Merge branch 'AF_PACKET-transport_offset-fix'

Maxim Mikityanskiy says:

====================
AF_PACKET transport_offset fix

This patch series contains the implementation of the RFC that was posted
on this mailing list previously:
https://www.spinics.net/lists/netdev/msg541709.html

It fixes having incorrect skb->transport_header values in cases when
dissect fails. Having correct values set by the kernel fixes mlx5
operation and allows to remove some unnecessary code flows in mlx5.

v2 changes:

- Rebase against the fresh net-next.
- Don't return bool from skb_probe_transport_header (and don't rename
  the function).
- WARN_ON_ONCE and error path in case of GSO without the L4 header.
====================

Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 18 insertions, 20 deletions

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c b/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c
index c1334a8ac8f3..e7aae45a01f8 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c
@@ -148,12 +148,8 @@ static inline int mlx5e_skb_l2_header_offset(struct sk_buff *skb)
 
 static inline int mlx5e_skb_l3_header_offset(struct sk_buff *skb)
 {
-	struct flow_keys keys;
-
 	if (skb_transport_header_was_set(skb))
 		return skb_transport_offset(skb);
-	else if (skb_flow_dissect_flow_keys(skb, &keys, 0))
-		return keys.control.thoff;
 	else
 		return mlx5e_skb_l2_header_offset(skb);
 }
@@ -172,15 +168,8 @@ static inline u16 mlx5e_calc_min_inline(enum mlx5_inline_modes mode,
 			hlen += VLAN_HLEN;
 		break;
 	case MLX5_INLINE_MODE_IP:
-		/* When transport header is set to zero, it means no transport
-		 * header. When transport header is set to 0xff's, it means
-		 * transport header wasn't set.
-		 */
-		if (skb_transport_offset(skb)) {
-			hlen = mlx5e_skb_l3_header_offset(skb);
-			break;
-		}
-		/* fall through */
+		hlen = mlx5e_skb_l3_header_offset(skb);
+		break;
 	case MLX5_INLINE_MODE_L2:
 	default:
 		hlen = mlx5e_skb_l2_header_offset(skb);
diff --git a/drivers/net/tap.c b/drivers/net/tap.c
index c0b52e48f0e6..2ea9b4976f4a 100644
--- a/drivers/net/tap.c
+++ b/drivers/net/tap.c
@@ -712,7 +712,7 @@ static ssize_t tap_get_user(struct tap_queue *q, void *msg_control,
 			goto err_kfree;
 	}
 
-	skb_probe_transport_header(skb, ETH_HLEN);
+	skb_probe_transport_header(skb);
 
 	/* Move network header to the right position for VLAN tagged packets */
 	if ((skb->protocol == htons(ETH_P_8021Q) ||
@@ -1187,7 +1187,7 @@ static int tap_get_user_xdp(struct tap_queue *q, struct xdp_buff *xdp)
 	tap = rcu_dereference(q->tap);
 	if (tap) {
 		skb->dev = tap->dev;
-		skb_probe_transport_header(skb, ETH_HLEN);
+		skb_probe_transport_header(skb);
 		dev_queue_xmit(skb);
 	} else {
 		kfree_skb(skb);
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index fed298c0cb39..80bff1b4ec17 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1929,7 +1929,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
 	}
 
 	skb_reset_network_header(skb);
-	skb_probe_transport_header(skb, 0);
+	skb_probe_transport_header(skb);
 
 	if (skb_xdp) {
 		struct bpf_prog *xdp_prog;
@@ -2482,7 +2482,7 @@ build:
 
 	skb->protocol = eth_type_trans(skb, tun->dev);
 	skb_reset_network_header(skb);
-	skb_probe_transport_header(skb, 0);
+	skb_probe_transport_header(skb);
 
 	if (skb_xdp) {
 		err = do_xdp_generic(xdp_prog, skb);
diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index 80aae3a32c2a..c801a832851c 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -1169,15 +1169,24 @@ static int xenvif_tx_submit(struct xenvif_queue *queue)
 			continue;
 		}
 
-		skb_probe_transport_header(skb, 0);
+		skb_probe_transport_header(skb);
 
 		/* If the packet is GSO then we will have just set up the
 		 * transport header offset in checksum_setup so it's now
 		 * straightforward to calculate gso_segs.
 		 */
 		if (skb_is_gso(skb)) {
-			int mss = skb_shinfo(skb)->gso_size;
-			int hdrlen = skb_transport_header(skb) -
+			int mss, hdrlen;
+
+			/* GSO implies having the L4 header. */
+			WARN_ON_ONCE(!skb_transport_header_was_set(skb));
+			if (unlikely(!skb_transport_header_was_set(skb))) {
+				kfree_skb(skb);
+				continue;
+			}
+
+			mss = skb_shinfo(skb)->gso_size;
+			hdrlen = skb_transport_header(skb) -
 				skb_mac_header(skb) +
 				tcp_hdrlen(skb);