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bpf: avoid preempt enable/disable in sockmap using tcp_skb_cb region

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SK_SKB BPF programs are run from the socket/tcp context but early in
the stack before much of the TCP metadata is needed in tcp_skb_cb. So
we can use some unused fields to place BPF metadata needed for SK_SKB
programs when implementing the redirect function.

This allows us to drop the preempt disable logic. It does however
require an API change so sk_redirect_map() has been updated to
additionally provide ctx_ptr to skb. Note, we do however continue to
disable/enable preemption around actual BPF program running to account
for map updates.

Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Acked-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:
John Fastabend
2017-10-18 07:10:36 -07:00
committed by David S. Miller
parent 435bf0d3f9
commit 34f79502bb
8 changed files with 36 additions and 30 deletions
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2
samples/sockmap/sockmap_kern.c
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@@ -62,7 +62,7 @@ int bpf_prog2(struct __sk_buff *skb)
ret = 1;
bpf_printk("sockmap: %d -> %d @ %d\n", lport, bpf_ntohl(rport), ret);
return bpf_sk_redirect_map(&sock_map, ret, 0);
return bpf_sk_redirect_map(skb, &sock_map, ret, 0);
}
SEC("sockops")