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Message-Id: <1339524380-2707-6-git-send-email-pablo@netfilter.org>
Date: Tue, 12 Jun 2012 20:06:18 +0200
From: pablo@...filter.org
To: netfilter-devel@...r.kernel.org
Cc: netdev@...r.kernel.org
Subject: [PATCH 5/7] netfilter: nfnetlink_queue: add NAT TCP sequence adjustment if packet mangled
From: Pablo Neira Ayuso <pablo@...filter.org>
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 <pablo@...filter.org>
---
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 ba65bfb..dca19e6 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 02bb6c2..7d8fb7b 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 af65958..2e59ad0 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 3b03a86..206d297 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 <net/netfilter/nf_nat_core.h>
#include <net/netfilter/nf_nat_protocol.h>
+#include <net/netfilter/nf_nat_helper.h>
#endif
#include <linux/netfilter/nfnetlink.h>
@@ -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 ab1fd1c..52ebf02 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;
@@ -766,6 +764,8 @@ 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)
@@ -788,20 +788,23 @@ 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]));
--
1.7.10
--
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