Merge branch 'tun-net'

Herbert Xu says:

====================
tun: Fix csum_start and TUN_PKT_STRIP

The first patch fixes a serious problem that breaks checksum offload
in VMs while the second patch fixes a problem that probably affects
no one.
====================
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/tun.c

@@ -1235,12 +1235,20 @@ 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;
+	int vnet_hdr_sz = 0;
+
+	if (vlan_tx_tag_present(skb))
+		vlan_hlen = VLAN_HLEN;
+
+	if (tun->flags & TUN_VNET_HDR)
+		vnet_hdr_sz = tun->vnet_hdr_sz;
 
 	if (!(tun->flags & TUN_NO_PI)) {
 		if ((len -= sizeof(pi)) < 0)
 			return -EINVAL;
 
-		if (len < skb->len) {
+		if (len < skb->len + vlan_hlen + vnet_hdr_sz) {
 			/* Packet will be striped */
 			pi.flags |= TUN_PKT_STRIP;
 		}
@@ -1250,9 +1258,9 @@ static ssize_t tun_put_user(struct tun_struct *tun,
 		total += sizeof(pi);
 	}
 
-	if (tun->flags & TUN_VNET_HDR) {
+	if (vnet_hdr_sz) {
 		struct virtio_net_hdr gso = { 0 }; /* no info leak */
-		if ((len -= tun->vnet_hdr_sz) < 0)
+		if ((len -= vnet_hdr_sz) < 0)
 			return -EINVAL;
 
 		if (skb_is_gso(skb)) {
@@ -1284,7 +1292,8 @@ 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;
@@ -1293,14 +1302,13 @@ static ssize_t tun_put_user(struct tun_struct *tun,
 		if (unlikely(memcpy_toiovecend(iv, (void *)&gso, total,
 					       sizeof(gso))))
 			return -EFAULT;
-		total += tun->vnet_hdr_sz;
+		total += vnet_hdr_sz;
 	}
 
 	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 +1319,6 @@ 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);