[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_ */