From fedbb6b4ff341c1e2120f4ffbf367fd78ac3e8f3 Mon Sep 17 00:00:00 2001 From: Shmulik Ladkani Date: Wed, 29 Jun 2016 21:47:03 +0300 Subject: [PATCH] ipv4: Fix ip_skb_dst_mtu to use the sk passed by ip_finish_output 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 Reviewed-by: Hannes Frederic Sowa Signed-off-by: David S. Miller --- include/net/ip.h | 5 ++--- net/bridge/br_netfilter_hooks.c | 2 +- net/ipv4/ip_output.c | 4 ++-- 3 files changed, 5 insertions(+), 6 deletions(-) diff --git a/include/net/ip.h b/include/net/ip.h index 37165fb..08f36cd 100644 --- a/include/net/ip.h +++ b/include/net/ip.h @@ -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; diff --git a/net/bridge/br_netfilter_hooks.c b/net/bridge/br_netfilter_hooks.c index 2d25979..77e7f69 100644 --- a/net/bridge/br_netfilter_hooks.c +++ b/net/bridge/br_netfilter_hooks.c @@ -700,7 +700,7 @@ static int br_nf_ip_fragment(struct net *net, struct sock *sk, struct sk_buff *skb, int (*output)(struct net *, struct sock *, struct sk_buff *)) { - unsigned int mtu = ip_skb_dst_mtu(skb); + unsigned int mtu = ip_skb_dst_mtu(sk, skb); struct iphdr *iph = ip_hdr(skb); if (unlikely(((iph->frag_off & htons(IP_DF)) && !skb->ignore_df) || diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c index 124bf0a..4bd4921 100644 --- a/net/ipv4/ip_output.c +++ b/net/ipv4/ip_output.c @@ -271,7 +271,7 @@ static int ip_finish_output(struct net *net, struct sock *sk, struct sk_buff *sk return dst_output(net, sk, skb); } #endif - mtu = ip_skb_dst_mtu(skb); + mtu = ip_skb_dst_mtu(sk, skb); if (skb_is_gso(skb)) return ip_finish_output_gso(net, sk, skb, mtu); @@ -541,7 +541,7 @@ int ip_do_fragment(struct net *net, struct sock *sk, struct sk_buff *skb, iph = ip_hdr(skb); - mtu = ip_skb_dst_mtu(skb); + mtu = ip_skb_dst_mtu(sk, skb); if (IPCB(skb)->frag_max_size && IPCB(skb)->frag_max_size < mtu) mtu = IPCB(skb)->frag_max_size; -- 2.7.4