[PATCH bpf 1/2] flow_dissector: support FLOW_DISSECTOR_KEY_ETH_ADDRS with BPF

[Stanislav Fomichev]

If we have a flow dissector BPF program attached to the namespace,
FLOW_DISSECTOR_KEY_ETH_ADDRS won't trigger because we exit early.

Handle FLOW_DISSECTOR_KEY_ETH_ADDRS before BPF and only if we have
an skb (used by tc-flower only).

Fixes: d58e468b1112 ("flow_dissector: implements flow dissector BPF hook")
Signed-off-by: Stanislav Fomichev <s...@google.com>
---
 net/core/flow_dissector.c | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index 9ca784c592ac..ba76d9168c8b 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -825,6 +825,18 @@ bool __skb_flow_dissect(const struct net *net,
                        else if (skb->sk)
                                net = sock_net(skb->sk);
                }
+
+               if (dissector_uses_key(flow_dissector,
+                                      FLOW_DISSECTOR_KEY_ETH_ADDRS)) {
+                       struct ethhdr *eth = eth_hdr(skb);
+                       struct flow_dissector_key_eth_addrs *key_eth_addrs;
+
+                       key_eth_addrs = 
skb_flow_dissector_target(flow_dissector,
+                                                                 
FLOW_DISSECTOR_KEY_ETH_ADDRS,
+                                                                 
target_container);
+                       memcpy(key_eth_addrs, &eth->h_dest,
+                              sizeof(*key_eth_addrs));
+               }
        }
 
        WARN_ON_ONCE(!net);
@@ -860,17 +872,6 @@ bool __skb_flow_dissect(const struct net *net,
                rcu_read_unlock();
        }
 
-       if (dissector_uses_key(flow_dissector,
-                              FLOW_DISSECTOR_KEY_ETH_ADDRS)) {
-               struct ethhdr *eth = eth_hdr(skb);
-               struct flow_dissector_key_eth_addrs *key_eth_addrs;
-
-               key_eth_addrs = skb_flow_dissector_target(flow_dissector,
-                                                         
FLOW_DISSECTOR_KEY_ETH_ADDRS,
-                                                         target_container);
-               memcpy(key_eth_addrs, &eth->h_dest, sizeof(*key_eth_addrs));
-       }
-
 proto_again:
        fdret = FLOW_DISSECT_RET_CONTINUE;
 
-- 
2.21.0.1020.gf2820cf01a-goog