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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.\" From: @(#)inet.4 8.1 (Berkeley) 6/5/93 33.\" $FreeBSD$ 34.\" 35.Dd January 26, 2012 36.Dt INET 4 37.Os 38.Sh NAME 39.Nm inet 40.Nd Internet protocol family 41.Sh SYNOPSIS 42.In sys/types.h 43.In netinet/in.h 44.Sh DESCRIPTION 45The Internet protocol family is a collection of protocols 46layered atop the 47.Em Internet Protocol 48.Pq Tn IP 49transport layer, and utilizing the Internet address format. 50The Internet family provides protocol support for the 51.Dv SOCK_STREAM , SOCK_DGRAM , 52and 53.Dv SOCK_RAW 54socket types; the 55.Dv SOCK_RAW 56interface provides access to the 57.Tn IP 58protocol. 59.Sh ADDRESSING 60Internet addresses are four byte quantities, stored in 61network standard format (on little endian machines, such as the 62.Tn alpha , 63.Tn amd64 , 64.Tn i386 65and 66.Tn ia64 67these are word and byte reversed). 68The include file 69.In netinet/in.h 70defines this address 71as a discriminated union. 72.Pp 73Sockets bound to the Internet protocol family utilize 74the following addressing structure, 75.Bd -literal -offset indent 76struct sockaddr_in { 77 uint8_t sin_len; 78 sa_family_t sin_family; 79 in_port_t sin_port; 80 struct in_addr sin_addr; 81 char sin_zero[8]; 82}; 83.Ed 84.Pp 85Sockets may be created with the local address 86.Dv INADDR_ANY 87to affect 88.Dq wildcard 89matching on incoming messages. 90The address in a 91.Xr connect 2 92or 93.Xr sendto 2 94call may be given as 95.Dv INADDR_ANY 96to mean 97.Dq this host . 98The distinguished address 99.Dv INADDR_BROADCAST 100is allowed as a shorthand for the broadcast address on the primary 101network if the first network configured supports broadcast. 102.Sh PROTOCOLS 103The Internet protocol family is comprised of 104the 105.Tn IP 106network protocol, Internet Control 107Message Protocol 108.Pq Tn ICMP , 109Internet Group Management Protocol 110.Pq Tn IGMP , 111Transmission Control 112Protocol 113.Pq Tn TCP , 114and User Datagram Protocol 115.Pq Tn UDP . 116.Tn TCP 117is used to support the 118.Dv SOCK_STREAM 119abstraction while 120.Tn UDP 121is used to support the 122.Dv SOCK_DGRAM 123abstraction. 124A raw interface to 125.Tn IP 126is available 127by creating an Internet socket of type 128.Dv SOCK_RAW . 129The 130.Tn ICMP 131message protocol is accessible from a raw socket. 132.Pp 133The 134.Nm 135address on an interface consist of the address itself, the 136netmask, either broadcast address in case of a broadcast 137interface or peers address in case of point-to-point interface. 138The following 139.Xr ioctl 2 140commands are provided for a datagram socket in the Internet domain: 141.Pp 142.Bl -tag -width ".Dv SIOCGIFBRDADDR" -offset indent -compact 143.It Dv SIOCAIFADDR 144Add address to an interface. 145The command requires 146.Ft struct in_aliasreq 147as argument. 148.It Dv SIOCDIFADDR 149Delete address from an interface. 150The command requires 151.Ft struct ifreq 152as argument. 153.It Dv SIOCGIFADDR 154.It Dv SIOCGIFBRDADDR 155.It Dv SIOCGIFDSTADDR 156.It Dv SIOCGIFNETMASK 157Return address information from interface. The returned value 158is in 159.Ft struct ifreq . 160This way of address information retrieval is obsoleted, a 161preferred way is to use 162.Xr getifaddrs 3 163API. 164.El 165.Ss MIB Variables 166A number of variables are implemented in the net.inet branch of the 167.Xr sysctl 3 168MIB. 169In addition to the variables supported by the transport protocols 170(for which the respective manual pages may be consulted), 171the following general variables are defined: 172.Bl -tag -width IPCTL_FASTFORWARDING 173.It Dv IPCTL_FORWARDING 174.Pq ip.forwarding 175Boolean: enable/disable forwarding of IP packets. 176Defaults to off. 177.It Dv IPCTL_FASTFORWARDING 178.Pq ip.fastforwarding 179Boolean: enable/disable the use of 180.Tn fast IP forwarding 181code. 182Defaults to off. 183When 184.Tn fast IP forwarding 185is enabled, IP packets are forwarded directly to the appropriate network 186interface with direct processing to completion, which greatly improves 187the throughput. 188All packets for local IP addresses, non-unicast, or with IP options are 189handled by the normal IP input processing path. 190All features of the normal (slow) IP forwarding path are supported 191including firewall (through 192.Xr pfil 9 193hooks) checking, except 194.Xr ipsec 4 195tunnel brokering. 196The 197.Tn IP fastforwarding 198path does not generate ICMP redirect or source quench messages. 199.It Dv IPCTL_SENDREDIRECTS 200.Pq ip.redirect 201Boolean: enable/disable sending of ICMP redirects in response to 202.Tn IP 203packets for which a better, and for the sender directly reachable, route 204and next hop is known. 205Defaults to on. 206.It Dv IPCTL_DEFTTL 207.Pq ip.ttl 208Integer: default time-to-live 209.Pq Dq TTL 210to use for outgoing 211.Tn IP 212packets. 213.It Dv IPCTL_ACCEPTSOURCEROUTE 214.Pq ip.accept_sourceroute 215Boolean: enable/disable accepting of source-routed IP packets (default false). 216.It Dv IPCTL_SOURCEROUTE 217.Pq ip.sourceroute 218Boolean: enable/disable forwarding of source-routed IP packets (default false). 219.It Dv IPCTL_RTEXPIRE 220.Pq ip.rtexpire 221Integer: lifetime in seconds of protocol-cloned 222.Tn IP 223routes after the last reference drops (default one hour). 224This value varies dynamically as described above. 225.It Dv IPCTL_RTMINEXPIRE 226.Pq ip.rtminexpire 227Integer: minimum value of ip.rtexpire (default ten seconds). 228This value has no effect on user modifications, but restricts the dynamic 229adaptation described above. 230.It Dv IPCTL_RTMAXCACHE 231.Pq ip.rtmaxcache 232Integer: trigger level of cached, unreferenced, protocol-cloned routes 233which initiates dynamic adaptation (default 128). 234.It Va ip.process_options 235Integer: control IP options processing. 236By setting this variable to 0, all IP options in the incoming packets 237will be ignored, and the packets will be passed unmodified. 238By setting to 1, IP options in the incoming packets will be processed 239accordingly. 240By setting to 2, an 241.Tn ICMP 242.Dq "prohibited by filter" 243message will be sent back in response to incoming packets with IP options. 244Default is 1. 245This 246.Xr sysctl 8 247variable affects packets destined for a local host as well as packets 248forwarded to some other host. 249.It Va ip.random_id 250Boolean: control IP IDs generation behaviour. 251Setting this 252.Xr sysctl 8 253to non-zero causes the ID field in IP packets to be randomized instead of 254incremented by 1 with each packet generated. 255This closes a minor information leak which allows remote observers to 256determine the rate of packet generation on the machine by watching the 257counter. 258In the same time, on high-speed links, it can decrease the ID reuse 259cycle greatly. 260Default is 0 (sequential IP IDs). 261IPv6 flow IDs and fragment IDs are always random. 262.It Va ip.maxfragpackets 263Integer: maximum number of fragmented packets the host will accept and hold 264in the reassembling queue simultaneously. 2650 means that the host will not accept any fragmented packets. 266\-1 means that the host will accept as many fragmented packets as it receives. 267.It Va ip.maxfragsperpacket 268Integer: maximum number of fragments the host will accept and hold 269in the reassembling queue for a packet. 2700 means that the host will not accept any fragmented packets. 271.El 272.Sh SEE ALSO 273.Xr ioctl 2 , 274.Xr socket 2 , 275.Xr getifaddrs 3 , 276.Xr sysctl 3 , 277.Xr icmp 4 , 278.Xr intro 4 , 279.Xr ip 4 , 280.Xr ipfirewall 4 , 281.Xr route 4 , 282.Xr tcp 4 , 283.Xr udp 4 , 284.Xr pfil 9 285.Rs 286.%T "An Introductory 4.3 BSD Interprocess Communication Tutorial" 287.%B PS1 288.%N 7 289.Re 290.Rs 291.%T "An Advanced 4.3 BSD Interprocess Communication Tutorial" 292.%B PS1 293.%N 8 294.Re 295.Sh HISTORY 296The 297.Nm 298protocol interface appeared in 299.Bx 4.2 . 300The 301.Dq protocol cloning 302code appeared in 303.Fx 2.1 . 304.Sh CAVEATS 305The Internet protocol support is subject to change as 306the Internet protocols develop. 307Users should not depend 308on details of the current implementation, but rather 309the services exported. 310