[INET]: Generalise tcp_tw_bucket, aka TIME_WAIT sockets

This paves the way to generalise the rest of the sock ID lookup
routines and saves some bytes in TCPv4 TIME_WAIT sockets on distro
kernels (where IPv6 is always built as a module):

[root@qemu ~]# grep tw_sock /proc/slabinfo
tw_sock_TCPv6  0  0  128  31  1
tw_sock_TCP    0  0   96  41  1
[root@qemu ~]#

Now if a protocol wants to use the TIME_WAIT generic infrastructure it
only has to set the sk_prot->twsk_obj_size field with the size of its
inet_timewait_sock derived sock and proto_register will create
sk_prot->twsk_slab, for now its only for INET sockets, but we can
introduce timewait_sock later if some non INET transport protocolo
wants to use this stuff.

Next changesets will take advantage of this new infrastructure to
generalise even more TCP code.

[acme@toy net-2.6.14]$ grep built-in /tmp/before.size /tmp/after.size
/tmp/before.size: 188646   11764    5068  205478   322a6 net/ipv4/built-in.o
/tmp/after.size:  188144   11764    5068  204976   320b0 net/ipv4/built-in.o
[acme@toy net-2.6.14]$

Tested with both IPv4 & IPv6 (::1 (localhost) & ::ffff:172.20.0.1
(qemu host)).

Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 11 insertions, 6 deletions

diff --git a/include/net/sock.h b/include/net/sock.h
index 391d00b5b7b..c902c57bf2b 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -88,6 +88,7 @@ do {	spin_lock_init(&((__sk)->sk_lock.slock)); \
 } while(0)
 
 struct sock;
+struct proto;
 
 /**
  *      struct sock_common - minimal network layer representation of sockets
@@ -98,10 +99,11 @@ struct sock;
  *      @skc_node: main hash linkage for various protocol lookup tables
  *      @skc_bind_node: bind hash linkage for various protocol lookup tables
  *      @skc_refcnt: reference count
+ *      @skc_prot: protocol handlers inside a network family
  *
  *      This is the minimal network layer representation of sockets, the header
- *      for struct sock and struct tcp_tw_bucket.
-  */
+ *      for struct sock and struct inet_timewait_sock.
+ */
 struct sock_common {
         unsigned short          skc_family;
         volatile unsigned char  skc_state;
@@ -110,11 +112,12 @@ struct sock_common {
         struct hlist_node       skc_node;
         struct hlist_node       skc_bind_node;
         atomic_t                skc_refcnt;
+        struct proto            *skc_prot;
 };
 
 /**
   *     struct sock - network layer representation of sockets
-  *     @__sk_common: shared layout with tcp_tw_bucket
+  *     @__sk_common: shared layout with inet_timewait_sock
   *     @sk_shutdown: mask of %SEND_SHUTDOWN and/or %RCV_SHUTDOWN
   *     @sk_userlocks: %SO_SNDBUF and %SO_RCVBUF settings
   *     @sk_lock:       synchronizer
@@ -140,7 +143,6 @@ struct sock_common {
   *     @sk_backlog: always used with the per-socket spinlock held
   *     @sk_callback_lock: used with the callbacks in the end of this struct
   *     @sk_error_queue: rarely used
-  *     @sk_prot: protocol handlers inside a network family
   *     @sk_prot_creator: sk_prot of original sock creator (see ipv6_setsockopt, IPV6_ADDRFORM for instance)
   *     @sk_err: last error
   *     @sk_err_soft: errors that don't cause failure but are the cause of a persistent failure not just 'timed out'
@@ -173,7 +175,7 @@ struct sock_common {
  */
 struct sock {
         /*
-         * Now struct tcp_tw_bucket also uses sock_common, so please just
+         * Now struct inet_timewait_sock also uses sock_common, so please just
          * don't add nothing before this first member (__sk_common) --acme
          */
         struct sock_common      __sk_common;
@@ -184,6 +186,7 @@ struct sock {
 #define sk_node                 __sk_common.skc_node
 #define sk_bind_node            __sk_common.skc_bind_node
 #define sk_refcnt               __sk_common.skc_refcnt
+#define sk_prot                 __sk_common.skc_prot
         unsigned char           sk_shutdown : 2,
                                 sk_no_check : 2,
                                 sk_userlocks : 4;
@@ -218,7 +221,6 @@ struct sock {
                 struct sk_buff *tail;
         } sk_backlog;
         struct sk_buff_head     sk_error_queue;
-        struct proto            *sk_prot;
         struct proto            *sk_prot_creator;
         rwlock_t                sk_callback_lock;
         int                     sk_err,
@@ -557,6 +559,9 @@ struct proto {
         kmem_cache_t            *slab;
         unsigned int            obj_size;
 
+        kmem_cache_t            *twsk_slab;
+        unsigned int            twsk_obj_size;
+
         struct request_sock_ops *rsk_prot;
 
         struct module           *owner;