diff options
| author | Patrick McHardy <kaber@trash.net> | 2012-08-26 19:13:55 +0200 |
|---|---|---|
| committer | Patrick McHardy <kaber@trash.net> | 2012-08-26 19:13:55 +0200 |
| commit | 5f2d04f1f9b52604fca6ee08a77972c0df67e082 (patch) | |
| tree | f4caa0aa602f6044f1fc20c6dfa89527183803d1 /net/ipv4 | |
| parent | 0fa7fa98dbcc2789409ed24e885485e645803d7f (diff) | |
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>
Diffstat (limited to 'net/ipv4')
| -rw-r--r-- | net/ipv4/ip_fragment.c | 8 | ||||
| -rw-r--r-- | net/ipv4/ip_output.c | 4 |
2 files changed, 10 insertions, 2 deletions
diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c index 8d07c973409c..fa6a12c51066 100644 --- a/net/ipv4/ip_fragment.c +++ b/net/ipv4/ip_fragment.c @@ -523,6 +523,10 @@ found: if (offset == 0) qp->q.last_in |= INET_FRAG_FIRST_IN; + if (ip_hdr(skb)->frag_off & htons(IP_DF) && + skb->len + ihl > qp->q.max_size) + qp->q.max_size = skb->len + ihl; + if (qp->q.last_in == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) && qp->q.meat == qp->q.len) return ip_frag_reasm(qp, prev, dev); @@ -646,9 +650,11 @@ static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev, head->next = NULL; head->dev = dev; head->tstamp = qp->q.stamp; + IPCB(head)->frag_max_size = qp->q.max_size; iph = ip_hdr(head); - iph->frag_off = 0; + /* max_size != 0 implies at least one fragment had IP_DF set */ + iph->frag_off = qp->q.max_size ? htons(IP_DF) : 0; iph->tot_len = htons(len); iph->tos |= ecn; IP_INC_STATS_BH(net, IPSTATS_MIB_REASMOKS); diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c index c196d749daf2..a5beab1dc958 100644 --- a/net/ipv4/ip_output.c +++ b/net/ipv4/ip_output.c @@ -467,7 +467,9 @@ int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *)) iph = ip_hdr(skb); - if (unlikely((iph->frag_off & htons(IP_DF)) && !skb->local_df)) { + if (unlikely(((iph->frag_off & htons(IP_DF)) && !skb->local_df) || + (IPCB(skb)->frag_max_size && + IPCB(skb)->frag_max_size > dst_mtu(&rt->dst)))) { IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS); icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED, htonl(ip_skb_dst_mtu(skb))); |