diff options
| author |   Florian Westphal <fw@strlen.de> | 2019-07-12 00:29:05 +0200 |
|---|---|---|
| committer |   Pablo Neira Ayuso <pablo@netfilter.org> | 2019-07-16 13:17:02 +0200 |
| commit | 959b69ef57db00cb33e9c4777400ae7183ebddd3 (patch) | |
| tree | 408fe33d807680e71ff3f9ae2b37c66ba64b65a1 /net | |
| parent | netfilter: synproxy: fix erroneous tcp mss option (diff) | |
| download | linux-dev-959b69ef57db00cb33e9c4777400ae7183ebddd3.tar.xz linux-dev-959b69ef57db00cb33e9c4777400ae7183ebddd3.zip | |
netfilter: conntrack: always store window size un-scaled
Jakub Jankowski reported following oddity:
After 3 way handshake completes, timeout of new connection is set to
max_retrans (300s) instead of established (5 days).
shortened excerpt from pcap provided:
25.070622 IP (flags [DF], proto TCP (6), length 52)
10.8.5.4.1025 > 10.8.1.2.80: Flags [S], seq 11, win 64240, [wscale 8]
26.070462 IP (flags [DF], proto TCP (6), length 48)
10.8.1.2.80 > 10.8.5.4.1025: Flags [S.], seq 82, ack 12, win 65535, [wscale 3]
27.070449 IP (flags [DF], proto TCP (6), length 40)
10.8.5.4.1025 > 10.8.1.2.80: Flags [.], ack 83, win 512, length 0
Turns out the last_win is of u16 type, but we store the scaled value:
512 << 8 (== 0x20000) becomes 0 window.
The Fixes tag is not correct, as the bug has existed forever, but
without that change all that this causes might cause is to mistake a
window update (to-nonzero-from-zero) for a retransmit.
Fixes: fbcd253d2448b8 ("netfilter: conntrack: lower timeout to RETRANS seconds if window is 0")
Reported-by: Jakub Jankowski <shasta@toxcorp.com>
Tested-by: Jakub Jankowski <shasta@toxcorp.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Acked-by: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Diffstat (limited to 'net')
| -rw-r--r-- | net/netfilter/nf_conntrack_proto_tcp.c | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/net/netfilter/nf_conntrack_proto_tcp.c b/net/netfilter/nf_conntrack_proto_tcp.c index d5fdfa00d683..85c1f8c213b0 100644 --- a/net/netfilter/nf_conntrack_proto_tcp.c +++ b/net/netfilter/nf_conntrack_proto_tcp.c @@ -472,6 +472,7 @@ 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; + u16 win_raw; s32 receiver_offset; bool res, in_recv_win; @@ -480,7 +481,8 @@ static bool tcp_in_window(const struct nf_conn *ct, */ seq = ntohl(tcph->seq); ack = sack = ntohl(tcph->ack_seq); - win = ntohs(tcph->window); + win_raw = ntohs(tcph->window); + win = win_raw; end = segment_seq_plus_len(seq, skb->len, dataoff, tcph); if (receiver->flags & IP_CT_TCP_FLAG_SACK_PERM) @@ -655,14 +657,14 @@ static bool tcp_in_window(const struct nf_conn *ct, && state->last_seq == seq && state->last_ack == ack && state->last_end == end - && state->last_win == win) + && state->last_win == win_raw) state->retrans++; else { state->last_dir = dir; state->last_seq = seq; state->last_ack = ack; state->last_end = end; - state->last_win = win; + state->last_win = win_raw; state->retrans = 0; } } |