[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, 20 insertions, 19 deletions

diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index e923d2f021aa..dd47e6da6fb3 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -190,6 +190,8 @@ static inline struct sock *get_cookie_sock(struct sock *sk, struct sk_buff *skb,
 struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
                              struct ip_options *opt)
 {
+        struct inet_request_sock *ireq;
+        struct tcp_request_sock *treq;
         struct tcp_sock *tp = tcp_sk(sk);
         __u32 cookie = ntohl(skb->h.th->ack_seq) - 1; 
         struct sock *ret = sk;
@@ -209,19 +211,20 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
 
         NET_INC_STATS_BH(LINUX_MIB_SYNCOOKIESRECV);
 
-        req = tcp_openreq_alloc();
         ret = NULL;
+        req = tcp_openreq_alloc(&or_ipv4); /* for safety */
         if (!req)
                 goto out;
 
-        req->rcv_isn            = htonl(skb->h.th->seq) - 1;
-        req->snt_isn            = cookie; 
+        ireq = inet_rsk(req);
+        treq = tcp_rsk(req);
+        treq->rcv_isn           = htonl(skb->h.th->seq) - 1;
+        treq->snt_isn           = cookie; 
         req->mss                = mss;
-        req->rmt_port           = skb->h.th->source;
-        req->af.v4_req.loc_addr = skb->nh.iph->daddr;
-        req->af.v4_req.rmt_addr = skb->nh.iph->saddr;
-        req->class              = &or_ipv4; /* for savety */
-        req->af.v4_req.opt      = NULL;
+        ireq->rmt_port          = skb->h.th->source;
+        ireq->loc_addr          = skb->nh.iph->daddr;
+        ireq->rmt_addr          = skb->nh.iph->saddr;
+        ireq->opt               = NULL;
 
         /* We throwed the options of the initial SYN away, so we hope
          * the ACK carries the same options again (see RFC1122 4.2.3.8)
@@ -229,17 +232,15 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
         if (opt && opt->optlen) {
                 int opt_size = sizeof(struct ip_options) + opt->optlen;
 
-                req->af.v4_req.opt = kmalloc(opt_size, GFP_ATOMIC);
-                if (req->af.v4_req.opt) {
-                        if (ip_options_echo(req->af.v4_req.opt, skb)) {
-                                kfree(req->af.v4_req.opt);
-                                req->af.v4_req.opt = NULL;
-                        }
+                ireq->opt = kmalloc(opt_size, GFP_ATOMIC);
+                if (ireq->opt != NULL && ip_options_echo(ireq->opt, skb)) {
+                        kfree(ireq->opt);
+                        ireq->opt = NULL;
                 }
         }
 
-        req->snd_wscale = req->rcv_wscale = req->tstamp_ok = 0;
-        req->wscale_ok  = req->sack_ok = 0; 
+        ireq->snd_wscale = ireq->rcv_wscale = ireq->tstamp_ok = 0;
+        ireq->wscale_ok  = ireq->sack_ok = 0; 
         req->expires    = 0UL; 
         req->retrans    = 0; 
         
@@ -253,8 +254,8 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
                 struct flowi fl = { .nl_u = { .ip4_u =
                                               { .daddr = ((opt && opt->srr) ?
                                                           opt->faddr :
-                                                          req->af.v4_req.rmt_addr),
-                                                .saddr = req->af.v4_req.loc_addr,
+                                                          ireq->rmt_addr),
+                                                .saddr = ireq->loc_addr,
                                                 .tos = RT_CONN_FLAGS(sk) } },
                                     .proto = IPPROTO_TCP,
                                     .uli_u = { .ports =
@@ -272,7 +273,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
                                   &req->rcv_wnd, &req->window_clamp, 
                                   0, &rcv_wscale);
         /* BTW win scale with syncookies is 0 by definition */
-        req->rcv_wscale   = rcv_wscale; 
+        ireq->rcv_wscale  = rcv_wscale; 
 
         ret = get_cookie_sock(sk, skb, req, &rt->u.dst);
 out:    return ret;