[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, 4 insertions, 2 deletions

diff --git a/include/net/x25.h b/include/net/x25.h
index 9dd70dd4a9b..8b39b98876e 100644
--- a/include/net/x25.h
+++ b/include/net/x25.h
@@ -79,6 +79,8 @@ enum {
 #define	X25_DEFAULT_PACKET_SIZE	X25_PS128		/* Default Packet Size */
 #define	X25_DEFAULT_THROUGHPUT	0x0A			/* Deafult Throughput */
 #define	X25_DEFAULT_REVERSE	0x00			/* Default Reverse Charging */
+#define X25_DENY_ACCPT_APPRV   0x01			/* Default value */
+#define X25_ALLOW_ACCPT_APPRV  0x00			/* Control enabled */
 
 #define X25_SMODULUS 		8
 #define	X25_EMODULUS		128
@@ -94,7 +96,7 @@ enum {
 #define	X25_FAC_CLASS_C		0x80
 #define	X25_FAC_CLASS_D		0xC0
 
-#define	X25_FAC_REVERSE		0x01
+#define	X25_FAC_REVERSE		0x01			/* also fast select */
 #define	X25_FAC_THROUGHPUT	0x02
 #define	X25_FAC_PACKET_SIZE	0x42
 #define	X25_FAC_WINDOW_SIZE	0x43
@@ -135,7 +137,7 @@ struct x25_sock {
 	struct x25_address	source_addr, dest_addr;
 	struct x25_neigh	*neighbour;
 	unsigned int		lci, cudmatchlength;
-	unsigned char		state, condition, qbitincl, intflag;
+	unsigned char		state, condition, qbitincl, intflag, accptapprv;
 	unsigned short		vs, vr, va, vl;
 	unsigned long		t2, t21, t22, t23;
 	unsigned short		fraglen;