[Cerowrt-devel] TFO crashes cerowrt 3.7.1-1

Fri Jan 4 22:02:20 EST 2013

Without TFO all worked fine.
The problem is when tfo server is on cero box.
I will try both ECN on on laptop and disabling ECN on cero with TFO on.
Will report the behavior seen.

Thanks,
Ketan.
On Jan 5, 2013 7:50 AM, "Yuchung Cheng" <ycheng at google.com> wrote:

> On Fri, Jan 4, 2013 at 5:59 PM, Ketan Kulkarni <ketkulka at gmail.com> wrote:
> > Well, I was trying polipo server on cero box and httping from laptop. On
> > both the boxes I set 3 in tcp_fastopen.
> >
> > The panic is seen only when server is on cero box.
> > If I run server on my laptop and httping from cero all TFO connections
> are
> > successful.
> > So I doubt its the only problem is SYN+DATA.
> Just to confirm: you meant the problem is SYN/data processing on the
> server side?
>
> Maybe we hit some ECN / TFO bug. Some crash log would be great. Thanks
> for trying TFO!
>
> >
> > Unfortunately I don't have the serial cable right now, and logread or
> dmesg
> > didn't print any logs before the cero router  restarted.
> >
> > Attached is the tcpdump capture on lo when client and server both run on
> > cero box.
> > HTH!
> >
> > If you (or anyone) can suggest more diagnostics, I will be glad to
> provide.
> >
> > On Jan 5, 2013 2:49 AM, "Jerry Chu" <hkchu at google.com> wrote:
> >>
> >> +ycheng
> >>
> >>
> >> On Fri, Jan 4, 2013 at 1:11 PM, Dave Taht <dave.taht at gmail.com> wrote:
> >>>
> >>> Hmm. I would lean towards there being an issue with the new (freshly
> >>> ported forward to 3.7.1) unaligned checksum code for mips based on
> >>> what you say here. Or an offload...
> >>>
> >>> As for the 239.x multicast issue, hmm... separate issue entirely.
> >>> Probably...
> >>>
> >>> And then there's TFO. I note that in order to use it properly you need
> >>> to turn it on in proc. Last I remember that was
> >>>
> >>> echo 3 > /proc/sys/net/ipv4/tcp_fastopen
> >>
> >>
> >> Correct - to enable the normal use of TFO for both client and server.
> >> There are other flags for advanced usage:
> >>  /* Bit Flags for sysctl_tcp_fastopen */
> >> #define TFO_CLIENT_ENABLE       1
> >> #define TFO_SERVER_ENABLE       2
> >> #define TFO_CLIENT_NO_COOKIE    4 /* Send data-in-SYN w/o cookie */
> >>
> >> /* Process SYN data but skip cookie validation */
> >> #define TFO_SERVER_COOKIE_NOT_CHKED     0x100
> >> /* Accept SYN data w/o any cookie option */
> >> #define TFO_SERVER_COOKIE_NOT_REQD      0x200
> >>
> >> /* Force enable TFO on all listeners, i.e., not requiring the
> >>  * TCP_FASTOPEN socket option. SOCKOPT1/2 determine how to set max_qlen.
> >>  */
> >> #define TFO_SERVER_WO_SOCKOPT1  0x400
> >> #define TFO_SERVER_WO_SOCKOPT2  0x800
> >> /* Always create TFO child sockets on a TFO listener even when
> >>  * cookie/data not present. (For testing purpose!)
> >>  */
> >> #define TFO_SERVER_ALWAYS       0x1000
> >>
> >>>
> >>> However that's an old memory and there is this tcp_fastopen_key file I
> >>> don't know anything about yet (this is such bleeding edge stuff!)
> >>>
> >>> ... and with tcp_fastopen disabled things should still work right...
> >>> so I'm thinking something else is busted in the stack.
> >>>
> >>> I've also observed a dns slowdown in what I've been testing but hadn't
> >>> dug into packet dumps. (and was assuming, until now, it was due to me
> >>> fiddling with ULAs inside the network) Thanks for digging this deep!
> >>>
> >>> I never said this first attempt at 3.7 for cero was going to be
> >>> perfect, but we've entered a new age of subtle problems here.
> >>>
> >>> I strongly suggest nobody else try this dev build as a default gw, and
> >>> that the TFO folk ignore the noise for now.
> >>
> >>
> >> SG.
> >>
> >> Jerry
> >>
> >>>
> >>>
> >>> I just got a 3.7.1 box built on x86_64 so as to a/b some captures.
> >>> Regrettably I'm short on time through the weekend...
> >>>
> >>> On Fri, Jan 4, 2013 at 12:42 PM, Maciej Soltysiak <
> maciej at soltysiak.com>
> >>> wrote:
> >>> > I am seeing something strange here, with polipo related to TFO but
> also
> >>> > DNS.
> >>> > When I just took 3.7.1-1 and set my windows 7 laptop to use
> >>> > gw.home.lan:8123
> >>> > as http proxy it didn't work. What I observed was:
> >>> > A) after quite a while polipo's response to browser was 504 Host
> >>> > www.osnews.com lookup failed: Timeout
> >>> > b) this error in ssh console: Host osnews.com lookup failed: Timeout
> >>> > (131072)
> >>> > c) Disabling TFO by adding option useTCPFastOpen 'false' to config
> >>> > 'polipo'
> >>> > 'general' works around the problem
> >>> > d) Alternatively, you can keep TFO enabled in polipo but change
> option
> >>> > 'dnsUseGethostbyname' from 'reluctantly' to 'true' (!)
> >>> > This is very weird, because TFO is TCP and the DNS queries fired off
> by
> >>> > polipo are UDP:
> >>> > root at OpenWrt:/tmp/log# tcpdump -n -v -vv -vvv -x -X -s 1500 -i lo
> >>> > 20:21:56.160245 IP (tos 0x0, ttl 64, id 50129, offset 0, flags [DF],
> >>> > proto
> >>> > UDP (17), length 60)
> >>> > 127.0.0.1.47304 > 127.0.0.1.53: [bad udp cksum 0xfe3b -> 0xd17f!]
> >>> > 55396+ A?
> >>> > www.osnews.com. (32)
> >>> > 0x0000: 4500 003c c3d1 4000 4011 78dd 7f00 0001 E..<.. at .@.x.....
> >>> > 0x0010: 7f00 0001 b8c8 0035 0028 fe3b d864 0100 .......5.(.;.d..
> >>> > 0x0020: 0001 0000 0000 0000 0377 7777 066f 736e .........www.osn
> >>> > 0x0030: 6577 7303 636f 6d00 0001 0001 ews.com.....
> >>> > 20:21:56.160319 IP (tos 0x0, ttl 64, id 50130, offset 0, flags [DF],
> >>> > proto
> >>> > UDP (17), length 60)
> >>> > 127.0.0.1.47304 > 127.0.0.1.53: [bad udp cksum 0xfe3b -> 0xd164!]
> >>> > 55396+
> >>> > AAAA? www.osnews.com. (32)
> >>> > 0x0000: 4500 003c c3d2 4000 4011 78dc 7f00 0001 E..<.. at .@.x.....
> >>> > 0x0010: 7f00 0001 b8c8 0035 0028 fe3b d864 0100 .......5.(.;.d..
> >>> > 0x0020: 0001 0000 0000 0000 0377 7777 066f 736e .........www.osn
> >>> > 0x0030: 6577 7303 636f 6d00 001c 0001 ews.com.....
> >>> > 20:21:56.169942 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF],
> proto
> >>> > UDP
> >>> > (17), length 123)
> >>> > 127.0.0.1.53 > 127.0.0.1.47304: [bad udp cksum 0xfe7a -> 0x5f73!]
> 55396
> >>> > q:
> >>> > A? www.osnews.com. 1/2/0 www.osnews.com. [29m3s] A 74.86.31.159 ns:
> >>> > osnews.com. [29m3s] NS ns2.swelter.net., osnews.com. [29m3s] NS
> >>> > ns1.swelter.net. (95)
> >>> > 0x0000: 4500 007b 0000 4000 4011 3c70 7f00 0001 E..{.. at .@.<p....
> >>> > 0x0010: 7f00 0001 0035 b8c8 0067 fe7a d864 8180 .....5...g.z.d..
> >>> > 0x0020: 0001 0001 0002 0000 0377 7777 066f 736e .........www.osn
> >>> > 0x0030: 6577 7303 636f 6d00 0001 0001 c00c 0001 ews.com.........
> >>> > 0x0040: 0001 0000 06cf 0004 4a56 1f9f c010 0002 ........JV......
> >>> > 0x0050: 0001 0000 06cf 0011 036e 7332 0773 7765 .........ns2.swe
> >>> > 0x0060: 6c74 6572 036e 6574 00c0 1000 0200 0100 lter.net........
> >>> > 0x0070: 0006 cf00 0603 6e73 31c0 40 ......ns1.@
> >>> > 20:21:56.173901 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF],
> proto
> >>> > UDP
> >>> > (17), length 135)
> >>> > 127.0.0.1.53 > 127.0.0.1.47304: [bad udp cksum 0xfe86 -> 0x8ecb!]
> 55396
> >>> > q:
> >>> > AAAA? www.osnews.com. 1/2/0 www.osnews.com. [54m44s] AAAA
> >>> > 2607:f0d0:1002:62::3 ns: osnews.com. [29m3s] NS ns1.swelter.net.,
> >>> > osnews.com. [29m3s] NS ns2.swelter.net. (107)
> >>> > 0x0000: 4500 0087 0000 4000 4011 3c64 7f00 0001 E..... at .@.<d....
> >>> > 0x0010: 7f00 0001 0035 b8c8 0073 fe86 d864 8180 .....5...s...d..
> >>> > 0x0020: 0001 0001 0002 0000 0377 7777 066f 736e .........www.osn
> >>> > 0x0030: 6577 7303 636f 6d00 001c 0001 c00c 001c ews.com.........
> >>> > 0x0040: 0001 0000 0cd4 0010 2607 f0d0 1002 0062 ........&......b
> >>> > 0x0050: 0000 0000 0000 0003 c010 0002 0001 0000 ................
> >>> > 0x0060: 06cf 0011 036e 7331 0773 7765 6c74 6572 .....ns1.swelter
> >>> > 0x0070: 036e 6574 00c0 1000 0200 0100 0006 cf00 .net............
> >>> > 0x0080: 0603 6e73 32c0 4c ..ns2.L
> >>> > This is the only DNS traffic I saw during the attempts. The tcpdumps
> >>> > have
> >>> > udp bad checksum but when I disabled TFO in polipo, the UDP where
> still
> >>> > bad
> >>> > checksum but they worked.
> >>> > Really weird.
> >>> > p.s. UPNP still works for port forwarding negotiation as it did in
> >>> > 3.6.11-4
> >>> > I still couldn't get the UPNP/SSDP broadcasts (udp to
> 239.255.255.250)
> >>> > to
> >>> > being forwarded between se00 and sw00/sw10. Last time it worked was
> >>> > ~3.3.8.
> >>> > I'm starting not to question why it doesn't work, I'm starting to
> >>> > wonder why
> >>> > it did work then ;-)
> >>> > Regards,
> >>> > Maciej
> >>> > On Fri, Jan 4, 2013 at 6:33 PM, Dave Taht <dave.taht at gmail.com>
> wrote:
> >>> >>
> >>> >> On Fri, Jan 4, 2013 at 9:27 AM, Eric Dumazet <edumazet at google.com>
> >>> >> wrote:
> >>> >> > Sorry, could you give us a copy of the panic stack trace ?
> >>> >>
> >>> >> I will get a serial console up on a wndr3800 by sunday. (sorry, just
> >>> >> landed in california, am in disarray)
> >>> >>
> >>> >> The latest dev build of cero for the wndr3800 and wndr3700v2 is at:
> >>> >>
> >>> >> http://snapon.lab.bufferbloat.net/~cero2/cerowrt/wndr/3.7.1-1/
> >>> >>
> >>> >> --
> >>> >> Dave Täht
> >>> >>
> >>> >> Fixing bufferbloat with cerowrt:
> >>> >> http://www.teklibre.com/cerowrt/subscribe.html
> >>> >> _______________________________________________
> >>> >> Cerowrt-devel mailing list
> >>> >> Cerowrt-devel at lists.bufferbloat.net
> >>> >> https://lists.bufferbloat.net/listinfo/cerowrt-devel
> >>> >
> >>> >
> >>>
> >>>
> >>>
> >>> --
> >>> Dave Täht
> >>>
> >>> Fixing bufferbloat with cerowrt:
> >>> http://www.teklibre.com/cerowrt/subscribe.html
> >>
> >>
> >
>
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