[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>

3 files changed, 80 insertions, 14 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;
diff --git a/net/x25/x25_facilities.c b/net/x25/x25_facilities.c
index a21bdb95f9a8..54278b962f4c 100644
--- a/net/x25/x25_facilities.c
+++ b/net/x25/x25_facilities.c
@@ -17,6 +17,8 @@
  *      X.25 001        Split from x25_subr.c
  *      mar/20/00       Daniela Squassoni Disabling/enabling of facilities 
  *                                        negotiation.
+ *      apr/14/05       Shaun Pereira - Allow fast select with no restriction
+ *                                      on response.
  */
 
 #include <linux/kernel.h>
@@ -43,9 +45,31 @@ int x25_parse_facilities(struct sk_buff *skb,
                 case X25_FAC_CLASS_A:
                         switch (*p) {
                         case X25_FAC_REVERSE:
-                                facilities->reverse = p[1] & 0x01;
-                                *vc_fac_mask |= X25_MASK_REVERSE;
-                                break;
+                                if((p[1] & 0x81) == 0x81) {
+                                        facilities->reverse = p[1] & 0x81;
+                                        *vc_fac_mask |= X25_MASK_REVERSE;
+                                        break;
+                                }
+
+                                if((p[1] & 0x01) == 0x01) {
+                                        facilities->reverse = p[1] & 0x01;
+                                        *vc_fac_mask |= X25_MASK_REVERSE;
+                                        break;
+                                }
+
+                                if((p[1] & 0x80) == 0x80) {
+                                        facilities->reverse = p[1] & 0x80;
+                                        *vc_fac_mask |= X25_MASK_REVERSE;
+                                        break;
+                                }
+
+                                if(p[1] == 0x00) {
+                                        facilities->reverse
+                                                = X25_DEFAULT_REVERSE;
+                                        *vc_fac_mask |= X25_MASK_REVERSE;
+                                        break;
+                                }
+
                         case X25_FAC_THROUGHPUT:
                                 facilities->throughput = p[1];
                                 *vc_fac_mask |= X25_MASK_THROUGHPUT;
@@ -122,7 +146,7 @@ int x25_create_facilities(unsigned char *buffer,
 
         if (facilities->reverse && (facil_mask & X25_MASK_REVERSE)) {
                 *p++ = X25_FAC_REVERSE;
-                *p++ = !!facilities->reverse;
+                *p++ = facilities->reverse;
         }
 
         if (facilities->throughput && (facil_mask & X25_MASK_THROUGHPUT)) {
@@ -171,7 +195,7 @@ int x25_negotiate_facilities(struct sk_buff *skb, struct sock *sk,
         /*
          *      They want reverse charging, we won't accept it.
          */
-        if (theirs.reverse && ours->reverse) {
+        if ((theirs.reverse & 0x01 ) && (ours->reverse & 0x01)) {
                 SOCK_DEBUG(sk, "X.25: rejecting reverse charging request");
                 return -1;
         }
diff --git a/net/x25/x25_subr.c b/net/x25/x25_subr.c
index c349bbd61684..7fd872ad0c20 100644
--- a/net/x25/x25_subr.c
+++ b/net/x25/x25_subr.c
@@ -19,6 +19,8 @@
  *      mar/20/00       Daniela Squassoni Disabling/enabling of facilities
  *                                        negotiation.
  *      jun/24/01       Arnaldo C. Melo   use skb_queue_purge, cleanups
+ *      apr/04/15       Shaun Pereira           Fast select with no
+ *                                              restriction on response.
  */
 
 #include <linux/kernel.h>
@@ -127,8 +129,12 @@ void x25_write_internal(struct sock *sk, int frametype)
                         len += 1 + X25_ADDR_LEN + X25_MAX_FAC_LEN +
                                X25_MAX_CUD_LEN;
                         break;
-                case X25_CALL_ACCEPTED:
-                        len += 1 + X25_MAX_FAC_LEN + X25_MAX_CUD_LEN;
+                case X25_CALL_ACCEPTED: /* fast sel with no restr on resp */
+                        if(x25->facilities.reverse & 0x80) {
+                                len += 1 + X25_MAX_FAC_LEN + X25_MAX_CUD_LEN;
+                        } else {
+                                len += 1 + X25_MAX_FAC_LEN;
+                        }
                         break;
                 case X25_CLEAR_REQUEST:
                 case X25_RESET_REQUEST:
@@ -203,9 +209,16 @@ void x25_write_internal(struct sock *sk, int frametype)
                                                         x25->vc_facil_mask);
                         dptr    = skb_put(skb, len);
                         memcpy(dptr, facilities, len);
-                        dptr = skb_put(skb, x25->calluserdata.cudlength);
-                        memcpy(dptr, x25->calluserdata.cuddata,
-                               x25->calluserdata.cudlength);
+
+                        /* fast select with no restriction on response
+                                allows call user data. Userland must
+                                ensure it is ours and not theirs */
+                        if(x25->facilities.reverse & 0x80) {
+                                dptr = skb_put(skb,
+                                        x25->calluserdata.cudlength);
+                                memcpy(dptr, x25->calluserdata.cuddata,
+                                       x25->calluserdata.cudlength);
+                        }
                         x25->calluserdata.cudlength = 0;
                         break;