udp: secondary hash on (local port, local address)

Extends udp_table to contain a secondary hash table.

socket anchor for this second hash is free, because UDP
doesnt use skc_bind_node : We define an union to hold
both skc_bind_node & a new hlist_nulls_node udp_portaddr_node

udp_lib_get_port() inserts sockets into second hash chain
(additional cost of one atomic op)

udp_lib_unhash() deletes socket from second hash chain
(additional cost of one atomic op)

Note : No spinlock lockdep annotation is needed, because
lock for the secondary hash chain is always get after
lock for primary hash chain.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 2 deletions

diff --git a/include/net/sock.h b/include/net/sock.h
index 827366b62680..3f1a4804bb3f 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -105,7 +105,7 @@ struct net;
 /**
  *      struct sock_common - minimal network layer representation of sockets
  *      @skc_node: main hash linkage for various protocol lookup tables
- *      @skc_nulls_node: main hash linkage for UDP/UDP-Lite protocol
+ *      @skc_nulls_node: main hash linkage for TCP/UDP/UDP-Lite protocol
  *      @skc_refcnt: reference count
  *      @skc_tx_queue_mapping: tx queue number for this connection
  *      @skc_hash: hash value used with various protocol lookup tables
@@ -115,6 +115,7 @@ struct net;
  *      @skc_reuse: %SO_REUSEADDR setting
  *      @skc_bound_dev_if: bound device index if != 0
  *      @skc_bind_node: bind hash linkage for various protocol lookup tables
+ *      @skc_portaddr_node: second hash linkage for UDP/UDP-Lite protocol
  *      @skc_prot: protocol handlers inside a network family
  *      @skc_net: reference to the network namespace of this socket
  *
@@ -140,7 +141,10 @@ struct sock_common {
         volatile unsigned char  skc_state;
         unsigned char           skc_reuse;
         int                     skc_bound_dev_if;
-        struct hlist_node       skc_bind_node;
+        union {
+                struct hlist_node       skc_bind_node;
+                struct hlist_nulls_node skc_portaddr_node;
+        };
         struct proto            *skc_prot;
 #ifdef CONFIG_NET_NS
         struct net              *skc_net;