mirror of https://github.com/mkerrisk/man-pages
253 lines
6.1 KiB
Groff
253 lines
6.1 KiB
Groff
.\" This man page is Copyright (C) 1998 Alan Cox.
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.\" Permission is granted to distribute possibly modified copies
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.\" of this page provided the header is included verbatim,
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.\" and in case of nontrivial modification author and date
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.\" of the modification is added to the header.
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.\" $Id: ddp.7,v 1.3 1999/05/13 11:33:22 freitag Exp $
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.TH DDP 7 1999-05-01 "Linux" "Linux Programmer's Manual"
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.SH NAME
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ddp \- Linux AppleTalk protocol implementation
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.SH SYNOPSIS
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.B #include <sys/socket.h>
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.br
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.B #include <netatalk/at.h>
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.sp
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.IB ddp_socket " = socket(PF_APPLETALK, SOCK_DGRAM, 0);"
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.br
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.IB raw_socket " = socket(PF_APPLETALK, SOCK_RAW, " protocol ");"
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.SH DESCRIPTION
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Linux implements the Appletalk protocols described in
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.IR "Inside Appletalk" .
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Only the DDP layer and AARP are present in
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the kernel.
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They are designed to be used via the
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.B netatalk
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protocol
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libraries.
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This page documents the interface for those who wish or need to
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use the DDP layer directly.
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.PP
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The communication between Appletalk and the user program works using a
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BSD-compatible socket interface.
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For more information on sockets, see
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.BR socket (7).
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.PP
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An AppleTalk socket is created by calling the
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.BR socket (2)
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function with a
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.B PF_APPLETALK
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socket family argument.
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Valid socket types are
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.B SOCK_DGRAM
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to open a
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.B ddp
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socket or
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.B SOCK_RAW
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to open a
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.B raw
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socket.
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.I protocol
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is the Appletalk protocol to be received or sent.
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For
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.B SOCK_RAW
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you must specify
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.BR ATPROTO_DDP .
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.PP
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Raw sockets may be only opened by a process with effective user ID 0
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or when the process has the
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.B CAP_NET_RAW
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capability.
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.SH "ADDRESS FORMAT"
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An Appletalk socket address is defined as a combination of a network number,
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a node number, and a port number.
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.PP
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.RS
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.nf
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struct at_addr {
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u_short s_net;
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u_char s_node;
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};
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struct sockaddr_atalk {
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sa_family_t sat_family; /* address family */
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u_char sat_port; /* port */
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struct at_addr sat_addr; /* net/node */
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};
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.ta
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.fi
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.RE
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.PP
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.I sat_family
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is always set to
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.BR AF_APPLETALK .
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.I sat_port
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contains the port.
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The port numbers below 129 are known as
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.I reserved ports.
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Only processes with the effective user ID 0 or the
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.B CAP_NET_BIND_SERVICE
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capability may
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.BR bind (2)
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to these sockets.
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.I sat_addr
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is the host address.
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The
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.I net
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member of
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.I struct at_addr
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contains the host network in network byte order.
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The value of
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.B AT_ANYNET
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is a
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wildcard and also implies \(lqthis network.\(rq
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The
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.I node
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member of
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.I struct at_addr
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contains the host node number.
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The value of
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.B AT_ANYNODE
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is a
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wildcard and also implies \(lqthis node.\(rq The value of
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.B ATADDR_BCAST
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is a link
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local broadcast address.
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.\" FIXME this doesn't make sense [johnl]
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.SH "SOCKET OPTIONS"
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No protocol-specific socket options are supported.
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.SH SYSCTLS
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IP supports a sysctl interface to configure some global AppleTalk
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parameters.
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The sysctls can be accessed by reading or writing the
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.I /proc/sys/net/atalk/*
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files or with the
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.BR sysctl (2)
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interface.
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.TP
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.B aarp-expiry-time
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The time interval (in seconds) before an AARP cache entry expires.
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.TP
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.B aarp-resolve-time
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The time interval (in seconds) before an AARP cache entry is resolved.
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.TP
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.B aarp-retransmit-limit
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The number of retransmissions of an AARP query before the node is declared
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dead.
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.TP
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.B aarp-tick-time
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The timer rate (in seconds) for the timer driving AARP.
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.PP
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The default values match the specification and should never need to be
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changed.
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.SH IOCTLS
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All ioctls described in
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.BR socket (7)
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apply to ddp.
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.\" FIXME Add a section about multicasting
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.SH NOTES
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Be very careful with the
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.B SO_BROADCAST
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option \- it is not privileged in Linux.
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It is easy to overload the network
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with careless sending to broadcast addresses.
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.SH VERSIONS
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Appletalk is supported by Linux 2.0 or higher.
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The
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.B sysctl
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interface is
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new in Linux 2.2.
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.SH ERRORS
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.\" FIXME document all errors. We should really fix the kernels to
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.\" give more uniform error returns (ENOMEM vs ENOBUFS, EPERM vs
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.\" EACCES etc.)
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.TP
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.B ENOTCONN
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The operation is only defined on a connected socket, but the socket wasn't
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connected.
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.TP
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.B EINVAL
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Invalid argument passed.
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.TP
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.B EMSGSIZE
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Datagram is bigger than the DDP MTU.
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.TP
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.B EACCES
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The user tried to execute an operation without the necessary permissions.
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These include sending to a broadcast address without
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having the broadcast flag set,
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and trying to bind to a reserved port without effective user ID 0 or
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.BR CAP_NET_BIND_SERVICE .
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.TP
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.B EADDRINUSE
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Tried to bind to an address already in use.
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.TP
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.BR ENOMEM " and " ENOBUFS
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Not enough memory available.
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.TP
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.BR ENOPROTOOPT " and " EOPNOTSUPP
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Invalid socket option passed.
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.TP
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.B EPERM
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User doesn't have permission to set high priority,
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make a configuration change,
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or send signals to the requested process or group,
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.TP
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.B EADDRNOTAVAIL
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A non-existent interface was requested or the requested source address was
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not local.
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.TP
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.B EAGAIN
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Operation on a nonblocking socket would block.
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.TP
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.B ESOCKTNOSUPPORT
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The socket was unconfigured, or an unknown socket type was requested.
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.TP
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.B EISCONN
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.BR connect (2)
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was called on an already connected socket.
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.TP
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.B EALREADY
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A connection operation on a non-blocking socket is already in progress.
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.TP
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.B ECONNABORTED
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A connection was closed during an
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.BR accept (2).
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.TP
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.B EPIPE
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The connection was unexpectedly closed or shut down by the other end.
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.TP
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.B ENOENT
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.B SIOCGSTAMP
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was called on a socket where no packet arrived.
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.TP
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.B EHOSTUNREACH
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No routing table entry matches the destination address.
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.TP
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.B ENODEV
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Network device not available or not capable of sending IP.
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.TP
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.B ENOPKG
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A kernel subsystem was not configured.
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.SH COMPATIBILITY
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The basic AppleTalk socket interface is compatible with
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.B netatalk
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on BSD-derived systems.
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Many BSD systems fail to check
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.B SO_BROADCAST
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when sending broadcast frames; this can lead to compatibility problems.
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.PP
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The
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raw
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socket mode is unique to Linux and exists to support the alternative CAP
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package and AppleTalk monitoring tools more easily.
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.SH BUGS
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There are too many inconsistent error values.
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.PP
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The ioctls used to configure routing tables, devices,
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AARP tables and other devices are not yet described.
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.SH "SEE ALSO"
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.BR recvmsg (2),
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.BR sendmsg (2),
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.BR capabilities (7),
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.BR socket (7)
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