ifb: fix packets checksum

Fixup the checksum for CHECKSUM_COMPLETE when pulling skbs on RX path. Otherwise we get splats when tc mirred is used to redirect packets to ifb.

Before fix:

nic: hw csum failure

---
 drivers/net/ifb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index 5f2897ec0edc..d345c61d476c 100644
@@ -102,7 +102,7 @@ static void ifb_ri_tasklet(unsigned long _txp)
 		if (!skb->tc_from_ingress) {
 			dev_queue_xmit(skb);
 		} else {
-			skb_pull(skb, skb->mac_len);
+			skb_pull_rcsum(skb, skb->mac_len);
 			netif_receive_skb(skb);
 		}
 	}

2.13.6

From: Jon Maxwell <[email protected]>
Date: Fri, 25 May 2018 07:38:29 +1000

This definitely seems correct, but I am really surprised a bug like this has lasted as long as it has.

So I'll let this sit for another day or two for review.

Sorry for the late reply I have been away for a few days. The customer never saw this on bnx2x. Then they switched to the mlx5 driver and it started happening continuously when doing iperf3 tests and also for other TCP traffic.

mlx5 uses CHECKSUM_COMPLETE. I think that bnx2x uses CHECKSUM UNNECESSARY which avoided the code path that triggers the csum failure message in __skb_checksum_complete(). It only logs the message for CHECKSUM_COMPLETE skbs. Probably few Linux users are using a combination of NIC drivers that use CHECKSUM_COMPLETE, tc mirred and ifb, which is why this has never been reported before.

This is very similar to commit 7be709af2b65.

From: Jon Maxwell <[email protected]>
Date: Fri, 25 May 2018 07:38:29 +1000

Applied.