245 lines
5.2 KiB
HTML
245 lines
5.2 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 IP-TCP_METRICS</TITLE>
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</HEAD><BODY>
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<H1>IP-TCP_METRICS</H1>
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Section: Linux (8)<BR>Updated: 23 Aug 2012<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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ip-tcp_metrics - management for TCP Metrics
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<A NAME="lbAC"> </A>
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<H2>SYNOPSIS</H2>
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<P>
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<BR>
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<B>ip</B>
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[ <I>OPTIONS</I> ]
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<B>tcp_metrics</B>
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{ <I>COMMAND</I> |
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<B>help</B> }
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<P>
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<P>
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<BR>
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<B>ip tcp_metrics</B> { <B>show</B> | <B>flush</B> }
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<I>SELECTOR</I>
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<P>
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<BR>
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<B>ip tcp_metrics delete </B>[<B> address </B>]
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<I>ADDRESS</I>
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<P>
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<BR>
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<I>SELECTOR</I> :=
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[ [ <B>address</B> ]
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<I>PREFIX</I> ]
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<P>
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<A NAME="lbAD"> </A>
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<H2>DESCRIPTION</H2>
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<B>ip tcp_metrics</B>
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is used to manipulate entries in the kernel that keep TCP information
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for IPv4 and IPv6 destinations. The entries are created when
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TCP sockets want to share information for destinations and are
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stored in a cache keyed by the destination address. The saved
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information may include values for metrics (initially obtained from
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routes), recent TSVAL for TIME-WAIT recycling purposes, state for the
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Fast Open feature, etc.
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For performance reasons the cache can not grow above configured limit
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and the older entries are replaced with fresh information, sometimes
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reclaimed and used for new destinations. The kernel never removes
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entries, they can be flushed only with this tool.
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<P>
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<A NAME="lbAE"> </A>
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<H3>ip tcp_metrics show - show cached entries</H3>
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<P>
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<DL COMPACT>
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<DT id="1"><B>address</B><I> PREFIX </I><B>(default)</B>
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<DD>
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IPv4/IPv6 prefix or address. If no prefix is provided all entries are shown.
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<P>
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</DL>
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<P>
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The output may contain the following information:
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<P>
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<B>age</B><I> <S.MMM></I><B>sec</B>
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- time after the entry was created, reset or updated with metrics
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from sockets. The entry is reset and refreshed on use with metrics from
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route if the metrics are not updated in last hour. Not all cached values
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reset the age on update.
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<P>
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<B>cwnd</B><I> <N></I>
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- CWND metric value
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<P>
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<B>fo_cookie</B><I> <HEX-STRING></I>
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- Cookie value received in SYN-ACK to be used by Fast Open for next SYNs
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<P>
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<B>fo_mss</B><I> <N></I>
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- MSS value received in SYN-ACK to be used by Fast Open for next SYNs
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<P>
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<B>fo_syn_drops</B><I> <N>/<S.MMM></I><B>sec ago</B>
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- Number of drops of initial outgoing Fast Open SYNs with data
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detected by monitoring the received SYN-ACK after SYN retransmission.
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The seconds show the time after last SYN drop and together with
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the drop count can be used to disable Fast Open for some time.
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<P>
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<B>reordering</B><I> <N></I>
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- Reordering metric value
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<P>
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<B>rtt</B><I> <N></I><B>us</B>
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- RTT metric value
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<P>
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<B>rttvar</B><I> <N></I><B>us</B>
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- RTTVAR metric value
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<P>
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<B>ssthresh</B><I> <SSTHRESH></I>
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- SSTHRESH metric value
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<P>
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<B>tw_ts</B><I> <TSVAL>/<SEC></I><B>sec ago</B>
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- recent TSVAL and the seconds after saving it into TIME-WAIT socket
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<P>
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<A NAME="lbAF"> </A>
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<H3>ip tcp_metrics delete - delete single entry</H3>
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<P>
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<DL COMPACT>
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<DT id="2"><B>address</B><I> ADDRESS </I><B>(default)</B>
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<DD>
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IPv4/IPv6 address. The address is a required argument.
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<P>
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</DL>
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<A NAME="lbAG"> </A>
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<H3>ip tcp_metrics flush - flush entries</H3>
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This command flushes the entries selected by some criteria.
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<P>
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<P>
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This command has the same arguments as
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<B>show.</B>
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<P>
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<A NAME="lbAH"> </A>
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<H2>EXAMPLES</H2>
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<P>
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ip tcp_metrics show address 192.168.0.0/24
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<DL COMPACT><DT id="3"><DD>
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Shows the entries for destinations from subnet
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</DL>
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<P>
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ip tcp_metrics show 192.168.0.0/24
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<DL COMPACT><DT id="4"><DD>
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The same but address keyword is optional
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</DL>
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<P>
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ip tcp_metrics
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<DL COMPACT><DT id="5"><DD>
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Show all is the default action
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</DL>
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<P>
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ip tcp_metrics delete 192.168.0.1
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<DL COMPACT><DT id="6"><DD>
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Removes the entry for 192.168.0.1 from cache.
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</DL>
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<P>
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ip tcp_metrics flush 192.168.0.0/24
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<DL COMPACT><DT id="7"><DD>
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Removes entries for destinations from subnet
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</DL>
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<P>
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ip tcp_metrics flush all
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<DL COMPACT><DT id="8"><DD>
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Removes all entries from cache
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</DL>
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<P>
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ip -6 tcp_metrics flush all
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<DL COMPACT><DT id="9"><DD>
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Removes all IPv6 entries from cache keeping the IPv4 entries.
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</DL>
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<P>
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<A NAME="lbAI"> </A>
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<H2>SEE ALSO</H2>
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<BR>
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<B><A HREF="/cgi-bin/man/man2html?8+ip">ip</A></B>(8)
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<P>
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<A NAME="lbAJ"> </A>
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<H2>AUTHOR</H2>
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Original Manpage by Julian Anastasov <<A HREF="mailto:ja@ssi.bg">ja@ssi.bg</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="10"><A HREF="#lbAB">NAME</A><DD>
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<DT id="11"><A HREF="#lbAC">SYNOPSIS</A><DD>
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<DT id="12"><A HREF="#lbAD">DESCRIPTION</A><DD>
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<DL>
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<DT id="13"><A HREF="#lbAE">ip tcp_metrics show - show cached entries</A><DD>
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<DT id="14"><A HREF="#lbAF">ip tcp_metrics delete - delete single entry</A><DD>
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<DT id="15"><A HREF="#lbAG">ip tcp_metrics flush - flush entries</A><DD>
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</DL>
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<DT id="16"><A HREF="#lbAH">EXAMPLES</A><DD>
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<DT id="17"><A HREF="#lbAI">SEE ALSO</A><DD>
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<DT id="18"><A HREF="#lbAJ">AUTHOR</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: 00:06:13 GMT, March 31, 2021
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</BODY>
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</HTML>
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