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.\" $Id: netintro.4,v 1.7 1997/02/22 13:24:38 peter Exp $ 34.\" 35.Dd November 30, 1993 36.Dt NETINTRO 4 37.Os BSD 4.2 38.Sh NAME 39.Nm networking 40.Nd introduction to networking facilities 41.Sh SYNOPSIS 42.Fd #include <sys/types.h> 43.Fd #include <sys/time.h> 44.Fd #include <sys/socket.h> 45.Fd #include <net/if.h> 46.Fd #include <net/route.h> 47.Sh DESCRIPTION 48This section is a general introduction to the networking facilities 49available in the system. 50Documentation in this part of section 514 is broken up into three areas: 52.Em protocol families 53(domains), 54.Em protocols , 55and 56.Em network interfaces . 57.Pp 58All network protocols are associated with a specific 59.Em protocol family . 60A protocol family provides basic services to the protocol 61implementation to allow it to function within a specific 62network environment. These services may include 63packet fragmentation and reassembly, routing, addressing, and 64basic transport. A protocol family may support multiple 65methods of addressing, though the current protocol implementations 66do not. A protocol family is normally comprised of a number 67of protocols, one per 68.Xr socket 2 69type. It is not required that a protocol family support 70all socket types. A protocol family may contain multiple 71protocols supporting the same socket abstraction. 72.Pp 73A protocol supports one of the socket abstractions detailed in 74.Xr socket 2 . 75A specific protocol may be accessed either by creating a 76socket of the appropriate type and protocol family, or 77by requesting the protocol explicitly when creating a socket. 78Protocols normally accept only one type of address format, 79usually determined by the addressing structure inherent in 80the design of the protocol family/network architecture. 81Certain semantics of the basic socket abstractions are 82protocol specific. All protocols are expected to support 83the basic model for their particular socket type, but may, 84in addition, provide non-standard facilities or extensions 85to a mechanism. For example, a protocol supporting the 86.Dv SOCK_STREAM 87abstraction may allow more than one byte of out-of-band 88data to be transmitted per out-of-band message. 89.Pp 90A network interface is similar to a device interface. 91Network interfaces comprise the lowest layer of the 92networking subsystem, interacting with the actual transport 93hardware. An interface may support one or more protocol 94families and/or address formats. 95The SYNOPSIS section of each network interface 96entry gives a sample specification 97of the related drivers for use in providing 98a system description to the 99.Xr config 8 100program. 101The DIAGNOSTICS section lists messages which may appear on the console 102and/or in the system error log, 103.Pa /var/log/messages 104(see 105.Xr syslogd 8 ) , 106due to errors in device operation. 107.Sh PROTOCOLS 108The system currently supports the 109Internet 110protocols, the Xerox Network Systems(tm) protocols, 111and some of the 112.Tn ISO OSI 113protocols. 114Raw socket interfaces are provided to the 115.Tn IP 116protocol 117layer of the 118Internet, and to the 119.Tn IDP 120protocol of Xerox 121.Tn NS . 122Consult the appropriate manual pages in this section for more 123information regarding the support for each protocol family. 124.Sh ADDRESSING 125Associated with each protocol family is an address 126format. All network address adhere to a general structure, 127called a sockaddr, described below. However, each protocol 128imposes finer and more specific structure, generally renaming 129the variant, which is discussed in the protocol family manual 130page alluded to above. 131.Bd -literal -offset indent 132 struct sockaddr { 133 u_char sa_len; 134 u_char sa_family; 135 char sa_data[14]; 136}; 137.Ed 138.Pp 139The field 140.Ar sa_len 141contains the total length of the of the structure, 142which may exceed 16 bytes. 143The following address values for 144.Ar sa_family 145are known to the system 146(and additional formats are defined for possible future implementation): 147.Bd -literal 148#define AF_UNIX 1 /* local to host (pipes, portals) */ 149#define AF_INET 2 /* internetwork: UDP, TCP, etc. */ 150#define AF_NS 6 /* Xerox NS protocols */ 151#define AF_CCITT 10 /* CCITT protocols, X.25 etc */ 152#define AF_HYLINK 15 /* NSC Hyperchannel */ 153#define AF_ISO 18 /* ISO protocols */ 154.Ed 155.Sh ROUTING 156.Tn UNIX 157provides some packet routing facilities. 158The kernel maintains a routing information database, which 159is used in selecting the appropriate network interface when 160transmitting packets. 161.Pp 162A user process (or possibly multiple co-operating processes) 163maintains this database by sending messages over a special kind 164of socket. 165This supplants fixed size 166.Xr ioctl 2 167used in earlier releases. 168.Pp 169This facility is described in 170.Xr route 4 . 171.Sh INTERFACES 172Each network interface in a system corresponds to a 173path through which messages may be sent and received. A network 174interface usually has a hardware device associated with it, though 175certain interfaces such as the loopback interface, 176.Xr lo 4 , 177do not. 178.Pp 179The following 180.Xr ioctl 2 181calls may be used to manipulate network interfaces. 182The 183.Fn ioctl 184is made on a socket (typically of type 185.Dv SOCK_DGRAM ) 186in the desired domain. 187Most of the requests supported in earlier releases 188take an 189.Ar ifreq 190structure as its parameter. This structure has the form 191.Bd -literal 192struct ifreq { 193#define IFNAMSIZ 16 194 char ifr_name[IFNAMSIZ]; /* if name, e.g. "en0" */ 195 union { 196 struct sockaddr ifru_addr; 197 struct sockaddr ifru_dstaddr; 198 struct sockaddr ifru_broadaddr; 199 short ifru_flags; 200 int ifru_metric; 201 int ifru_mtu; 202 int ifru_phys; 203 caddr_t ifru_data; 204 } ifr_ifru; 205#define ifr_addr ifr_ifru.ifru_addr /* address */ 206#define ifr_dstaddr ifr_ifru.ifru_dstaddr /* other end of p-to-p link */ 207#define ifr_broadaddr ifr_ifru.ifru_broadaddr /* broadcast address */ 208#define ifr_flags ifr_ifru.ifru_flags /* flags */ 209#define ifr_metric ifr_ifru.ifru_metric /* metric */ 210#define ifr_mtu ifr_ifru.ifru_mtu /* mtu */ 211#define ifr_phys ifr_ifru.ifru_phys /* physical wire */ 212#define ifr_data ifr_ifru.ifru_data /* for use by interface */ 213}; 214.Ed 215.Pp 216Calls which are now deprecated are: 217.Bl -tag -width SIOCGIFBRDADDR 218.It Dv SIOCSIFADDR 219Set interface address for protocol family. Following the address 220assignment, the ``initialization'' routine for 221the interface is called. 222.It Dv SIOCSIFDSTADDR 223Set point to point address for protocol family and interface. 224.It Dv SIOCSIFBRDADDR 225Set broadcast address for protocol family and interface. 226.El 227.Pp 228.Fn Ioctl 229requests to obtain addresses and requests both to set and 230retrieve other data are still fully supported 231and use the 232.Ar ifreq 233structure: 234.Bl -tag -width SIOCGIFBRDADDR 235.It Dv SIOCGIFADDR 236Get interface address for protocol family. 237.It Dv SIOCGIFDSTADDR 238Get point to point address for protocol family and interface. 239.It Dv SIOCGIFBRDADDR 240Get broadcast address for protocol family and interface. 241.It Dv SIOCSIFFLAGS 242Set interface flags field. If the interface is marked down, 243any processes currently routing packets through the interface 244are notified; 245some interfaces may be reset so that incoming packets are no longer received. 246When marked up again, the interface is reinitialized. 247.It Dv SIOCGIFFLAGS 248Get interface flags. 249.It Dv SIOCSIFMETRIC 250Set interface routing metric. 251The metric is used only by user-level routers. 252.It Dv SIOCGIFMETRIC 253Get interface metric. 254.El 255.Pp 256There are two requests that make use of a new structure: 257.Bl -tag -width SIOCGIFBRDADDR 258.It Dv SIOCAIFADDR 259An interface may have more than one address associated with it 260in some protocols. This request provides a means to 261add additional addresses (or modify characteristics of the 262primary address if the default address for the address family 263is specified). Rather than making separate calls to 264set destination or broadcast addresses, or network masks 265(now an integral feature of multiple protocols) 266a separate structure is used to specify all three facets simultaneously 267(see below). 268One would use a slightly tailored version of this struct specific 269to each family (replacing each sockaddr by one 270of the family-specific type). 271Where the sockaddr itself is larger than the 272default size, one needs to modify the 273.Fn ioctl 274identifier itself to include the total size, as described in 275.Fn ioctl . 276.It Dv SIOCDIFADDR 277This requests deletes the specified address from the list 278associated with an interface. It also uses the 279.Ar if_aliasreq 280structure to allow for the possibility of protocols allowing 281multiple masks or destination addresses, and also adopts the 282convention that specification of the default address means 283to delete the first address for the interface belonging to 284the address family in which the original socket was opened. 285.It Dv SIOCGIFCONF 286Get interface configuration list. This request takes an 287.Ar ifconf 288structure (see below) as a value-result parameter. The 289.Ar ifc_len 290field should be initially set to the size of the buffer 291pointed to by 292.Ar ifc_buf . 293On return it will contain the length, in bytes, of the 294configuration list. 295.El 296.Bd -literal 297/* 298* Structure used in SIOCAIFCONF request. 299*/ 300struct ifaliasreq { 301 char ifra_name[IFNAMSIZ]; /* if name, e.g. "en0" */ 302 struct sockaddr ifra_addr; 303 struct sockaddr ifra_broadaddr; 304 struct sockaddr ifra_mask; 305}; 306.Ed 307.Pp 308.Bd -literal 309/* 310* Structure used in SIOCGIFCONF request. 311* Used to retrieve interface configuration 312* for machine (useful for programs which 313* must know all networks accessible). 314*/ 315struct ifconf { 316 int ifc_len; /* size of associated buffer */ 317 union { 318 caddr_t ifcu_buf; 319 struct ifreq *ifcu_req; 320 } ifc_ifcu; 321#define ifc_buf ifc_ifcu.ifcu_buf /* buffer address */ 322#define ifc_req ifc_ifcu.ifcu_req /* array of structures returned */ 323}; 324.Ed 325.Sh SEE ALSO 326.Xr ioctl 2 , 327.Xr socket 2 , 328.Xr intro 4 , 329.Xr config 8 , 330.Xr routed 8 331.Sh HISTORY 332The 333.Nm netintro 334manual appeared in 335.Bx 4.3 tahoe . 336