From 42c1edd345c8412d96e7a362ee06feb7be73bb6c Mon Sep 17 00:00:00 2001 From: Julian Anastasov Date: Thu, 16 Jun 2011 17:29:22 +0200 Subject: [PATCH] netfilter: nf_nat: avoid double seq_adjust for loopback Avoid double seq adjustment for loopback traffic because it causes silent repetition of TCP data. One example is passive FTP with DNAT rule and difference in the length of IP addresses. This patch adds check if packet is sent and received via loopback device. As the same conntrack is used both for outgoing and incoming direction, we restrict seq adjustment to happen only in POSTROUTING. Signed-off-by: Julian Anastasov Signed-off-by: Patrick McHardy --- include/net/netfilter/nf_conntrack.h | 6 ++++++ net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c | 4 +++- 2 files changed, 9 insertions(+), 1 deletion(-) diff --git a/include/net/netfilter/nf_conntrack.h b/include/net/netfilter/nf_conntrack.h index c7c42e7acc3..5d4f8e586e3 100644 --- a/include/net/netfilter/nf_conntrack.h +++ b/include/net/netfilter/nf_conntrack.h @@ -307,6 +307,12 @@ static inline int nf_ct_is_untracked(const struct nf_conn *ct) return test_bit(IPS_UNTRACKED_BIT, &ct->status); } +/* Packet is received from loopback */ +static inline bool nf_is_loopback_packet(const struct sk_buff *skb) +{ + return skb->dev && skb->skb_iif && skb->dev->flags & IFF_LOOPBACK; +} + extern int nf_conntrack_set_hashsize(const char *val, struct kernel_param *kp); extern unsigned int nf_conntrack_htable_size; extern unsigned int nf_conntrack_max; diff --git a/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c b/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c index db10075dd88..de9da21113a 100644 --- a/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c +++ b/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c @@ -121,7 +121,9 @@ static unsigned int ipv4_confirm(unsigned int hooknum, return ret; } - if (test_bit(IPS_SEQ_ADJUST_BIT, &ct->status)) { + /* adjust seqs for loopback traffic only in outgoing direction */ + if (test_bit(IPS_SEQ_ADJUST_BIT, &ct->status) && + !nf_is_loopback_packet(skb)) { typeof(nf_nat_seq_adjust_hook) seq_adjust; seq_adjust = rcu_dereference(nf_nat_seq_adjust_hook); -- 2.41.0