Ubuntu Manpage: ddp - Linux AppleTalk protocol implementation

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.

COLOPHON

       This  page  is  part  of  release  5.10  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/.