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

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

       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
       AF_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 spec-
       ify ATPROTO_DDP.

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

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

           struct at_addr {
               unsigned short s_net;
               unsigned char  s_node;

           struct sockaddr_atalk {
               sa_family_t    sat_family;    /* address family */
               unsigned 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  mem-
       ber  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
              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

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

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

              Tried to bind to an address already in use.

              A  nonexistent  interface  was requested or the requested source
              address was not local.

       EAGAIN Operation on a nonblocking socket would block.

              A connection operation on a nonblocking  socket  is  already  in

              A connection was closed during an accept(2).

              No routing table entry matches the destination address.

       EINVAL Invalid argument passed.

              connect(2) was called on an already connected socket.

              Datagram is bigger than the DDP MTU.

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

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

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

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

              The  socket  was  unconfigured,  or  an  unknown socket type was

       Appletalk is supported by Linux 2.0 or higher.   The  /proc  interfaces
       exist since Linux 2.2.

       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.

       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 alter-
       native CAP package and AppleTalk monitoring tools more easily.

       There are too many inconsistent error values.

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

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

       This  page  is  part of release 3.54 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

Linux                             2008-11-20                            DDP(7)
Man Pages Copyright Respective Owners. Site Copyright (C) 1994 - 2019 Hurricane Electric. All Rights Reserved.