1 .\" Copyright (c) 1983, 1991, 1993
2 .\" The Regents of the University of California. All rights reserved.
4 .\" Redistribution and use in source and binary forms, with or without
5 .\" modification, are permitted provided that the following conditions
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.
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
32 .\" @(#)ip.4 8.2 (Berkeley) 11/30/93
33 .\" $FreeBSD: src/share/man/man4/ip.4,v 1.13.2.9 2002/05/02 02:40:26 silby Exp $
34 .\" $DragonFly: src/share/man/man4/ip.4,v 1.3 2006/02/10 19:01:09 swildner Exp $
47 .Fn socket AF_INET SOCK_RAW proto
50 is the transport layer protocol used
51 by the Internet protocol family.
52 Options may be set at the
55 when using higher-level protocols that are based on
61 It may also be accessed
64 when developing new protocols, or
65 special-purpose applications.
74 may be used to provide
76 options to be transmitted in the
78 header of each outgoing packet
79 or to examine the header options on incoming packets.
81 options may be used with any socket type in the Internet family.
84 options to be sent is that specified by the
86 protocol specification (RFC-791), with one exception:
87 the list of addresses for Source Route options must include the first-hop
88 gateway at the beginning of the list of gateways.
89 The first-hop gateway address will be extracted from the option list
90 and the size adjusted accordingly before use.
91 To disable previously specified options,
92 use a zero-length buffer:
94 setsockopt(s, IPPROTO_IP, IP_OPTIONS, NULL, 0);
100 may be used to set the type-of-service and time-to-live
104 .Dv SOCK_STREAM , SOCK_DGRAM ,
110 int tos = IPTOS_LOWDELAY; /* see <netinet/ip.h> */
111 setsockopt(s, IPPROTO_IP, IP_TOS, &tos, sizeof(tos));
113 int ttl = 60; /* max = 255 */
114 setsockopt(s, IPPROTO_IP, IP_TTL, &ttl, sizeof(ttl));
119 option is enabled on a
124 call will return the destination
129 The msg_control field in the msghdr structure points to a buffer
130 that contains a cmsghdr structure followed by the
133 The cmsghdr fields have the following values:
135 cmsg_len = sizeof(struct in_addr)
136 cmsg_level = IPPROTO_IP
137 cmsg_type = IP_RECVDSTADDR
141 may be used to set the port range used for selecting a local port number
142 on a socket with an unspecified (zero) port number.
145 .Bl -tag -width IP_PORTRANGE_DEFAULT
146 .It Dv IP_PORTRANGE_DEFAULT
147 use the default range of values, normally
150 .Dv IPPORT_USERRESERVED .
151 This is adjustable through the sysctl setting:
152 .Sy net.inet.ip.portrange.first
154 .Sy net.inet.ip.portrange.last .
155 .It Dv IP_PORTRANGE_HIGH
156 use a high range of values, normally
157 .Dv IPPORT_HIFIRSTAUTO
159 .Dv IPPORT_HILASTAUTO .
160 This is adjustable through the sysctl setting:
161 .Sy net.inet.ip.portrange.hifirst
163 .Sy net.inet.ip.portrange.hilast .
164 .It Dv IP_PORTRANGE_LOW
165 use a low range of ports, which are normally restricted to
166 privileged processes on
168 systems. The range is normally from
169 .Dv IPPORT_RESERVED - 1
171 .Li IPPORT_RESERVEDSTART
173 This is adjustable through the sysctl setting:
174 .Sy net.inet.ip.portrange.lowfirst
176 .Sy net.inet.ip.portrange.lowlast .
178 .Ss "Multicast Options"
180 multicasting is supported only on
186 and only on networks where the interface
187 driver supports multicasting.
191 option changes the time-to-live (TTL)
192 for outgoing multicast datagrams
193 in order to control the scope of the multicasts:
195 u_char ttl; /* range: 0 to 255, default = 1 */
196 setsockopt(s, IPPROTO_IP, IP_MULTICAST_TTL, &ttl, sizeof(ttl));
199 Datagrams with a TTL of 1 are not forwarded beyond the local network.
200 Multicast datagrams with a TTL of 0 will not be transmitted on any network,
201 but may be delivered locally if the sending host belongs to the destination
202 group and if multicast loopback has not been disabled on the sending socket
203 (see below). Multicast datagrams with TTL greater than 1 may be forwarded
204 to other networks if a multicast router is attached to the local network.
206 For hosts with multiple interfaces, each multicast transmission is
207 sent from the primary network interface.
210 option overrides the default for
211 subsequent transmissions from a given socket:
214 setsockopt(s, IPPROTO_IP, IP_MULTICAST_IF, &addr, sizeof(addr));
217 where "addr" is the local
219 address of the desired interface or
221 to specify the default interface.
222 An interface's local IP address and multicast capability can
228 Normal applications should not need to use this option.
230 If a multicast datagram is sent to a group to which the sending host itself
231 belongs (on the outgoing interface), a copy of the datagram is, by default,
232 looped back by the IP layer for local delivery.
234 .Dv IP_MULTICAST_LOOP
235 option gives the sender explicit control
236 over whether or not subsequent datagrams are looped back:
238 u_char loop; /* 0 = disable, 1 = enable (default) */
239 setsockopt(s, IPPROTO_IP, IP_MULTICAST_LOOP, &loop, sizeof(loop));
243 improves performance for applications that may have no more than one
244 instance on a single host (such as a router daemon), by eliminating
245 the overhead of receiving their own transmissions. It should generally not
246 be used by applications for which there may be more than one instance on a
247 single host (such as a conferencing program) or for which the sender does
248 not belong to the destination group (such as a time querying program).
250 A multicast datagram sent with an initial TTL greater than 1 may be delivered
251 to the sending host on a different interface from that on which it was sent,
252 if the host belongs to the destination group on that other interface. The
253 loopback control option has no effect on such delivery.
255 A host must become a member of a multicast group before it can receive
256 datagrams sent to the group. To join a multicast group, use the
257 .Dv IP_ADD_MEMBERSHIP
261 setsockopt(s, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq, sizeof(mreq));
266 is the following structure:
269 struct in_addr imr_multiaddr; /* IP multicast address of group */
270 struct in_addr imr_interface; /* local IP address of interface */
278 to choose the default multicast interface,
281 address of a particular multicast-capable interface if
282 the host is multihomed.
283 Membership is associated with a single interface;
284 programs running on multihomed hosts may need to
285 join the same group on more than one interface.
287 .Dv IP_MAX_MEMBERSHIPS
288 (currently 20) memberships may be added on a
291 To drop a membership, use:
294 setsockopt(s, IPPROTO_IP, IP_DROP_MEMBERSHIP, &mreq, sizeof(mreq));
299 contains the same values as used to add the membership.
300 Memberships are dropped when the socket is closed or the process exits.
301 .\"-----------------------
305 sockets are connectionless,
306 and are normally used with the
312 call may also be used to fix the destination for future
313 packets (in which case the
321 system calls may be used).
325 is 0, the default protocol
328 packets, and only incoming packets destined for that protocol
332 is non-zero, that protocol number will be used on outgoing packets
333 and to filter incoming packets.
335 Outgoing packets automatically have an
338 them (based on the destination address and the protocol
339 number the socket is created with),
343 Incoming packets are received with
345 header and options intact.
348 indicates the complete IP header is included with the data
349 and may be used only with the
353 #include <netinet/in_systm.h>
354 #include <netinet/ip.h>
356 int hincl = 1; /* 1 = on, 0 = off */
357 setsockopt(s, IPPROTO_IP, IP_HDRINCL, &hincl, sizeof(hincl));
362 releases, the program must set all
363 the fields of the IP header, including the following:
365 ip->ip_v = IPVERSION;
366 ip->ip_hl = hlen >> 2;
367 ip->ip_id = 0; /* 0 means kernel set appropriate value */
371 If the header source address is set to
373 the kernel will choose an appropriate address.
375 A socket operation may fail with one of the following errors returned:
378 when trying to establish a connection on a socket which
379 already has one, or when trying to send a datagram with the destination
380 address specified and the socket is already connected;
382 when trying to send a datagram, but
383 no destination address is specified, and the socket hasn't been
386 when the system runs out of memory for
387 an internal data structure;
388 .It Bq Er EADDRNOTAVAIL
389 when an attempt is made to create a
390 socket with a network address for which no network interface
393 when an attempt is made to create
394 a raw IP socket by a non-privileged process.
397 The following errors specific to
399 may occur when setting or getting
402 .Bl -tag -width EADDRNOTAVAILxx
404 An unknown socket option name was given.
406 The IP option field was improperly formed;
407 an option field was shorter than the minimum value
408 or longer than the option buffer provided.