Pawel, On Saturday 20 November 2004 04:46, Pawel Worach wrote: > I bumped into a wierd problem with SACK. > > Basically my setup is. > 192.168.1.10 .-crossover 192.168.1.200 > ftp server fxp0<->wireless ap<-> ~~~ <->laptop wireless ath0 > > I run ftp from the laptop to the server. > This is what happens: > ftp> get zero > local: zero remote: zero > 200 EPRT command successful. > 150 Opening BINARY mode data connection for 'zero'. > 476 KB 299.53 KB/s > 426 Data connection: Operation not permitted. > 487424 bytes received in 00:01 (299.49 KB/s) > > I started to look at tcpdump while this was happening and quickly > noticed that the connection got dropped by PF when SACK kicked in. > > pf: BAD state: TCP 192.168.1.10:20 192.168.1.10:20 192.168.1.200:50640 > [lo=3604799807 high=3604800103 win=33304 modulator=0 wscale=1] > [lo=4089843176 high=4089909784 win=33304 modulator=0 wscale=1] > 4:4 FPA seq=3604799807 ack=4089843176 len=296 ackskew=0 pkts=2497:1693 > dir=out ,fwd > pf: State failure on: 1 |
This is an "off by one" due to the FIN flag - I suppose. 3604799807 + 296 is 3604800103, but the +1 from the FIN flag brings that out of window and causes PF to drop the packet. > Nov 20 04:27:40 <kern.crit> darkstar kernel: pf: BAD state: TCP > 192.168.1.10:20 192.168.1.10:20 192.168.1.200:58378 [lo=1373010668 > high=1373010980 win=33304 mod ulator=0 wscale=1] [lo=3742879382 > high=3742945990 win=33304 modulator=0 wscale=1 ] 4:4 A seq=1373010668 > ack=3742879382 len=1448 ackskew=0 pkts=1266:851 dir=out,f wd > Nov 20 04:27:40 <kern.crit> darkstar kernel: pf: State failure on: 1 > | Nov 20 04:27:40 <kern.crit> darkstar kernel: pf: BAD state: TCP > 192.168.1.10:20 192.168.1.10:20 192.168.1.200:58378 [lo=1373010668 > high=1373010980 win=33304 mod ulator=0 wscale=1] [lo=3742879382 > high=3742945990 win=33304 modulator=0 wscale=1 ] 4:4 A seq=1373010668 > ack=3742879382 len=1448 ackskew=0 pkts=1266:851 dir=out,f wd These two make no sense at all (at least to me). seq + len is over the window by 1136 and I don't have the slightest clue why that would be the case. I am also a bit surprised that the two (three) state failures are so close together (04:27:35 and 04:27:40). Really strange. > If I disable sack on the ftp server everything works fine. > > I can reproduce this problem 100%, I have never managed to transfer more > than 3Mb via ftp when SACK is on, with it off I see no problems, 11Mbit > wireless at ~650Kb/s > > Attached are three tcpdumps of the ftp data channel after a 'get > /dev/zero'. (I picked out the smallest ones, dropped after about 400kb of > zeros) They didn't make it to the Mailinglist - I am afraid. Can you upload it somewhere or try to resend it via private mail? I'd be very interested. > related pf.conf rules, on ftp server: > pass out log quick on fxp0 inet proto tcp from fxp0 to any flags S/SA keep > state queue (bulk, fast) > and on client: > pass in log quick inet proto tcp from any port 20 to <firewall> port >= > 1024 flags S/SA keep state > > Any ideas? More info? Not yet. But the "off by one" that triggered the first failure should be tracked. I am not a TCP-expert myself, so I hope somebody can jump in here. Thanks. -- /"\ Best regards, | [EMAIL PROTECTED] \ / Max Laier | ICQ #67774661 X http://pf4freebsd.love2party.net/ | [EMAIL PROTECTED] / \ ASCII Ribbon Campaign | Against HTML Mail and News
pgpOObOg0gRUP.pgp
Description: PGP signature
