netdev - [PATCH v2] AF_PACKET doesnt strip VLAN information

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Message-Id: <20200718091732.8761-1-srirakr2@cisco.com>
Date:   Sat, 18 Jul 2020 14:47:31 +0530
From:   Sriram Krishnan <srirakr2@...co.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     xe-linux-external@...co.com,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2] AF_PACKET doesnt strip VLAN information

When an application sends with AF_PACKET and places a vlan header on
the raw packet; then the AF_PACKET needs to move the tag into the skb
so that it gets processed normally through the rest of the transmit
path.

This is particularly a problem on Hyper-V where the host only allows
vlan in the offload info.

Cc: xe-linux-external@...co.com
Cc: Sriram Krishnan <srirakr2@...co.com>
Signed-off-by: Sriram Krishnan <srirakr2@...co.com>
---
 net/packet/af_packet.c | 26 ++++++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 29bd405adbbd..10988639561e 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1857,15 +1857,35 @@ 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)
+static int packet_parse_headers(struct sk_buff *skb, struct socket *sock)
 {
 	if ((!skb->protocol || skb->protocol == htons(ETH_P_ALL)) &&
 	    sock->type == SOCK_RAW) {
+		__be16 ethertype;
+
 		skb_reset_mac_header(skb);
+
+		ethertype = eth_hdr(skb)->h_proto;
+		/*
+		 * If Vlan tag is present in the packet
+		 *  move it to skb
+		*/
+		if (eth_type_vlan(ethertype)) {
+			int err;
+			__be16 vlan_tci;
+
+			err = __skb_vlan_pop(skb, &vlan_tci);
+			if (unlikely(err))
+				return err;
+
+			__vlan_hwaccel_put_tag(skb, ethertype, vlan_tci);
+		}
+
 		skb->protocol = dev_parse_header_protocol(skb);
 	}
 
 	skb_probe_transport_header(skb);
+	return 0;
 }
 
 /*
@@ -1987,7 +2007,9 @@ static int packet_sendmsg_spkt(struct socket *sock, struct msghdr *msg,
 	if (unlikely(extra_len == 4))
 		skb->no_fcs = 1;
 
-	packet_parse_headers(skb, sock);
+	err = packet_parse_headers(skb, sock);
+	if (err)
+		goto out_unlock;
 
 	dev_queue_xmit(skb);
 	rcu_read_unlock();
-- 
2.24.0