From 8c88f87cb27ad09086940bdd3e6955e5325ec89a Mon Sep 17 00:00:00 2001 From: Pablo Neira Ayuso Date: Thu, 7 Jun 2012 13:31:25 +0200 Subject: [PATCH] netfilter: nfnetlink_queue: add NAT TCP sequence adjustment if packet mangled User-space programs that receive traffic via NFQUEUE may mangle packets. If NAT is enabled, this usually puzzles sequence tracking, leading to traffic disruptions. With this patch, nfnl_queue will make the corresponding NAT TCP sequence adjustment if: 1) The packet has been mangled, 2) the NFQA_CFG_F_CONNTRACK flag has been set, and 3) NAT is detected. There are some records on the Internet complaning about this issue: http://stackoverflow.com/questions/260757/packet-mangling-utilities-besides-iptables By now, we only support TCP since we have no helpers for DCCP or SCTP. Better to add this if we ever have some helper over those layer 4 protocols. Signed-off-by: Pablo Neira Ayuso --- include/linux/netfilter.h | 2 ++ include/net/netfilter/nf_nat_helper.h | 4 ++++ net/ipv4/netfilter/nf_nat_helper.c | 13 +++++++++++++ net/netfilter/nf_conntrack_netlink.c | 4 ++++ net/netfilter/nfnetlink_queue.c | 19 +++++++++++-------- 5 files changed, 34 insertions(+), 8 deletions(-) diff --git a/include/linux/netfilter.h b/include/linux/netfilter.h index ba65bfbd7f7..dca19e61b30 100644 --- a/include/linux/netfilter.h +++ b/include/linux/netfilter.h @@ -401,6 +401,8 @@ struct nfq_ct_hook { size_t (*build_size)(const struct nf_conn *ct); int (*build)(struct sk_buff *skb, struct nf_conn *ct); int (*parse)(const struct nlattr *attr, struct nf_conn *ct); + void (*seq_adjust)(struct sk_buff *skb, struct nf_conn *ct, + u32 ctinfo, int off); }; extern struct nfq_ct_hook *nfq_ct_hook; #else diff --git a/include/net/netfilter/nf_nat_helper.h b/include/net/netfilter/nf_nat_helper.h index 02bb6c29dc3..7d8fb7b46c4 100644 --- a/include/net/netfilter/nf_nat_helper.h +++ b/include/net/netfilter/nf_nat_helper.h @@ -54,4 +54,8 @@ extern void nf_nat_follow_master(struct nf_conn *ct, extern s16 nf_nat_get_offset(const struct nf_conn *ct, enum ip_conntrack_dir dir, u32 seq); + +extern void nf_nat_tcp_seq_adjust(struct sk_buff *skb, struct nf_conn *ct, + u32 dir, int off); + #endif diff --git a/net/ipv4/netfilter/nf_nat_helper.c b/net/ipv4/netfilter/nf_nat_helper.c index af65958f630..2e59ad0b90c 100644 --- a/net/ipv4/netfilter/nf_nat_helper.c +++ b/net/ipv4/netfilter/nf_nat_helper.c @@ -153,6 +153,19 @@ void nf_nat_set_seq_adjust(struct nf_conn *ct, enum ip_conntrack_info ctinfo, } EXPORT_SYMBOL_GPL(nf_nat_set_seq_adjust); +void nf_nat_tcp_seq_adjust(struct sk_buff *skb, struct nf_conn *ct, + u32 ctinfo, int off) +{ + const struct tcphdr *th; + + if (nf_ct_protonum(ct) != IPPROTO_TCP) + return; + + th = (struct tcphdr *)(skb_network_header(skb)+ ip_hdrlen(skb)); + nf_nat_set_seq_adjust(ct, ctinfo, th->seq, off); +} +EXPORT_SYMBOL_GPL(nf_nat_tcp_seq_adjust); + static void nf_nat_csum(struct sk_buff *skb, const struct iphdr *iph, void *data, int datalen, __sum16 *check, int oldlen) { diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c index d304d591795..8be0ab9b475 100644 --- a/net/netfilter/nf_conntrack_netlink.c +++ b/net/netfilter/nf_conntrack_netlink.c @@ -46,6 +46,7 @@ #ifdef CONFIG_NF_NAT_NEEDED #include #include +#include #endif #include @@ -1751,6 +1752,9 @@ static struct nfq_ct_hook ctnetlink_nfqueue_hook = { .build_size = ctnetlink_nfqueue_build_size, .build = ctnetlink_nfqueue_build, .parse = ctnetlink_nfqueue_parse, +#ifdef CONFIG_NF_NAT_NEEDED + .seq_adjust = nf_nat_tcp_seq_adjust, +#endif }; #endif /* CONFIG_NETFILTER_NETLINK_QUEUE */ diff --git a/net/netfilter/nfnetlink_queue.c b/net/netfilter/nfnetlink_queue.c index 647923ae923..ff82c7933df 100644 --- a/net/netfilter/nfnetlink_queue.c +++ b/net/netfilter/nfnetlink_queue.c @@ -502,12 +502,10 @@ err_out: } static int -nfqnl_mangle(void *data, int data_len, struct nf_queue_entry *e) +nfqnl_mangle(void *data, int data_len, struct nf_queue_entry *e, int diff) { struct sk_buff *nskb; - int diff; - diff = data_len - e->skb->len; if (diff < 0) { if (pskb_trim(e->skb, data_len)) return -ENOMEM; @@ -767,6 +765,8 @@ nfqnl_recv_verdict(struct sock *ctnl, struct sk_buff *skb, unsigned int verdict; struct nf_queue_entry *entry; struct nfq_ct_hook *nfq_ct; + enum ip_conntrack_info uninitialized_var(ctinfo); + struct nf_conn *ct = NULL; queue = instance_lookup(queue_num); if (!queue) @@ -789,20 +789,23 @@ nfqnl_recv_verdict(struct sock *ctnl, struct sk_buff *skb, nfq_ct = rcu_dereference(nfq_ct_hook); if (nfq_ct != NULL && (queue->flags & NFQA_CFG_F_CONNTRACK) && nfqa[NFQA_CT]) { - enum ip_conntrack_info ctinfo; - struct nf_conn *ct; - ct = nf_ct_get(entry->skb, &ctinfo); if (ct && !nf_ct_is_untracked(ct)) nfq_ct->parse(nfqa[NFQA_CT], ct); } - rcu_read_unlock(); if (nfqa[NFQA_PAYLOAD]) { + u16 payload_len = nla_len(nfqa[NFQA_PAYLOAD]); + int diff = payload_len - entry->skb->len; + if (nfqnl_mangle(nla_data(nfqa[NFQA_PAYLOAD]), - nla_len(nfqa[NFQA_PAYLOAD]), entry) < 0) + payload_len, entry, diff) < 0) verdict = NF_DROP; + + if (ct && (ct->status & IPS_NAT_MASK) && diff) + nfq_ct->seq_adjust(skb, ct, ctinfo, diff); } + rcu_read_unlock(); if (nfqa[NFQA_MARK]) entry->skb->mark = ntohl(nla_get_be32(nfqa[NFQA_MARK])); -- 2.41.0