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>

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 */
 	case MLX5_INLINE_MODE_L2:
 	default:
 		hlen = mlx5e_skb_l2_header_offset(skb);

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);

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 @@ static int tun_xdp_one(struct tun_struct *tun,
 
 	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);

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);
 

include/linux/etherdevice.h

@@ -44,6 +44,7 @@ int eth_header_cache(const struct neighbour *neigh, struct hh_cache *hh,
 		     __be16 type);
 void eth_header_cache_update(struct hh_cache *hh, const struct net_device *dev,
 			     const unsigned char *haddr);
+__be16 eth_header_parse_protocol(const struct sk_buff *skb);
 int eth_prepare_mac_addr_change(struct net_device *dev, void *p);
 void eth_commit_mac_addr_change(struct net_device *dev, void *p);
 int eth_mac_addr(struct net_device *dev, void *p);

include/linux/netdevice.h

@@ -274,6 +274,7 @@ struct header_ops {
 				const struct net_device *dev,
 				const unsigned char *haddr);
 	bool	(*validate)(const char *ll_header, unsigned int len);
+	__be16	(*parse_protocol)(const struct sk_buff *skb);
 };
 
 /* These flag bits are private to the generic network queueing
@@ -2939,6 +2940,15 @@ static inline int dev_parse_header(const struct sk_buff *skb,
 	return dev->header_ops->parse(skb, haddr);
 }
 
+static inline __be16 dev_parse_header_protocol(const struct sk_buff *skb)
+{
+	const struct net_device *dev = skb->dev;
+
+	if (!dev->header_ops || !dev->header_ops->parse_protocol)
+		return 0;
+	return dev->header_ops->parse_protocol(skb);
+}
+
 /* ll_header must have at least hard_header_len allocated */
 static inline bool dev_validate_header(const struct net_device *dev,
 				       char *ll_header, int len)

include/linux/skbuff.h

@@ -2429,8 +2429,7 @@ static inline void skb_pop_mac_header(struct sk_buff *skb)
 	skb->mac_header = skb->network_header;
 }
 
-static inline void skb_probe_transport_header(struct sk_buff *skb,
-					      const int offset_hint)
+static inline void skb_probe_transport_header(struct sk_buff *skb)
 {
 	struct flow_keys_basic keys;
 
@@ -2439,8 +2438,6 @@ static inline void skb_probe_transport_header(struct sk_buff *skb,
 
 	if (skb_flow_dissect_flow_keys_basic(skb, &keys, NULL, 0, 0, 0, 0))
 		skb_set_transport_header(skb, keys.control.thoff);
-	else if (offset_hint >= 0)
-		skb_set_transport_header(skb, offset_hint);
 }
 
 static inline void skb_mac_header_rebuild(struct sk_buff *skb)

include/linux/virtio_net.h

@@ -62,7 +62,7 @@ static inline int virtio_net_hdr_to_skb(struct sk_buff *skb,
 		 * probe and drop if does not match one of the above types.
 		 */
 		if (gso_type) {
-			skb_probe_transport_header(skb, -1);
+			skb_probe_transport_header(skb);
 			if (!skb_transport_header_was_set(skb))
 				return -EINVAL;
 		}

net/ethernet/eth.c

@@ -264,6 +264,18 @@ void eth_header_cache_update(struct hh_cache *hh,
 }
 EXPORT_SYMBOL(eth_header_cache_update);
 
+/**
+ * eth_header_parser_protocol - extract protocol from L2 header
+ * @skb: packet to extract protocol from
+ */
+__be16 eth_header_parse_protocol(const struct sk_buff *skb)
+{
+	const struct ethhdr *eth = eth_hdr(skb);
+
+	return eth->h_proto;
+}
+EXPORT_SYMBOL(eth_header_parse_protocol);
+
 /**
  * eth_prepare_mac_addr_change - prepare for mac change
  * @dev: network device
@@ -346,6 +358,7 @@ const struct header_ops eth_header_ops ____cacheline_aligned = {
 	.parse		= eth_header_parse,
 	.cache		= eth_header_cache,
 	.cache_update	= eth_header_cache_update,
+	.parse_protocol	= eth_header_parse_protocol,
 };
 
 /**

net/packet/af_packet.c

@@ -1850,6 +1850,15 @@ static int packet_rcv_spkt(struct sk_buff *skb, struct net_device *dev,
 	return 0;
 }
 
+static void packet_parse_headers(struct sk_buff *skb, struct socket *sock)
+{
+	if (!skb->protocol && sock->type == SOCK_RAW) {
+		skb_reset_mac_header(skb);
+		skb->protocol = dev_parse_header_protocol(skb);
+	}
+
+	skb_probe_transport_header(skb);
+}
 
 /*
  *	Output a raw packet to a device layer. This bypasses all the other
@@ -1970,7 +1979,7 @@ static int packet_sendmsg_spkt(struct socket *sock, struct msghdr *msg,
 	if (unlikely(extra_len == 4))
 		skb->no_fcs = 1;
 
-	skb_probe_transport_header(skb, 0);
+	packet_parse_headers(skb, sock);
 
 	dev_queue_xmit(skb);
 	rcu_read_unlock();
@@ -2404,15 +2413,6 @@ static void tpacket_destruct_skb(struct sk_buff *skb)
 	sock_wfree(skb);
 }
 
-static void tpacket_set_protocol(const struct net_device *dev,
-				 struct sk_buff *skb)
-{
-	if (dev->type == ARPHRD_ETHER) {
-		skb_reset_mac_header(skb);
-		skb->protocol = eth_hdr(skb)->h_proto;
-	}
-}
-
 static int __packet_snd_vnet_parse(struct virtio_net_hdr *vnet_hdr, size_t len)
 {
 	if ((vnet_hdr->flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) &&
@@ -2483,8 +2483,6 @@ static int tpacket_fill_skb(struct packet_sock *po, struct sk_buff *skb,
 			return err;
 		if (!dev_validate_header(dev, skb->data, hdrlen))
 			return -EINVAL;
-		if (!skb->protocol)
-			tpacket_set_protocol(dev, skb);
 
 		data += hdrlen;
 		to_write -= hdrlen;
@@ -2519,7 +2517,7 @@ static int tpacket_fill_skb(struct packet_sock *po, struct sk_buff *skb,
 		len = ((to_write > len_max) ? len_max : to_write);
 	}
 
-	skb_probe_transport_header(skb, 0);
+	packet_parse_headers(skb, sock);
 
 	return tp_len;
 }
@@ -2925,7 +2923,7 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len)
 		virtio_net_hdr_set_proto(skb, &vnet_hdr);
 	}
 
-	skb_probe_transport_header(skb, reserve);
+	packet_parse_headers(skb, sock);
 
 	if (unlikely(extra_len == 4))
 		skb->no_fcs = 1;