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28 .\" From: @(#)inet.4 8.1 (Berkeley) 6/5/93
36 .Nd Internet protocol family
41 The Internet protocol family is a collection of protocols
45 transport layer, and utilizing the Internet address format.
46 The Internet family provides protocol support for the
47 .Dv SOCK_STREAM , SOCK_DGRAM ,
52 interface provides access to the
56 Internet addresses are four byte quantities, stored in
57 network standard format (on little endian machines, such as the
62 these are word and byte reversed).
66 as a discriminated union.
68 Sockets bound to the Internet protocol family utilize
69 the following addressing structure,
70 .Bd -literal -offset indent
73 sa_family_t sin_family;
75 struct in_addr sin_addr;
80 Sockets may be created with the local address
84 matching on incoming messages.
93 The distinguished address
95 is allowed as a shorthand for the broadcast address on the primary
96 network if the first network configured supports broadcast.
98 The Internet protocol family is comprised of
101 network protocol, Internet Control
104 Internet Group Management Protocol
109 and User Datagram Protocol
112 is used to support the
116 is used to support the
122 by creating an Internet socket of type
126 message protocol is accessible from a raw socket.
130 address on an interface consist of the address itself, the
131 netmask, either broadcast address in case of a broadcast
132 interface or peers address in case of point-to-point interface.
135 commands are provided for a datagram socket in the Internet domain:
137 .Bl -tag -width ".Dv SIOCGIFBRDADDR" -offset indent -compact
139 Add address to an interface.
141 .Ft struct in_aliasreq
144 Delete address from an interface.
149 .It Dv SIOCGIFBRDADDR
150 .It Dv SIOCGIFDSTADDR
151 .It Dv SIOCGIFNETMASK
152 Return address information from interface. The returned value
155 This way of address information retrieval is obsoleted, a
156 preferred way is to use
161 A number of variables are implemented in the net.inet branch of the
164 In addition to the variables supported by the transport protocols
165 (for which the respective manual pages may be consulted),
166 the following general variables are defined:
167 .Bl -tag -width IPCTL_FASTFORWARDING
168 .It Dv IPCTL_FORWARDING
170 Boolean: enable/disable forwarding of IP packets.
172 .It Dv IPCTL_FASTFORWARDING
173 .Pq ip.fastforwarding
174 Boolean: enable/disable the use of
175 .Tn fast IP forwarding
179 .Tn fast IP forwarding
180 is enabled, IP packets are forwarded directly to the appropriate network
181 interface with direct processing to completion, which greatly improves
183 All packets for local IP addresses, non-unicast, or with IP options are
184 handled by the normal IP input processing path.
185 All features of the normal (slow) IP forwarding path are supported
186 including firewall (through
188 hooks) checking, except
192 .Tn IP fastforwarding
193 path does not generate ICMP redirect or source quench messages.
194 .It Dv IPCTL_SENDREDIRECTS
196 Boolean: enable/disable sending of ICMP redirects in response to
198 packets for which a better, and for the sender directly reachable, route
199 and next hop is known.
203 Integer: default time-to-live
208 .It Dv IPCTL_ACCEPTSOURCEROUTE
209 .Pq ip.accept_sourceroute
210 Boolean: enable/disable accepting of source-routed IP packets (default false).
211 .It Dv IPCTL_SOURCEROUTE
213 Boolean: enable/disable forwarding of source-routed IP packets (default false).
214 .It Va ip.process_options
215 Integer: control IP options processing.
216 By setting this variable to 0, all IP options in the incoming packets
217 will be ignored, and the packets will be passed unmodified.
218 By setting to 1, IP options in the incoming packets will be processed
222 .Dq "prohibited by filter"
223 message will be sent back in response to incoming packets with IP options.
227 variable affects packets destined for a local host as well as packets
228 forwarded to some other host.
230 Boolean: control IP IDs generation behaviour.
233 to non-zero causes the ID field in IP packets to be randomized instead of
234 incremented by 1 with each packet generated.
235 This closes a minor information leak which allows remote observers to
236 determine the rate of packet generation on the machine by watching the
238 In the same time, on high-speed links, it can decrease the ID reuse
240 Default is 0 (sequential IP IDs).
241 IPv6 flow IDs and fragment IDs are always random.
242 .It Va ip.maxfragpackets
243 Integer: maximum number of fragmented packets the host will accept and hold
244 in the reassembling queue simultaneously.
245 0 means that the host will not accept any fragmented packets.
246 \-1 means that the host will accept as many fragmented packets as it receives.
247 .It Va ip.maxfragsperpacket
248 Integer: maximum number of fragments the host will accept and hold
249 in the reassembling queue for a packet.
250 0 means that the host will not accept any fragmented packets.
266 .%T "An Introductory 4.3 BSD Interprocess Communication Tutorial"
271 .%T "An Advanced 4.3 BSD Interprocess Communication Tutorial"
278 protocol interface appeared in
285 The Internet protocol support is subject to change as
286 the Internet protocols develop.
287 Users should not depend
288 on details of the current implementation, but rather
289 the services exported.