On Fri, Apr 29, 2016 at 11:19:05AM -0700, Stephen Hemminger wrote:
> On Fri, 29 Apr 2016 13:35:48 -0400
> Neil Horman <nhor...@tuxdriver.com> wrote:
>
> > This was recently reported to me, and reproduced on the latest net kernel,
> > when
> > attempting to run netperf from a host that had a netem qdisc attached to the
> > egress interface:
> >
> > [ 788.073771] ------------[ cut here ]------------
> > [ 788.096716] WARNING: at net/core/dev.c:2253
> > skb_warn_bad_offload+0xcd/0xda()
> > [ 788.129521] bnx2: caps=(0x00000001801949b3, 0x0000000000000000) len=2962
> > data_len=0 gso_size=1448 gso_type=1 ip_summed=3
> > [ 788.182150] Modules linked in: sch_netem kvm_amd kvm crc32_pclmul
> > ipmi_ssif
> > ghash_clmulni_intel sp5100_tco amd64_edac_mod aesni_intel lrw gf128mul
> > glue_helper ablk_helper edac_mce_amd cryptd pcspkr sg edac_core hpilo
> > ipmi_si
> > i2c_piix4 k10temp fam15h_power hpwdt ipmi_msghandler shpchp acpi_power_meter
> > pcc_cpufreq nfsd auth_rpcgss nfs_acl lockd grace sunrpc ip_tables xfs
> > libcrc32c
> > sd_mod crc_t10dif crct10dif_generic mgag200 syscopyarea sysfillrect
> > sysimgblt
> > i2c_algo_bit drm_kms_helper ahci ata_generic pata_acpi ttm libahci
> > crct10dif_pclmul pata_atiixp tg3 libata crct10dif_common drm crc32c_intel
> > ptp
> > serio_raw bnx2 r8169 hpsa pps_core i2c_core mii dm_mirror dm_region_hash
> > dm_log
> > dm_mod
> > [ 788.465294] CPU: 16 PID: 0 Comm: swapper/16 Tainted: G W
> > ------------ 3.10.0-327.el7.x86_64 #1
> > [ 788.511521] Hardware name: HP ProLiant DL385p Gen8, BIOS A28 12/17/2012
> > [ 788.542260] ffff880437c036b8 f7afc56532a53db9 ffff880437c03670
> > ffffffff816351f1
> > [ 788.576332] ffff880437c036a8 ffffffff8107b200 ffff880633e74200
> > ffff880231674000
> > [ 788.611943] 0000000000000001 0000000000000003 0000000000000000
> > ffff880437c03710
> > [ 788.647241] Call Trace:
> > [ 788.658817] <IRQ> [<ffffffff816351f1>] dump_stack+0x19/0x1b
> > [ 788.686193] [<ffffffff8107b200>] warn_slowpath_common+0x70/0xb0
> > [ 788.713803] [<ffffffff8107b29c>] warn_slowpath_fmt+0x5c/0x80
> > [ 788.741314] [<ffffffff812f92f3>] ? ___ratelimit+0x93/0x100
> > [ 788.767018] [<ffffffff81637f49>] skb_warn_bad_offload+0xcd/0xda
> > [ 788.796117] [<ffffffff8152950c>] skb_checksum_help+0x17c/0x190
> > [ 788.823392] [<ffffffffa01463a1>] netem_enqueue+0x741/0x7c0 [sch_netem]
> > [ 788.854487] [<ffffffff8152cb58>] dev_queue_xmit+0x2a8/0x570
> > [ 788.880870] [<ffffffff8156ae1d>] ip_finish_output+0x53d/0x7d0
> > ...
> >
> > The problem occurs because netem is not prepared to handle GSO packets (as
> > it
> > uses skb_checksum_help in its enqueue path, which cannot manipulate these
> > frames).
> >
> > The solution I think is to simply segment the skb in a simmilar fashion to
> > the
> > way we do in __dev_queue_xmit (via validate_xmit_skb), with some minor
> > changes.
> > When we decide to corrupt an skb, if the frame is GSO, we segment it,
> > corrupt
> > the first segment, and enqueue the remaining ones.
> >
> > tested successfully by myself on the latest net kernel, to whcih this
> > applies
> >
> > Signed-off-by: Neil Horman <nhor...@tuxdriver.com>
> > CC: Jamal Hadi Salim <j...@mojatatu.com>
> > CC: "David S. Miller" <da...@davemloft.net>
> > CC: ne...@lists.linux-foundation.org
> > CC: eric.duma...@gmail.com
> >
>
> This looks like a good idea.
>
> Please cleanup the formatting issues:
>
> This was recently reported to me, and reproduced on the latest net kernel,
> when
>
> WARNING: 'whcih' may be misspelled - perhaps 'which'?
> #93:
> tested successfully by myself on the latest net kernel, to whcih this applies
>
> ERROR: "foo* bar" should be "foo *bar"
> #130: FILE: net/sched/sch_netem.c:402:
> +static struct sk_buff* netem_segment(struct sk_buff *skb, struct Qdisc *sch)
>
>
> CHECK: braces {} should be used on all arms of this statement
> #164: FILE: net/sched/sch_netem.c:479:
> + if (skb_is_gso(skb)) {
> [...]
> + } else
> [...]
>
> CHECK: braces {} should be used on all arms of this statement
> #198: FILE: net/sched/sch_netem.c:562:
> + if (rc != NET_XMIT_SUCCESS) {
> [...]
> + } else
> [...]
>
>
>
>
>
>
Will, do when I get back to the office monday
Thanks!
Neil
