flow_dissector: For stripped vlan, get vlan info from skb->vlan_tci

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 stripped vlan packets correctly.
In some flows, vlan doesn't exist in skb->data anymore when applying
flow dissection on the skb, fix that.

In case vlan info wasn't stripped before applying flow_dissector (RPS
flow for example), or in case of skb with multiple vlans (e.g. 802.1ad),
get the vlan info from skb->data. The flow_dissector correctly skips
any number of vlans and stores only the first level vlan.

Fixes: 0744dd00c1b1 ('net: introduce skb_flow_dissect()')
Signed-off-by: Hadar Hen Zion <hadarh@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index 91028ae..362d693 100644 (file)
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -119,12 +119,14 @@ bool __skb_flow_dissect(const struct sk_buff *skb,
        struct flow_dissector_key_ports *key_ports;
        struct flow_dissector_key_tags *key_tags;
        struct flow_dissector_key_keyid *key_keyid;
+       bool skip_vlan = false;
        u8 ip_proto = 0;
        bool ret = false;
 
        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);
        }
@@ -243,23 +245,39 @@ 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 (skb_vlan_tag_present(skb))
+                       proto = skb->protocol;
+
+               if (!skb_vlan_tag_present(skb) ||
+                   proto == cpu_to_be16(ETH_P_8021Q) ||
+                   proto == cpu_to_be16(ETH_P_8021AD)) {
+                       struct vlan_hdr _vlan;
+
+                       vlan = __skb_header_pointer(skb, nhoff, sizeof(_vlan),
+                                                   data, hlen, &_vlan);
+                       if (!vlan)
+                               goto out_bad;
+                       proto = vlan->h_vlan_encapsulated_proto;
+                       nhoff += sizeof(*vlan);
+                       if (skip_vlan)
+                               goto again;
+               }
 
+               skip_vlan = true;
                if (dissector_uses_key(flow_dissector,
                                       FLOW_DISSECTOR_KEY_VLANID)) {
                        key_tags = skb_flow_dissector_target(flow_dissector,
                                                             FLOW_DISSECTOR_KEY_VLANID,
                                                             target_container);
 
-                       key_tags->vlan_id = skb_vlan_tag_get_id(skb);
+                       if (skb_vlan_tag_present(skb))
+                               key_tags->vlan_id = skb_vlan_tag_get_id(skb);
+                       else
+                               key_tags->vlan_id = ntohs(vlan->h_vlan_TCI) &
+                                       VLAN_VID_MASK;
                }
 
-               proto = vlan->h_vlan_encapsulated_proto;
-               nhoff += sizeof(*vlan);
                goto again;
        }
        case htons(ETH_P_PPP_SES): {