[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, 12 deletions

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index fa24e7ae1f40..f3c8747caf91 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1358,6 +1358,7 @@ int tcp_send_synack(struct sock *sk)
 struct sk_buff * tcp_make_synack(struct sock *sk, struct dst_entry *dst,
                                  struct open_request *req)
 {
+        struct inet_request_sock *ireq = inet_rsk(req);
         struct tcp_sock *tp = tcp_sk(sk);
         struct tcphdr *th;
         int tcp_header_size;
@@ -1373,47 +1374,47 @@ struct sk_buff * tcp_make_synack(struct sock *sk, struct dst_entry *dst,
         skb->dst = dst_clone(dst);
 
         tcp_header_size = (sizeof(struct tcphdr) + TCPOLEN_MSS +
-                           (req->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0) +
-                           (req->wscale_ok ? TCPOLEN_WSCALE_ALIGNED : 0) +
+                           (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0) +
+                           (ireq->wscale_ok ? TCPOLEN_WSCALE_ALIGNED : 0) +
                            /* SACK_PERM is in the place of NOP NOP of TS */
-                           ((req->sack_ok && !req->tstamp_ok) ? TCPOLEN_SACKPERM_ALIGNED : 0));
+                           ((ireq->sack_ok && !ireq->tstamp_ok) ? TCPOLEN_SACKPERM_ALIGNED : 0));
         skb->h.th = th = (struct tcphdr *) skb_push(skb, tcp_header_size);
 
         memset(th, 0, sizeof(struct tcphdr));
         th->syn = 1;
         th->ack = 1;
         if (dst->dev->features&NETIF_F_TSO)
-                req->ecn_ok = 0;
+                ireq->ecn_ok = 0;
         TCP_ECN_make_synack(req, th);
         th->source = inet_sk(sk)->sport;
-        th->dest = req->rmt_port;
-        TCP_SKB_CB(skb)->seq = req->snt_isn;
+        th->dest = ireq->rmt_port;
+        TCP_SKB_CB(skb)->seq = tcp_rsk(req)->snt_isn;
         TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq + 1;
         TCP_SKB_CB(skb)->sacked = 0;
         skb_shinfo(skb)->tso_segs = 1;
         skb_shinfo(skb)->tso_size = 0;
         th->seq = htonl(TCP_SKB_CB(skb)->seq);
-        th->ack_seq = htonl(req->rcv_isn + 1);
+        th->ack_seq = htonl(tcp_rsk(req)->rcv_isn + 1);
         if (req->rcv_wnd == 0) { /* ignored for retransmitted syns */
                 __u8 rcv_wscale; 
                 /* Set this up on the first call only */
                 req->window_clamp = tp->window_clamp ? : dst_metric(dst, RTAX_WINDOW);
                 /* tcp_full_space because it is guaranteed to be the first packet */
                 tcp_select_initial_window(tcp_full_space(sk), 
-                        dst_metric(dst, RTAX_ADVMSS) - (req->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0),
+                        dst_metric(dst, RTAX_ADVMSS) - (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0),
                         &req->rcv_wnd,
                         &req->window_clamp,
-                        req->wscale_ok,
+                        ireq->wscale_ok,
                         &rcv_wscale);
-                req->rcv_wscale = rcv_wscale; 
+                ireq->rcv_wscale = rcv_wscale; 
         }
 
         /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
         th->window = htons(req->rcv_wnd);
 
         TCP_SKB_CB(skb)->when = tcp_time_stamp;
-        tcp_syn_build_options((__u32 *)(th + 1), dst_metric(dst, RTAX_ADVMSS), req->tstamp_ok,
-                              req->sack_ok, req->wscale_ok, req->rcv_wscale,
+        tcp_syn_build_options((__u32 *)(th + 1), dst_metric(dst, RTAX_ADVMSS), ireq->tstamp_ok,
+                              ireq->sack_ok, ireq->wscale_ok, ireq->rcv_wscale,
                               TCP_SKB_CB(skb)->when,
                               req->ts_recent);