Commit a3a9f79e361e864f0e9d75ebe2a0cb43d17c4272
1 parent
308ff823eb
netfilter: tcp conntrack: fix unacknowledged data detection with NAT
When NAT helpers change the TCP packet size, the highest seen sequence number needs to be corrected. This is currently only done upwards, when the packet size is reduced the sequence number is unchanged. This causes TCP conntrack to falsely detect unacknowledged data and decrease the timeout. Fix by updating the highest seen sequence number in both directions after packet mangling. Tested-by: Krzysztof Piotr Oledzki <ole@ans.pl> Signed-off-by: Patrick McHardy <kaber@trash.net>
Showing 3 changed files with 16 additions and 11 deletions Side-by-side Diff
include/net/netfilter/nf_conntrack.h
| ... | ... | @@ -258,8 +258,8 @@ |
| 258 | 258 | /* Update TCP window tracking data when NAT mangles the packet */ |
| 259 | 259 | extern void nf_conntrack_tcp_update(const struct sk_buff *skb, |
| 260 | 260 | unsigned int dataoff, |
| 261 | - struct nf_conn *ct, | |
| 262 | - int dir); | |
| 261 | + struct nf_conn *ct, int dir, | |
| 262 | + s16 offset); | |
| 263 | 263 | |
| 264 | 264 | /* Fake conntrack entry for untracked connections */ |
| 265 | 265 | extern struct nf_conn nf_conntrack_untracked; |
net/ipv4/netfilter/nf_nat_helper.c
| ... | ... | @@ -191,7 +191,8 @@ |
| 191 | 191 | ct, ctinfo); |
| 192 | 192 | /* Tell TCP window tracking about seq change */ |
| 193 | 193 | nf_conntrack_tcp_update(skb, ip_hdrlen(skb), |
| 194 | - ct, CTINFO2DIR(ctinfo)); | |
| 194 | + ct, CTINFO2DIR(ctinfo), | |
| 195 | + (int)rep_len - (int)match_len); | |
| 195 | 196 | |
| 196 | 197 | nf_conntrack_event_cache(IPCT_NATSEQADJ, ct); |
| 197 | 198 | } |
| ... | ... | @@ -377,6 +378,7 @@ |
| 377 | 378 | struct tcphdr *tcph; |
| 378 | 379 | int dir; |
| 379 | 380 | __be32 newseq, newack; |
| 381 | + s16 seqoff, ackoff; | |
| 380 | 382 | struct nf_conn_nat *nat = nfct_nat(ct); |
| 381 | 383 | struct nf_nat_seq *this_way, *other_way; |
| 382 | 384 | |
| 383 | 385 | |
| 384 | 386 | |
| 385 | 387 | |
| 386 | 388 | |
| ... | ... | @@ -390,16 +392,19 @@ |
| 390 | 392 | |
| 391 | 393 | tcph = (void *)skb->data + ip_hdrlen(skb); |
| 392 | 394 | if (after(ntohl(tcph->seq), this_way->correction_pos)) |
| 393 | - newseq = htonl(ntohl(tcph->seq) + this_way->offset_after); | |
| 395 | + seqoff = this_way->offset_after; | |
| 394 | 396 | else |
| 395 | - newseq = htonl(ntohl(tcph->seq) + this_way->offset_before); | |
| 397 | + seqoff = this_way->offset_before; | |
| 396 | 398 | |
| 397 | 399 | if (after(ntohl(tcph->ack_seq) - other_way->offset_before, |
| 398 | 400 | other_way->correction_pos)) |
| 399 | - newack = htonl(ntohl(tcph->ack_seq) - other_way->offset_after); | |
| 401 | + ackoff = other_way->offset_after; | |
| 400 | 402 | else |
| 401 | - newack = htonl(ntohl(tcph->ack_seq) - other_way->offset_before); | |
| 403 | + ackoff = other_way->offset_before; | |
| 402 | 404 | |
| 405 | + newseq = htonl(ntohl(tcph->seq) + seqoff); | |
| 406 | + newack = htonl(ntohl(tcph->ack_seq) - ackoff); | |
| 407 | + | |
| 403 | 408 | inet_proto_csum_replace4(&tcph->check, skb, tcph->seq, newseq, 0); |
| 404 | 409 | inet_proto_csum_replace4(&tcph->check, skb, tcph->ack_seq, newack, 0); |
| 405 | 410 | |
| ... | ... | @@ -413,7 +418,7 @@ |
| 413 | 418 | if (!nf_nat_sack_adjust(skb, tcph, ct, ctinfo)) |
| 414 | 419 | return 0; |
| 415 | 420 | |
| 416 | - nf_conntrack_tcp_update(skb, ip_hdrlen(skb), ct, dir); | |
| 421 | + nf_conntrack_tcp_update(skb, ip_hdrlen(skb), ct, dir, seqoff); | |
| 417 | 422 | |
| 418 | 423 | return 1; |
| 419 | 424 | } |
net/netfilter/nf_conntrack_proto_tcp.c
| ... | ... | @@ -720,8 +720,8 @@ |
| 720 | 720 | /* Caller must linearize skb at tcp header. */ |
| 721 | 721 | void nf_conntrack_tcp_update(const struct sk_buff *skb, |
| 722 | 722 | unsigned int dataoff, |
| 723 | - struct nf_conn *ct, | |
| 724 | - int dir) | |
| 723 | + struct nf_conn *ct, int dir, | |
| 724 | + s16 offset) | |
| 725 | 725 | { |
| 726 | 726 | const struct tcphdr *tcph = (const void *)skb->data + dataoff; |
| 727 | 727 | const struct ip_ct_tcp_state *sender = &ct->proto.tcp.seen[dir]; |
| ... | ... | @@ -734,7 +734,7 @@ |
| 734 | 734 | /* |
| 735 | 735 | * We have to worry for the ack in the reply packet only... |
| 736 | 736 | */ |
| 737 | - if (after(end, ct->proto.tcp.seen[dir].td_end)) | |
| 737 | + if (ct->proto.tcp.seen[dir].td_end + offset == end) | |
| 738 | 738 | ct->proto.tcp.seen[dir].td_end = end; |
| 739 | 739 | ct->proto.tcp.last_end = end; |
| 740 | 740 | spin_unlock_bh(&ct->lock); |