redonkable/alistair23-linux
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bpf: drop unnecessary test in cls_bpf_classify and tcf_bpf

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The skb_mac_header_was_set() test in cls_bpf's and act_bpf's fast-path is
actually unnecessary and can be removed altogether. This was added by
commit a166151cbe ("bpf: fix bpf helpers to use skb->mac_header relative
offsets"), which was later on improved by 3431205e03 ("bpf: make programs
see skb->data == L2 for ingress and egress"). We're always guaranteed to
have valid mac header at the time we invoke cls_bpf_classify() or tcf_bpf().

Reason is that since 6d1ccff627 ("net: reset mac header in dev_start_xmit()")
we do skb_reset_mac_header() in __dev_queue_xmit() before we could call
into sch_handle_egress() or any subsequent enqueue. sch_handle_ingress()
always sees a valid mac header as well (things like skb_reset_mac_len()
would badly fail otherwise). Thus, drop the unnecessary test in classifier
and action case.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Daniel Borkmann 2016-09-12 23:38:42 +02:00 committed by David S. Miller
parent 07c0f09e23
commit 04b3f8de4b
2 changed files with 0 additions and 6 deletions
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3
net/sched/act_bpf.c
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@ -44,9 +44,6 @@ static int tcf_bpf(struct sk_buff *skb, const struct tc_action *act,
int action, filter_res;
bool at_ingress = G_TC_AT(skb->tc_verd) & AT_INGRESS;
if (unlikely(!skb_mac_header_was_set(skb)))
return TC_ACT_UNSPEC;
tcf_lastuse_update(&prog->tcf_tm);
bstats_cpu_update(this_cpu_ptr(prog->common.cpu_bstats), skb);

3
net/sched/cls_bpf.c
View file

@ -83,9 +83,6 @@ static int cls_bpf_classify(struct sk_buff *skb, const struct tcf_proto *tp,
struct cls_bpf_prog *prog;
int ret = -1;
if (unlikely(!skb_mac_header_was_set(skb)))
return -1;
/* Needed here for accessing maps. */
rcu_read_lock();
list_for_each_entry_rcu(prog, &head->plist, link) {