[PATCH net-next 1/4] flow_dissector: Get vlan info from skb->vlan_tci instead of skb->data

[Hadar Hen Zion]

Early in the datapath skb_vlan_untag function is called, stripped
the vlan from the skb and set skb->vlan_tci and skb->vlan_proto fields.

The current dissection doesn't handle vlan packets correctly.  Vlan
doesn't exist in skb->data anymore when applying flow dissection on the
skb, fix that.

Fixes: 0744dd00c1b1 ('net: introduce skb_flow_dissect()')
Signed-off-by: Hadar Hen Zion <had...@mellanox.com>
---
 net/core/flow_dissector.c | 13 +++----------
 1 file changed, 3 insertions(+), 10 deletions(-)

diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index 61ad43f..6060fc2 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -122,7 +122,8 @@ bool __skb_flow_dissect(const struct sk_buff *skb,
 
        if (!data) {
                data = skb->data;
-               proto = skb->protocol;
+               proto = skb_vlan_tag_present(skb) ?
+                        skb->vlan_proto : skb->protocol;
                nhoff = skb_network_offset(skb);
                hlen = skb_headlen(skb);
        }
@@ -240,13 +241,6 @@ ipv6:
        }
        case htons(ETH_P_8021AD):
        case htons(ETH_P_8021Q): {
-               const struct vlan_hdr *vlan;
-               struct vlan_hdr _vlan;
-
-               vlan = __skb_header_pointer(skb, nhoff, sizeof(_vlan), data, 
hlen, &_vlan);
-               if (!vlan)
-                       goto out_bad;
-
                if (dissector_uses_key(flow_dissector,
                                       FLOW_DISSECTOR_KEY_VLANID)) {
                        key_tags = skb_flow_dissector_target(flow_dissector,
@@ -256,8 +250,7 @@ ipv6:
                        key_tags->vlan_id = skb_vlan_tag_get_id(skb);
                }
 
-               proto = vlan->h_vlan_encapsulated_proto;
-               nhoff += sizeof(*vlan);
+               proto = skb->protocol;
                goto again;
        }
        case htons(ETH_P_PPP_SES): {
-- 
1.8.3.1