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NAME    [Toc]    [Back]

       ddp - Linux AppleTalk protocol implementation

SYNOPSIS    [Toc]    [Back]

       #include <sys/socket.h>
       #include <netatalk/at.h>

       ddp_socket = socket(PF_APPLETALK, SOCK_DGRAM, 0);
       raw_socket = socket(PF_APPLETALK, SOCK_RAW, protocol);

DESCRIPTION    [Toc]    [Back]

       Linux implements the Appletalk protocols described in Inside Appletalk.
       Only the DDP layer and  AARP  are  present  in  the  kernel.  They  are
       designed to be used via the netatalk protocol libraries. This page documents
 the interface for those who wish or need to use  the  DDP  layer

       The  communication between Appletalk and the user program works using a
       BSD-compatible socket interface. For more information on  sockets,  see

       An AppleTalk socket is created by calling the socket(2) function with a
       PF_APPLETALK socket family argument. Valid socket types are  SOCK_DGRAM
       to open a ddp socket or SOCK_RAW to open a raw socket.  protocol is the
       Appletalk protocol to be received or sent. For SOCK_RAW you must  specify

       Raw sockets may be only opened by a process with effective user id 0 or
       when the process has the CAP_NET_RAW capability.

ADDRESS FORMAT    [Toc]    [Back]

       An Appletalk socket address is defined as a combination	of  a  network
       number, a node number, and a port number.

	      struct at_addr {
		  u_short	  s_net;
		  u_char	  s_node;

	      struct sockaddr_atalk {
		  sa_family_t	  sat_family; /* address family */
		  u_char	  sat_port;   /* port */
		  struct at_addr  sat_addr;   /* net/node */

       sat_family  is always set to AF_APPLETALK.  sat_port contains the port.
       The port numbers below 129 are known as reserved ports.	Only processes
       with the effective user id 0 or the CAP_NET_BIND_SERVICE capability may
       bind(2) to these sockets.  sat_addr is the host address.  The net  member
  of struct at_addr contains the host network in network byte order.
       The value of AT_ANYNET is a wildcard and also implies  "this  network."
       The  node  member of struct at_addr contains the host node number.  The
       value of AT_ANYNODE is a wildcard and also  implies  "this  node."  The
       value of ATADDR_BCAST is a link local broadcast address.

SOCKET OPTIONS    [Toc]    [Back]

       No protocol-specific socket options are supported.

SYSCTLS    [Toc]    [Back]

       IP  supports  a	sysctl	interface  to  configure some global AppleTalk
       parameters.  The sysctls can be accessed  by  reading  or  writing  the
       /proc/sys/net/atalk/* files or with the sysctl(2) interface.

	      The  time  interval  (in	seconds)  before  an  AARP cache entry

	      The time interval (in seconds) before an	AARP  cache  entry  is

	      The  number  of retransmissions of an AARP query before the node
	      is declared dead.

	      The timer rate (in seconds) for the timer driving AARP.

       The default values match the specification and should never need to  be

IOCTLS    [Toc]    [Back]

       All ioctls described in socket(7) apply to ddp.

NOTES    [Toc]    [Back]

       Be  very careful with the SO_BROADCAST option - it is not privileged in
       Linux. It is easy to overload the  network  with  careless  sending  to
       broadcast addresses.

VERSIONS    [Toc]    [Back]

       Appletalk  is supported by Linux 2.0 or higher. The sysctl interface is
       new in Linux 2.2.

ERRORS    [Toc]    [Back]

	      The operation is only defined on a  connected  socket,  but  the
	      socket wasn't connected.

       EINVAL Invalid argument passed.

       EMSGSIZE    [Toc]    [Back]
	      Datagram is bigger than the DDP MTU.

       EACCES The  user  tried	to  execute an operation without the necessary
	      permissions. These include sending to a broadcast address  without
  having  the	broadcast  flag  set,  and trying to bind to a
	      reserved port without effective user id 0  or  CAP_NET_BIND_SER-

       EADDRINUSE    [Toc]    [Back]
	      Tried to bind to an address already in use.

	      Not enough memory available.

	      Invalid socket option passed.

       EPERM  User  doesn't  have permission to set high priority, make a configuration
 change, or send signals to the requested  process  or

       EADDRNOTAVAIL    [Toc]    [Back]
	      A  non-existent  interface was requested or the requested source
	      address was not local.

       EAGAIN Operation on a nonblocking socket would block.

       ESOCKTNOSUPPORT    [Toc]    [Back]
	      The socket was unconfigured,  or	an  unknown  socket  type  was

       EISCONN    [Toc]    [Back]
	      connect(2) was called on an already connected socket.

       EALREADY    [Toc]    [Back]
	      A  connection  operation	on a non-blocking socket is already in

       ECONNABORTED    [Toc]    [Back]
	      A connection was closed during an accept(2).

       EPIPE  The connection was unexpectedly closed or shut down by the other

       ENOENT SIOCGSTAMP was called on a socket where no packet arrived.

       EHOSTUNREACH    [Toc]    [Back]
	      No routing table entry matches the destination address.

       ENODEV Network device not available or not capable of sending IP.

       ENOPKG A kernel subsystem was not configured.

COMPATIBILITY    [Toc]    [Back]

       The  basic  AppleTalk  socket  interface is compatible with netatalk on
       BSD-derived systems. Many BSD systems fail to check  SO_BROADCAST  when
       sending broadcast frames; this can lead to compatibility problems.

       The raw socket mode is unique to Linux and exists to support the alternative
 CAP package and AppleTalk monitoring tools more easily.

BUGS    [Toc]    [Back]

       There are too many inconsistent error values.

       The ioctls used to configure routing tables, devices, AARP  tables  and
       other devices are not yet described.

SEE ALSO    [Toc]    [Back]

       sendmsg(2), recvmsg(2), socket(7)

Linux Man Page			  1999-05-01				DDP(7)
[ Back ]
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