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.TH "IP\-TCP_METRICS" 8 "23 Aug 2012" "iproute2" "Linux"
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ip-tcp_metrics \- management for TCP Metrics
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.RI "{ " COMMAND " | "
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.BR "ip tcp_metrics" " { " show " | " flush " }
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.BR "ip tcp_metrics delete " [ " address " ]
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.RB "[ [ " address " ] "
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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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.SS ip tcp_metrics show - show cached entries
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.BI address " PREFIX " (default)
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IPv4/IPv6 prefix or address. If no prefix is provided all entries are shown.
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The output may contain the following information:
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.BI age " <S.MMM>" sec
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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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.BI fo_cookie " <HEX-STRING>"
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- Cookie value received in SYN-ACK to be used by Fast Open for next SYNs
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- MSS value received in SYN-ACK to be used by Fast Open for next SYNs
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.BI fo_syn_drops " <N>/<S.MMM>" "sec ago"
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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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- Reordering metric value
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.BI ssthresh " <SSTHRESH>"
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- SSTHRESH metric value
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.BI tw_ts " <TSVAL>/<SEC>" "sec ago"
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- recent TSVAL and the seconds after saving it into TIME-WAIT socket
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.SS ip tcp_metrics delete - delete single entry
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.BI address " ADDRESS " (default)
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IPv4/IPv6 address. The address is a required argument.
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.SS ip tcp_metrics flush - flush entries
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This command flushes the entries selected by some criteria.
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This command has the same arguments as
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ip tcp_metrics show address 192.168.0.0/24
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Shows the entries for destinations from subnet
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ip tcp_metrics show 192.168.0.0/24
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The same but address keyword is optional
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Show all is the default action
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ip tcp_metrics delete 192.168.0.1
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Removes the entry for 192.168.0.1 from cache.
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ip tcp_metrics flush 192.168.0.0/24
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Removes entries for destinations from subnet
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ip tcp_metrics flush all
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Removes all entries from cache
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ip -6 tcp_metrics flush all
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Removes all IPv6 entries from cache keeping the IPv4 entries.
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Original Manpage by Julian Anastasov <ja@ssi.bg>
added
removed
man/man8/ip-tcp_metrics.8
