fb24f088ae
little endian and big endian and with 32 and 64 bit pointers. It already has the hooks to be used for HARP, NATM and ngATM.
97 lines
2.8 KiB
Groff
97 lines
2.8 KiB
Groff
.\" $FreeBSD$
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.\"
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.Dd December 29, 1997
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.Dt NATM 4
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.Os
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.Sh NAME
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.Nm natm
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.Nd Native Mode ATM protocol layer
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.Sh DESCRIPTION
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The
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.Bx
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ATM software comes with a
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.Em native mode ATM protocol layer
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which provides socket level access to AAL0 and AAL5 virtual circuits.
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To enable this protocol layer, add
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.Dl options NATM
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to your kernel configuration file and re-make the kernel (don't forget
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to do
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.Dq make clean ) .
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.Sh NATM API
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The NATM layer uses a
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.Dv struct sockaddr_natm
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to specify a virtual circuit:
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.Bd -literal -offset indent
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struct sockaddr_natm {
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u_int8_t snatm_len; /* length */
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u_int8_t snatm_family; /* AF_NATM */
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char snatm_if[IFNAMSIZ]; /* interface name */
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u_int16_t snatm_vci; /* vci */
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u_int8_t snatm_vpi; /* vpi */
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};
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.Ed
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.Pp
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To create an AAL5 connection to a virtual circuit with VPI 0, VCI 201
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one would use the following:
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.Bd -literal -offset indent
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struct sockaddr_natm snatm;
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int s, r;
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s = socket(AF_NATM, SOCK_STREAM, PROTO_NATMAAL5);
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/* note: PROTO_NATMAAL0 is AAL0 */
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if (s < 0) { perror("socket"); exit(1); }
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bzero(&snatm, sizeof(snatm));
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snatm.snatm_len = sizeof(snatm);
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snatm.snatm_family = AF_NATM;
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sprintf(snatm.snatm_if, "en0");
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snatm.snatm_vci = 201;
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snatm.snatm_vpi = 0;
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r = connect(s, (struct sockaddr *)&snatm, sizeof(snatm));
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if (r < 0) { perror("connect"); exit(1); }
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/* s now connected to ATM! */
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.Ed
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.Pp
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The
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.Fn socket
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call simply creates an unconnected NATM socket. The
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.Fn connect
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call associates an unconnected NATM socket with a
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virtual circuit and tells the driver to enable that virtual circuit
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for receiving data. After the
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.Fn connect
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call one can
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.Fn read
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or
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.Fn write
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to the socket to perform ATM I/O.
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.Sh Internal NATM operation
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Internally, the NATM protocol layer keeps a list of all active virtual
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circuits on the system in
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.Dv natm_pcbs .
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This includes circuits currently being used for IP to prevent NATM and
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IP from clashing over virtual circuit usage.
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.Pp
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When a virtual circuit is enabled for receiving data, the NATM
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protocol layer passes the address of the protocol control block down
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to the driver as a receive
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.Dq handle .
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When inbound data arrives, the driver passes the data back with the
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appropriate receive handle. The NATM layer uses this to avoid the
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overhead of a protocol control block lookup. This allows us to take
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advantage of the fact that ATM has already demultiplexed the data for
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us.
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.Sh CAVEAT
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The NATM protocol support is subject to change as
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the ATM protocols develop. Users should not depend
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on details of the current implementation, but rather
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the services exported.
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.Sh SEE ALSO
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.Xr en 4 ,
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.Xr hatm 4 ,
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.Xr fatm 4 ,
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.Xr natmip 4
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.Sh AUTHORS
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.An Chuck Cranor
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of Washington University implemented the NATM protocol layer
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along with the EN ATM driver in 1996 for
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.Nx .
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