On Mon, Jun 27, 2016 at 2:44 PM, Cong Wang <xiyou.wangc...@gmail.com> wrote: > On Mon, Jun 27, 2016 at 2:08 PM, Or Gerlitz <gerlitz...@gmail.com> wrote: >> On Mon, Jun 27, 2016 at 9:22 PM, Cong Wang <xiyou.wangc...@gmail.com> wrote: >>> The stack doesn't trust the complete csum by hardware >>> even when it is correct. >> >> Can you explain that a little further? > > Sure, here is the code in __skb_checksum_complete(): > > /* skb->csum holds pseudo checksum */ > sum = csum_fold(csum_add(skb->csum, csum)); > if (likely(!sum)) { > if (unlikely(skb->ip_summed == CHECKSUM_COMPLETE) && > !skb->csum_complete_sw) > netdev_rx_csum_fault(skb->dev); > } > > So when sum == 0, it means the checksum is correct. And > we already set ->ip_summed to CHECKSUM_COMPLETE > after check_csum(), and ->csum_complete_sw is initialized > to 0 when we allocate the skb. This is why we trigger > netdev_rx_csum_fault(). > Yes, but this also means that the driver gave the stack a checksum complete value that was incorrect. That's an error.
Tom > >> >>> In the case we fix csum by ourself >>> probably it is safe to just mark it as completed by software. >> >>> This should shut up a kernel warning from netdev_rx_csum_fault() >>> with mlx4 driver for ICMP packets. >> >> can you point/paste the exact warning and how to reproduce that? is >> that as simple as running ping and/or ping6? > > Yes, ping is enough to reproduce it every time. > > The warning is below: > > [ 8693.680997] eth0: hw csum failure > [ 8693.681003] CPU: 5 PID: 34 Comm: ksoftirqd/5 Not tainted 4.1.20-t6.el5 #1 > [ 8693.681005] Hardware name: SYNNEX HYVE-ZEUS/X9DRD-iF, BIOS 3.0.4 12/06/2013 > [ 8693.681008] 0000000000000000 ffff88085c15fae8 ffffffff81502872 > ffff881051397800 > [ 8693.681011] ffff881054c08b01 ffff88085c15fb08 ffffffff814569c5 > 0000000000000000 > [ 8693.681014] ffff8808572d7200 ffff88085c15fb38 ffffffff81450738 > ffff8808572d7200 > [ 8693.681017] Call Trace: > [ 8693.681025] [<ffffffff81502872>] dump_stack+0x4d/0x63 > [ 8693.681030] [<ffffffff814569c5>] netdev_rx_csum_fault+0x38/0x3c > [ 8693.681033] [<ffffffff81450738>] __skb_checksum_complete+0x6e/0xb6 > [ 8693.681036] [<ffffffff814b65d8>] icmp_rcv+0x17a/0x32f > [ 8693.681040] [<ffffffff8148b7f0>] ip_local_deliver_finish+0xd1/0x153 > [ 8693.681042] [<ffffffff8148b9f7>] ip_local_deliver+0x8d/0x94 > [ 8693.681045] [<ffffffff8148b71f>] ? > xfrm4_policy_check.constprop.6+0x55/0x55 > [ 8693.681048] [<ffffffff8148b651>] ip_rcv_finish+0x289/0x2cc > [ 8693.681050] [<ffffffff8148bc7b>] ip_rcv+0x27d/0x30a > [ 8693.681053] [<ffffffff81457e01>] __netif_receive_skb_core+0x3f2/0x483 > [ 8693.681056] [<ffffffff81457eaa>] __netif_receive_skb+0x18/0x5a > [ 8693.681058] [<ffffffff81457f7c>] process_backlog+0x90/0x10c > [ 8693.681061] [<ffffffff814596e0>] net_rx_action+0x101/0x2aa > [ 8693.681066] [<ffffffff8106c39f>] __do_softirq+0x10c/0x26d > [ 8693.681068] [<ffffffff8106c51a>] run_ksoftirqd+0x1a/0x2f > [ 8693.681071] [<ffffffff81083675>] smpboot_thread_fn+0x149/0x167 > [ 8693.681074] [<ffffffff8108352c>] ? sort_range+0x24/0x24 > [ 8693.681076] [<ffffffff8108352c>] ? sort_range+0x24/0x24 > [ 8693.681080] [<ffffffff81080d9c>] kthread+0xae/0xb6 > [ 8693.681082] [<ffffffff81080303>] ? add_sysfs_param.isra.4+0xe1/0x18c > [ 8693.681085] [<ffffffff81080cee>] ? __kthread_parkme+0x61/0x61 > [ 8693.681088] [<ffffffff81508152>] ret_from_fork+0x42/0x70 > [ 8693.681090] [<ffffffff81080cee>] ? __kthread_parkme+0x61/0x61