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().
>
>> 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
