[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, 15 insertions, 0 deletions

diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index b88fe05fdcb..5d295b1b3de 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -179,6 +179,7 @@ struct tcp_info
 #include <linux/skbuff.h>
 #include <linux/ip.h>
 #include <net/sock.h>
+#include <net/inet_timewait_sock.h>
 
 /* This defines a selective acknowledgement block. */
 struct tcp_sack_block {
@@ -387,6 +388,20 @@ static inline struct tcp_sock *tcp_sk(const struct sock *sk)
 	return (struct tcp_sock *)sk;
 }
 
+struct tcp_timewait_sock {
+	struct inet_timewait_sock tw_sk;
+	__u32			  tw_rcv_nxt;
+	__u32			  tw_snd_nxt;
+	__u32			  tw_rcv_wnd;
+	__u32			  tw_ts_recent;
+	long			  tw_ts_recent_stamp;
+};
+
+static inline struct tcp_timewait_sock *tcp_twsk(const struct sock *sk)
+{
+	return (struct tcp_timewait_sock *)sk;
+}
+
 static inline void *tcp_ca(const struct tcp_sock *tp)
 {
 	return (void *) tp->ca_priv;