[X25]: Fast select with no restriction on response

This patch is a follow up to patch 1 regarding "Selective Sub Address
matching with call user data".  It allows use of the Fast-Select-Acceptance
optional user facility for X.25.

This patch just implements fast select with no restriction on response
(NRR).  What this means (according to ITU-T Recomendation 10/96 section
6.16) is that if in an incoming call packet, the relevant facility bits are
set for fast-select-NRR, then the called DTE can issue a direct response to
the incoming packet using a call-accepted packet that contains
call-user-data.  This patch allows such a response.  

The called DTE can also respond with a clear-request packet that contains
call-user-data.  However, this feature is currently not implemented by the
patch.

How is Fast Select Acceptance used?
By default, the system does not allow fast select acceptance (as before).
To enable a response to fast select acceptance,  
After a listen socket in created and bound as follows
	socket(AF_X25, SOCK_SEQPACKET, 0);
	bind(call_soc, (struct sockaddr *)&locl_addr, sizeof(locl_addr));
but before a listen system call is made, the following ioctl should be used.
	ioctl(call_soc,SIOCX25CALLACCPTAPPRV);
Now the listen system call can be made
	listen(call_soc, 4);
After this, an incoming-call packet will be accepted, but no call-accepted 
packet will be sent back until the following system call is made on the socket
that accepts the call
	ioctl(vc_soc,SIOCX25SENDCALLACCPT);
The network (or cisco xot router used for testing here) will allow the 
application server's call-user-data in the call-accepted packet, 
provided the call-request was made with Fast-select NRR.

Signed-off-by: Shaun Pereira <spereira@tusc.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 33 insertions, 4 deletions

diff --git a/net/x25/af_x25.c b/net/x25/af_x25.c
index e17d84a55d5e..04bec047fa9a 100644
--- a/net/x25/af_x25.c
+++ b/net/x25/af_x25.c
@@ -31,6 +31,8 @@
  *                                      x25_proc.c, using seq_file
  *      2005-04-02      Shaun Pereira   Selective sub address matching
  *                                      with call user data
+ *      2005-04-15      Shaun Pereira   Fast select with no restriction on
+ *                                      response
  */
 
 #include <linux/config.h>
@@ -502,6 +504,8 @@ static int x25_create(struct socket *sock, int protocol)
         x25->t2    = sysctl_x25_ack_holdback_timeout;
         x25->state = X25_STATE_0;
         x25->cudmatchlength = 0;
+        x25->accptapprv = X25_DENY_ACCPT_APPRV;         /* normally no cud  */
+                                                        /* on call accept   */
 
         x25->facilities.winsize_in  = X25_DEFAULT_WINDOW_SIZE;
         x25->facilities.winsize_out = X25_DEFAULT_WINDOW_SIZE;
@@ -551,6 +555,7 @@ static struct sock *x25_make_new(struct sock *osk)
         x25->facilities = ox25->facilities;
         x25->qbitincl   = ox25->qbitincl;
         x25->cudmatchlength = ox25->cudmatchlength;
+        x25->accptapprv = ox25->accptapprv;
 
         x25_init_timers(sk);
 out:
@@ -900,9 +905,11 @@ int x25_rx_call_request(struct sk_buff *skb, struct x25_neigh *nb,
         makex25->vc_facil_mask &= ~X25_MASK_REVERSE;
         makex25->cudmatchlength = x25_sk(sk)->cudmatchlength;
 
-        x25_write_internal(make, X25_CALL_ACCEPTED);
-
-        makex25->state = X25_STATE_3;
+        /* Normally all calls are accepted immediatly */
+        if(makex25->accptapprv & X25_DENY_ACCPT_APPRV) {
+                x25_write_internal(make, X25_CALL_ACCEPTED);
+                makex25->state = X25_STATE_3;
+        }
 
         /*
          *      Incoming Call User Data.
@@ -1294,7 +1301,8 @@ static int x25_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
                         if (facilities.throughput < 0x03 ||
                             facilities.throughput > 0xDD)
                                 break;
-                        if (facilities.reverse && facilities.reverse != 1)
+                        if (facilities.reverse &&
+                                (facilities.reverse | 0x81)!= 0x81)
                                 break;
                         x25->facilities = facilities;
                         rc = 0;
@@ -1348,6 +1356,27 @@ static int x25_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
                         break;
                 }
 
+                case SIOCX25CALLACCPTAPPRV: {
+                        rc = -EINVAL;
+                        if (sk->sk_state != TCP_CLOSE)
+                                break;
+                        x25->accptapprv = X25_ALLOW_ACCPT_APPRV;
+                        rc = 0;
+                        break;
+                }
+
+                case SIOCX25SENDCALLACCPT:  {
+                        rc = -EINVAL;
+                        if (sk->sk_state != TCP_ESTABLISHED)
+                                break;
+                        if (x25->accptapprv)    /* must call accptapprv above */
+                                break;
+                        x25_write_internal(sk, X25_CALL_ACCEPTED);
+                        x25->state = X25_STATE_3;
+                        rc = 0;
+                        break;
+                }
+
                 default:
                         rc = dev_ioctl(cmd, argp);
                         break;