openbsd-manpages-netintro.sgml

eCos/RedBoot for勤研ARM AnywhereII(4510) 含全部源代码

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<SECT1 id="openbsd-manpages-netintro">
<TITLE>OpenBSD networking facilities</TITLE>
<SCREEN>

NAME
     networking - introduction to networking facilities

SYNOPSIS
     #include &lt;sys/socket.h>
     #include &lt;net/route.h>
     #include &lt;net/if.h>

DESCRIPTION
     This section is a general introduction to the networking facilities
     available in the system.  The general introduction on this page is 
     broken up into three areas: protocol families (domains), protocols, 
     and network interfaces.

     All network protocols are associated with a specific protocol family. A
     protocol family provides basic services to the protocol implementation 
     to allow it to function within a specific network environment.  These 
     services may include packet fragmentation and reassembly, routing, 
     addressing, and basic transport.  A protocol family may support multiple 
     methods of addressing, though the current protocol implementations do not.
     A protocol family is normally comprised of a number of protocols, one per
     <link linkend="net-common-tcpip-manpages-socket">socket</link> type. It is not required that a protocol family support all
     socket types.  A protocol family may contain multiple protocols support-
     ing the same socket abstraction.

     A protocol supports one of the socket abstractions detailed in <link linkend="net-common-tcpip-manpages-socket">socket</link>.
     A specific protocol may be accessed either by creating a socket of the
     appropriate type and protocol family, or by requesting the protocol ex-
     plicitly when creating a socket.  Protocols normally accept only one type
     of address format, usually determined by the addressing structure inher-
     ent in the design of the protocol family/network architecture.  Certain
     semantics of the basic socket abstractions are protocol specific.  All
     protocols are expected to support the basic model for their particular
     socket type, but may, in addition, provide non-standard facilities or ex-
     tensions to a mechanism.  For example, a protocol supporting the
     SOCK_STREAM abstraction may allow more than one byte of out-of-band data
     to be transmitted per out-of-band message.

     A network interface is similar to a device interface.  Network interfaces
     comprise the lowest layer of the networking subsystem, interacting with
     the actual transport hardware.  An interface may support one or more pro-
     tocol families and/or address formats. 

PROTOCOL
     The system currently supports the Internet protocols. Raw socket interfaces
     are provided to the IP protocol layer of the Internet. 

ADDRESSING
     Associated with each protocol family is an address format.  All network
     addresses adhere to a general structure, called a sockaddr, described be-
     low.  However, each protocol imposes a finer, more specific structure,
     generally renaming the variant, which is discussed in the protocol family
     manual page alluded to above.

           struct sockaddr {
                   u_int8_t        sa_len;
                   sa_family_t     sa_family;
                   char            sa_data[14];
           };

     The field sa_len contains the total length of the structure, which may
     exceed 16 bytes.  The following address values for sa_family are known to
     the system (and additional formats are defined for possible future imple-
     mentation):

     #define    AF_UNIX      1    /* local to host (pipes, portals) */
     #define    AF_INET      2    /* internetwork: UDP, TCP, etc. */
     #define    AF_NS        6    /* Xerox NS protocols */
     #define    AF_CCITT     10   /* CCITT protocols, X.25 etc */
     #define    AF_HYLINK    15   /* NSC Hyperchannel */
     #define    AF_APPLETALK 16   /* AppleTalk */
     #define    AF_ISO       18   /* ISO protocols */
     #define    AF_IPX       23   /* Novell Internet Protocol */
     #define    AF_INET6     24   /* IPv6 */
     #define    AF_NATM      27   /* native ATM access */

ROUTING
     OpenBSD provides some packet routing facilities.  The kernel maintains a
     routing information database, which is used in selecting the appropriate
     network interface when transmitting packets.

     This facility is however, untested in eCos ports.

INTERFACES
     Each network interface in a system corresponds to a path through which
     messages may be sent and received.  A network interface usually has a
     hardware device associated with it, though certain interfaces such as the
     loopback interface, lo, do not.

     The following ioctl calls may be used to manipulate network interfaces