DDP (7)

SYNOPSIS

#include <sys/socket.h> #include <netatalk/at.h> ddp_socket " = socket(PF_APPLETALK, SOCK_DGRAM, 0);" raw_socket " = socket(PF_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 PF_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 only opened 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.

4n 20n 32n
struct at_addr {
        u_short s_net;
        u_char  s_node;
};

struct sockaddr_atalk {
        sa_family_t     sat_family;     /* address family */
        u_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 \(lqthis network.\(rq The node member of struct at_addr contains the host node number. The value of AT_ANYNODE is a wildcard and also implies \(lqthis node.\(rq The value of ATADDR_BCAST is a link local broadcast address.