1.\" Copyright (c) 1983, 1990, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)netintro.4 8.2 (Berkeley) 11/30/93 33.\" 34.Dd November 30, 1993 35.Dt NETINTRO 4 36.Os BSD 4.2 37.Sh NAME 38.Nm networking 39.Nd introduction to networking facilities 40.Sh SYNOPSIS 41.Fd #include <sys/socket.h> 42.Fd #include <net/route.h> 43.Fd #include <net/if.h> 44.Sh DESCRIPTION 45This section is a general introduction to the networking facilities 46available in the system. 47Documentation in this part of section 484 is broken up into three areas: 49.Em protocol families 50(domains), 51.Em protocols , 52and 53.Em network interfaces . 54.Pp 55All network protocols are associated with a specific 56.Em protocol family . 57A protocol family provides basic services to the protocol 58implementation to allow it to function within a specific 59network environment. These services may include 60packet fragmentation and reassembly, routing, addressing, and 61basic transport. A protocol family may support multiple 62methods of addressing, though the current protocol implementations 63do not. A protocol family is normally comprised of a number 64of protocols, one per 65.Xr socket 2 66type. It is not required that a protocol family support 67all socket types. A protocol family may contain multiple 68protocols supporting the same socket abstraction. 69.Pp 70A protocol supports one of the socket abstractions detailed in 71.Xr socket 2 . 72A specific protocol may be accessed either by creating a 73socket of the appropriate type and protocol family, or 74by requesting the protocol explicitly when creating a socket. 75Protocols normally accept only one type of address format, 76usually determined by the addressing structure inherent in 77the design of the protocol family/network architecture. 78Certain semantics of the basic socket abstractions are 79protocol specific. All protocols are expected to support 80the basic model for their particular socket type, but may, 81in addition, provide non-standard facilities or extensions 82to a mechanism. For example, a protocol supporting the 83.Dv SOCK_STREAM 84abstraction may allow more than one byte of out-of-band 85data to be transmitted per out-of-band message. 86.Pp 87A network interface is similar to a device interface. 88Network interfaces comprise the lowest layer of the 89networking subsystem, interacting with the actual transport 90hardware. An interface may support one or more protocol 91families and/or address formats. 92The SYNOPSIS section of each network interface 93entry gives a sample specification 94of the related drivers for use in providing 95a system description to the 96.Xr config 8 97program. 98The DIAGNOSTICS section lists messages which may appear on the console 99and/or in the system error log, 100.Pa /var/log/messages 101(see 102.Xr syslogd 8 ) , 103due to errors in device operation. 104.Sh PROTOCOLS 105The system currently supports the 106Internet 107protocols, the Xerox Network Systems(tm) protocols, 108and some of the 109.Tn ISO OSI 110protocols. 111Raw socket interfaces are provided to the 112.Tn IP 113protocol 114layer of the 115Internet, and to the 116.Tn IDP 117protocol of Xerox 118.Tn NS . 119Consult the appropriate manual pages in this section for more 120information regarding the support for each protocol family. 121.Sh ADDRESSING 122Associated with each protocol family is an address 123format. All network address adhere to a general structure, 124called a sockaddr, described below. However, each protocol 125imposes finer and more specific structure, generally renaming 126the variant, which is discussed in the protocol family manual 127page alluded to above. 128.Bd -literal -offset indent 129 struct sockaddr { 130 u_char sa_len; 131 u_char sa_family; 132 char sa_data[14]; 133}; 134.Ed 135.Pp 136The field 137.Ar sa_len 138contains the total length of the of the structure, 139which may exceed 16 bytes. 140The following address values for 141.Ar sa_family 142are known to the system 143(and additional formats are defined for possible future implementation): 144.Bd -literal 145#define AF_UNIX 1 /* local to host (pipes, portals) */ 146#define AF_INET 2 /* internetwork: UDP, TCP, etc. */ 147#define AF_NS 6 /* Xerox NS protocols */ 148#define AF_CCITT 10 /* CCITT protocols, X.25 etc */ 149#define AF_HYLINK 15 /* NSC Hyperchannel */ 150#define AF_ISO 18 /* ISO protocols */ 151.Ed 152.Sh ROUTING 153.Tn UNIX 154provides some packet routing facilities. 155The kernel maintains a routing information database, which 156is used in selecting the appropriate network interface when 157transmitting packets. 158.Pp 159A user process (or possibly multiple co-operating processes) 160maintains this database by sending messages over a special kind 161of socket. 162This supplants fixed size 163.Xr ioctl 2 164used in earlier releases. 165.Pp 166This facility is described in 167.Xr route 4 . 168.Sh INTERFACES 169Each network interface in a system corresponds to a 170path through which messages may be sent and received. A network 171interface usually has a hardware device associated with it, though 172certain interfaces such as the loopback interface, 173.Xr lo 4 , 174do not. 175.Pp 176The following 177.Xr ioctl 2 178calls may be used to manipulate network interfaces. 179The 180.Fn ioctl 181is made on a socket (typically of type 182.Dv SOCK_DGRAM ) 183in the desired domain. 184Most of the requests supported in earlier releases 185take an 186.Ar ifreq 187structure as its parameter. This structure has the form 188.Bd -literal 189struct ifreq { 190#define IFNAMSIZ 16 191 char ifr_name[IFNAMSIZ]; /* if name, e.g. "en0" */ 192 union { 193 struct sockaddr ifru_addr; 194 struct sockaddr ifru_dstaddr; 195 struct sockaddr ifru_broadaddr; 196 short ifru_flags; 197 int ifru_metric; 198 caddr_t ifru_data; 199 } ifr_ifru; 200#define ifr_addr ifr_ifru.ifru_addr /* address */ 201#define ifr_dstaddr ifr_ifru.ifru_dstaddr /* other end of p-to-p link */ 202#define ifr_broadaddr ifr_ifru.ifru_broadaddr /* broadcast address */ 203#define ifr_flags ifr_ifru.ifru_flags /* flags */ 204#define ifr_metric ifr_ifru.ifru_metric /* metric */ 205#define ifr_data ifr_ifru.ifru_data /* for use by interface */ 206}; 207.Ed 208.Pp 209Calls which are now deprecated are: 210.Bl -tag -width SIOCGIFBRDADDR 211.It Dv SIOCSIFADDR 212Set interface address for protocol family. Following the address 213assignment, the ``initialization'' routine for 214the interface is called. 215.It Dv SIOCSIFDSTADDR 216Set point to point address for protocol family and interface. 217.It Dv SIOCSIFBRDADDR 218Set broadcast address for protocol family and interface. 219.El 220.Pp 221.Fn Ioctl 222requests to obtain addresses and requests both to set and 223retrieve other data are still fully supported 224and use the 225.Ar ifreq 226structure: 227.Bl -tag -width SIOCGIFBRDADDR 228.It Dv SIOCGIFADDR 229Get interface address for protocol family. 230.It Dv SIOCGIFDSTADDR 231Get point to point address for protocol family and interface. 232.It Dv SIOCGIFBRDADDR 233Get broadcast address for protocol family and interface. 234.It Dv SIOCSIFFLAGS 235Set interface flags field. If the interface is marked down, 236any processes currently routing packets through the interface 237are notified; 238some interfaces may be reset so that incoming packets are no longer received. 239When marked up again, the interface is reinitialized. 240.It Dv SIOCGIFFLAGS 241Get interface flags. 242.It Dv SIOCSIFMETRIC 243Set interface routing metric. 244The metric is used only by user-level routers. 245.It Dv SIOCGIFMETRIC 246Get interface metric. 247.El 248.Pp 249There are two requests that make use of a new structure: 250.Bl -tag -width SIOCGIFBRDADDR 251.It Dv SIOCAIFADDR 252An interface may have more than one address associated with it 253in some protocols. This request provides a means to 254add additional addresses (or modify characteristics of the 255primary address if the default address for the address family 256is specified). Rather than making separate calls to 257set destination or broadcast addresses, or network masks 258(now an integral feature of multiple protocols) 259a separate structure is used to specify all three facets simultaneously 260(see below). 261One would use a slightly tailored version of this struct specific 262to each family (replacing each sockaddr by one 263of the family-specific type). 264Where the sockaddr itself is larger than the 265default size, one needs to modify the 266.Fn ioctl 267identifier itself to include the total size, as described in 268.Fn ioctl . 269.It Dv SIOCDIFADDR 270This requests deletes the specified address from the list 271associated with an interface. It also uses the 272.Ar if_aliasreq 273structure to allow for the possibility of protocols allowing 274multiple masks or destination addresses, and also adopts the 275convention that specification of the default address means 276to delete the first address for the interface belonging to 277the address family in which the original socket was opened. 278.It Dv SIOCGIFCONF 279Get interface configuration list. This request takes an 280.Ar ifconf 281structure (see below) as a value-result parameter. The 282.Ar ifc_len 283field should be initially set to the size of the buffer 284pointed to by 285.Ar ifc_buf . 286On return it will contain the length, in bytes, of the 287configuration list. 288.El 289.Bd -literal 290/* 291* Structure used in SIOCAIFCONF request. 292*/ 293struct ifaliasreq { 294 char ifra_name[IFNAMSIZ]; /* if name, e.g. "en0" */ 295 struct sockaddr ifra_addr; 296 struct sockaddr ifra_broadaddr; 297 struct sockaddr ifra_mask; 298}; 299.Ed 300.Pp 301.Bd -literal 302/* 303* Structure used in SIOCGIFCONF request. 304* Used to retrieve interface configuration 305* for machine (useful for programs which 306* must know all networks accessible). 307*/ 308struct ifconf { 309 int ifc_len; /* size of associated buffer */ 310 union { 311 caddr_t ifcu_buf; 312 struct ifreq *ifcu_req; 313 } ifc_ifcu; 314#define ifc_buf ifc_ifcu.ifcu_buf /* buffer address */ 315#define ifc_req ifc_ifcu.ifcu_req /* array of structures returned */ 316}; 317.Ed 318.Sh SEE ALSO 319.Xr socket 2 , 320.Xr ioctl 2 , 321.Xr intro 4 , 322.Xr config 8 , 323.Xr routed 8 324.Sh HISTORY 325The 326.Nm netintro 327manual appeared in 328.Bx 4.3 tahoe . 329