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
       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
       directly.

       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
       specify 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
       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
       No protocol-specific socket options are supported.

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

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

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

       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
              without having the broadcast flag set, and trying to bind to a
              reserved 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
              configuration 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
              requested.

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
       alternative 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 5.03 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)