From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: [PATCHv3] netem: Segment GSO packets on enqueue Date: Fri, 29 Apr 2016 11:19:05 -0700 Message-ID: <20160429111905.09b4b2e2@xeon-e3> References: <1461692618-21333-1-git-send-email-nhorman@tuxdriver.com> <1461951348-3920-1-git-send-email-nhorman@tuxdriver.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, Jamal Hadi Salim , "David S. Miller" , netem@lists.linux-foundation.org, eric.dumazet@gmail.com To: Neil Horman Return-path: Received: from mail-pf0-f170.google.com ([209.85.192.170]:35647 "EHLO mail-pf0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750875AbcD2SSy (ORCPT ); Fri, 29 Apr 2016 14:18:54 -0400 Received: by mail-pf0-f170.google.com with SMTP id 77so18641644pfv.2 for ; Fri, 29 Apr 2016 11:18:54 -0700 (PDT) In-Reply-To: <1461951348-3920-1-git-send-email-nhorman@tuxdriver.com> Sender: netdev-owner@vger.kernel.org List-ID: On Fri, 29 Apr 2016 13:35:48 -0400 Neil Horman 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] [] dump_stack+0x19/0x1b > [ 788.686193] [] warn_slowpath_common+0x70/0xb0 > [ 788.713803] [] warn_slowpath_fmt+0x5c/0x80 > [ 788.741314] [] ? ___ratelimit+0x93/0x100 > [ 788.767018] [] skb_warn_bad_offload+0xcd/0xda > [ 788.796117] [] skb_checksum_help+0x17c/0x190 > [ 788.823392] [] netem_enqueue+0x741/0x7c0 [sch_netem] > [ 788.854487] [] dev_queue_xmit+0x2a8/0x570 > [ 788.880870] [] 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 > CC: Jamal Hadi Salim > CC: "David S. Miller" > CC: netem@lists.linux-foundation.org > CC: eric.dumazet@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 [...]