From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julian Anastasov Subject: [PATCH v2] netfilter: avoid double seq_adjust for loopback Date: Wed, 8 Jun 2011 09:31:05 +0300 (EEST) Message-ID: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII To: Patrick McHardy , Pablo Neira Ayuso , netfilter-devel@vger.kernel.org, netdev@vger.kernel.org Return-path: Sender: netfilter-devel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org 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 --- diff -urp v2.6.39/linux/include/net/netfilter/nf_conntrack.h linux/include/net/netfilter/nf_conntrack.h --- v2.6.39/linux/include/net/netfilter/nf_conntrack.h 2011-05-20 10:38:04.000000000 +0300 +++ linux/include/net/netfilter/nf_conntrack.h 2011-06-08 08:29:58.880272586 +0300 @@ -308,6 +308,12 @@ static inline int nf_ct_is_untracked(con 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 -urp v2.6.39/linux/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c linux/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c --- v2.6.39/linux/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c 2010-08-02 09:37:49.000000000 +0300 +++ linux/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c 2011-06-08 08:34:15.594269592 +0300 @@ -121,7 +121,9 @@ static unsigned int ipv4_confirm(unsigne 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);