[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, 142 insertions, 0 deletions

diff --git a/include/net/inet_timewait_sock.h b/include/net/inet_timewait_sock.h
new file mode 100644
index 000000000000..ce117048f2fd
--- /dev/null
+++ b/include/net/inet_timewait_sock.h
@@ -0,0 +1,142 @@
+/*
+ * INET		An implementation of the TCP/IP protocol suite for the LINUX
+ *		operating system.  INET is implemented using the  BSD Socket
+ *		interface as the means of communication with the user level.
+ *
+ *		Definitions for a generic INET TIMEWAIT sock
+ *
+ *		From code originally in net/tcp.h
+ *
+ *		This program is free software; you can redistribute it and/or
+ *		modify it under the terms of the GNU General Public License
+ *		as published by the Free Software Foundation; either version
+ *		2 of the License, or (at your option) any later version.
+ */
+#ifndef _INET_TIMEWAIT_SOCK_
+#define _INET_TIMEWAIT_SOCK_
+
+#include <linux/config.h>
+
+#include <linux/list.h>
+#include <linux/types.h>
+
+#include <net/sock.h>
+#include <net/tcp_states.h>
+
+#include <asm/atomic.h>
+
+#if (BITS_PER_LONG == 64)
+#define INET_TIMEWAIT_ADDRCMP_ALIGN_BYTES 8
+#else
+#define INET_TIMEWAIT_ADDRCMP_ALIGN_BYTES 4
+#endif
+
+struct inet_bind_bucket;
+
+/*
+ * This is a TIME_WAIT sock. It works around the memory consumption
+ * problems of sockets in such a state on heavily loaded servers, but
+ * without violating the protocol specification.
+ */
+struct inet_timewait_sock {
+	/*
+	 * Now struct sock also uses sock_common, so please just
+	 * don't add nothing before this first member (__tw_common) --acme
+	 */
+	struct sock_common	__tw_common;
+#define tw_family		__tw_common.skc_family
+#define tw_state		__tw_common.skc_state
+#define tw_reuse		__tw_common.skc_reuse
+#define tw_bound_dev_if		__tw_common.skc_bound_dev_if
+#define tw_node			__tw_common.skc_node
+#define tw_bind_node		__tw_common.skc_bind_node
+#define tw_refcnt		__tw_common.skc_refcnt
+#define tw_prot			__tw_common.skc_prot
+	volatile unsigned char	tw_substate;
+	/* 3 bits hole, try to pack */
+	unsigned char		tw_rcv_wscale;
+	/* Socket demultiplex comparisons on incoming packets. */
+	/* these five are in inet_sock */
+	__u16			tw_sport;
+	__u32			tw_daddr __attribute__((aligned(INET_TIMEWAIT_ADDRCMP_ALIGN_BYTES)));
+	__u32			tw_rcv_saddr;
+	__u16			tw_dport;
+	__u16			tw_num;
+	/* And these are ours. */
+	__u8			tw_ipv6only:1;
+	/* 31 bits hole, try to pack */
+	int			tw_hashent;
+	int			tw_timeout;
+	unsigned long		tw_ttd;
+	struct inet_bind_bucket	*tw_tb;
+	struct hlist_node	tw_death_node;
+};
+
+static inline void inet_twsk_add_node(struct inet_timewait_sock *tw,
+				      struct hlist_head *list)
+{
+	hlist_add_head(&tw->tw_node, list);
+}
+
+static inline void inet_twsk_add_bind_node(struct inet_timewait_sock *tw,
+					   struct hlist_head *list)
+{
+	hlist_add_head(&tw->tw_bind_node, list);
+}
+
+static inline int inet_twsk_dead_hashed(const struct inet_timewait_sock *tw)
+{
+	return tw->tw_death_node.pprev != NULL;
+}
+
+static inline void inet_twsk_dead_node_init(struct inet_timewait_sock *tw)
+{
+	tw->tw_death_node.pprev = NULL;
+}
+
+static inline void __inet_twsk_del_dead_node(struct inet_timewait_sock *tw)
+{
+	__hlist_del(&tw->tw_death_node);
+	inet_twsk_dead_node_init(tw);
+}
+
+static inline int inet_twsk_del_dead_node(struct inet_timewait_sock *tw)
+{
+	if (inet_twsk_dead_hashed(tw)) {
+		__inet_twsk_del_dead_node(tw);
+		return 1;
+	}
+	return 0;
+}
+
+#define inet_twsk_for_each(tw, node, head) \
+	hlist_for_each_entry(tw, node, head, tw_node)
+
+#define inet_twsk_for_each_inmate(tw, node, jail) \
+	hlist_for_each_entry(tw, node, jail, tw_death_node)
+
+#define inet_twsk_for_each_inmate_safe(tw, node, safe, jail) \
+	hlist_for_each_entry_safe(tw, node, safe, jail, tw_death_node)
+
+static inline struct inet_timewait_sock *inet_twsk(const struct sock *sk)
+{
+	return (struct inet_timewait_sock *)sk;
+}
+
+static inline u32 inet_rcv_saddr(const struct sock *sk)
+{
+	return likely(sk->sk_state != TCP_TIME_WAIT) ?
+		inet_sk(sk)->rcv_saddr : inet_twsk(sk)->tw_rcv_saddr;
+}
+
+static inline void inet_twsk_put(struct inet_timewait_sock *tw)
+{
+	if (atomic_dec_and_test(&tw->tw_refcnt)) {
+#ifdef SOCK_REFCNT_DEBUG
+		printk(KERN_DEBUG "%s timewait_sock %p released\n",
+		       tw->tw_prot->name, tw);
+#endif
+		kmem_cache_free(tw->tw_prot->twsk_slab, tw);
+	}
+}
+#endif	/* _INET_TIMEWAIT_SOCK_ */