[NET] Generalise TCP's struct open_request minisock infrastructure

Kept this first changeset minimal, without changing existing names to
ease peer review.

Basicaly tcp_openreq_alloc now receives the or_calltable, that in turn
has two new members:

->slab, that replaces tcp_openreq_cachep
->obj_size, to inform the size of the openreq descendant for
  a specific protocol

The protocol specific fields in struct open_request were moved to a
class hierarchy, with the things that are common to all connection
oriented PF_INET protocols in struct inet_request_sock, the TCP ones
in tcp_request_sock, that is an inet_request_sock, that is an
open_request.

I.e. this uses the same approach used for the struct sock class
hierarchy, with sk_prot indicating if the protocol wants to use the
open_request infrastructure by filling in sk_prot->rsk_prot with an
or_calltable.

Results? Performance is improved and TCP v4 now uses only 64 bytes per
open request minisock, down from 96 without this patch :-)

Next changeset will rename some of the structs, fields and functions
mentioned above, struct or_calltable is way unclear, better name it
struct request_sock_ops, s/struct open_request/struct request_sock/g,
etc.

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

1 files changed, 77 insertions, 0 deletions

diff --git a/include/net/request_sock.h b/include/net/request_sock.h
new file mode 100644
index 0000000..9502f55
--- /dev/null
+++ b/include/net/request_sock.h
@@ -0,0 +1,77 @@
+/*
+ * NET		Generic infrastructure for Network protocols.
+ *
+ *		Definitions for request_sock 
+ *
+ * Authors:	Arnaldo Carvalho de Melo <acme@conectiva.com.br>
+ *
+ * 		From code originally in include/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 _REQUEST_SOCK_H
+#define _REQUEST_SOCK_H
+
+#include <linux/slab.h>
+#include <linux/types.h>
+#include <net/sock.h>
+
+struct open_request;
+struct sk_buff;
+struct dst_entry;
+struct proto;
+
+struct or_calltable {
+	int		family;
+	kmem_cache_t	*slab;
+	int		obj_size;
+	int		(*rtx_syn_ack)(struct sock *sk,
+				       struct open_request *req,
+				       struct dst_entry *dst);
+	void		(*send_ack)(struct sk_buff *skb,
+				    struct open_request *req);
+	void		(*send_reset)(struct sk_buff *skb);
+	void		(*destructor)(struct open_request *req);
+};
+
+/* struct open_request - mini sock to represent a connection request
+ */
+struct open_request {
+	struct open_request		*dl_next; /* Must be first member! */
+	u16				mss;
+	u8				retrans;
+	u8				__pad;
+	/* The following two fields can be easily recomputed I think -AK */
+	u32				window_clamp; /* window clamp at creation time */
+	u32				rcv_wnd;	  /* rcv_wnd offered first time */
+	u32				ts_recent;
+	unsigned long			expires;
+	struct or_calltable		*class;
+	struct sock			*sk;
+};
+
+static inline struct open_request *tcp_openreq_alloc(struct or_calltable *class)
+{
+	struct open_request *req = kmem_cache_alloc(class->slab, SLAB_ATOMIC);
+
+	if (req != NULL)
+		req->class = class;
+
+	return req;
+}
+
+static inline void tcp_openreq_fastfree(struct open_request *req)
+{
+	kmem_cache_free(req->class->slab, req);
+}
+
+static inline void tcp_openreq_free(struct open_request *req)
+{
+	req->class->destructor(req);
+	tcp_openreq_fastfree(req);
+}
+
+#endif /* _REQUEST_SOCK_H */