diff options
| author |   Eric Dumazet <edumazet@google.com> | 2021-10-25 09:48:24 -0700 |
|---|---|---|
| committer |   Jakub Kicinski <kuba@kernel.org> | 2021-10-25 18:02:14 -0700 |
| commit | 020e71a3cf7f50c0f2c54cf2444067b76fe6d785 (patch) | |
| tree | 34f7f3b49927f2807a6a72bd488328484a728e00 /net/ipv4/tcp_ipv4.c | |
| parent | ipv4: annotate data races arount inet->min_ttl (diff) | |
| download | linux-dev-020e71a3cf7f50c0f2c54cf2444067b76fe6d785.tar.xz linux-dev-020e71a3cf7f50c0f2c54cf2444067b76fe6d785.zip | |
ipv4: guard IP_MINTTL with a static key
RFC 5082 IP_MINTTL option is rarely used on hosts.
Add a static key to remove from TCP fast path useless code,
and potential cache line miss to fetch inet_sk(sk)->min_ttl
Note that once ip4_min_ttl 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/ipv4/tcp_ipv4.c')
| -rw-r--r-- | net/ipv4/tcp_ipv4.c | 20 |
1 files changed, 12 insertions, 8 deletions
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index a9cbc8e6b796..13d868c43284 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -508,10 +508,12 @@ int tcp_v4_err(struct sk_buff *skb, u32 info) if (sk->sk_state == TCP_CLOSE) goto out; - /* min_ttl can be changed concurrently from do_ip_setsockopt() */ - if (unlikely(iph->ttl < READ_ONCE(inet_sk(sk)->min_ttl))) { - __NET_INC_STATS(net, LINUX_MIB_TCPMINTTLDROP); - goto out; + if (static_branch_unlikely(&ip4_min_ttl)) { + /* min_ttl can be changed concurrently from do_ip_setsockopt() */ + if (unlikely(iph->ttl < READ_ONCE(inet_sk(sk)->min_ttl))) { + __NET_INC_STATS(net, LINUX_MIB_TCPMINTTLDROP); + goto out; + } } tp = tcp_sk(sk); @@ -2070,10 +2072,12 @@ process: } } - /* min_ttl can be changed concurrently from do_ip_setsockopt() */ - if (unlikely(iph->ttl < READ_ONCE(inet_sk(sk)->min_ttl))) { - __NET_INC_STATS(net, LINUX_MIB_TCPMINTTLDROP); - goto discard_and_relse; + if (static_branch_unlikely(&ip4_min_ttl)) { + /* min_ttl can be changed concurrently from do_ip_setsockopt() */ + if (unlikely(iph->ttl < READ_ONCE(inet_sk(sk)->min_ttl))) { + __NET_INC_STATS(net, LINUX_MIB_TCPMINTTLDROP); + goto discard_and_relse; + } } if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb)) |