netdev - [PATCH net 1/2] net/af_packet: adjust network header position for VLAN tagged packets

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Date:   Mon, 18 Apr 2022 12:43:38 +0800
From:   Hangbin Liu <liuhangbin@...il.com>
To:     netdev@...r.kernel.org
Cc:     "Michael S . Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Maxim Mikityanskiy <maximmi@...lanox.com>,
        Willem de Bruijn <willemb@...gle.com>,
        virtualization@...ts.linux-foundation.org,
        Balazs Nemeth <bnemeth@...hat.com>,
        Mike Pattrick <mailmpattric@...hat.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Hangbin Liu <liuhangbin@...il.com>,
        Flavio Leitner <fbl@...hat.com>
Subject: [PATCH net 1/2] net/af_packet: adjust network header position for VLAN tagged packets

Flavio reported that the kernel drops GSO VLAN tagged packet if it's
created with socket(AF_PACKET, SOCK_RAW, 0) plus virtio_net_hdr.

The reason is AF_PACKET doesn't adjust the skb network header if there is
a VLAN tag. Then after virtio_net_hdr_set_proto() called, the skb->protocol
will be set to ETH_P_IP/IPv6. And in later inet/ipv6_gso_segment() the skb
is dropped as network header position is invalid.

Fix it by adjusting network header position in packet_parse_headers()
and move the function before calling virtio_net_hdr_* functions.

I also moved skb->no_fcs setting upper to make all skb setting together
and keep consistence of function packet_sendmsg_spkt().

No need to update tpacket_snd() as it calls packet_parse_headers() in
tpacket_fill_skb() before calling virtio_net_hdr_* functions.

Fixes: 75c65772c3d1 ("net/packet: Ask driver for protocol if not provided by user")
Reported-by: Flavio Leitner <fbl@...hat.com>
Signed-off-by: Hangbin Liu <liuhangbin@...il.com>
---
 net/packet/af_packet.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 002d2b9c69dd..cfdbda28ef82 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1924,12 +1924,20 @@ static int packet_rcv_spkt(struct sk_buff *skb, struct net_device *dev,
 
 static void packet_parse_headers(struct sk_buff *skb, struct socket *sock)
 {
+	int depth;
+
 	if ((!skb->protocol || skb->protocol == htons(ETH_P_ALL)) &&
 	    sock->type == SOCK_RAW) {
 		skb_reset_mac_header(skb);
 		skb->protocol = dev_parse_header_protocol(skb);
 	}
 
+	/* Move network header to the right position for VLAN tagged packets */
+	if (likely(skb->dev->type == ARPHRD_ETHER) &&
+	    eth_type_vlan(skb->protocol) &&
+	    __vlan_get_protocol(skb, skb->protocol, &depth) != 0)
+		skb_set_network_header(skb, depth);
+
 	skb_probe_transport_header(skb);
 }
 
@@ -3047,6 +3055,11 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len)
 	skb->mark = sockc.mark;
 	skb->tstamp = sockc.transmit_time;
 
+	if (unlikely(extra_len == 4))
+		skb->no_fcs = 1;
+
+	packet_parse_headers(skb, sock);
+
 	if (has_vnet_hdr) {
 		err = virtio_net_hdr_to_skb(skb, &vnet_hdr, vio_le());
 		if (err)
@@ -3055,11 +3068,6 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len)
 		virtio_net_hdr_set_proto(skb, &vnet_hdr);
 	}
 
-	packet_parse_headers(skb, sock);
-
-	if (unlikely(extra_len == 4))
-		skb->no_fcs = 1;
-
 	err = po->xmit(skb);
 	if (unlikely(err != 0)) {
 		if (err > 0)
-- 
2.35.1