1DDP(7) Linux Programmer's Manual DDP(7)
2
6 ddp - Linux AppleTalk protocol implementation
7
9 #include <sys/socket.h>
10 #include <netatalk/at.h>
11 ddp_socket = socket(AF_APPLETALK, SOCK_DGRAM, 0);
13 raw_socket = socket(AF_APPLETALK, SOCK_RAW, protocol);
14
16 Linux implements the AppleTalk protocols described in Inside AppleTalk.
17 Only the DDP layer and AARP are present in the kernel. They are
18 designed to be used via the netatalk protocol libraries. This page
19 documents the interface for those who wish or need to use the DDP layer
20 directly.
21 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 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 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 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 struct at_addr {
40 unsigned short s_net;
41 unsigned char s_node;
42 };
43 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 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 Socket options
61 No protocol-specific socket options are supported.
62 /proc interfaces
64 IP supports a set of /proc interfaces to configure some global
65 AppleTalk parameters. The parameters can be accessed by reading or
66 writing files in the directory /proc/sys/net/atalk/.
67 aarp-expiry-time
69 The time interval (in seconds) before an AARP cache entry
70 expires.
71 aarp-resolve-time
73 The time interval (in seconds) before an AARP cache entry is
74 resolved.
75 aarp-retransmit-limit
77 The number of retransmissions of an AARP query before the node
78 is declared dead.
79 aarp-tick-time
81 The timer rate (in seconds) for the timer driving AARP.
82 The default values match the specification and should never need to be
84 changed.
85 Ioctls
87 All ioctls described in socket(7) apply to DDP.
88
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
93 reserved port without effective user ID 0 or CAP_NET_BIND_SER‐
94 VICE.
95 EADDRINUSE
97 Tried to bind to an address already in use.
98 EADDRNOTAVAIL
100 A nonexistent interface was requested or the requested source
101 address was not local.
102 EAGAIN Operation on a nonblocking socket would block.
104 EALREADY
106 A connection operation on a nonblocking socket is already in
107 progress.
108 ECONNABORTED
110 A connection was closed during an accept(2).
111 EHOSTUNREACH
113 No routing table entry matches the destination address.
114 EINVAL Invalid argument passed.
116 EISCONN
118 connect(2) was called on an already connected socket.
119 EMSGSIZE
121 Datagram is bigger than the DDP MTU.
122 ENODEV Network device not available or not capable of sending IP.
124 ENOENT SIOCGSTAMP was called on a socket where no packet arrived.
126 ENOMEM and ENOBUFS
128 Not enough memory available.
129 ENOPKG A kernel subsystem was not configured.
131 ENOPROTOOPT and EOPNOTSUPP
133 Invalid socket option passed.
134 ENOTCONN
136 The operation is defined only on a connected socket, but the
137 socket wasn't connected.
138 EPERM User doesn't have permission to set high priority, make a con‐
140 figuration change, or send signals to the requested process or
141 group.
142 EPIPE The connection was unexpectedly closed or shut down by the other
144 end.
145 ESOCKTNOSUPPORT
147 The socket was unconfigured, or an unknown socket type was
148 requested.
149
151 AppleTalk is supported by Linux 2.0 or higher. The /proc interfaces
152 exist since Linux 2.2.
153
155 Be very careful with the SO_BROADCAST option; it is not privileged in
156 Linux. It is easy to overload the network with careless sending to
157 broadcast addresses.
158 Compatibility
160 The basic AppleTalk socket interface is compatible with netatalk on
161 BSD-derived systems. Many BSD systems fail to check SO_BROADCAST when
162 sending broadcast frames; this can lead to compatibility problems.
163 The raw socket mode is unique to Linux and exists to support the alter‐
165 native CAP package and AppleTalk monitoring tools more easily.
166
168 There are too many inconsistent error values.
169 The ioctls used to configure routing tables, devices, AARP tables, and
171 other devices are not yet described.
172
174 recvmsg(2), sendmsg(2), capabilities(7), socket(7)
175
177 This page is part of release 5.04 of the Linux man-pages project. A
178 description of the project, information about reporting bugs, and the
179 latest version of this page, can be found at
180 https://www.kernel.org/doc/man-pages/.
181Linux 2017-09-15 DDP(7)