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netfilter: nf_nat: fix NAT issue in 2.6.30.4+

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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 a3a9f79e36).
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@blackhole.kfki.hu>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jozsef Kadlecsik
2009-11-06 00:43:42 -08:00
committed by David S. Miller
parent f5209b4446
commit f9dd09c7f7
6 changed files with 67 additions and 54 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
net/netfilter/nf_conntrack_core.c
View File

@ -1350,6 +1350,11 @@ 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;
@ -1367,6 +1372,9 @@ 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;

64
net/netfilter/nf_conntrack_proto_tcp.c
View File

@ -492,6 +492,21 @@ 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,
@ -506,6 +521,7 @@ 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;
/*
@ -519,11 +535,16 @@ 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,
@ -613,8 +634,8 @@ 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,
@ -700,7 +721,7 @@ 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)"
@ -715,39 +736,6 @@ 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);
spin_lock_bh(&ct->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;
spin_unlock_bh(&ct->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