[PATCH net v2 1/3] net/sched: act_csum: pull all VLAN headers before checksumming

[Davide Caratti]

TC 'csum' action needs to read the packets' ethertype. In case the value
is encoded in unstripped/nested VLAN headers, call pskb_may_pull() to be
sure that all tags are in the linear part of skb. While at it, move this
code in a helper function: other TC actions (like 'pedit' and 'skbedit')
might need to read the innermost ethertype.

Fixes: 2ecba2d1e45b ("net: sched: act_csum: Fix csum calc for tagged packets")
CC: Eli Britstein <el...@mellanox.com>
CC: Li Shuang <shu...@redhat.com>
Suggested-by: Eric Dumazet <eric.duma...@gmail.com>
Signed-off-by: Davide Caratti <dcara...@redhat.com>
---
 include/net/pkt_cls.h | 21 +++++++++++++++++++++
 net/sched/act_csum.c  | 14 ++------------
 2 files changed, 23 insertions(+), 12 deletions(-)

diff --git a/include/net/pkt_cls.h b/include/net/pkt_cls.h
index 514e3c80ecc1..0215dfbda9ac 100644
--- a/include/net/pkt_cls.h
+++ b/include/net/pkt_cls.h
@@ -953,4 +953,25 @@ struct tc_root_qopt_offload {
        bool ingress;
 };
 
+static inline int tc_skb_pull_vlans(struct sk_buff *skb,
+                                   unsigned int *hdr_count,
+                                   __be16 *proto)
+{
+       if (skb_vlan_tag_present(skb))
+               *proto = skb->protocol;
+
+       while (eth_type_vlan(*proto)) {
+               struct vlan_hdr *vlan;
+
+               if (unlikely(!pskb_may_pull(skb, VLAN_HLEN)))
+                       return -ENOMEM;
+
+               vlan = (struct vlan_hdr *)skb->data;
+               *proto = vlan->h_vlan_encapsulated_proto;
+               skb_pull(skb, VLAN_HLEN);
+               skb_reset_network_header(skb);
+               (*hdr_count)++;
+       }
+       return 0;
+}
 #endif
diff --git a/net/sched/act_csum.c b/net/sched/act_csum.c
index 14bb525e355e..e8308ddcae9d 100644
--- a/net/sched/act_csum.c
+++ b/net/sched/act_csum.c
@@ -574,7 +574,6 @@ static int tcf_csum_act(struct sk_buff *skb, const struct 
tc_action *a,
                        struct tcf_result *res)
 {
        struct tcf_csum *p = to_tcf_csum(a);
-       bool orig_vlan_tag_present = false;
        unsigned int vlan_hdr_count = 0;
        struct tcf_csum_params *params;
        u32 update_flags;
@@ -604,17 +603,8 @@ static int tcf_csum_act(struct sk_buff *skb, const struct 
tc_action *a,
                break;
        case cpu_to_be16(ETH_P_8021AD): /* fall through */
        case cpu_to_be16(ETH_P_8021Q):
-               if (skb_vlan_tag_present(skb) && !orig_vlan_tag_present) {
-                       protocol = skb->protocol;
-                       orig_vlan_tag_present = true;
-               } else {
-                       struct vlan_hdr *vlan = (struct vlan_hdr *)skb->data;
-
-                       protocol = vlan->h_vlan_encapsulated_proto;
-                       skb_pull(skb, VLAN_HLEN);
-                       skb_reset_network_header(skb);
-                       vlan_hdr_count++;
-               }
+               if (tc_skb_pull_vlans(skb, &vlan_hdr_count, &protocol))
+                       goto drop;
                goto again;
        }
 
-- 
2.20.1