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Commit f9ca8f74 authored by Jason Wang's avatar Jason Wang Committed by David S. Miller
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netback: set transport header before passing it to kernel 



Currently, for the packets receives from netback, before doing header check,
kernel just reset the transport header in netif_receive_skb() which pretends non
l4 header. This is suboptimal for precise packet length estimation (introduced
in 1def9238: net_sched: more precise pkt_len computation) which needs correct l4
header for gso packets.

The patch just reuse the header probed by netback for partial checksum packets
and tries to use skb_flow_dissect() for other cases, if both fail, just pretend
no l4 header.

Cc: Eric Dumazet <edumazet@google.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: default avatarJason Wang <jasowang@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent c1aad275

drivers/net/xen-netback/netback.c

+12 −0
Original line number Diff line number Diff line
@@ -39,6 +39,7 @@ 
#include <linux/udp.h>



#include <net/tcp.h>

#include <net/flow_keys.h>



#include <xen/xen.h>

#include <xen/events.h>
@@ -1184,6 +1185,7 @@ static int checksum_setup(struct xenvif *vif, struct sk_buff *skb) 
	if (th >= skb_tail_pointer(skb))

		goto out;



	skb_set_transport_header(skb, 4 * iph->ihl);

	skb->csum_start = th - skb->head;

	switch (iph->protocol) {

	case IPPROTO_TCP:
@@ -1495,6 +1497,7 @@ static void xen_netbk_tx_submit(struct xen_netbk *netbk) 


		skb->dev      = vif->dev;

		skb->protocol = eth_type_trans(skb, skb->dev);

		skb_reset_network_header(skb);



		if (checksum_setup(vif, skb)) {

			netdev_dbg(vif->dev,
@@ -1503,6 +1506,15 @@ static void xen_netbk_tx_submit(struct xen_netbk *netbk) 
			continue;

		}



		if (!skb_transport_header_was_set(skb)) {

			struct flow_keys keys;



			if (skb_flow_dissect(skb, &keys))

				skb_set_transport_header(skb, keys.thoff);

			else

				skb_reset_transport_header(skb);

		}



		vif->dev->stats.rx_bytes += skb->len;

		vif->dev->stats.rx_packets++;