216 lines
5.4 KiB
HTML
216 lines
5.4 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<HTML><HEAD><TITLE>Man page of RTNETLINK</TITLE>
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</HEAD><BODY>
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<H1>RTNETLINK</H1>
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Section: Linux Programmer's Manual (3)<BR>Updated: 2014-09-06<BR><A HREF="#index">Index</A>
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<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
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<A NAME="lbAB"> </A>
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<H2>NAME</H2>
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rtnetlink - macros to manipulate rtnetlink messages
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<A NAME="lbAC"> </A>
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<H2>SYNOPSIS</H2>
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<B>#include <<A HREF="file:///usr/include/asm/types.h">asm/types.h</A>></B>
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<BR>
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<B>#include <<A HREF="file:///usr/include/linux/netlink.h">linux/netlink.h</A>></B>
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<BR>
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<B>#include <<A HREF="file:///usr/include/linux/rtnetlink.h">linux/rtnetlink.h</A>></B>
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<BR>
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<B>#include <<A HREF="file:///usr/include/sys/socket.h">sys/socket.h</A>></B>
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<P>
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<B>rtnetlink_socket = socket(AF_NETLINK, int </B><I>socket_type</I><B>, NETLINK_ROUTE);</B>
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<P>
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<B>int RTA_OK(struct rtattr *</B><I>rta</I><B>, int </B><I>rtabuflen</I><B>);</B>
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<P>
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<B>void *RTA_DATA(struct rtattr *</B><I>rta</I><B>);</B>
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<P>
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<B>unsigned int RTA_PAYLOAD(struct rtattr *</B><I>rta</I><B>);</B>
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<P>
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<B>struct rtattr *RTA_NEXT(struct rtattr *</B><I>rta</I><B>, unsigned int </B><I>rtabuflen</I><B>);</B>
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<P>
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<B>unsigned int RTA_LENGTH(unsigned int </B><I>length</I><B>);</B>
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<P>
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<B>unsigned int RTA_SPACE(unsigned int length</B><I>);</I>
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<A NAME="lbAD"> </A>
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<H2>DESCRIPTION</H2>
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All
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<B><A HREF="/cgi-bin/man/man2html?7+rtnetlink">rtnetlink</A></B>(7)
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messages consist of a
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<B><A HREF="/cgi-bin/man/man2html?7+netlink">netlink</A></B>(7)
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message header and appended attributes.
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The attributes should be manipulated only using the macros provided here.
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<P>
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<B>RTA_OK(</B><I>rta</I><B>, </B><I>attrlen</I><B>)</B>
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returns true if
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<I>rta</I>
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points to a valid routing attribute;
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<I>attrlen</I>
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is the running length of the attribute buffer.
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When not true then you must assume there are no more attributes in the
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message, even if
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<I>attrlen</I>
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is nonzero.
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<P>
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<B>RTA_DATA(</B><I>rta</I><B>)</B>
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returns a pointer to the start of this attribute's data.
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<P>
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<B>RTA_PAYLOAD(</B><I>rta</I><B>)</B>
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returns the length of this attribute's data.
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<P>
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<B>RTA_NEXT(</B><I>rta</I><B>, </B><I>attrlen</I><B>)</B>
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gets the next attribute after
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<I>rta</I>.
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Calling this macro will update
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<I>attrlen</I>.
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You should use
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<B>RTA_OK</B>
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to check the validity of the returned pointer.
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<P>
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<B>RTA_LENGTH(</B><I>len</I><B>)</B>
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returns the length which is required for
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<I>len</I>
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bytes of data plus the header.
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<P>
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<B>RTA_SPACE(</B><I>len</I><B>)</B>
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returns the amount of space which will be needed in a message with
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<I>len</I>
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bytes of data.
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<A NAME="lbAE"> </A>
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<H2>CONFORMING TO</H2>
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These macros are nonstandard Linux extensions.
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<A NAME="lbAF"> </A>
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<H2>BUGS</H2>
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This manual page is incomplete.
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<A NAME="lbAG"> </A>
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<H2>EXAMPLE</H2>
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Creating a rtnetlink message to set the MTU of a device:
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<P>
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#include <<A HREF="file:///usr/include/linux/rtnetlink.h">linux/rtnetlink.h</A>>
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<P>
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...
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<P>
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struct {
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<BR> struct nlmsghdr nh;
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<BR> struct ifinfomsg if;
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<BR> char attrbuf[512];
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} req;
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<P>
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struct rtattr *rta;
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unsigned int mtu = 1000;
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<P>
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int rtnetlink_sk = socket(AF_NETLINK, SOCK_DGRAM, NETLINK_ROUTE);
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<P>
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memset(&req, 0, sizeof(req));
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req.nh.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifinfomsg));
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req.nh.nlmsg_flags = NLM_F_REQUEST;
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req.nh.nlmsg_type = RTM_NEWLINK;
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req.if.ifi_family = AF_UNSPEC;
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req.if.ifi_index = INTERFACE_INDEX;
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req.if.ifi_change = 0xffffffff; /* ??? */
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rta = (struct rtattr *)(((char *) &req) +
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<BR> NLMSG_ALIGN(req.nh.nlmsg_len));
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rta->rta_type = IFLA_MTU;
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rta->rta_len = RTA_LENGTH(sizeof(unsigned int));
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req.nh.nlmsg_len = NLMSG_ALIGN(req.nh.nlmsg_len) +
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<BR> RTA_LENGTH(sizeof(mtu));
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memcpy(RTA_DATA(rta), &mtu, sizeof(mtu));
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send(rtnetlink_sk, &req, req.nh.nlmsg_len, 0);
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<A NAME="lbAH"> </A>
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<H2>SEE ALSO</H2>
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<B><A HREF="/cgi-bin/man/man2html?3+netlink">netlink</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?7+netlink">netlink</A></B>(7),
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<B><A HREF="/cgi-bin/man/man2html?7+rtnetlink">rtnetlink</A></B>(7)
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<A NAME="lbAI"> </A>
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<H2>COLOPHON</H2>
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This page is part of release 5.05 of the Linux
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<I>man-pages</I>
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project.
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A description of the project,
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information about reporting bugs,
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and the latest version of this page,
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can be found at
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<A HREF="https://www.kernel.org/doc/man-pages/.">https://www.kernel.org/doc/man-pages/.</A>
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<P>
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<HR>
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<A NAME="index"> </A><H2>Index</H2>
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<DL>
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<DT id="1"><A HREF="#lbAB">NAME</A><DD>
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<DT id="2"><A HREF="#lbAC">SYNOPSIS</A><DD>
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<DT id="3"><A HREF="#lbAD">DESCRIPTION</A><DD>
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<DT id="4"><A HREF="#lbAE">CONFORMING TO</A><DD>
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<DT id="5"><A HREF="#lbAF">BUGS</A><DD>
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<DT id="6"><A HREF="#lbAG">EXAMPLE</A><DD>
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<DT id="7"><A HREF="#lbAH">SEE ALSO</A><DD>
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<DT id="8"><A HREF="#lbAI">COLOPHON</A><DD>
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</DL>
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<HR>
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This document was created by
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<A HREF="/cgi-bin/man/man2html">man2html</A>,
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using the manual pages.<BR>
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Time: 00:05:54 GMT, March 31, 2021
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</BODY>
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</HTML>
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