On Thu, Jun 13, 2013 at 12:51:38PM +0200, Florian Westphal wrote: > Hi. > > With nf_conntrack_tcp_loose = 1, stray packets will create > conntrack with 5 days-timeout. Is this necessary? > > I ask, because I've got following tcp trace: > > > 192.168.x is initiator/origin, 10.184. is responder/reply, connection is establised by usual 3whs, > data was transmitted in both directions) > > A 55:07 (id 12053, [DF], TCP, len 40) 192.168.x.52792 > 10.184.y.80: F, 426:426(0) ack 9237 win 255 > B 55:07 (id 6129, [DF], TCP, len 40) 10.184.y.80 > 192.168.x.52792: ., ack 427 win 123 > C 56:08 (id 6130, [DF], TCP, len 40) 10.184.y.80 > 192.168.x.52792: F, 9237:9237(0) ack 427 win 123 > D 56:08 (id 12159, [DF], TCP, len 40) 192.168.x.52792 > 10.184.y.80: ., ack 9238 win 255 > > D is last packet seen for that connection. Notice 61 second pause between B and C. > > From conntrack POV, we have following state transitions: > [NEW] tcp 6 60 SYN_RECV .. > [UPDATE] tcp 6 432000 ESTABLISHED .. > [UPDATE] tcp 6 120 FIN_WAIT .. (triggered by packet A) > [UPDATE] tcp 6 60 CLOSE_WAIT .. (triggered by packet B) > [DESTROY] tcp 6 (triggered by 60-second CLOSE_WAIT timeout) > [NEW] tcp 6 432034 ESTABLISHED .. [UNREPLIED] (triggered by packet D) > > Result is that, after a couple of hours, conntrack table starts to fill up > with UNREPLIED crud. > > Follwing changes fix it: > - set loose=0 (avoids bogus NEW connection), OR, > - set net.ipv4.netfilter.ip_conntrack_tcp_timeout_close_wait=65 > (avoids NEW connection, new state transitions are: > [UPDATE] tcp 6 60 CLOSE_WAIT .. (triggered by packet B) > [UPDATE] tcp 6 30 LAST_ACK .. (triggered by C) > [UPDATE] tcp 6 120 TIME_WAIT .. (triggered by D) > > However, I think conntrack shouldn't insert a just-picked > up connection with default ESTABLISHED timeout value. Suggestion: > > diff --git a/net/netfilter/nf_conntrack_proto_tcp.c b/net/netfilter/nf_conntrack_proto_tcp.c > index 4d4d8f1..33ca4f3 100644 > --- a/net/netfilter/nf_conntrack_proto_tcp.c > +++ b/net/netfilter/nf_conntrack_proto_tcp.c > @@ -1043,6 +1043,11 @@ static int tcp_packet(struct nf_conn *ct, > nf_ct_kill_acct(ct, ctinfo, skb); > return NF_ACCEPT; > } > + /* loose=1 picked up existing connection, avoid large timeout */ > + if (old_state == TCP_CONNTRACK_NONE && > + new_state == TCP_CONNTRACK_ESTABLISHED && > + timeout > timeouts[TCP_CONNTRACK_UNACK]) > + timeout = timeouts[TCP_CONNTRACK_UNACK]; > } else if (!test_bit(IPS_ASSURED_BIT, &ct->status) > && (old_state == TCP_CONNTRACK_SYN_RECV > || old_state == TCP_CONNTRACK_ESTABLISHED) > > Jozsef, If you aggree I would make a formal submission. This sounds reasonable to me. conntrackd is adding entries using a small timeout for recovered flows, which is a similar approach. Jozsef? -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
