• Shaun Pereira's avatar
    [X25]: Selective sub-address matching with call user data. · cb65d506
    Shaun Pereira authored
    From: Shaun Pereira <spereira@tusc.com.au>
    
    This is the first (independent of the second) patch of two that I am
    working on with x25 on linux (tested with xot on a cisco router).  Details
    are as follows.
    
    Current state of module:
    
    A server using the current implementation (2.6.11.7) of the x25 module will
    accept a call request/ incoming call packet at the listening x.25 address,
    from all callers to that address, as long as NO call user data is present
    in the packet header.
    
    If the server needs to choose to accept a particular call request/ incoming
    call packet arriving at its listening x25 address, then the kernel has to
    allow a match of call user data present in the call request packet with its
    own.  This is required when multiple servers listen at the same x25 address
    and device interface.  The kernel currently matches ALL call user data, if
    present.
    
    Current Changes:
    
    This patch is a follow up to the patch submitted previously by Andrew
    Hendry, and allows the user to selectively control the number of octets of
    call user data in the call request packet, that the kernel will match.  By
    default no call user data is matched, even if call user data is present. 
    To allow call user data matching, a cudmatchlength > 0 has to be passed
    into the kernel after which the passed number of octets will be matched. 
    Otherwise the kernel behavior is exactly as the original implementation.
    
    This patch also ensures that as is normally the case, no call user data
    will be present in the Call accepted / call connected packet sent back to
    the caller 
    
    Future Changes on next patch:
    
    There are cases however when call user data may be present in the call
    accepted packet.  According to the X.25 recommendation (ITU-T 10/96)
    section 5.2.3.2 call user data may be present in the call accepted packet
    provided the fast select facility is used.  My next patch will include this
    fast select utility and the ability to send up to 128 octets call user data
    in the call accepted packet provided the fast select facility is used.  I
    am currently testing this, again with xot on linux and cisco.  
    Signed-off-by: default avatarShaun Pereira <spereira@tusc.com.au>
    
    (With a fix from Alexey Dobriyan <adobriyan@gmail.com>)
    Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    cb65d506
x25_subr.c 8.67 KB