netback: set transport header before passing it to kernel

[ Upstream commit f9ca8f74399f9195fd8e01f67a8424a8d33efa55 ]

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.

Signed-off-by: Jason Wang <jasowang@redhat.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index 8099e9d3edda278453ac010e973653c50261ed1f..401e4140ab972c9eecc33334821c3086e82b33b2 100644 (file)
--- 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>
@@ -1352,6 +1353,7 @@ 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:
@@ -1665,6 +1667,7 @@ 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,
@@ -1673,6 +1676,15 @@ 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++;