queue-3.18/packets-always-register-packet-sk-in-the-same-order.patch

   1 From foo@baz Thu Mar 28 23:25:55 CET 2019
   2 From: Maxime Chevallier <maxime.chevallier@bootlin.com>
   3 Date: Sat, 16 Mar 2019 14:41:30 +0100
   4 Subject: packets: Always register packet sk in the same order
   5
   6 From: Maxime Chevallier <maxime.chevallier@bootlin.com>
   7
   8 [ Upstream commit a4dc6a49156b1f8d6e17251ffda17c9e6a5db78a ]
   9
  10 When using fanouts with AF_PACKET, the demux functions such as
  11 fanout_demux_cpu will return an index in the fanout socket array, which
  12 corresponds to the selected socket.
  13
  14 The ordering of this array depends on the order the sockets were added
  15 to a given fanout group, so for FANOUT_CPU this means sockets are bound
  16 to cpus in the order they are configured, which is OK.
  17
  18 However, when stopping then restarting the interface these sockets are
  19 bound to, the sockets are reassigned to the fanout group in the reverse
  20 order, due to the fact that they were inserted at the head of the
  21 interface's AF_PACKET socket list.
  22
  23 This means that traffic that was directed to the first socket in the
  24 fanout group is now directed to the last one after an interface restart.
  25
  26 In the case of FANOUT_CPU, traffic from CPU0 will be directed to the
  27 socket that used to receive traffic from the last CPU after an interface
  28 restart.
  29
  30 This commit introduces a helper to add a socket at the tail of a list,
  31 then uses it to register AF_PACKET sockets.
  32
  33 Note that this changes the order in which sockets are listed in /proc and
  34 with sock_diag.
  35
  36 Fixes: dc99f600698d ("packet: Add fanout support")
  37 Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
  38 Acked-by: Willem de Bruijn <willemb@google.com>
  39 Signed-off-by: David S. Miller <davem@davemloft.net>
  40 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  41 ---
  42  include/net/sock.h     |    6 ++++++
  43  net/packet/af_packet.c |    2 +-
  44  2 files changed, 7 insertions(+), 1 deletion(-)
  45
  46 --- a/include/net/sock.h
  47 +++ b/include/net/sock.h
  48 @@ -626,6 +626,12 @@ static inline void sk_add_node_rcu(struc
  49         hlist_add_head_rcu(&sk->sk_node, list);
  50  }
  51
  52 +static inline void sk_add_node_tail_rcu(struct sock *sk, struct hlist_head *list)
  53 +{
  54 +       sock_hold(sk);
  55 +       hlist_add_tail_rcu(&sk->sk_node, list);
  56 +}
  57 +
  58  static inline void __sk_nulls_add_node_rcu(struct sock *sk, struct hlist_nulls_head *list)
  59  {
  60         hlist_nulls_add_head_rcu(&sk->sk_nulls_node, list);
  61 --- a/net/packet/af_packet.c
  62 +++ b/net/packet/af_packet.c
  63 @@ -2878,7 +2878,7 @@ static int packet_create(struct net *net
  64         }
  65
  66         mutex_lock(&net->packet.sklist_lock);
  67 -       sk_add_node_rcu(sk, &net->packet.sklist);
  68 +       sk_add_node_tail_rcu(sk, &net->packet.sklist);
  69         mutex_unlock(&net->packet.sklist_lock);
  70
  71         preempt_disable();