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authorFlorian Westphal <fw@strlen.de>2019-07-12 00:29:05 +0200
committerPablo Neira Ayuso <pablo@netfilter.org>2019-07-16 13:17:02 +0200
commit959b69ef57db00cb33e9c4777400ae7183ebddd3 (patch)
tree408fe33d807680e71ff3f9ae2b37c66ba64b65a1 /net
parentb83329fb473f29d34d85d642e3a3313bb2871fa9 (diff)
downloadlinux-959b69ef57db00cb33e9c4777400ae7183ebddd3.tar.bz2
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.c8
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;
}
}