NAME
ddp - Linux AppleTalk protocol implementation SYNOPSIS
#include
#include
ddpsocket = socket(AFAPPLETALK, SOCKDGRAM, 0); rawsocket = socket(AFAPPLETALK, SOCKRAW, 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 AFAPPLETALK socket family argument. Valid socket types are SOCKDGRAM to open a ddp socket or SOCKRAW to open a raw socket. protocol is the Appletalk protocol to be received or sent. For SOCKRAW you must spec‐ ify ATPROTODDP. Raw sockets may be opened only by a process with effective user ID 0 or when the process has the CAPNETRAW capability. Address format An Appletalk socket address is defined as a combination of a network number, a node number, and a port number. struct ataddr { unsigned short snet; unsigned char snode; }; struct sockaddratalk { safamilyt satfamily; /* address family */ unsigned char satport; /* port */ struct ataddr sataddr; /* net/node */ }; satfamily is always set to AFAPPLETALK. satport contains the port. The port numbers below 129 are known as reserved ports. Only processes with the effective user ID 0 or the CAPNETBINDSERVICE capability may bind(2) to these sockets. sataddr is the host address. The net mem‐ ber of struct ataddr contains the host network in network byte order. The value of ATANYNET is a wildcard and also implies “this network.” The node member of struct ataddr contains the host node number. The value of ATANYNODE is a wildcard and also implies “this node.” The value of ATADDRBCAST 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 with‐ out having the broadcast flag set, and trying to bind to a reserved port without effective user ID 0 or CAPNETBINDSER‐ VICE. 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 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 SOBROADCAST 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 SOBROADCAST 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 3.53 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)