tun: Fix csum_start with VLAN acceleration

When VLAN acceleration is in use on the xmit path, we end up
setting csum_start to the wrong place.  The result is that the
whoever ends up doing the checksum setting will corrupt the packet
instead of writing the checksum to the expected location, usually
this means writing the checksum with an offset of -4.

This patch fixes this by adjusting csum_start when VLAN acceleration
is detected.

Fixes: 6680ec68eff4 ("tuntap: hardware vlan tx support")
Cc: stable@vger.kernel.org
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 7302398f0b1fff89ffe4a4e373e936c928180645..57e6bf75a6325a154cd852573de1b916a6cc29d8 100644 (file)
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1235,6 +1235,10 @@ static ssize_t tun_put_user(struct tun_struct *tun,
        struct tun_pi pi = { 0, skb->protocol };
        ssize_t total = 0;
        int vlan_offset = 0, copied;
+       int vlan_hlen = 0;
+
+       if (vlan_tx_tag_present(skb))
+               vlan_hlen = VLAN_HLEN;
 
        if (!(tun->flags & TUN_NO_PI)) {
                if ((len -= sizeof(pi)) < 0)
@@ -1284,7 +1288,8 @@ static ssize_t tun_put_user(struct tun_struct *tun,
 
                if (skb->ip_summed == CHECKSUM_PARTIAL) {
                        gso.flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
-                       gso.csum_start = skb_checksum_start_offset(skb);
+                       gso.csum_start = skb_checksum_start_offset(skb) +
+                                        vlan_hlen;
                        gso.csum_offset = skb->csum_offset;
                } else if (skb->ip_summed == CHECKSUM_UNNECESSARY) {
                        gso.flags = VIRTIO_NET_HDR_F_DATA_VALID;
@@ -1297,10 +1302,9 @@ static ssize_t tun_put_user(struct tun_struct *tun,
        }
 
        copied = total;
-       total += skb->len;
-       if (!vlan_tx_tag_present(skb)) {
-               len = min_t(int, skb->len, len);
-       } else {
+       len = min_t(int, skb->len + vlan_hlen, len);
+       total += skb->len + vlan_hlen;
+       if (vlan_hlen) {
                int copy, ret;
                struct {
                        __be16 h_vlan_proto;
@@ -1311,8 +1315,6 @@ static ssize_t tun_put_user(struct tun_struct *tun,
                veth.h_vlan_TCI = htons(vlan_tx_tag_get(skb));
 
                vlan_offset = offsetof(struct vlan_ethhdr, h_vlan_proto);
-               len = min_t(int, skb->len + VLAN_HLEN, len);
-               total += VLAN_HLEN;
 
                copy = min_t(int, vlan_offset, len);
                ret = skb_copy_datagram_const_iovec(skb, 0, iv, copied, copy);