| Message ID | CAMDZJNUyaXnVp7jAH-E_d-X__zikoa=-3ypHo64aOnqra7TbRw@mail.gmail.com |
|---|---|
| State | RFC, archived |
| Delegated to: | David Miller |
| Headers | show |
> In a case, there is also warn info. The test topo is shown as below. Thanks for testing the patch, Tonghao. > The warn info is shown as below [1]. If we change the CHECKSUM_NONE to > CHECKSUM_UNNECESSARY in the udp4_ufo_fragment(). > and we should add a check in skb_needs_check() when outputting a packet. > > diff --git a/net/core/dev.c b/net/core/dev.c > index 416137c..8fe12a7 100644 > --- a/net/core/dev.c > +++ b/net/core/dev.c > @@ -2670,6 +2670,7 @@ static inline bool skb_needs_check(struct > sk_buff *skb, bool tx_path) > { > if (tx_path) > return skb->ip_summed != CHECKSUM_PARTIAL && > + skb->ip_summed != CHECKSUM_UNNECESSARY && > skb->ip_summed != CHECKSUM_NONE; Good catch. Only, the CHECKSUM_NONE case was added specifically to work around this UFO issue on the tx path in commit 6e7bc478c9a0 ("net: skb_needs_check() accepts CHECKSUM_NONE for tx"). If we change the value generated by UFO, we can remove that statement, so + skb->ip_summed != CHECKSUM_UNNECESSARY; - skb->ip_summed != CHECKSUM_NONE; Else the entire check becomes a NOOP. These are the only three valid states on tx. With very few codepaths generating CHECKSUM_UNNECESSARY to begin with, it arguably already is practically a NOOP. I need to look more closely what the statement is intended to protect against, before we relax it even further. The patch will need the same UFO change in ipv6_ufo_fragment. I also had to verify that it is indeed correct to use CHECKSUM_UNNECESSARY for this case. It is not commonly used as alias for CHECKSUM_NONE on the tx path. And indeed does not carry the exact same meaning. It was defined as "no need to checksum" on tx for protocols that skb_checksum_help does not support: http://patchwork.ozlabs.org/patch/146567/ Given that, it should be fine to use in this case.
>> @@ -2670,6 +2670,7 @@ static inline bool skb_needs_check(struct >> sk_buff *skb, bool tx_path) >> { >> if (tx_path) >> return skb->ip_summed != CHECKSUM_PARTIAL && >> + skb->ip_summed != CHECKSUM_UNNECESSARY && >> skb->ip_summed != CHECKSUM_NONE; > > Good catch. Only, the CHECKSUM_NONE case was added specifically to > work around this UFO issue on the tx path in commit 6e7bc478c9a0 > ("net: skb_needs_check() accepts CHECKSUM_NONE for tx"). If we change > the value generated by UFO, we can remove that statement, so > > + skb->ip_summed != CHECKSUM_UNNECESSARY; > - skb->ip_summed != CHECKSUM_NONE; > > Else the entire check becomes a NOOP. These are the only three valid > states on tx. With very few codepaths generating CHECKSUM_UNNECESSARY > to begin with, it arguably already is practically a NOOP. I need to > look more closely what the statement is intended to protect against, > before we relax it even further. On transmit, packets entering skb_gso_segment are expected to always have ip_summed CHECKSUM_PARTIAL. This check was added to track down unexpected exceptions in commit 67fd1a731ff1 ("net: Add debug info to track down GSO checksum bug"). Only when called for the second time, after skb_mac_gso_segment, do we have to possibly handle the case where the GSO layer computes the checksum and changes ip_summed. Since this only goes into 4.11 to 4.13, making two separate skb_needs_check variants for these two call sites seems overkill. I will send the simple fix to convert CHECKSUM_NONE to CHECKSUM_UNNECESSARY. As a side effect of removing UFO in 4.14-rc1, we can also revert commit 6e7bc478c9a0 ("net: skb_needs_check() accepts CHECKSUM_NONE for tx") in net-next.
Thanks, I send a patch, which will revert commit 6e7bc478c9a0 in net-next. On Wed, Aug 9, 2017 at 1:46 AM, Willem de Bruijn <willemdebruijn.kernel@gmail.com> wrote: >>> @@ -2670,6 +2670,7 @@ static inline bool skb_needs_check(struct >>> sk_buff *skb, bool tx_path) >>> { >>> if (tx_path) >>> return skb->ip_summed != CHECKSUM_PARTIAL && >>> + skb->ip_summed != CHECKSUM_UNNECESSARY && >>> skb->ip_summed != CHECKSUM_NONE; >> >> Good catch. Only, the CHECKSUM_NONE case was added specifically to >> work around this UFO issue on the tx path in commit 6e7bc478c9a0 >> ("net: skb_needs_check() accepts CHECKSUM_NONE for tx"). If we change >> the value generated by UFO, we can remove that statement, so >> >> + skb->ip_summed != CHECKSUM_UNNECESSARY; >> - skb->ip_summed != CHECKSUM_NONE; >> >> Else the entire check becomes a NOOP. These are the only three valid >> states on tx. With very few codepaths generating CHECKSUM_UNNECESSARY >> to begin with, it arguably already is practically a NOOP. I need to >> look more closely what the statement is intended to protect against, >> before we relax it even further. > > On transmit, packets entering skb_gso_segment are expected to always > have ip_summed CHECKSUM_PARTIAL. This check was added to track down > unexpected exceptions in commit 67fd1a731ff1 ("net: Add debug info to > track down GSO checksum bug"). > > Only when called for the second time, after skb_mac_gso_segment, do we > have to possibly handle the case where the GSO layer computes the > checksum and changes ip_summed. > > Since this only goes into 4.11 to 4.13, making two separate > skb_needs_check variants for these two call sites seems overkill. I > will send the simple fix to convert CHECKSUM_NONE to > CHECKSUM_UNNECESSARY. > > As a side effect of removing UFO in 4.14-rc1, we can also revert > commit 6e7bc478c9a0 ("net: skb_needs_check() accepts CHECKSUM_NONE for > tx") in net-next.
diff --git a/net/core/dev.c b/net/core/dev.c index 416137c..8fe12a7 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -2670,6 +2670,7 @@ static inline bool skb_needs_check(struct sk_buff *skb, bool tx_path) { if (tx_path) return skb->ip_summed != CHECKSUM_PARTIAL && + skb->ip_summed != CHECKSUM_UNNECESSARY && skb->ip_summed != CHECKSUM_NONE; return skb->ip_summed == CHECKSUM_NONE; diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c index 7812501..0932c85 100644 --- a/net/ipv4/udp_offload.c +++ b/net/ipv4/udp_offload.c @@ -235,7 +235,7 @@ static struct sk_buff *udp4_ufo_fragment(struct sk_buff *skb, if (uh->check == 0) uh->check = CSUM_MANGLED_0; - skb->ip_summed = CHECKSUM_NONE; + skb->ip_summed = CHECKSUM_UNNECESSARY; /* If there is no outer header we can fake a checksum offload
Hi Willem In a case, there is also warn info. The test topo is shown as below. VM01: veth1 and eth0 in the VM01 are inserted to ovs br0. veth0(IP: 172.16.34.100/24) —— veth1--br0--eth0 iperf3 -c 172.168.100.13 -i 1 -P 10 -t 10 -u -b 1000M -l 10K VM02 eth0(IP: 172.16.34.200/24) iperf3 -s The warn info is shown as below [1]. If we change the CHECKSUM_NONE to CHECKSUM_UNNECESSARY in the udp4_ufo_fragment(). and we should add a check in skb_needs_check() when outputting a packet. * due to the fact that we have already done the checksum in [1]: [ 1291.596232] vmxnet3: caps=(0x0000006000214ba9, 0x0000000000000000) len=10282 data_len=10240 gso_size=1480 gso_type=2 ip_summed=1 [ 1291.596239] ------------[ cut here ]------------ [ 1291.596242] WARNING: CPU: 1 PID: 2203 at net/core/dev.c:2564 skb_warn_bad_offload+0xd3/0xde [ 1291.596242] Modules linked in: veth udp_tunnel gre openvswitch nf_conntrack_ipv6 nf_nat_ipv6 nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_defrag_ipv6 nf_nat nf_conntrack cfg80211 rfkill ext4 jbd2 mbcache sb_edac coretemp crct10dif_pclmul crc32_pclmul ghash_clmulni_intel pcbc aesni_intel crypto_simd glue_helper ppdev vmw_balloon cryptd vmw_vmci sg i2c_piix4 pcspkr parport_pc parport shpchp ip_tables xfs libcrc32c sd_mod ata_generic pata_acpi vmwgfx drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops ttm drm crc32c_intel serio_raw vmxnet3 ata_piix mptspi libata scsi_transport_spi mptscsih mptbase i2c_core floppy dm_mirror dm_region_hash dm_log dm_mod [ 1291.596280] CPU: 1 PID: 2203 Comm: iperf3 Tainted: G W 4.12.0+ #1 [ 1291.596280] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 09/21/2015 [ 1291.596281] task: ffff8be36f5e9680 task.stack: ffffb6c840d44000 [ 1291.596283] RIP: 0010:skb_warn_bad_offload+0xd3/0xde [ 1291.596284] RSP: 0018:ffff8be3796438c8 EFLAGS: 00010246 [ 1291.596285] RAX: 0000000000000074 RBX: ffff8be363ff9f00 RCX: 0000000000000006 [ 1291.596286] RDX: 0000000000000000 RSI: 0000000000000086 RDI: ffff8be37964e0a0 [ 1291.596287] RBP: ffff8be3796438f0 R08: 0000000000000000 R09: 0000000000000bf2 [ 1291.596287] R10: 0000000000000004 R11: 0000000000000bf1 R12: ffff8be3660f0000 [ 1291.596288] R13: 0000000000000001 R14: 0000000000000000 R15: ffff8be3660f0000 [ 1291.596289] FS: 00007f8d93bdb740(0000) GS:ffff8be379640000(0000) knlGS:0000000000000000 [ 1291.596290] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 1291.596291] CR2: 0000555f94a6e0c8 CR3: 000000012b84a000 CR4: 00000000001406e0 [ 1291.596296] Call Trace: [ 1291.596297] <IRQ> [ 1291.596300] __skb_gso_segment+0x15d/0x170 [ 1291.596301] validate_xmit_skb+0x12d/0x2b0 [ 1291.596303] validate_xmit_skb_list+0x42/0x70 [ 1291.596306] sch_direct_xmit+0xd0/0x1b0 [ 1291.596308] __dev_queue_xmit+0x42e/0x630 [ 1291.596310] ? hrtimer_interrupt+0xd2/0x1a0 [ 1291.596312] dev_queue_xmit+0x10/0x20 [ 1291.596315] ovs_vport_send+0xc2/0x150 [openvswitch] [ 1291.596318] do_output+0x53/0xf0 [openvswitch] [ 1291.596322] do_execute_actions+0x9bc/0x9d0 [openvswitch] [ 1291.596324] ? __bpf_prog_run+0x385/0x1310 [ 1291.596327] ovs_execute_actions+0x40/0x120 [openvswitch] [ 1291.596330] ovs_dp_process_packet+0x84/0x120 [openvswitch] [ 1291.596333] ? ovs_ct_update_key+0x9a/0xe0 [openvswitch] [ 1291.596336] ovs_vport_receive+0x73/0xd0 [openvswitch] [ 1291.596339] ? handle_irq_event_percpu+0x54/0x80 [ 1291.596340] ? handle_irq_event+0x46/0x60 [ 1291.596342] ? handle_edge_irq+0x8d/0x130 [ 1291.596344] ? handle_irq+0xab/0x120 [ 1291.596346] ? irq_exit+0x77/0xf0 [ 1291.596348] ? do_IRQ+0x51/0xd0 [ 1291.596352] netdev_frame_hook+0xd3/0x160 [openvswitch] [ 1291.596355] __netif_receive_skb_core+0x1da/0x9e0 [ 1291.596358] ? vport_netdev_free+0x30/0x30 [openvswitch] [ 1291.596360] ? kfree_skbmem+0x5a/0x60 [ 1291.596361] ? consume_skb+0x34/0x90 [ 1291.596363] __netif_receive_skb+0x18/0x60 [ 1291.596365] process_backlog+0x95/0x140 [ 1291.596367] net_rx_action+0x26c/0x3b0 [ 1291.596369] __do_softirq+0xc9/0x269 [ 1291.596371] do_softirq_own_stack+0x1c/0x30 [ 1291.596372] </IRQ> [ 1291.596374] do_softirq+0x50/0x60 [ 1291.596375] __local_bh_enable_ip+0x5a/0x70 [ 1291.596377] ip_finish_output2+0x15e/0x390 [ 1291.596380] ip_finish_output+0x136/0x1e0 [ 1291.596382] ip_output+0x76/0xe0 [ 1291.596384] ? ip_fragment.constprop.53+0x80/0x80 [ 1291.596386] ip_local_out+0x35/0x40 [ 1291.596387] ip_send_skb+0x19/0x40 [ 1291.596390] udp_send_skb+0x172/0x280 [ 1291.596391] udp_sendmsg+0x2cf/0xa60 [ 1291.596393] ? ip_reply_glue_bits+0x50/0x50 [ 1291.596396] ? sock_has_perm+0x75/0x90 [ 1291.596398] inet_sendmsg+0x31/0xb0 [ 1291.596399] sock_sendmsg+0x38/0x50 [ 1291.596401] sock_write_iter+0x85/0xf0 [ 1291.596403] __vfs_write+0xe3/0x160 [ 1291.596405] vfs_write+0xb2/0x1b0 [ 1291.596407] ? syscall_trace_enter+0x1d0/0x2b0 [ 1291.596408] SyS_write+0x55/0xc0 [ 1291.596411] do_syscall_64+0x67/0x150 [ 1291.596412] entry_SYSCALL64_slow_path+0x25/0x25 [ 1291.596413] RIP: 0033:0x7f8d931cdc60 [ 1291.596414] RSP: 002b:00007ffc0790e9c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 [ 1291.596415] RAX: ffffffffffffffda RBX: 0000000000002800 RCX: 00007f8d931cdc60 [ 1291.596417] RDX: 0000000000002800 RSI: 00007f8d93bc9000 RDI: 0000000000000012 [ 1291.596417] RBP: 00007f8d93bc9000 R08: 0000000000000000 R09: 000000000000003d [ 1291.596418] R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000000012 [ 1291.596419] R13: 0000000000002800 R14: 0000000000000001 R15: 00007ffc0790ea40 [ 1291.596420] Code: 8d 94 24 d0 00 00 00 48 0f 44 ce 4d 85 e4 44 89 54 24 08 48 0f 44 d6 89 3c 24 48 89 c6 48 c7 c7 80 65 ac 8f 31 c0 e8 a7 bd a5 ff <0f> ff 48 83 c4 18 5b 41 5c 5d c3 55 48 89 f2 31 c0 89 fe 48 c7 [ 1291.596447] ---[ end trace b66534f41f98ceda ]--- On Tue, Aug 8, 2017 at 7:44 AM, Tonghao Zhang <xiangxia.m.yue@gmail.com> wrote: > That is fine to me. I have tested it. Thanks. > > On Mon, Aug 7, 2017 at 12:42 PM, Willem de Bruijn > <willemdebruijn.kernel@gmail.com> wrote: >>> The openvswitch kernel module calls the __skb_gso_segment()(and sets >>> tx_path = false) when passing packets to userspace. The UFO will set >>> the ip_summed to CHECKSUM_NONE. There are a lot of warn logs. The warn >>> log is shown as below. I guess we should revert the patch. >> >> Indeed, the software UFO code computes the checksum and >> sets ip_summed to CHECKSUM_NONE, as is correct on the >> egress path. >> >> Commit 6e7bc478c9a0 ("net: skb_needs_check() accepts >> CHECKSUM_NONE for tx") revised the tx_path case in >> skb_needs_check to avoid the warning exactly for the UFO case. >> >> We cannot just make an exception for CHECKSUM_NONE in the >> !tx_path case, as the entire statement then becomes false: >> >> return skb->ip_summed == CHECKSUM_NONE; >> >> Since on egress CHECKSUM_UNNECESSARY is equivalent to >> CHECKSUM_NONE, it should be fine to update the UFO code >> to set that, instead: >> >> @@ -235,7 +235,7 @@ static struct sk_buff *udp4_ufo_fragment(struct >> sk_buff *skb, >> if (uh->check == 0) >> uh->check = CSUM_MANGLED_0; >> >> - skb->ip_summed = CHECKSUM_NONE; >> + skb->ip_summed = CHECKSUM_UNNECESSARY;