I could get a chance to get the backtrace from serial port. I didnt do the kgdb session yet. To iterate, the crash occurs on TFO server on mips platform. The call trace looks like this [ 1024.530000] Call Trace: [ 1024.530000] [<801fc7f4>] reqsk_fastopen_remove+0x30/0x17c [ 1024.530000] [<8024a36c>] tcp_rcv_state_process+0x7b4/0xc28 [ 1024.530000] [<802516ec>] tcp_v4_do_rcv+0x21c/0x274 [ 1024.530000] [<80253c74>] tcp_v4_rcv+0x5b4/0x974 [ 1024.530000] [<802320f0>] ip_local_deliver_finish+0x168/0x29c [ 1024.530000] [<80207100>] __netif_receive_skb+0x63c/0x6c0 [ 1024.530000] [] ieee80211_deliver_skb+0x1b8/0x220 [mac80211] [ 1024.530000] [] ieee80211_rx_handlers.part.12+0x1654/0x23e0 [mac80211] [ 1024.530000] [] ieee80211_prepare_and_rx_handle+0xa6c/0xaf0 [mac80211] [ 1024.530000] [] ieee80211_rx+0x810/0x8d8 [mac80211] [ 1024.530000] [] ath_rx_tasklet+0xf4c/0x10a4 [ath9k] [ 1024.530000] [] ath9k_tasklet+0x104/0x174 [ath9k] [ 1024.530000] [<800793b8>] tasklet_action+0x78/0xc8 [ 1024.530000] [<80078c08>] __do_softirq+0xb0/0x184 [ 1024.530000] [<80078d8c>] do_softirq+0x48/0x68 [ 1024.530000] [<80078fa8>] irq_exit+0x4c/0x7c [ 1024.530000] [<8006330c>] ret_from_irq+0x0/0x4 [ 1024.530000] [ 1024.530000] Code: 8e510208 30d300ff 2c420001 <00028036> 0c01e2a7 ac80048c 8e220008 2442ffff ae220008 [ 1024.940000] ---[ end trace a47ff22dd20a96c1 ]---[ 1024.950000] Kernel panic - not syncing: Fatal exception in interrupt I suspect this is the line responsible for this crash void reqsk_fastopen_remove(struct sock *sk, struct request_sock *req, bool reset) { struct sock *lsk = tcp_rsk(req)->listener; struct fastopen_queue *fastopenq = inet_csk(lsk)->icsk_accept_ queue.fastopenq; >>>>> BUG_ON(!spin_is_locked(&sk-> sk_lock.slock) && !sock_owned_by_user(sk)); tcp_sk(sk)->fastopen_rsk = NULL; spin_lock_bh(&fastopenq->lock); fastopenq->qlen--; tcp_rsk(req)->listener = NULL; Please see more details here http://www.bufferbloat.net/issues/418#change-1706 Thanks, Ketan On Jan 6, 2013 12:43 AM, "Ketan Kulkarni" wrote: > > Disabling ECN on cero box has no effect. > The box crashed with with ECN disabled. > Also tried enabling ECN on x86 and it didnt crash in either case. The > tcpdump on cero lo is updated at - > https://www.bufferbloat.net/issues/418#change-1703 > It is exactly similar to the previously attached "lo_capture.txt" but > with ECN disabled. > > I might try getting serial cable on Sunday to get the crash details. > Till then probably I cannot provide the crash logs as logread/dmesg > does not print anything. > > Thanks, > Ketan > > On Sat, Jan 5, 2013 at 8:32 AM, Ketan Kulkarni wrote: > > 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" wrote: > >> > >> On Fri, Jan 4, 2013 at 5:59 PM, Ketan Kulkarni 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" wrote: > >> >> > >> >> +ycheng > >> >> > >> >> > >> >> On Fri, Jan 4, 2013 at 1:11 PM, Dave Taht 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 > >> >>> > >> >>> 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@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..<..@.@.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..<..@.@.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..{..@.@. >> >>> > 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.....@.@. >> >>> > 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 > >> >>> > wrote: > >> >>> >> > >> >>> >> On Fri, Jan 4, 2013 at 9:27 AM, Eric Dumazet < edumazet@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@lists.bufferbloat.net > >> >>> >> https://lists.bufferbloat.net/listinfo/cerowrt-devel > >> >>> > > >> >>> > > >> >>> > >> >>> > >> >>> > >> >>> -- > >> >>> Dave Täht > >> >>> > >> >>> Fixing bufferbloat with cerowrt: > >> >>> http://www.teklibre.com/cerowrt/subscribe.html > >> >> > >> >> > >> >