• Shaun Pereira's avatar
    [X25]: Fast select with no restriction on response · ebc3f64b
    Shaun Pereira authored
    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: default avatarShaun Pereira <spereira@tusc.com.au>
    Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    ebc3f64b
x25_facilities.c 6.34 KB