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net/tcp: Disable TCP-MD5 static key on tcp_md5sig_info destruction

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To do that, separate two scenarios:
- where it's the first MD5 key on the system, which means that enabling
  of the static key may need to sleep;
- copying of an existing key from a listening socket to the request
  socket upon receiving a signed TCP segment, where static key was
  already enabled (when the key was added to the listening socket).

Now the life-time of the static branch for TCP-MD5 is until:
- last tcp_md5sig_info is destroyed
- last socket in time-wait state with MD5 key is closed.

Which means that after all sockets with TCP-MD5 keys are gone, the
system gets back the performance of disabled md5-key static branch.

While at here, provide static_key_fast_inc() helper that does ref
counter increment in atomic fashion (without grabbing cpus_read_lock()
on CONFIG_JUMP_LABEL=y). This is needed to add a new user for
a static_key when the caller controls the lifetime of another user.

Signed-off-by: Dmitry Safonov <dima@arista.com>
Acked-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Dmitry Safonov
2022-11-23 17:38:57 +00:00
committed by Jakub Kicinski
parent f62c7517ff
commit 459837b522
6 changed files with 84 additions and 32 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
net/ipv4/tcp_output.c
View File

@@ -766,7 +766,7 @@ static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
*md5 = NULL;
#ifdef CONFIG_TCP_MD5SIG
if (static_branch_unlikely(&tcp_md5_needed) &&
if (static_branch_unlikely(&tcp_md5_needed.key) &&
rcu_access_pointer(tp->md5sig_info)) {
*md5 = tp->af_specific->md5_lookup(sk, sk);
if (*md5) {
@@ -922,7 +922,7 @@ static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb
*md5 = NULL;
#ifdef CONFIG_TCP_MD5SIG
if (static_branch_unlikely(&tcp_md5_needed) &&
if (static_branch_unlikely(&tcp_md5_needed.key) &&
rcu_access_pointer(tp->md5sig_info)) {
*md5 = tp->af_specific->md5_lookup(sk, sk);
if (*md5) {