[PATCH bpf 2/5] net/flow_dissector: pass flow_keys->n_proto to BPF programs

[Stanislav Fomichev]

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 <s...@google.com>
---
 net/core/flow_dissector.c                    | 1 +
 tools/testing/selftests/bpf/progs/bpf_flow.c | 6 ++++--
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index bb1a54747d64..9b84250039df 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -707,6 +707,7 @@ bool __skb_flow_bpf_dissect(struct bpf_prog *prog,
        /* Pass parameters to the BPF program */
        memset(flow_keys, 0, sizeof(*flow_keys));
        cb->qdisc_cb.flow_keys = flow_keys;
+       flow_keys->n_proto = skb->protocol;
        flow_keys->nhoff = skb_network_offset(skb);
        flow_keys->thoff = flow_keys->nhoff;
 
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);
 }
 
-- 
2.21.0.392.gf8f6787159e-goog