target/linux/generic/backport-5.4/080-wireguard-0101-wireguard-send-receive-use-explicit-unlikely-branch-.patch

   1 From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
   2 From: "Jason A. Donenfeld" <Jason@zx2c4.com>
   3 Date: Wed, 6 May 2020 15:33:06 -0600
   4 Subject: [PATCH] wireguard: send/receive: use explicit unlikely branch instead
   5  of implicit coalescing
   6
   7 commit 243f2148937adc72bcaaa590d482d599c936efde upstream.
   8
   9 It's very unlikely that send will become true. It's nearly always false
  10 between 0 and 120 seconds of a session, and in most cases becomes true
  11 only between 120 and 121 seconds before becoming false again. So,
  12 unlikely(send) is clearly the right option here.
  13
  14 What happened before was that we had this complex boolean expression
  15 with multiple likely and unlikely clauses nested. Since this is
  16 evaluated left-to-right anyway, the whole thing got converted to
  17 unlikely. So, we can clean this up to better represent what's going on.
  18
  19 The generated code is the same.
  20
  21 Suggested-by: Sultan Alsawaf <sultan@kerneltoast.com>
  22 Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
  23 Signed-off-by: David S. Miller <davem@davemloft.net>
  24 Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
  25 ---
  26  drivers/net/wireguard/receive.c | 13 ++++++-------
  27  drivers/net/wireguard/send.c    | 15 ++++++---------
  28  2 files changed, 12 insertions(+), 16 deletions(-)
  29
  30 --- a/drivers/net/wireguard/receive.c
  31 +++ b/drivers/net/wireguard/receive.c
  32 @@ -226,21 +226,20 @@ void wg_packet_handshake_receive_worker(
  33  static void keep_key_fresh(struct wg_peer *peer)
  34  {
  35         struct noise_keypair *keypair;
  36 -       bool send = false;
  37 +       bool send;
  38
  39         if (peer->sent_lastminute_handshake)
  40                 return;
  41
  42         rcu_read_lock_bh();
  43         keypair = rcu_dereference_bh(peer->keypairs.current_keypair);
  44 -       if (likely(keypair && READ_ONCE(keypair->sending.is_valid)) &&
  45 -           keypair->i_am_the_initiator &&
  46 -           unlikely(wg_birthdate_has_expired(keypair->sending.birthdate,
  47 -                       REJECT_AFTER_TIME - KEEPALIVE_TIMEOUT - REKEY_TIMEOUT)))
  48 -               send = true;
  49 +       send = keypair && READ_ONCE(keypair->sending.is_valid) &&
  50 +              keypair->i_am_the_initiator &&
  51 +              wg_birthdate_has_expired(keypair->sending.birthdate,
  52 +                       REJECT_AFTER_TIME - KEEPALIVE_TIMEOUT - REKEY_TIMEOUT);
  53         rcu_read_unlock_bh();
  54
  55 -       if (send) {
  56 +       if (unlikely(send)) {
  57                 peer->sent_lastminute_handshake = true;
  58                 wg_packet_send_queued_handshake_initiation(peer, false);
  59         }
  60 --- a/drivers/net/wireguard/send.c
  61 +++ b/drivers/net/wireguard/send.c
  62 @@ -124,20 +124,17 @@ void wg_packet_send_handshake_cookie(str
  63  static void keep_key_fresh(struct wg_peer *peer)
  64  {
  65         struct noise_keypair *keypair;
  66 -       bool send = false;
  67 +       bool send;
  68
  69         rcu_read_lock_bh();
  70         keypair = rcu_dereference_bh(peer->keypairs.current_keypair);
  71 -       if (likely(keypair && READ_ONCE(keypair->sending.is_valid)) &&
  72 -           (unlikely(atomic64_read(&keypair->sending.counter.counter) >
  73 -                     REKEY_AFTER_MESSAGES) ||
  74 -            (keypair->i_am_the_initiator &&
  75 -             unlikely(wg_birthdate_has_expired(keypair->sending.birthdate,
  76 -                                               REKEY_AFTER_TIME)))))
  77 -               send = true;
  78 +       send = keypair && READ_ONCE(keypair->sending.is_valid) &&
  79 +              (atomic64_read(&keypair->sending.counter.counter) > REKEY_AFTER_MESSAGES ||
  80 +               (keypair->i_am_the_initiator &&
  81 +                wg_birthdate_has_expired(keypair->sending.birthdate, REKEY_AFTER_TIME)));
  82         rcu_read_unlock_bh();
  83
  84 -       if (send)
  85 +       if (unlikely(send))
  86                 wg_packet_send_queued_handshake_initiation(peer, false);
  87  }
  88