net/flow_dissector: pass flow_keys->n_proto to BPF programs

This is a preparation for the next commit that would prohibit access to
the most fields of __sk_buff from the BPF programs.

Instead of requiring BPF flow dissector programs to look into skb,
pass all input data in the flow_keys.

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

1 files changed, 4 insertions, 2 deletions

diff --git a/tools/testing/selftests/bpf/progs/bpf_flow.c b/tools/testing/selftests/bpf/progs/bpf_flow.c
index f177c7a6a6c7..75b17cada539 100644
--- a/tools/testing/selftests/bpf/progs/bpf_flow.c
+++ b/tools/testing/selftests/bpf/progs/bpf_flow.c
@@ -92,7 +92,6 @@ static __always_inline int parse_eth_proto(struct __sk_buff *skb, __be16 proto)
 {
         struct bpf_flow_keys *keys = skb->flow_keys;
 
-        keys->n_proto = proto;
         switch (proto) {
         case bpf_htons(ETH_P_IP):
                 bpf_tail_call(skb, &jmp_table, IP);
@@ -119,7 +118,9 @@ static __always_inline int parse_eth_proto(struct __sk_buff *skb, __be16 proto)
 SEC("flow_dissector")
 int _dissect(struct __sk_buff *skb)
 {
-        return parse_eth_proto(skb, skb->protocol);
+        struct bpf_flow_keys *keys = skb->flow_keys;
+
+        return parse_eth_proto(skb, keys->n_proto);
 }
 
 /* Parses on IPPROTO_* */
@@ -358,6 +359,7 @@ PROG(VLAN)(struct __sk_buff *skb)
             vlan->h_vlan_encapsulated_proto == bpf_htons(ETH_P_8021Q))
                 return BPF_DROP;
 
+        keys->n_proto = vlan->h_vlan_encapsulated_proto;
         return parse_eth_proto(skb, vlan->h_vlan_encapsulated_proto);
 }