netdev - [PATCH 4/7] net/packet: Ask driver for protocol if not provided by user

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Date:   Mon, 14 Jan 2019 13:19:02 +0000
From:   Maxim Mikityanskiy <maximmi@...lanox.com>
To:     "David S. Miller" <davem@...emloft.net>,
        Saeed Mahameed <saeedm@...lanox.com>,
        Willem de Bruijn <willemb@...gle.com>,
        Jason Wang <jasowang@...hat.com>,
        Eric Dumazet <edumazet@...gle.com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Eran Ben Elisha <eranbe@...lanox.com>,
        Tariq Toukan <tariqt@...lanox.com>,
        Maxim Mikityanskiy <maximmi@...lanox.com>
Subject: [PATCH 4/7] net/packet: Ask driver for protocol if not provided by
 user

If a socket was created with socket(AF_PACKET, SOCK_RAW, 0), the
protocol number is unavailable. Try to ask the driver to extract it from
the L2 header in order for skb_try_probe_transport_header to succeed.

Signed-off-by: Maxim Mikityanskiy <maximmi@...lanox.com>
---
 net/packet/af_packet.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 8fc76e68777a..d1d89749a17a 100644
--- a/net/packet/af_packet.c
+++ b/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_try_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_try_probe_transport_header(skb);
+	packet_parse_headers(skb, sock);
 
 	dev_queue_xmit(skb);
 	rcu_read_unlock();
@@ -2519,7 +2528,7 @@ static int tpacket_fill_skb(struct packet_sock *po, struct sk_buff *skb,
 		len = ((to_write > len_max) ? len_max : to_write);
 	}
 
-	skb_try_probe_transport_header(skb);
+	packet_parse_headers(skb, sock);
 
 	return tp_len;
 }
@@ -2924,7 +2933,7 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len)
 		virtio_net_hdr_set_proto(skb, &vnet_hdr);
 	}
 
-	skb_try_probe_transport_header(skb);
+	packet_parse_headers(skb, sock);
 
 	if (unlikely(extra_len == 4))
 		skb->no_fcs = 1;
-- 
2.19.1