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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.
153 The returned value is in
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_ACCEPTSOURCEROUTE
168 .It Dv IPCTL_FORWARDING
170 Boolean: enable/disable forwarding of IP packets.
172 .It Dv IPCTL_SENDREDIRECTS
174 Boolean: enable/disable sending of ICMP redirects in response to
176 packets for which a better, and for the sender directly reachable, route
177 and next hop is known.
181 Integer: default time-to-live
186 .It Dv IPCTL_ACCEPTSOURCEROUTE
187 .Pq ip.accept_sourceroute
188 Boolean: enable/disable accepting of source-routed IP packets (default false).
189 .It Dv IPCTL_SOURCEROUTE
191 Boolean: enable/disable forwarding of source-routed IP packets (default false).
192 .It Va ip.process_options
193 Integer: control IP options processing.
194 By setting this variable to 0, all IP options in the incoming packets
195 will be ignored, and the packets will be passed unmodified.
196 By setting to 1, IP options in the incoming packets will be processed
200 .Dq "prohibited by filter"
201 message will be sent back in response to incoming packets with IP options.
205 variable affects packets destined for a local host as well as packets
206 forwarded to some other host.
208 Boolean: control IP IDs generation behaviour.
209 True value enables RFC6864 support, which specifies that IP ID field of
211 datagrams can be set to any value.
213 .Fx implementation sets it to zero.
216 Boolean: control IP IDs generation behaviour.
219 to 1 causes the ID field in
221 IP datagrams (or all IP datagrams, if
223 is disabled) to be randomized instead of incremented by 1 with each packet
225 This closes a minor information leak which allows remote observers to
226 determine the rate of packet generation on the machine by watching the
228 At the same time, on high-speed links, it can decrease the ID reuse
230 Default is 0 (sequential IP IDs).
231 IPv6 flow IDs and fragment IDs are always random.
233 Integer: maximum number of fragments the host will accept and simultaneously
234 hold across all reassembly queues in all VNETs.
235 If set to 0, reassembly is disabled.
236 If set to -1, this limit is not applied.
237 This limit is recalculated when the number of mbuf clusters is changed.
238 This is a global limit.
239 .It Va ip.maxfragpackets
240 Integer: maximum number of fragmented packets the host will accept and
241 simultaneously hold in the reassembly queue for a particular VNET.
242 0 means that the host will not accept any fragmented packets for that VNET.
243 \-1 means that the host will not apply this limit for that VNET.
244 This limit is recalculated when the number of mbuf clusters is changed.
245 This is a per-VNET limit.
246 .It Va ip.maxfragbucketsize
247 Integer: maximum number of reassembly queues per bucket.
248 Fragmented packets are hashed to buckets.
249 Each bucket has a list of reassembly queues.
250 The system must compare the incoming packets to the existing reassembly queues
251 in the bucket to find a matching reassembly queue.
252 To preserve system resources, the system limits the number of reassembly
253 queues allowed in each bucket.
254 This limit is recalculated when the number of mbuf clusters is changed or
256 .Va ip.maxfragpackets
258 This is a per-VNET limit.
259 .It Va ip.maxfragsperpacket
260 Integer: maximum number of fragments the host will accept and hold
261 in the reassembly queue for a packet.
262 0 means that the host will not accept any fragmented packets for the VNET.
263 This is a per-VNET limit.
279 .%T "An Introductory 4.3 BSD Interprocess Communication Tutorial"
284 .%T "An Advanced 4.3 BSD Interprocess Communication Tutorial"
291 protocol interface appeared in
298 The Internet protocol support is subject to change as
299 the Internet protocols develop.
300 Users should not depend
301 on details of the current implementation, but rather
302 the services exported.