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1.1     ! root        1: .\" Copyright (c) 1983, 1990 The Regents of the University of California.
        !             2: .\" All rights reserved.
        !             3: .\"
        !             4: .\" Redistribution and use in source and binary forms are permitted provided
        !             5: .\" that: (1) source distributions retain this entire copyright notice and
        !             6: .\" comment, and (2) distributions including binaries display the following
        !             7: .\" acknowledgement:  ``This product includes software developed by the
        !             8: .\" University of California, Berkeley and its contributors'' in the
        !             9: .\" documentation or other materials provided with the distribution and in
        !            10: .\" all advertising materials mentioning features or use of this software.
        !            11: .\" Neither the name of the University nor the names of its contributors may
        !            12: .\" be used to endorse or promote products derived from this software without
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        !            14: .\" THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
        !            15: .\" WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
        !            16: .\" MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
        !            17: .\"
        !            18: .\"    @(#)netintro.4  6.9 (Berkeley) 6/23/90
        !            19: .\"
        !            20: .TH NETINTRO 4 "June 23, 1990"
        !            21: .UC 5
        !            22: .SH NAME
        !            23: networking \- introduction to networking facilities
        !            24: .SH SYNOPSIS
        !            25: .nf
        !            26: .ft B
        !            27: #include <sys/socket.h>
        !            28: #include <net/route.h>
        !            29: #include <net/if.h>
        !            30: .fi R
        !            31: .fi
        !            32: .SH DESCRIPTION
        !            33: .de _d
        !            34: .if t .ta .6i 2.1i 2.6i
        !            35: .\" 2.94 went to 2.6, 3.64 to 3.30
        !            36: .if n .ta .84i 2.6i 3.30i
        !            37: ..
        !            38: .de _f
        !            39: .if t .ta .5i 1.25i 2.5i
        !            40: .\" 3.5i went to 3.8i
        !            41: .if n .ta .7i 1.75i 3.8i
        !            42: ..
        !            43: This section is a general introduction to the networking facilities
        !            44: available in the system.
        !            45: Documentation in this part of section
        !            46: 4 is broken up into three areas:
        !            47: .I "protocol families
        !            48: (domains),
        !            49: .IR protocols ,
        !            50: and
        !            51: .IR "network interfaces" .
        !            52: .\" Entries describing a protocol family are marked ``4F,''
        !            53: .\" while entries describing protocol use are marked ``4P.''
        !            54: .\" Hardware support for network interfaces are found
        !            55: .\" among the standard ``4'' entries.
        !            56: .PP
        !            57: All network protocols are associated with a specific
        !            58: .IR "protocol family" .
        !            59: A protocol family provides basic services to the protocol
        !            60: implementation to allow it to function within a specific
        !            61: network environment.  These services may include 
        !            62: packet fragmentation and reassembly, routing, addressing, and 
        !            63: basic transport.  A protocol family may support multiple
        !            64: methods of addressing, though the current protocol implementations
        !            65: do not.  A protocol family is normally comprised of a number
        !            66: of protocols, one per
        !            67: .IR socket (2)
        !            68: type.  It is not required that a protocol family support
        !            69: all socket types.  A protocol family may contain multiple
        !            70: protocols supporting the same socket abstraction. 
        !            71: .PP
        !            72: A protocol supports one of the socket abstractions detailed
        !            73: in
        !            74: .IR socket (2).
        !            75: A specific protocol may be accessed either by creating a
        !            76: socket of the appropriate type and protocol family, or
        !            77: by requesting the protocol explicitly when creating a socket.
        !            78: Protocols normally accept only one type of address format,
        !            79: usually determined by the addressing structure inherent in
        !            80: the design of the protocol family/network architecture.
        !            81: Certain semantics of the basic socket abstractions are
        !            82: protocol specific.  All protocols are expected to support
        !            83: the basic model for their particular socket type, but may,
        !            84: in addition, provide non-standard facilities or extensions
        !            85: to a mechanism.  For example, a protocol supporting the
        !            86: SOCK_STREAM
        !            87: abstraction may allow more than one byte of out-of-band
        !            88: data to be transmitted per out-of-band message.
        !            89: .PP
        !            90: A network interface is similar to a device interface.
        !            91: Network interfaces comprise the lowest layer of the
        !            92: networking subsystem, interacting with the actual transport
        !            93: hardware.  An interface may support one or more protocol
        !            94: families and/or address formats.
        !            95: The SYNOPSIS section of each network interface
        !            96: entry gives a sample specification
        !            97: of the related drivers for use in providing
        !            98: a system description to the
        !            99: .IR config (8)
        !           100: program.
        !           101: The DIAGNOSTICS section lists messages which may appear on the console
        !           102: and/or in the system error log,
        !           103: .I /var/log/messages
        !           104: (see
        !           105: .IR syslogd (8)),
        !           106: due to errors in device operation.
        !           107: .SH PROTOCOLS
        !           108: The system currently supports the DARPA Internet
        !           109: protocols, the Xerox Network Systems(tm) protocols,
        !           110: and some of the ISO OSI protocols.
        !           111: Raw socket interfaces are provided to the IP protocol
        !           112: layer of the DARPA Internet, to the IMP link layer (1822), and to
        !           113: the IDP protocol of Xerox NS.
        !           114: Consult the appropriate manual pages in this section for more
        !           115: information regarding the support for each protocol family.
        !           116: .SH ADDRESSING
        !           117: Associated with each protocol family is an address
        !           118: format.  All network address adhere to a general structure,
        !           119: called a sockaddr, described below. However, each protocol
        !           120: imposes finer and more specific structure, generally renaming
        !           121: the variant, which is discussed in the protocol family manual
        !           122: page alluded to above.
        !           123: .nf
        !           124: ._f
        !           125: struct sockaddr {
        !           126:        u_char  sa_len;
        !           127:        u_char  sa_family;
        !           128:        char    sa_data[14];
        !           129: };
        !           130: .sp 1
        !           131: .fi
        !           132: The field sa_len contains the total length of the of the structure,
        !           133: which may exceed 16 bytes.
        !           134: The following address values for
        !           135: .I sa_family
        !           136: are known to the system
        !           137: (and additional formats are defined for possible future implementation):
        !           138: .sp 1
        !           139: .nf
        !           140: ._d
        !           141: #define        AF_UNIX 1       /* local to host (pipes, portals) */
        !           142: #define        AF_INET 2       /* internetwork: UDP, TCP, etc. */
        !           143: #define        AF_IMPLINK      3       /* arpanet imp addresses */
        !           144: #define        AF_NS   6       /* Xerox NS protocols */
        !           145: #define        AF_CCITT        10      /* CCITT protocols, X.25 etc */
        !           146: #define        AF_HYLINK       15      /* NSC Hyperchannel */
        !           147: #define        AF_ISO  18      /* ISO protocols */
        !           148: .fi
        !           149: .SH ROUTING
        !           150: .PP
        !           151: .UX
        !           152: provides some packet routing facilities.
        !           153: The kernel maintains a routing information database, which
        !           154: is used in selecting the appropriate network interface when
        !           155: transmitting packets.
        !           156: .PP
        !           157: A user process (or possibly multiple co-operating processes)
        !           158: maintains this database by sending messages over a special kind
        !           159: of socket.
        !           160: This supplants fixed size
        !           161: .IR ioctl 's
        !           162: used in earlier releases.
        !           163: .PP
        !           164: This facility is described in
        !           165: .IR route (4).
        !           166: .SH INTERFACES
        !           167: Each network interface in a system corresponds to a
        !           168: path through which messages may be sent and received.  A network
        !           169: interface usually has a hardware device associated with it, though
        !           170: certain interfaces such as the loopback interface,
        !           171: .IR lo (4),
        !           172: do not.
        !           173: .PP
        !           174: The following 
        !           175: .I ioctl
        !           176: calls may be used to manipulate network interfaces.
        !           177: The
        !           178: .I ioctl
        !           179: is made on a socket (typically of type SOCK_DGRAM)
        !           180: in the desired domain.
        !           181: Most of the requests supported in earlier releases 
        !           182: take an
        !           183: .I ifreq
        !           184: structure as its parameter.  This structure has the form
        !           185: .PP
        !           186: .nf
        !           187: ._d
        !           188: .DT
        !           189: struct ifreq {
        !           190: #define        IFNAMSIZ        16
        !           191:        char    ifr_name[IFNAMSIZE];            /* 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: .fi
        !           208: Calls which are now depricated are:
        !           209: .TP
        !           210: SIOCSIFADDR
        !           211: Set interface address for protocol family.  Following the address
        !           212: assignment, the ``initialization'' routine for
        !           213: the interface is called.
        !           214: .TP
        !           215: SIOCSIFDSTADDR
        !           216: Set point to point address for protocol family and interface.
        !           217: .TP
        !           218: SIOCSIFBRDADDR
        !           219: Set broadcast address for protocol family and interface.
        !           220: .LP
        !           221: .I Ioctls
        !           222: requests to obtain addresses and requests both to set and
        !           223: retreive other data are still fully supported
        !           224: and use the
        !           225: .I ifreq
        !           226: structure:
        !           227: .TP
        !           228: SIOCGIFADDR
        !           229: Get interface address for protocol family.
        !           230: .TP
        !           231: SIOCGIFDSTADDR
        !           232: Get point to point address for protocol family and interface.
        !           233: .TP
        !           234: SIOCGIFBRDADDR
        !           235: Get broadcast address for protocol family and interface.
        !           236: .TP
        !           237: SIOCSIFFLAGS
        !           238: Set interface flags field.  If the interface is marked down,
        !           239: any processes currently routing packets through the interface
        !           240: are notified;
        !           241: some interfaces may be reset so that incoming packets are no longer received.
        !           242: When marked up again, the interface is reinitialized.
        !           243: .TP
        !           244: SIOCGIFFLAGS
        !           245: Get interface flags.
        !           246: .TP
        !           247: SIOCSIFMETRIC
        !           248: Set interface routing metric.
        !           249: The metric is used only by user-level routers.
        !           250: .TP
        !           251: SIOCGIFMETRIC
        !           252: Get interface metric.
        !           253: .LP
        !           254: There are two requests that make use of a new structure:
        !           255: .TP
        !           256: SIOCAIFADDR
        !           257: An interface may have more than one address associated with it
        !           258: in some protocols.  This request provides a means to
        !           259: add additional addresses (or modify characteristics of the
        !           260: primary address if the default address for the address family
        !           261: is specified).  Rather than making separate calls to
        !           262: set destination or broadcast addresses, or network masks
        !           263: (now an integral feature of multiple protocols)
        !           264: a separate structure is used to specify all three facets simultaneously:
        !           265: .nf
        !           266: 
        !           267: .ta \w'struct  'u +\w'struct  'u +\w'sockaddr  'u +\w'ifra_broaddadr   'u
        !           268: struct ifaliasreq {
        !           269:        char    ifra_name[IFNAMSIZ];            /* if name, e.g. "en0" */
        !           270:        struct  sockaddr        ifra_addr;
        !           271:        struct  sockaddr        ifra_broadaddr;
        !           272:        struct  sockaddr        ifra_mask;
        !           273: };
        !           274: .fi
        !           275: One would use a slightly tailored version of this struct specific
        !           276: to each family (replacing each sockaddr by one
        !           277: of the family-specific type).
        !           278: Where the sockaddr itself is larger than the
        !           279: default size, one needs to modify the
        !           280: .I ioctl
        !           281: identifier itself to include the total size, as described in
        !           282: .IR ioctl (2).
        !           283: .TP
        !           284: SIOCDIFADDR
        !           285: This requests deletes the specified address from the list
        !           286: associated with an interface.  It also uses the if_aliasreq
        !           287: structure to allow for the possibility of protocols allowing
        !           288: multiple masks or destination addresses, and also adopts the
        !           289: convention that specification of the default address means
        !           290: to delete the first address for the interface belonging to
        !           291: the address family in which the original socket was opened.
        !           292: .TP
        !           293: SIOCGIFCONF
        !           294: Get interface configuration list.  This request takes an
        !           295: .I ifconf
        !           296: structure (see below) as a value-result parameter.  The 
        !           297: .I ifc_len
        !           298: field should be initially set to the size of the buffer
        !           299: pointed to by 
        !           300: .IR ifc_buf .
        !           301: On return it will contain the length, in bytes, of the
        !           302: configuration list.
        !           303: .PP
        !           304: ._d
        !           305: .nf
        !           306: .DT
        !           307: /*
        !           308:  * Structure used in SIOCGIFCONF request.
        !           309:  * Used to retrieve interface configuration
        !           310:  * for machine (useful for programs which
        !           311:  * must know all networks accessible).
        !           312:  */
        !           313: struct ifconf {
        !           314:        int     ifc_len;                /* size of associated buffer */
        !           315:        union {
        !           316:                caddr_t ifcu_buf;
        !           317:                struct  ifreq *ifcu_req;
        !           318:        } ifc_ifcu;
        !           319: #define        ifc_buf ifc_ifcu.ifcu_buf       /* buffer address */
        !           320: #define        ifc_req ifc_ifcu.ifcu_req       /* array of structures returned */
        !           321: };
        !           322: .fi
        !           323: .SH SEE ALSO
        !           324: socket(2), ioctl(2), intro(4), config(8), routed(8C)

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