ipv4: fix path MTU discovery with connection tracking
IPv4 conntrack defragments incoming packet at the PRE_ROUTING hook and
(in case of forwarded packets) refragments them at POST_ROUTING
independent of the IP_DF flag. Refragmentation uses the dst_mtu() of
the local route without caring about the original fragment sizes,
thereby breaking PMTUD.
This patch fixes this by keeping track of the largest received fragment
with IP_DF set and generates an ICMP fragmentation required error during
refragmentation if that size exceeds the MTU.
Signed-off-by: Patrick McHardy <kaber@trash.net>
Acked-by: Eric Dumazet <edumazet@google.com>
Acked-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/ip.h b/include/net/ip.h
index 5a5d84d..0707fb9 100644
--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -42,6 +42,8 @@
#define IPSKB_XFRM_TRANSFORMED 4
#define IPSKB_FRAG_COMPLETE 8
#define IPSKB_REROUTED 16
+
+ u16 frag_max_size;
};
static inline unsigned int ip_hdrlen(const struct sk_buff *skb)