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: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 12 insertions, 0 deletions

diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index aa28550fc9b6..fc8faa74b250 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -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++;