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ipv4: Fix ip_skb_dst_mtu to use the sk passed by ip_finish_output

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ip_skb_dst_mtu uses skb->sk, assuming it is an AF_INET socket (e.g. it
calls ip_sk_use_pmtu which casts sk as an inet_sk).

However, in the case of UDP tunneling, the skb->sk is not necessarily an
inet socket (could be AF_PACKET socket, or AF_UNSPEC if arriving from
tun/tap).

OTOH, the sk passed as an argument throughout IP stack's output path is
the one which is of PMTU interest:
 - In case of local sockets, sk is same as skb->sk;
 - In case of a udp tunnel, sk is the tunneling socket.

Fix, by passing ip_finish_output's sk to ip_skb_dst_mtu.
This augments 7026b1ddb6 'netfilter: Pass socket pointer down through okfn().'

Signed-off-by: Shmulik Ladkani <shmulik.ladkani@gmail.com>
Reviewed-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Shmulik Ladkani
2016-06-29 21:47:03 +03:00
committed by David S. Miller
parent 5ab0d6a016
commit fedbb6b4ff
3 changed files with 5 additions and 6 deletions
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5
include/net/ip.h
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@@ -313,10 +313,9 @@ static inline unsigned int ip_dst_mtu_maybe_forward(const struct dst_entry *dst,
return min(dst->dev->mtu, IP_MAX_MTU);
}
static inline unsigned int ip_skb_dst_mtu(const struct sk_buff *skb)
static inline unsigned int ip_skb_dst_mtu(struct sock *sk,
const struct sk_buff *skb)
{
struct sock *sk = skb->sk;
if (!sk || !sk_fullsock(sk) || ip_sk_use_pmtu(sk)) {
bool forwarding = IPCB(skb)->flags & IPSKB_FORWARDED;