Home Man
Search
Today's Posts
Register

Linux & Unix Commands - Search Man Pages

OpenDarwin 7.2.1 - man page for netintro (opendarwin section 4)

NETINTRO(4)			   BSD Kernel Interfaces Manual 		      NETINTRO(4)

NAME
     networking -- introduction to networking facilities

SYNOPSIS
     #include <sys/socket.h>
     #include <net/route.h>
     #include <net/if.h>

DESCRIPTION
     This section is a general introduction to the networking facilities available in the system.
     Documentation in this part of section 4 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 spe-
     cific 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 nor-
     mally comprised of a number of protocols, one per socket(2) type.	It is not required that a
     protocol family support all socket types.	A protocol family may contain multiple protocols
     supporting the same socket abstraction.

     A protocol supports one of the socket abstractions detailed in socket(2).	A specific proto-
     col may be accessed either by creating a socket of the appropriate type and protocol family,
     or by requesting the protocol explicitly when creating a socket.  Protocols normally accept
     only one type of address format, usually determined by the addressing structure inherent 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 facili-
     ties or extensions 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 low-
     est layer of the networking subsystem, interacting with the actual transport hardware.  An
     interface may support one or more protocol families and/or address formats.  The SYNOPSIS
     section of each network interface entry gives a sample specification of the related drivers
     for use in providing a system description to the config(8) program.  The DIAGNOSTICS section
     lists messages which may appear on the console and/or in the system error log,
     /var/log/messages (see syslogd(8)), due to errors in device operation.

PROTOCOLS
     The system currently supports the Internet protocols, the Xerox Network Systems(tm) proto-
     cols, and some of the ISO OSI protocols.  Raw socket interfaces are provided to the IP pro-
     tocol layer of the Internet, and to the IDP protocol of Xerox NS.	Consult the appropriate
     manual pages in this section for more information regarding the support for each protocol
     family.

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

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

     The field sa_len contains the total length of the 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 implementation):

     #define	AF_UNIX      1	  /* local to host (pipes) */
     #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_ISO	     18   /* ISO protocols */

ROUTING
     Mac OS X provides some packet routing facilities.	The kernel maintains a routing informa-
     tion database, which is used in selecting the appropriate network interface when transmit-
     ting packets.

     A user process (or possibly multiple co-operating processes) maintains this database by
     sending messages over a special kind of socket.  This supplants fixed size ioctl(2) used in
     earlier releases.

     This facility is described in route(4).

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(4), do not.

     The following ioctl calls may be used to manipulate network interfaces.  The ioctl is made
     on a socket (typically of type SOCK_DGRAM) in the desired domain.	Most of the requests sup-
     ported in earlier releases take an ifreq structure as its parameter.  This structure has the
     form

     struct  ifreq {
     #define	IFNAMSIZ    16
	 char	 ifr_name[IFNAMSIZ];	     /* if name, e.g. "en0" */
	 union {
	     struct    sockaddr ifru_addr;
	     struct    sockaddr ifru_dstaddr;
	     struct    sockaddr ifru_broadaddr;
	     short     ifru_flags;
	     int       ifru_metric;
	     caddr_t   ifru_data;
	 } ifr_ifru;
     #define ifr_addr	   ifr_ifru.ifru_addr	 /* address */
     #define ifr_dstaddr   ifr_ifru.ifru_dstaddr /* other end of p-to-p link */
     #define ifr_broadaddr ifr_ifru.ifru_broadaddr /* broadcast address */
     #define ifr_flags	   ifr_ifru.ifru_flags	 /* flags */
     #define ifr_metric    ifr_ifru.ifru_metric  /* metric */
     #define ifr_data	   ifr_ifru.ifru_data	 /* for use by interface */
     };

     Calls which are now deprecated are:

     SIOCSIFADDR     Set interface address for protocol family.  Following the address assign-
		     ment, the ``initialization'' routine for the interface is called.

     SIOCSIFDSTADDR  Set point to point address for protocol family and interface.

     SIOCSIFBRDADDR  Set broadcast address for protocol family and interface.

     Ioctl requests to obtain addresses and requests both to set and retrieve other data are
     still fully supported and use the ifreq structure:

     SIOCGIFADDR     Get interface address for protocol family.

     SIOCGIFDSTADDR  Get point to point address for protocol family and interface.

     SIOCGIFBRDADDR  Get broadcast address for protocol family and interface.

     SIOCSIFFLAGS    Set interface flags field.  If the interface is marked down, any processes
		     currently routing packets through the interface are notified; some inter-
		     faces may be reset so that incoming packets are no longer received.  When
		     marked up again, the interface is reinitialized.

     SIOCGIFFLAGS    Get interface flags.

     SIOCSIFMETRIC   Set interface routing metric.  The metric is used only by user-level
		     routers.

     SIOCGIFMETRIC   Get interface metric.

     There are two requests that make use of a new structure:

     SIOCAIFADDR     An interface may have more than one address associated with it in some pro-
		     tocols.  This request provides a means to add additional addresses (or mod-
		     ify characteristics of the primary address if the default address for the
		     address family is specified).  Rather than making separate calls to set des-
		     tination or broadcast addresses, or network masks (now an integral feature
		     of multiple protocols) a separate structure is used to specify all three
		     facets simultaneously (see below).  One would use a slightly tailored ver-
		     sion of this struct specific to each family (replacing each sockaddr by one
		     of the family-specific type).  Where the sockaddr itself is larger than the
		     default size, one needs to modify the ioctl identifier itself to include the
		     total size, as described in ioctl.

     SIOCDIFADDR     This requests deletes the specified address from the list associated with an
		     interface.  It also uses the if_aliasreq structure to allow for the possi-
		     bility of protocols allowing multiple masks or destination addresses, and
		     also adopts the convention that specification of the default address means
		     to delete the first address for the interface belonging to the address fam-
		     ily in which the original socket was opened.

     SIOCGIFCONF     Get interface configuration list.	This request takes an ifconf structure
		     (see below) as a value-result parameter.  The ifc_len field should be ini-
		     tially set to the size of the buffer pointed to by ifc_buf.  On return it
		     will contain the length, in bytes, of the configuration list.

     /*
     * Structure used in SIOCAIFADDR request.
     */
     struct ifaliasreq {
	     char    ifra_name[IFNAMSIZ];   /* if name, e.g. "en0" */
	     struct  sockaddr	     ifra_addr;
	     struct  sockaddr	     ifra_broadaddr;
	     struct  sockaddr	     ifra_mask;
     };

     /*
     * Structure used in SIOCGIFCONF request.
     * Used to retrieve interface configuration
     * for machine (useful for programs which
     * must know all networks accessible).
     */
     struct ifconf {
	 int   ifc_len; 	     /* size of associated buffer */
	 union {
	     caddr_t	ifcu_buf;
	     struct	ifreq *ifcu_req;
	 } ifc_ifcu;
     #define ifc_buf ifc_ifcu.ifcu_buf /* buffer address */
     #define ifc_req ifc_ifcu.ifcu_req /* array of structures returned */
     };

SEE ALSO
     socket(2), ioctl(2), intro(4), config(8), routed(8)

HISTORY
     The netintro manual appeared in 4.3BSD-Tahoe.

4.2 Berkeley Distribution		November 30, 1993		4.2 Berkeley Distribution


All times are GMT -4. The time now is 12:14 PM.

Unix & Linux Forums Content Copyrightę1993-2018. All Rights Reserved.
UNIX.COM Login
Username:
Password:  
Show Password