On Wed, 2016-08-03 at 20:36 -0300, Marcelo Ricardo Leitner wrote: > Hi, > > I have two namespaces linked with a veth and netem in one of them adding 20ms > latency, and doing netperf from one to another. I'm on commit > 7cf210dc267861360cf6968b69bf512475aca985, net updated today, and I'm hitting > this: > > [ 1043.024555] WARNING: CPU: 3 PID: 19902 at > ...../linux/net/core/skbuff.c:4289 skb_try_coalesce+0x414/0x430 > [ 1043.024556] Kernel panic - not syncing: panic_on_warn set ... > > [ 1043.024601] CPU: 3 PID: 19902 Comm: netserver Not tainted 4.7.0-standard+ > #20 > [ 1043.024631] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS > 1.9.1-1.fc24 04/01/2014 > [ 1043.024667] 0000000000000086 00000000db033d46 ffff880035733ad8 > ffffffff813d630d > [ 1043.024705] 0000000000000000 ffffffff81a35655 ffff880035733b60 > ffffffff811b5e3d > [ 1043.024741] ffff880000000008 ffff880035733b70 ffff880035733b08 > 00000000db033d46 > [ 1043.024777] Call Trace: > [ 1043.024794] [<ffffffff813d630d>] dump_stack+0x63/0x86 > [ 1043.024818] [<ffffffff811b5e3d>] panic+0xe4/0x226 > [ 1043.024842] [<ffffffff816ae244>] ? skb_try_coalesce+0x414/0x430 > [ 1043.024870] [<ffffffff810a5f13>] __warn+0xe3/0xf0 > [ 1043.024892] [<ffffffff810a602d>] warn_slowpath_null+0x1d/0x20 > [ 1043.024919] [<ffffffff816ae244>] skb_try_coalesce+0x414/0x430 > [ 1043.024945] [<ffffffff817165f3>] tcp_try_coalesce+0x63/0xd0 > [ 1043.024977] [<ffffffff81718497>] tcp_queue_rcv+0x57/0x140 > [ 1043.025003] [<ffffffff8171e132>] tcp_rcv_established+0x3f2/0x6f0 > [ 1043.025029] [<ffffffff81728815>] tcp_v4_do_rcv+0x145/0x200 > [ 1043.025054] [<ffffffff816a4387>] __release_sock+0x87/0xf0 > [ 1043.025078] [<ffffffff816a4420>] release_sock+0x30/0xa0 > [ 1043.025102] [<ffffffff81711d8c>] tcp_recvmsg+0x5fc/0xb70 > [ 1043.025126] [<ffffffff8174051e>] inet_recvmsg+0x7e/0xb0 > [ 1043.025151] [<ffffffff8169f61d>] sock_recvmsg+0x3d/0x50 > [ 1043.025175] [<ffffffff8169f85a>] SYSC_recvfrom+0xda/0x150 > [ 1043.025201] [<ffffffff811157df>] ? do_setitimer+0x1bf/0x220 > [ 1043.025226] [<ffffffff81115891>] ? alarm_setitimer+0x51/0x90 > [ 1043.025252] [<ffffffff816a0bbe>] SyS_recvfrom+0xe/0x10 > [ 1043.025277] [<ffffffff817df132>] entry_SYSCALL_64_fastpath+0x1a/0xa4 > > That's: > WARN_ON_ONCE(delta < len); > > Netperf command line is: > netperf -cC -l 10 -t TCP_STREAM \ > -H 192.168.10.1 -L 192.168.10.2 > > netem is added on netperf/client side. > > It triggers it right at the beginning of the test. > > I can reproduce it 100% of the times with above setup. > - Removing netem made it stop reproducing. > - Reducing netem latency to 10ms, still warns > - Reducing netem latency to 1ms, still warns > - Reducing netem latency to 0ms, it stops reproducing it > > This system is not generating a kdump, I'm looking into it.
This is caused by the skb_orphan_partial() call from netem. This breaks if packet is re-injected instead of being sent to a physical NIC.
