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Networking facilities
INtime SDK v7.1 > About INtime > Networking and I/O > Networking facilities


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

This section introduces the networking facilities available in the system. Documentation 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 socket 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. A specific protocol 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 facilities 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 lowest 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 DIAGNOSTICS section lists messages which may appear on the console and/or in the system error log, due to errors in device operation.


The system currently supports the Internet protocols. Raw socket interfaces are provided to the IP protocol layer of the Internet. Consult the appropriate manual pages in this section for more information regarding the support for each protocol family.


Associated with each protocol family is an address format. All network addresses 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 protocol 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 structure, which may exceed 16 bytes. The following address value for sa_family is known to the system:

#define AF_INET      2    /* internetwork: UDP, TCP, etc. */


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


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. The ioctl() is made on a socket (typically of type SOCK_DGRAM) in the desired domain. Most of the requests supported 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[2];
             short     ifru_index;
             int       ifru_metric;
             int       ifru_mtu;
             int       ifru_phys;
             int       ifru_media;
             caddr_t   ifru_data;
             int       ifru_cap[2];
         } 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[0]  /* flags (low 16 bits) */
     #define ifr_flagshigh ifr_ifru.ifru_flags[1]  /* flags (high 16 bits) */
     #define ifr_metric    ifr_ifru.ifru_metric    /* metric */
     #define ifr_mtu       ifr_ifru.ifru_mtu       /* mtu */
     #define ifr_phys      ifr_ifru.ifru_phys      /* physical wire */
     #define ifr_media     ifr_ifru.ifru_media     /* physical media */
     #define ifr_data      ifr_ifru.ifru_data      /* for use by interface */
     #define ifr_reqcap    ifr_ifru.ifru_cap[0]    /* requested capabilities */
     #define ifr_curcap    ifr_ifru.ifru_cap[1]    /* current capabilities */
     #define ifr_index     ifr_ifru.ifru_index     /* interface index */

Calls which are now deprecated are:

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

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

     * Structure used in SIOCAIFCONF 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 */

     /* Structure used in SIOCIFGCLONERS request. */
     struct if_clonereq {
             int     ifcr_total;     /* total cloners (out) */
             int     ifcr_count;     /* room for this many in user buffer */
             char    *ifcr_buffer;   /* buffer for cloner names */


Versions Link to
INtime 4.0 netlib.lib
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