Hi Patrick,
Please consider applying and submitting the patch below.
Vitezslav Samel discovered that since 2.6.30.4+ active FTP can not work
over NAT. The "cause" of the problem was a fix of unacknowledged data
detection with NAT (commit a3a9f79e361e864f0e9d75ebe2a0cb43d17c4272).
However, actually, that fix uncovered a long standing bug in TCP conntrack:
when NAT was enabled, we simply updated the max of the right edge of
the segments we have seen (td_end), by the offset NAT produced with
changing IP/port in the data. However, we did not update the other parameter
(td_maxend) which is affected by the NAT offset. Thus that could drift
away from the correct value and thus resulted breaking active FTP.
The patch below fixes the issue by *not* updating the conntrack parameters
from NAT, but instead taking into account the NAT offsets in conntrack in a
consistent way. (Updating from NAT would be more harder and expensive because
it'd need to re-calculate parameters we already calculated in conntrack.)
Signed-off-by: Jozsef Kadlecsik <kadlec@xxxxxxxxxxxxxxxxx>
diff --git a/include/net/netfilter/nf_conntrack.h b/include/net/netfilter/nf_conntrack.h
index 5d9a848..a96b835 100644
--- a/include/net/netfilter/nf_conntrack.h
+++ b/include/net/netfilter/nf_conntrack.h
@@ -252,11 +252,9 @@ static inline bool nf_ct_kill(struct nf_conn *ct)
}
/* These are for NAT. Icky. */
-/* Update TCP window tracking data when NAT mangles the packet */
-extern void nf_conntrack_tcp_update(const struct sk_buff *skb,
- unsigned int dataoff,
- struct nf_conn *ct, int dir,
- s16 offset);
+extern s16 (*nf_ct_nat_offset)(const struct nf_conn *ct,
+ enum ip_conntrack_dir dir,
+ u32 seq);
/* Fake conntrack entry for untracked connections */
extern struct nf_conn nf_conntrack_untracked;
diff --git a/include/net/netfilter/nf_nat_helper.h b/include/net/netfilter/nf_nat_helper.h
index 237a961..4222220 100644
--- a/include/net/netfilter/nf_nat_helper.h
+++ b/include/net/netfilter/nf_nat_helper.h
@@ -32,4 +32,8 @@ extern int (*nf_nat_seq_adjust_hook)(struct sk_buff *skb,
* to port ct->master->saved_proto. */
extern void nf_nat_follow_master(struct nf_conn *ct,
struct nf_conntrack_expect *this);
+
+extern s16 nf_nat_get_offset(const struct nf_conn *ct,
+ enum ip_conntrack_dir dir,
+ u32 seq);
#endif
diff --git a/net/ipv4/netfilter/nf_nat_core.c b/net/ipv4/netfilter/nf_nat_core.c
index 3229e0a..a622a83 100644
--- a/net/ipv4/netfilter/nf_nat_core.c
+++ b/net/ipv4/netfilter/nf_nat_core.c
@@ -750,6 +750,8 @@ static int __init nf_nat_init(void)
BUG_ON(nfnetlink_parse_nat_setup_hook != NULL);
rcu_assign_pointer(nfnetlink_parse_nat_setup_hook,
nfnetlink_parse_nat_setup);
+ BUG_ON(nf_ct_nat_offset != NULL);
+ rcu_assign_pointer(nf_ct_nat_offset, nf_nat_get_offset);
return 0;
cleanup_extend:
@@ -764,6 +766,7 @@ static void __exit nf_nat_cleanup(void)
nf_ct_extend_unregister(&nat_extend);
rcu_assign_pointer(nf_nat_seq_adjust_hook, NULL);
rcu_assign_pointer(nfnetlink_parse_nat_setup_hook, NULL);
+ rcu_assign_pointer(nf_ct_nat_offset, NULL);
synchronize_net();
}
diff --git a/net/ipv4/netfilter/nf_nat_helper.c b/net/ipv4/netfilter/nf_nat_helper.c
index 05ede41..79e28ad 100644
--- a/net/ipv4/netfilter/nf_nat_helper.c
+++ b/net/ipv4/netfilter/nf_nat_helper.c
@@ -73,6 +73,28 @@ adjust_tcp_sequence(u32 seq,
DUMP_OFFSET(this_way);
}
+/* Get the offset value, for conntrack */
+s16 nf_nat_get_offset(const struct nf_conn *ct,
+ enum ip_conntrack_dir dir,
+ u32 seq)
+{
+ struct nf_conn_nat *nat = nfct_nat(ct);
+ struct nf_nat_seq *this_way;
+ s16 offset;
+
+ if (!nat)
+ return 0;
+
+ this_way = &nat->seq[dir];
+ spin_lock_bh(&nf_nat_seqofs_lock);
+ offset = after(seq, this_way->correction_pos)
+ ? this_way->offset_after : this_way->offset_before;
+ spin_unlock_bh(&nf_nat_seqofs_lock);
+
+ return offset;
+}
+EXPORT_SYMBOL_GPL(nf_nat_get_offset);
+
/* Frobs data inside this packet, which is linear. */
static void mangle_contents(struct sk_buff *skb,
unsigned int dataoff,
@@ -189,11 +211,6 @@ nf_nat_mangle_tcp_packet(struct sk_buff *skb,
adjust_tcp_sequence(ntohl(tcph->seq),
(int)rep_len - (int)match_len,
ct, ctinfo);
- /* Tell TCP window tracking about seq change */
- nf_conntrack_tcp_update(skb, ip_hdrlen(skb),
- ct, CTINFO2DIR(ctinfo),
- (int)rep_len - (int)match_len);
-
nf_conntrack_event_cache(IPCT_NATSEQADJ, ct);
}
return 1;
@@ -415,12 +432,7 @@ nf_nat_seq_adjust(struct sk_buff *skb,
tcph->seq = newseq;
tcph->ack_seq = newack;
- if (!nf_nat_sack_adjust(skb, tcph, ct, ctinfo))
- return 0;
-
- nf_conntrack_tcp_update(skb, ip_hdrlen(skb), ct, dir, seqoff);
-
- return 1;
+ return nf_nat_sack_adjust(skb, tcph, ct, ctinfo);
}
/* Setup NAT on this expected conntrack so it follows master. */
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 0d961ee..f1e0c08 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -1296,6 +1296,11 @@ err_stat:
return ret;
}
+s16 (*nf_ct_nat_offset)(const struct nf_conn *ct,
+ enum ip_conntrack_dir dir,
+ u32 seq);
+EXPORT_SYMBOL_GPL(nf_ct_nat_offset);
+
int nf_conntrack_init(struct net *net)
{
int ret;
@@ -1313,6 +1318,9 @@ int nf_conntrack_init(struct net *net)
/* For use by REJECT target */
rcu_assign_pointer(ip_ct_attach, nf_conntrack_attach);
rcu_assign_pointer(nf_ct_destroy, destroy_conntrack);
+
+ /* Howto get NAT offsets */
+ rcu_assign_pointer(nf_ct_nat_offset, NULL);
}
return 0;
diff --git a/net/netfilter/nf_conntrack_proto_tcp.c b/net/netfilter/nf_conntrack_proto_tcp.c
index a38bc22..bea9428 100644
--- a/net/netfilter/nf_conntrack_proto_tcp.c
+++ b/net/netfilter/nf_conntrack_proto_tcp.c
@@ -482,6 +482,21 @@ static void tcp_sack(const struct sk_buff *skb, unsigned int dataoff,
}
}
+#ifdef CONFIG_NF_NAT_NEEDED
+static inline s16 nat_offset(const struct nf_conn *ct,
+ enum ip_conntrack_dir dir,
+ u32 seq)
+{
+ typeof(nf_ct_nat_offset) get_offset = rcu_dereference(nf_ct_nat_offset);
+
+ return get_offset != NULL ? get_offset(ct, dir, seq) : 0;
+}
+#define NAT_OFFSET(pf, ct, dir, seq) \
+ (pf == NFPROTO_IPV4 ? nat_offset(ct, dir, seq) : 0)
+#else
+#define NAT_OFFSET(pf, ct, dir, seq) 0
+#endif
+
static bool tcp_in_window(const struct nf_conn *ct,
struct ip_ct_tcp *state,
enum ip_conntrack_dir dir,
@@ -496,6 +511,7 @@ static bool tcp_in_window(const struct nf_conn *ct,
struct ip_ct_tcp_state *receiver = &state->seen[!dir];
const struct nf_conntrack_tuple *tuple = &ct->tuplehash[dir].tuple;
__u32 seq, ack, sack, end, win, swin;
+ s16 receiver_offset;
bool res;
/*
@@ -509,11 +525,16 @@ static bool tcp_in_window(const struct nf_conn *ct,
if (receiver->flags & IP_CT_TCP_FLAG_SACK_PERM)
tcp_sack(skb, dataoff, tcph, &sack);
+ /* Take into account NAT sequence number mangling */
+ receiver_offset = NAT_OFFSET(pf, ct, !dir, ack - 1);
+ ack -= receiver_offset;
+ sack -= receiver_offset;
+
pr_debug("tcp_in_window: START\n");
pr_debug("tcp_in_window: ");
nf_ct_dump_tuple(tuple);
- pr_debug("seq=%u ack=%u sack=%u win=%u end=%u\n",
- seq, ack, sack, win, end);
+ pr_debug("seq=%u ack=%u+(%d) sack=%u+(%d) win=%u end=%u\n",
+ seq, ack, receiver_offset, sack, receiver_offset, win, end);
pr_debug("tcp_in_window: sender end=%u maxend=%u maxwin=%u scale=%i "
"receiver end=%u maxend=%u maxwin=%u scale=%i\n",
sender->td_end, sender->td_maxend, sender->td_maxwin,
@@ -599,8 +620,8 @@ static bool tcp_in_window(const struct nf_conn *ct,
pr_debug("tcp_in_window: ");
nf_ct_dump_tuple(tuple);
- pr_debug("seq=%u ack=%u sack =%u win=%u end=%u\n",
- seq, ack, sack, win, end);
+ pr_debug("seq=%u ack=%u+(%d) sack=%u+(%d) win=%u end=%u\n",
+ seq, ack, receiver_offset, sack, receiver_offset, win, end);
pr_debug("tcp_in_window: sender end=%u maxend=%u maxwin=%u scale=%i "
"receiver end=%u maxend=%u maxwin=%u scale=%i\n",
sender->td_end, sender->td_maxend, sender->td_maxwin,
@@ -686,7 +707,7 @@ static bool tcp_in_window(const struct nf_conn *ct,
before(seq, sender->td_maxend + 1) ?
after(end, sender->td_end - receiver->td_maxwin - 1) ?
before(sack, receiver->td_end + 1) ?
- after(ack, receiver->td_end - MAXACKWINDOW(sender)) ? "BUG"
+ after(sack, receiver->td_end - MAXACKWINDOW(sender) - 1) ? "BUG"
: "ACK is under the lower bound (possible overly delayed ACK)"
: "ACK is over the upper bound (ACKed data not seen yet)"
: "SEQ is under the lower bound (already ACKed data retransmitted)"
@@ -701,39 +722,6 @@ static bool tcp_in_window(const struct nf_conn *ct,
return res;
}
-#ifdef CONFIG_NF_NAT_NEEDED
-/* Update sender->td_end after NAT successfully mangled the packet */
-/* Caller must linearize skb at tcp header. */
-void nf_conntrack_tcp_update(const struct sk_buff *skb,
- unsigned int dataoff,
- struct nf_conn *ct, int dir,
- s16 offset)
-{
- const struct tcphdr *tcph = (const void *)skb->data + dataoff;
- const struct ip_ct_tcp_state *sender = &ct->proto.tcp.seen[dir];
- const struct ip_ct_tcp_state *receiver = &ct->proto.tcp.seen[!dir];
- __u32 end;
-
- end = segment_seq_plus_len(ntohl(tcph->seq), skb->len, dataoff, tcph);
-
- write_lock_bh(&tcp_lock);
- /*
- * We have to worry for the ack in the reply packet only...
- */
- if (ct->proto.tcp.seen[dir].td_end + offset == end)
- ct->proto.tcp.seen[dir].td_end = end;
- ct->proto.tcp.last_end = end;
- write_unlock_bh(&tcp_lock);
- pr_debug("tcp_update: sender end=%u maxend=%u maxwin=%u scale=%i "
- "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
- sender->td_end, sender->td_maxend, sender->td_maxwin,
- sender->td_scale,
- receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
- receiver->td_scale);
-}
-EXPORT_SYMBOL_GPL(nf_conntrack_tcp_update);
-#endif
-
#define TH_FIN 0x01
#define TH_SYN 0x02
#define TH_RST 0x04
Best regards,
Jozsef
-
E-mail : kadlec@xxxxxxxxxxxxxxxxx, kadlec@xxxxxxxxxxxx
PGP key : http://www.kfki.hu/~kadlec/pgp_public_key.txt
Address : KFKI Research Institute for Particle and Nuclear Physics
H-1525 Budapest 114, POB. 49, Hungary
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