1DDP(7)                     Linux Programmer's Manual                    DDP(7)
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NAME

6       ddp - Linux AppleTalk protocol implementation
7

SYNOPSIS

9       #include <sys/socket.h>
10       #include <netatalk/at.h>
11
12       ddp_socket = socket(AF_APPLETALK, SOCK_DGRAM, 0);
13       raw_socket = socket(AF_APPLETALK, SOCK_RAW, protocol);
14

DESCRIPTION

16       Linux implements the AppleTalk protocols described in Inside AppleTalk.
17       Only the DDP layer and AARP are present in the kernel.   They  are  de‐
18       signed to be used via the netatalk protocol libraries.  This page docu‐
19       ments the interface for those who wish or need to use the DDP layer di‐
20       rectly.
21
22       The  communication between AppleTalk and the user program works using a
23       BSD-compatible socket interface.  For more information on sockets,  see
24       socket(7).
25
26       An AppleTalk socket is created by calling the socket(2) function with a
27       AF_APPLETALK socket family argument.  Valid socket types are SOCK_DGRAM
28       to open a ddp socket or SOCK_RAW to open a raw socket.  protocol is the
29       AppleTalk protocol to be received or sent.  For SOCK_RAW you must spec‐
30       ify ATPROTO_DDP.
31
32       Raw sockets may be opened only by a process with effective user ID 0 or
33       when the process has the CAP_NET_RAW capability.
34
35   Address format
36       An AppleTalk socket address is defined as a combination  of  a  network
37       number, a node number, and a port number.
38
39           struct at_addr {
40               unsigned short s_net;
41               unsigned char  s_node;
42           };
43
44           struct sockaddr_atalk {
45               sa_family_t    sat_family;    /* address family */
46               unsigned char  sat_port;      /* port */
47               struct at_addr sat_addr;      /* net/node */
48           };
49
50       sat_family  is always set to AF_APPLETALK.  sat_port contains the port.
51       The port numbers below 129 are known as reserved ports.  Only processes
52       with the effective user ID 0 or the CAP_NET_BIND_SERVICE capability may
53       bind(2) to these sockets.  sat_addr is the host address.  The net  mem‐
54       ber  of struct at_addr contains the host network in network byte order.
55       The value of AT_ANYNET is a wildcard and also implies  “this  network.”
56       The  node  member of struct at_addr contains the host node number.  The
57       value of AT_ANYNODE is a wildcard and also  implies  “this  node.”  The
58       value of ATADDR_BCAST is a link local broadcast address.
59
60   Socket options
61       No protocol-specific socket options are supported.
62
63   /proc interfaces
64       IP  supports  a  set  of  /proc interfaces to configure some global Ap‐
65       pleTalk parameters.  The parameters can be accessed by reading or writ‐
66       ing files in the directory /proc/sys/net/atalk/.
67
68       aarp-expiry-time
69              The  time  interval  (in seconds) before an AARP cache entry ex‐
70              pires.
71
72       aarp-resolve-time
73              The time interval (in seconds) before an AARP cache entry is re‐
74              solved.
75
76       aarp-retransmit-limit
77              The  number  of retransmissions of an AARP query before the node
78              is declared dead.
79
80       aarp-tick-time
81              The timer rate (in seconds) for the timer driving AARP.
82
83       The default values match the specification and should never need to  be
84       changed.
85
86   Ioctls
87       All ioctls described in socket(7) apply to DDP.
88

ERRORS

90       EACCES The  user  tried  to  execute an operation without the necessary
91              permissions.  These include sending to a broadcast address with‐
92              out  having  the broadcast flag set, and trying to bind to a re‐
93              served port without effective user ID 0 or CAP_NET_BIND_SERVICE.
94
95       EADDRINUSE
96              Tried to bind to an address already in use.
97
98       EADDRNOTAVAIL
99              A nonexistent interface was requested or  the  requested  source
100              address was not local.
101
102       EAGAIN Operation on a nonblocking socket would block.
103
104       EALREADY
105              A  connection  operation  on  a nonblocking socket is already in
106              progress.
107
108       ECONNABORTED
109              A connection was closed during an accept(2).
110
111       EHOSTUNREACH
112              No routing table entry matches the destination address.
113
114       EINVAL Invalid argument passed.
115
116       EISCONN
117              connect(2) was called on an already connected socket.
118
119       EMSGSIZE
120              Datagram is bigger than the DDP MTU.
121
122       ENODEV Network device not available or not capable of sending IP.
123
124       ENOENT SIOCGSTAMP was called on a socket where no packet arrived.
125
126       ENOMEM and ENOBUFS
127              Not enough memory available.
128
129       ENOPKG A kernel subsystem was not configured.
130
131       ENOPROTOOPT and EOPNOTSUPP
132              Invalid socket option passed.
133
134       ENOTCONN
135              The operation is defined only on a  connected  socket,  but  the
136              socket wasn't connected.
137
138       EPERM  User  doesn't  have permission to set high priority, make a con‐
139              figuration change, or send signals to the requested  process  or
140              group.
141
142       EPIPE  The connection was unexpectedly closed or shut down by the other
143              end.
144
145       ESOCKTNOSUPPORT
146              The socket was unconfigured, or an unknown socket type  was  re‐
147              quested.
148

VERSIONS

150       AppleTalk  is  supported  by Linux 2.0 or higher.  The /proc interfaces
151       exist since Linux 2.2.
152

NOTES

154       Be very careful with the SO_BROADCAST option; it is not  privileged  in
155       Linux.   It  is  easy  to overload the network with careless sending to
156       broadcast addresses.
157
158   Compatibility
159       The basic AppleTalk socket interface is  compatible  with  netatalk  on
160       BSD-derived  systems.  Many BSD systems fail to check SO_BROADCAST when
161       sending broadcast frames; this can lead to compatibility problems.
162
163       The raw socket mode is unique to Linux and exists to support the alter‐
164       native CAP package and AppleTalk monitoring tools more easily.
165

BUGS

167       There are too many inconsistent error values.
168
169       The  ioctls used to configure routing tables, devices, AARP tables, and
170       other devices are not yet described.
171

SEE ALSO

173       recvmsg(2), sendmsg(2), capabilities(7), socket(7)
174

COLOPHON

176       This page is part of release 5.13 of the Linux  man-pages  project.   A
177       description  of  the project, information about reporting bugs, and the
178       latest    version    of    this    page,    can     be     found     at
179       https://www.kernel.org/doc/man-pages/.
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183Linux                             2021-03-22                            DDP(7)
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