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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>
This commit is contained in:
Stanislav Fomichev 2019-04-01 13:57:31 -07:00 committed by Daniel Borkmann
parent 2c3af7d901
commit 822fe61795
2 changed files with 5 additions and 2 deletions
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1
net/core/flow_dissector.c
View File

@ -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;

6
tools/testing/selftests/bpf/progs/bpf_flow.c
View File

@ -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);
}