diff options
| author |   Eric Dumazet <edumazet@google.com> | 2021-10-25 09:48:22 -0700 |
|---|---|---|
| committer |   Jakub Kicinski <kuba@kernel.org> | 2021-10-25 18:02:13 -0700 |
| commit | 790eb67374d43f66102a80821d22188b6a0bc3bb (patch) | |
| tree | 0f6306b5f3870c87d9075ca3738cbe636703affc /net/ipv6/tcp_ipv6.c | |
| parent | ipv6: annotate data races around np->min_hopcount (diff) | |
| download | linux-dev-790eb67374d43f66102a80821d22188b6a0bc3bb.tar.xz linux-dev-790eb67374d43f66102a80821d22188b6a0bc3bb.zip | |
ipv6: guard IPV6_MINHOPCOUNT with a static key
RFC 5082 IPV6_MINHOPCOUNT is rarely used on hosts.
Add a static key to remove from TCP fast path useless code,
and potential cache line miss to fetch tcp_inet6_sk(sk)->min_hopcount
Note that once ip6_min_hopcount static key has been enabled,
it stays enabled until next boot.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net/ipv6/tcp_ipv6.c')
| -rw-r--r-- | net/ipv6/tcp_ipv6.c | 21 |
1 files changed, 13 insertions, 8 deletions
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c index c93b2d48bb89..6945583c0fa4 100644 --- a/net/ipv6/tcp_ipv6.c +++ b/net/ipv6/tcp_ipv6.c @@ -414,10 +414,12 @@ static int tcp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt, if (sk->sk_state == TCP_CLOSE) goto out; - /* min_hopcount can be changed concurrently from do_ipv6_setsockopt() */ - if (ipv6_hdr(skb)->hop_limit < READ_ONCE(tcp_inet6_sk(sk)->min_hopcount)) { - __NET_INC_STATS(net, LINUX_MIB_TCPMINTTLDROP); - goto out; + if (static_branch_unlikely(&ip6_min_hopcount)) { + /* min_hopcount can be changed concurrently from do_ipv6_setsockopt() */ + if (ipv6_hdr(skb)->hop_limit < READ_ONCE(tcp_inet6_sk(sk)->min_hopcount)) { + __NET_INC_STATS(net, LINUX_MIB_TCPMINTTLDROP); + goto out; + } } tp = tcp_sk(sk); @@ -1727,10 +1729,13 @@ process: return 0; } } - /* min_hopcount can be changed concurrently from do_ipv6_setsockopt() */ - if (hdr->hop_limit < READ_ONCE(tcp_inet6_sk(sk)->min_hopcount)) { - __NET_INC_STATS(net, LINUX_MIB_TCPMINTTLDROP); - goto discard_and_relse; + + if (static_branch_unlikely(&ip6_min_hopcount)) { + /* min_hopcount can be changed concurrently from do_ipv6_setsockopt() */ + if (hdr->hop_limit < READ_ONCE(tcp_inet6_sk(sk)->min_hopcount)) { + __NET_INC_STATS(net, LINUX_MIB_TCPMINTTLDROP); + goto discard_and_relse; + } } if (!xfrm6_policy_check(sk, XFRM_POLICY_IN, skb)) |