Thread (3 messages) 3 messages, 2 authors, 2015-05-12

Re: [PATCH] xen-netfront: reset skb transport header before checksum

From: Eric Dumazet <hidden>
Date: 2015-05-12 01:51:35

On Mon, 2015-05-11 at 18:34 -0700, Venkat Venkatsubra wrote:
quoted hunk ↗ jump to hunk
In ed1f50c3a ("net: add skb_checksum_setup") some checksum functions
were introduced in core. Subsequent change b5cf66cd1 ("xen-netfront:
use new skb_checksum_setup function") made use of those functions to
replace its own implementation. With that change ip_hdr() and tcp_hdr()
were not pointing at the right place. d554f73df ("xen-netfront: reset
skb network header before checksum") fixed the ip_hdr().

This patch fixes tcp_hdr().

We saw this problem when LRO was enabled on the host and it results in
netfront setting skb->ip_summed to CHECKSUM_UNNECESSARY.

Signed-off-by: Venkat Venkatsubra <redacted>
---
 drivers/net/xen-netfront.c | 1 +
 1 file changed, 1 insertion(+)
diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index 3f45afd..ed5c242 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -889,6 +889,7 @@ static int handle_incoming_queue(struct netfront_queue *queue,
 		/* Ethernet work: Delayed to here as it peeks the header. */
 		skb->protocol = eth_type_trans(skb, queue->info->netdev);
 		skb_reset_network_header(skb);
+		skb_set_transport_header(skb, ip_hdrlen(skb));
 
 		if (checksum_setup(queue->info->netdev, skb)) {
 			kfree_skb(skb);
This looks bogus for IPv6.

I would rather fix skb_checksum_setup_ip() and
skb_checksum_setup_ipv6(), since you already use correctly
skb_maybe_pull_tail() there.

In general, setting network and transport header at this point seems
extra work.
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