flow_dissector: handle no-skb use case

When called without skb, gather all required data from the
__skb_flow_dissect's arguments and use recently introduces
no-skb mode of bpf flow dissector.

Note: WARN_ON_ONCE(!net) will now trigger for eth_get_headlen users.

Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index b466fbf..998256c 100644 (file)
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1279,11 +1279,6 @@ struct bpf_flow_dissector;
 bool bpf_flow_dissect(struct bpf_prog *prog, struct bpf_flow_dissector *ctx,
                      __be16 proto, int nhoff, int hlen);
 
-struct bpf_flow_keys;
-bool __skb_flow_bpf_dissect(struct bpf_prog *prog,
-                           const struct sk_buff *skb,
-                           struct flow_dissector *flow_dissector,
-                           struct bpf_flow_keys *flow_keys);
 bool __skb_flow_dissect(const struct net *net,
                        const struct sk_buff *skb,
                        struct flow_dissector *flow_dissector,

diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index f32c7e7..fac712c 100644 (file)
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -683,22 +683,6 @@ static void __skb_flow_bpf_to_target(const struct bpf_flow_keys *flow_keys,
        }
 }
 
-bool __skb_flow_bpf_dissect(struct bpf_prog *prog,
-                           const struct sk_buff *skb,
-                           struct flow_dissector *flow_dissector,
-                           struct bpf_flow_keys *flow_keys)
-{
-       struct bpf_flow_dissector ctx = {
-               .flow_keys = flow_keys,
-               .skb = skb,
-               .data = skb->data,
-               .data_end = skb->data + skb_headlen(skb),
-       };
-
-       return bpf_flow_dissect(prog, &ctx, skb->protocol,
-                               skb_network_offset(skb), skb_headlen(skb));
-}
-
 bool bpf_flow_dissect(struct bpf_prog *prog, struct bpf_flow_dissector *ctx,
                      __be16 proto, int nhoff, int hlen)
 {
@@ -753,6 +737,7 @@ bool __skb_flow_dissect(const struct net *net,
        struct flow_dissector_key_icmp *key_icmp;
        struct flow_dissector_key_tags *key_tags;
        struct flow_dissector_key_vlan *key_vlan;
+       struct bpf_prog *attached = NULL;
        enum flow_dissect_ret fdret;
        enum flow_dissector_key_id dissector_vlan = FLOW_DISSECTOR_KEY_MAX;
        int num_hdrs = 0;
@@ -795,26 +780,39 @@ bool __skb_flow_dissect(const struct net *net,
                                              target_container);
 
        if (skb) {
-               struct bpf_flow_keys flow_keys;
-               struct bpf_prog *attached = NULL;
-
-               rcu_read_lock();
                if (!net) {
                        if (skb->dev)
                                net = dev_net(skb->dev);
                        else if (skb->sk)
                                net = sock_net(skb->sk);
-                       else
-                               WARN_ON_ONCE(1);
                }
+       }
 
-               if (net)
-                       attached = rcu_dereference(net->flow_dissector_prog);
+       WARN_ON_ONCE(!net);
+       if (net) {
+               rcu_read_lock();
+               attached = rcu_dereference(net->flow_dissector_prog);
 
                if (attached) {
-                       ret = __skb_flow_bpf_dissect(attached, skb,
-                                                    flow_dissector,
-                                                    &flow_keys);
+                       struct bpf_flow_keys flow_keys;
+                       struct bpf_flow_dissector ctx = {
+                               .flow_keys = &flow_keys,
+                               .data = data,
+                               .data_end = data + hlen,
+                       };
+                       __be16 n_proto = proto;
+
+                       if (skb) {
+                               ctx.skb = skb;
+                               /* we can't use 'proto' in the skb case
+                                * because it might be set to skb->vlan_proto
+                                * which has been pulled from the data
+                                */
+                               n_proto = skb->protocol;
+                       }
+
+                       ret = bpf_flow_dissect(attached, &ctx, n_proto, nhoff,
+                                              hlen);
                        __skb_flow_bpf_to_target(&flow_keys, flow_dissector,
                                                 target_container);
                        rcu_read_unlock();