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| author | Jacob McDonnell <jacob@jacobmcdonnell.com> | 2026-04-25 19:59:05 -0400 |
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| committer | Jacob McDonnell <jacob@jacobmcdonnell.com> | 2026-04-25 19:59:05 -0400 |
| commit | 1f19f33e45791ea59aed048796fc68672c6723a5 (patch) | |
| tree | 54625fba89e91d1c2177801ec635e8528bba937f /static/netbsd/man4/ip.4 3.html | |
| parent | ac5e55f5f2af5b92794c2aded46c6bae85b5f5ed (diff) | |
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diff --git a/static/netbsd/man4/ip.4 3.html b/static/netbsd/man4/ip.4 3.html deleted file mode 100644 index bf3581ba..00000000 --- a/static/netbsd/man4/ip.4 3.html +++ /dev/null @@ -1,379 +0,0 @@ -<table class="head"> - <tr> - <td class="head-ltitle">IP(4)</td> - <td class="head-vol">Device Drivers Manual</td> - <td class="head-rtitle">IP(4)</td> - </tr> -</table> -<div class="manual-text"> -<section class="Sh"> -<h1 class="Sh" id="NAME"><a class="permalink" href="#NAME">NAME</a></h1> -<p class="Pp"><code class="Nm">ip</code> — <span class="Nd">Internet - Protocol</span></p> -</section> -<section class="Sh"> -<h1 class="Sh" id="SYNOPSIS"><a class="permalink" href="#SYNOPSIS">SYNOPSIS</a></h1> -<p class="Pp"><code class="In">#include - <<a class="In">sys/socket.h</a>></code> - <br/> - <code class="In">#include <<a class="In">netinet/in.h</a>></code></p> -<p class="Pp"><var class="Ft">int</var> - <br/> - <code class="Fn">socket</code>(<var class="Fa" style="white-space: nowrap;">AF_INET</var>, - <var class="Fa" style="white-space: nowrap;">SOCK_RAW</var>, - <var class="Fa" style="white-space: nowrap;">proto</var>);</p> -</section> -<section class="Sh"> -<h1 class="Sh" id="DESCRIPTION"><a class="permalink" href="#DESCRIPTION">DESCRIPTION</a></h1> -<p class="Pp">IP is the network layer protocol used by the Internet protocol - family. Options may be set at the IP level when using higher-level protocols - that are based on IP (such as TCP and UDP). It may also be accessed through - a “raw socket” when developing new protocols, or - special-purpose applications.</p> -<p class="Pp">There are several IP-level - <a class="Xr">setsockopt(2)</a>/<a class="Xr">getsockopt(2)</a> options. - <code class="Dv">IP_OPTIONS</code> may be used to provide IP options to be - transmitted in the IP header of each outgoing packet or to examine the - header options on incoming packets. IP options may be used with any socket - type in the Internet family. The format of IP options to be sent is that - specified by the IP protocol specification (RFC 791), with one exception: - the list of addresses for Source Route options must include the first-hop - gateway at the beginning of the list of gateways. The first-hop gateway - address will be extracted from the option list and the size adjusted - accordingly before use. To disable previously specified options, use a - zero-length buffer:</p> -<div class="Bd Pp Li"> -<pre>setsockopt(s, IPPROTO_IP, IP_OPTIONS, NULL, 0);</pre> -</div> -<p class="Pp"><code class="Dv">IP_TOS</code> and <code class="Dv">IP_TTL</code> - may be used to set the type-of-service and time-to-live fields in the IP - header for <code class="Dv">SOCK_STREAM</code> and - <code class="Dv">SOCK_DGRAM</code> sockets. For example,</p> -<div class="Bd Pp Li"> -<pre>int tos = IPTOS_LOWDELAY; /* see <netinet/ip.h> */ -setsockopt(s, IPPROTO_IP, IP_TOS, &tos, sizeof(tos)); - -int ttl = 60; /* max = 255 */ -setsockopt(s, IPPROTO_IP, IP_TTL, &ttl, sizeof(ttl));</pre> -</div> -<p class="Pp"><code class="Dv">IP_IPSEC_POLICY</code> controls IPSec policy for - sockets. For example,</p> -<div class="Bd Pp Li"> -<pre>const char *policy = "in ipsec ah/transport//require"; -char *buf = ipsec_set_policy(policy, strlen(policy)); -setsockopt(s, IPPROTO_IP, IP_IPSEC_POLICY, buf, ipsec_get_policylen(buf));</pre> -</div> -<p class="Pp">The <code class="Dv">IP_RECVPKTINFO</code> option can be used to - turn on receiving of information about the destination address of the - packet, and the interface index. The information is passed in a - <var class="Vt">struct in_pktinfo</var> structure, which contains</p> -<div class="Bd Pp Li"> -<pre> struct in_addr ipi_addr; /* the source or destination address */ - unsigned int ipi_ifindex; /* the interface index */</pre> -</div> -<p class="Pp">and added to the control portion of the message: The cmsghdr - fields have the following values:</p> -<div class="Bd Pp Li"> -<pre>cmsg_len = CMSG_LEN(sizeof(struct in_pktinfo)) -cmsg_level = IPPROTO_IP -cmsg_type = IP_PKTINFO</pre> -</div> -<p class="Pp">For <a class="Xr">sendmsg(2)</a>, the source address or output - interface can be specified by adding an <code class="Dv">IP_PKTINFO</code> - message to the control part of the message on a - <code class="Dv">SOCK_DGRAM</code> or <code class="Dv">SOCK_RAW</code> - socket. Setting ipi_ifindex will cause the primary address of that interface - to be used; setting ipi_addr will directly choose that address. The - <code class="Dv">IP_PKTINFO</code> cmsghdr structure from a received message - may be used unchanged, in which case the outgoing message will be sent from - the address the incoming message was received on.</p> -<p class="Pp">Setting the <code class="Dv">IP_PKTINFO</code> option on a socket, - with the same <var class="Vt">struct in_pktinfo</var> structure, will set - the default source address to be used until set again, unless explicitly - overridden on a per-packet basis, as above.</p> -<p class="Pp">The <code class="Dv">IP_PORTALGO</code> can be used to randomize - the port selection. Valid algorithms are described in - <a class="Xr">rfc6056(7)</a> and their respective constants are in - <code class="In"><<a class="In">netinet/portalgo.h</a>></code>. For - example,</p> -<div class="Bd Pp Li"> -<pre>int algo = PORTALGO_ALGO_RANDOM_PICK; /* see <netinet/portalgo.h> */ -setsockopt(s, IPPROTO_IP, IP_PORTALGO, &algo, sizeof(algo));</pre> -</div> -<p class="Pp">The port selection can be also viewed and controlled at a global - level for all IP sockets using the following <a class="Xr">sysctl(7)</a> - variables: <code class="Dv">net.inet.ip.anonportalgo.available</code> and - <code class="Dv">net.inet.ip.anonportalgo.selected</code>.</p> -<p class="Pp"><code class="Dv">IP_PORTRANGE</code> controls how ephemeral ports - are allocated for <code class="Dv">SOCK_STREAM</code> and - <code class="Dv">SOCK_DGRAM</code> sockets. For example,</p> -<div class="Bd Pp Li"> -<pre>int range = IP_PORTRANGE_LOW; /* see <netinet/in.h> */ -setsockopt(s, IPPROTO_IP, IP_PORTRANGE, &range, sizeof(range));</pre> -</div> -<p class="Pp">If the <code class="Dv">IP_RECVDSTADDR</code> option is enabled on - a <code class="Dv">SOCK_DGRAM</code> or <code class="Dv">SOCK_RAW</code> - socket, the <a class="Xr">recvmsg(2)</a> call will return the destination IP - address for a UDP datagram. The msg_control field in the msghdr structure - points to a buffer that contains a cmsghdr structure followed by the IP - address. The cmsghdr fields have the following values:</p> -<div class="Bd Pp Li"> -<pre>cmsg_len = CMSG_LEN(sizeof(struct in_addr)) -cmsg_level = IPPROTO_IP -cmsg_type = IP_RECVDSTADDR</pre> -</div> -<p class="Pp">For <a class="Xr">sendmsg(2)</a>, the source address can be - specified by adding <code class="Dv">IP_SENDSRCADDR</code> to the control - part of the message on a <code class="Dv">SOCK_DGRAM</code> or - <code class="Dv">SOCK_RAW</code> socket. The - <code class="Dv">IP_RECVDSTADDR</code> cmsghdr structure from a received - message may be used unchanged, in which case the outgoing message will be - sent from the address the incoming message was received on.</p> -<p class="Pp">If the <code class="Dv">IP_RECVIF</code> option is enabled on a - <code class="Dv">SOCK_DGRAM</code> or <code class="Dv">SOCK_RAW</code> - socket, the <a class="Xr">recvmsg(2)</a> call will return a struct - sockaddr_dl corresponding to the interface on which the packet was received. - the msg_control field in the msghdr structure points to a buffer that - contains a cmsghdr structure followed by the struct sockaddr_dl. The cmsghdr - fields have the following values:</p> -<div class="Bd Pp Li"> -<pre>cmsg_len = CMSG_LEN(sizeof(struct sockaddr_dl)) -cmsg_level = IPPROTO_IP -cmsg_type = IP_RECVIF</pre> -</div> -<p class="Pp">If the <code class="Dv">IP_BINDANY</code> option is enabled on a - <code class="Dv">SOCK_STREAM</code>, <code class="Dv">SOCK_DGRAM</code>, or - a <code class="Dv">SOCK_RAW</code> socket, one can <a class="Xr">bind(2)</a> - to any address, even one not bound to any available network interface in the - system. This functionality (in conjunction with special firewall rules) can - be used for implementing a transparent proxy. The - <code class="Dv">KAUTH_REQ_NETWORK_BIND_ANYADDR</code> privilege is needed - to set this option.</p> -<p class="Pp">If the <code class="Dv">IP_RECVTTL</code> option is enabled on a - <code class="Dv">SOCK_DGRAM</code> socket, the <a class="Xr">recvmsg(2)</a> - call will return the TTL of the received datagram. The msg_control field in - the msghdr structure points to a buffer that contains a cmsghdr structure - followed by the TTL value. The cmsghdr fields have the following values:</p> -<div class="Bd Pp Li"> -<pre>cmsg_len = CMSG_LEN(sizeof(uint8_t)) -cmsg_level = IPPROTO_IP -cmsg_type = IP_RECVTTL</pre> -</div> -<p class="Pp" id="Generalized">The <code class="Dv">IP_MINTTL</code> option may - be used on <code class="Dv">SOCK_DGRAM</code> or - <code class="Dv">SOCK_STREAM</code> sockets to discard packets with a TTL - lower than the option value. This can be used to implement the - <a class="permalink" href="#Generalized"><i class="Em">Generalized TTL - Security Mechanism (GTSM)</i></a> according to RFC 3682. To discard all - packets with a TTL lower than 255:</p> -<div class="Bd Pp Bd-indent Li"> -<pre>int minttl = 255; -setsockopt(s, IPPROTO_IP, IP_MINTTL, &minttl, sizeof(minttl));</pre> -</div> -<section class="Ss"> -<h2 class="Ss" id="MULTICAST_OPTIONS"><a class="permalink" href="#MULTICAST_OPTIONS">MULTICAST - OPTIONS</a></h2> -<p class="Pp">IP multicasting is supported only on - <code class="Dv">AF_INET</code> sockets of type - <code class="Dv">SOCK_DGRAM</code> and <code class="Dv">SOCK_RAW</code>, and - only on networks where the interface driver supports multicasting.</p> -<p class="Pp">The <code class="Dv">IP_MULTICAST_TTL</code> option changes the - time-to-live (TTL) for outgoing multicast datagrams in order to control the - scope of the multicasts:</p> -<div class="Bd Pp Li"> -<pre>u_char ttl; /* range: 0 to 255, default = 1 */ -setsockopt(s, IPPROTO_IP, IP_MULTICAST_TTL, &ttl, sizeof(ttl));</pre> -</div> -<p class="Pp">Datagrams with a TTL of 1 are not forwarded beyond the local - network. Multicast datagrams with a TTL of 0 will not be transmitted on any - network, but may be delivered locally if the sending host belongs to the - destination group and if multicast loopback has not been disabled on the - sending socket (see below). Multicast datagrams with TTL greater than 1 may - be forwarded to other networks if a multicast router is attached to the - local network.</p> -<p class="Pp">For hosts with multiple interfaces, each multicast transmission is - sent from the primary network interface. The - <code class="Dv">IP_MULTICAST_IF</code> option overrides the default for - subsequent transmissions from a given socket:</p> -<div class="Bd Pp Li"> -<pre>struct in_addr addr; -setsockopt(s, IPPROTO_IP, IP_MULTICAST_IF, &addr, sizeof(addr));</pre> -</div> -<p class="Pp">where "addr" is the local IP address of the desired - interface or <code class="Dv">INADDR_ANY</code> to specify the default - interface. An interface's local IP address and multicast capability can be - obtained via the <code class="Dv">SIOCGIFCONF</code> and - <code class="Dv">SIOCGIFFLAGS</code> ioctls. An application may also specify - an alternative to the default network interface by index:</p> -<div class="Bd Pp Li"> -<pre>struct uint32_t idx = htonl(ifindex); -setsockopt(s, IPPROTO_IP, IP_MULTICAST_IF, &idx, sizeof(idx));</pre> -</div> -<p class="Pp">where "ifindex" is an interface index as returned by - <a class="Xr">if_nametoindex(3)</a>.</p> -<p class="Pp">Normal applications should not need to use - <code class="Dv">IP_MULTICAST_IF</code>.</p> -<p class="Pp">If a multicast datagram is sent to a group to which the sending - host itself belongs (on the outgoing interface), a copy of the datagram is, - by default, looped back by the IP layer for local delivery. The - <code class="Dv">IP_MULTICAST_LOOP</code> option gives the sender explicit - control over whether or not subsequent datagrams are looped back:</p> -<div class="Bd Pp Li"> -<pre>u_char loop; /* 0 = disable, 1 = enable (default) */ -setsockopt(s, IPPROTO_IP, IP_MULTICAST_LOOP, &loop, sizeof(loop));</pre> -</div> -<p class="Pp">This option improves performance for applications that may have no - more than one instance on a single host (such as a router demon), by - eliminating the overhead of receiving their own transmissions. It should - generally not be used by applications for which there may be more than one - instance on a single host (such as a conferencing program) or for which the - sender does not belong to the destination group (such as a time querying - program).</p> -<p class="Pp">A multicast datagram sent with an initial TTL greater than 1 may - be delivered to the sending host on a different interface from that on which - it was sent, if the host belongs to the destination group on that other - interface. The loopback control option has no effect on such delivery.</p> -<p class="Pp">A host must become a member of a multicast group before it can - receive datagrams sent to the group. To join a multicast group, use the - <code class="Dv">IP_ADD_MEMBERSHIP</code> option:</p> -<div class="Bd Pp Li"> -<pre>struct ip_mreq mreq; -setsockopt(s, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq, sizeof(mreq));</pre> -</div> -<p class="Pp">where <var class="Fa">mreq</var> is the following structure:</p> -<div class="Bd Pp Li"> -<pre>struct ip_mreq { - struct in_addr imr_multiaddr; /* multicast group to join */ - struct in_addr imr_interface; /* interface to join on */ -}</pre> -</div> -<p class="Pp"><code class="Dv">imr_interface</code> should be - <code class="Dv">INADDR_ANY</code> to choose the default multicast - interface, or the IP address of a particular multicast-capable interface if - the host is multihomed. Membership is associated with a single interface; - programs running on multihomed hosts may need to join the same group on more - than one interface. Up to <code class="Dv">IP_MAX_MEMBERSHIPS</code> - (currently 20) memberships may be added on a single socket.</p> -<p class="Pp">To drop a membership, use:</p> -<div class="Bd Pp Li"> -<pre>struct ip_mreq mreq; -setsockopt(s, IPPROTO_IP, IP_DROP_MEMBERSHIP, &mreq, sizeof(mreq));</pre> -</div> -<p class="Pp">where <var class="Fa">mreq</var> contains the same values as used - to add the membership. Memberships are dropped when the socket is closed or - the process exits.</p> -</section> -<section class="Ss"> -<h2 class="Ss" id="RAW_IP_SOCKETS"><a class="permalink" href="#RAW_IP_SOCKETS">RAW - IP SOCKETS</a></h2> -<p class="Pp">Raw IP sockets are connectionless, and are normally used with the - <a class="Xr">sendto(2)</a> and <a class="Xr">recvfrom(2)</a> calls, though - the <a class="Xr">connect(2)</a> call may also be used to fix the - destination for future packets (in which case the <a class="Xr">read(2)</a> - or <a class="Xr">recv(2)</a> and <a class="Xr">write(2)</a> or - <a class="Xr">send(2)</a> system calls may be used).</p> -<p class="Pp">If <var class="Fa">proto</var> is 0, the default protocol - <code class="Dv">IPPROTO_RAW</code> is used for outgoing packets, and only - incoming packets destined for that protocol are received. If - <var class="Fa">proto</var> is non-zero, that protocol number will be used - on outgoing packets and to filter incoming packets.</p> -<p class="Pp">Outgoing packets automatically have an IP header prepended to them - (based on the destination address and the protocol number the socket is - created with), unless the <code class="Dv">IP_HDRINCL</code> option has been - set. Incoming packets are received with IP header and options intact.</p> -<p class="Pp"><code class="Dv">IP_HDRINCL</code> indicates the complete IP - header is included with the data and may be used only with the - <code class="Dv">SOCK_RAW</code> type.</p> -<div class="Bd Pp Li"> -<pre>#include <netinet/ip.h> - -int hincl = 1; /* 1 = on, 0 = off */ -setsockopt(s, IPPROTO_IP, IP_HDRINCL, &hincl, sizeof(hincl));</pre> -</div> -<p class="Pp">Unlike previous <span class="Ux">BSD</span> releases, the program - must set all the fields of the IP header, including the following:</p> -<div class="Bd Pp Li"> -<pre>ip->ip_v = IPVERSION; -ip->ip_hl = hlen >> 2; -ip->ip_id = 0; /* 0 means kernel set appropriate value */ -ip->ip_off = offset;</pre> -</div> -<p class="Pp">If the header source address is set to - <code class="Dv">INADDR_ANY</code>, the kernel will choose an appropriate - address.</p> -</section> -</section> -<section class="Sh"> -<h1 class="Sh" id="DIAGNOSTICS"><a class="permalink" href="#DIAGNOSTICS">DIAGNOSTICS</a></h1> -<p class="Pp">A socket operation may fail with one of the following errors - returned:</p> -<dl class="Bl-tag"> - <dt>[<code class="Er">EACCES</code>]</dt> - <dd>when an attempt is made to create a raw IP socket by a non-privileged - process.</dd> - <dt>[<code class="Er">EADDRNOTAVAIL</code>]</dt> - <dd>when an attempt is made to create a socket with a network address for - which no network interface exists.</dd> - <dt>[<code class="Er">EISCONN</code>]</dt> - <dd>when trying to establish a connection on a socket which already has one, - or when trying to send a datagram with the destination address specified - and the socket is already connected;</dd> - <dt>[<code class="Er">ENOBUFS</code>]</dt> - <dd>when the system runs out of memory for an internal data structure;</dd> - <dt>[<code class="Er">ENOTCONN</code>]</dt> - <dd>when trying to send a datagram, but no destination address is specified, - and the socket hasn't been connected;</dd> -</dl> -<p class="Pp">The following errors specific to IP may occur when setting or - getting IP options:</p> -<dl class="Bl-tag"> - <dt>[<code class="Er">EINVAL</code>]</dt> - <dd>An unknown socket option name was given; or the IP option field was - improperly formed; an option field was shorter than the minimum value or - longer than the option buffer provided.</dd> -</dl> -</section> -<section class="Sh"> -<h1 class="Sh" id="COMPATIBILITY"><a class="permalink" href="#COMPATIBILITY">COMPATIBILITY</a></h1> -<p class="Pp">The <code class="Dv">IP_RECVPKTINFO</code> option is used because - it is directly compatible with Solaris, AIX, etc., and the - <code class="Dv">IP_PKTINFO</code> option is intended to be used in their - manner, to set the default source address for outgoing packets on a - <code class="Dv">SOCK_DGRAM</code> or <code class="Dv">SOCK_RAW</code> - socket. For compatibility with Linux, however, if you attempt to set the - <code class="Dv">IP_PKTINFO</code> option, using an integer parameter as a - boolean value, this will transparently manipulate the - <code class="Dv">IP_RECVPKTINFO</code> option instead. Source code - compatibility with both environments is thus maintained.</p> -</section> -<section class="Sh"> -<h1 class="Sh" id="SEE_ALSO"><a class="permalink" href="#SEE_ALSO">SEE - ALSO</a></h1> -<p class="Pp"><a class="Xr">getsockopt(2)</a>, <a class="Xr">recv(2)</a>, - <a class="Xr">send(2)</a>, <a class="Xr">CMSG_DATA(3)</a>, - <a class="Xr">ipsec_set_policy(3)</a>, <a class="Xr">icmp(4)</a>, - <a class="Xr">inet(4)</a>, <a class="Xr">intro(4)</a></p> -<p class="Pp"><cite class="Rs"><span class="RsT">Internet Protocol</span>, - <span class="RsR">RFC</span>, <span class="RsN">791</span>, - <span class="RsD">September 1981</span>.</cite></p> -<p class="Pp"><cite class="Rs"><span class="RsT">Host Extensions for IP - Multicasting</span>, <span class="RsR">RFC</span>, - <span class="RsN">1112</span>, <span class="RsD">August - 1989</span>.</cite></p> -<p class="Pp"><cite class="Rs"><span class="RsT">Requirements for Internet Hosts - — Communication Layers</span>, <span class="RsR">RFC</span>, - <span class="RsN">1122</span>, <span class="RsD">October - 1989</span>.</cite></p> -</section> -<section class="Sh"> -<h1 class="Sh" id="HISTORY"><a class="permalink" href="#HISTORY">HISTORY</a></h1> -<p class="Pp">The <code class="Nm">ip</code> protocol appeared in - <span class="Ux">4.2BSD</span>.</p> -</section> -</div> -<table class="foot"> - <tr> - <td class="foot-date">September 8, 2020</td> - <td class="foot-os">NetBSD 10.1</td> - </tr> -</table> |