[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, 13 insertions, 0 deletions

diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index ab0d0efbf240..98acdbf3d446 100644
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -193,6 +193,19 @@ struct inet6_skb_parm {
 
 #define IP6CB(skb)      ((struct inet6_skb_parm*)((skb)->cb))
 
+struct tcp6_request_sock {
+        struct tcp_request_sock req;
+        struct in6_addr         loc_addr;
+        struct in6_addr         rmt_addr;
+        struct sk_buff          *pktopts;
+        int                     iif;
+};
+
+static inline struct tcp6_request_sock *tcp6_rsk(const struct open_request *sk)
+{
+        return (struct tcp6_request_sock *)sk;
+}
+
 /**
  * struct ipv6_pinfo - ipv6 private area
  *