes: 044a832a7779c ("xfrm: Fix local error reporting crash with interfamily tunnels")
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

diff --git a/net/ipv4/xfrm4_output.c b/net/ipv4/xfrm4_output.c
index 2878dbf..41a2613 100644 (file)
--- a/net/ipv4/xfrm4_output.c
+++ b/net/ipv4/xfrm4_output.c
@@ -30,6 +30,8 @@ static int xfrm4_tunnel_check_size(struct sk_buff *skb)
 
        mtu = dst_mtu(skb_dst(skb));
        if (skb->len > mtu) {
+               skb->protocol = htons(ETH_P_IP);
+
                if (skb->sk)
                        xfrm_local_error(skb, mtu);
                else

diff --git a/net/ipv6/xfrm6_output.c b/net/ipv6/xfrm6_output.c
index be033f2..e15feb7 100644 (file)
--- a/net/ipv6/xfrm6_output.c
+++ b/net/ipv6/xfrm6_output.c
@@ -79,6 +79,7 @@ static int xfrm6_tunnel_check_size(struct sk_buff *skb)
 
        if (!skb->ignore_df && skb->len > mtu) {
                skb->dev = dst->dev;
+               skb->protocol = htons(ETH_P_IPV6);
 
                if (xfrm6_local_dontfrag(skb))
                        xfrm6_local_rxpmtu(skb, mtu);