tuntap: set transport header before passing it to kernel

[ Upstream commit 38502af77e07b5d6650b9ff99a0b482d86366592 ]

Currently, for the packets receives from tuntap, before doing header check,
kernel just reset the transport header in netif_receive_skb() which pretends no
l4 header. This is suboptimal for precise packet length estimation (introduced
in 1def9238) which needs correct l4 header for gso packets.

So this patch set the transport header to csum_start for partial checksum
packets, otherwise it first try skb_flow_dissect(), if it fails, just reset the
transport header.

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

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 7d3e73340dd549122a7e31b853ccd4bfcf03b42c..8ad822e855ee55ae451dde8d0a1b6e2e9efdd3c4 100644 (file)
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -70,6 +70,7 @@
 #include <net/sock.h>
 
 #include <asm/uaccess.h>
+#include <net/flow_keys.h>
 
 /* Uncomment to enable debugging */
 /* #define TUN_DEBUG 1 */
@@ -1051,6 +1052,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
        bool zerocopy = false;
        int err;
        u32 rxhash;
+       struct flow_keys keys;
 
        if (!(tun->flags & TUN_NO_PI)) {
                if ((len -= sizeof(pi)) > total_len)
@@ -1205,6 +1207,14 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
        }
 
        skb_reset_network_header(skb);
+
+       if (skb->ip_summed == CHECKSUM_PARTIAL)
+               skb_set_transport_header(skb, skb_checksum_start_offset(skb));
+       else if (skb_flow_dissect(skb, &keys))
+               skb_set_transport_header(skb, keys.thoff);
+       else
+               skb_reset_transport_header(skb);
+
        rxhash = skb_get_rxhash(skb);
        netif_rx_ni(skb);