[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 000000000000..9502f5587931
--- /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 */