ddp

DDP(7)                     Linux Programmer's Manual                    DDP(7)

NAME
       ddp - Linux AppleTalk protocol implementation

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

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

DESCRIPTION
       Linux implements the AppleTalk protocols described in Inside AppleTalk.
       Only the DDP layer and AARP are present in the kernel.   They  are  de-
       signed to be used via the netatalk protocol libraries.  This page docu-
       ments the interface for those who wish or need to use the DDP layer di-
       rectly.

       The  communication between AppleTalk and the user program works using a
       BSD-compatible socket interface.  For more information on sockets,  see
       socket(7).

       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
       No protocol-specific socket options are supported.

   /proc interfaces
       IP  supports  a  set  of  /proc interfaces to configure some global Ap-
       pleTalk parameters.  The parameters can be accessed by reading or writ-
       ing files in the directory /proc/sys/net/atalk/.

       aarp-expiry-time
              The  time  interval  (in seconds) before an AARP cache entry ex-
              pires.

       aarp-resolve-time
              The time interval (in seconds) before an AARP cache entry is re-
              solved.

       aarp-retransmit-limit
              The  number  of retransmissions of an AARP query before the node
              is declared dead.

       aarp-tick-time
              The timer rate (in seconds) for the timer driving AARP.

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

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

ERRORS
       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 re-
              served port without effective user ID 0 or CAP_NET_BIND_SERVICE.

       EADDRINUSE
              Tried to bind to an address already in use.

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

       EAGAIN Operation on a nonblocking socket would block.

       EALREADY
              A  connection  operation  on  a nonblocking socket is already in
              progress.

       ECONNABORTED
              A connection was closed during an accept(2).

       EHOSTUNREACH
              No routing table entry matches the destination address.

       EINVAL Invalid argument passed.

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

       EMSGSIZE
              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.

       ENOMEM and ENOBUFS
              Not enough memory available.

       ENOPKG A kernel subsystem was not configured.

       ENOPROTOOPT and EOPNOTSUPP
              Invalid socket option passed.

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

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

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

       ESOCKTNOSUPPORT
              The socket was unconfigured, or an unknown socket type  was  re-
              quested.

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

NOTES
       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.

   Compatibility
       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.

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

COLOPHON
       This page is part of release 5.05 of the Linux  man-pages  project.   A
       description  of  the project, information about reporting bugs, and the
       latest    version    of    this    page,    can     be     found     at
       https://www.kernel.org/doc/man-pages/.

Linux                             2017-09-15                            DDP(7)