[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, 11 insertions, 0 deletions

diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index 14a55e3e3a50..86771b37b80d 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -230,6 +230,17 @@ struct tcp_options_received {
         __u16   mss_clamp;      /* Maximal mss, negotiated at connection setup */
 };
 
+struct tcp_request_sock {
+        struct inet_request_sock req;
+        __u32                    rcv_isn;
+        __u32                    snt_isn;
+};
+
+static inline struct tcp_request_sock *tcp_rsk(const struct open_request *req)
+{
+        return (struct tcp_request_sock *)req;
+}
+
 struct tcp_sock {
         /* inet_sock has to be the first member of tcp_sock */
         struct inet_sock        inet;