| .TH "IP\-TCP_METRICS" 8 "23 Aug 2012" "iproute2" "Linux" |
| .SH "NAME" |
| ip-tcp_metrics \- management for TCP Metrics |
| .SH "SYNOPSIS" |
| .sp |
| .ad l |
| .in +8 |
| .ti -8 |
| .B ip |
| .RI "[ " OPTIONS " ]" |
| .B tcp_metrics |
| .RI "{ " COMMAND " | " |
| .BR help " }" |
| .sp |
| |
| .ti -8 |
| .BR "ip tcp_metrics" " { " show " | " flush " } |
| .IR SELECTOR |
| |
| .ti -8 |
| .BR "ip tcp_metrics delete " [ " address " ] |
| .IR ADDRESS |
| |
| .ti -8 |
| .IR SELECTOR " := " |
| .RB "[ [ " address " ] " |
| .IR PREFIX " ]" |
| |
| .SH "DESCRIPTION" |
| .B ip tcp_metrics |
| is used to manipulate entries in the kernel that keep TCP information |
| for IPv4 and IPv6 destinations. The entries are created when |
| TCP sockets want to share information for destinations and are |
| stored in a cache keyed by the destination address. The saved |
| information may include values for metrics (initially obtained from |
| routes), recent TSVAL for TIME-WAIT recycling purposes, state for the |
| Fast Open feature, etc. |
| For performance reasons the cache can not grow above configured limit |
| and the older entries are replaced with fresh information, sometimes |
| reclaimed and used for new destinations. The kernel never removes |
| entries, they can be flushed only with this tool. |
| |
| .SS ip tcp_metrics show - show cached entries |
| |
| .TP |
| .BI address " PREFIX " (default) |
| IPv4/IPv6 prefix or address. If no prefix is provided all entries are shown. |
| |
| .LP |
| The output may contain the following information: |
| |
| .BI age " <S.MMM>" sec |
| - time after the entry was created, reset or updated with metrics |
| from sockets. The entry is reset and refreshed on use with metrics from |
| route if the metrics are not updated in last hour. Not all cached values |
| reset the age on update. |
| |
| .BI cwnd " <N>" |
| - CWND metric value |
| |
| .BI fo_cookie " <HEX-STRING>" |
| - Cookie value received in SYN-ACK to be used by Fast Open for next SYNs |
| |
| .BI fo_mss " <N>" |
| - MSS value received in SYN-ACK to be used by Fast Open for next SYNs |
| |
| .BI fo_syn_drops " <N>/<S.MMM>" "sec ago" |
| - Number of drops of initial outgoing Fast Open SYNs with data |
| detected by monitoring the received SYN-ACK after SYN retransmission. |
| The seconds show the time after last SYN drop and together with |
| the drop count can be used to disable Fast Open for some time. |
| |
| .BI reordering " <N>" |
| - Reordering metric value |
| |
| .BI rtt " <N>" us |
| - RTT metric value |
| |
| .BI rttvar " <N>" us |
| - RTTVAR metric value |
| |
| .BI ssthresh " <SSTHRESH>" |
| - SSTHRESH metric value |
| |
| .BI tw_ts " <TSVAL>/<SEC>" "sec ago" |
| - recent TSVAL and the seconds after saving it into TIME-WAIT socket |
| |
| .SS ip tcp_metrics delete - delete single entry |
| |
| .TP |
| .BI address " ADDRESS " (default) |
| IPv4/IPv6 address. The address is a required argument. |
| |
| .SS ip tcp_metrics flush - flush entries |
| This command flushes the entries selected by some criteria. |
| |
| .PP |
| This command has the same arguments as |
| .B show. |
| |
| .SH "EXAMPLES" |
| .PP |
| ip tcp_metrics show address 192.168.0.0/24 |
| .RS 4 |
| Shows the entries for destinations from subnet |
| .RE |
| .PP |
| ip tcp_metrics show 192.168.0.0/24 |
| .RS 4 |
| The same but address keyword is optional |
| .RE |
| .PP |
| ip tcp_metrics |
| .RS 4 |
| Show all is the default action |
| .RE |
| .PP |
| ip tcp_metrics delete 192.168.0.1 |
| .RS 4 |
| Removes the entry for 192.168.0.1 from cache. |
| .RE |
| .PP |
| ip tcp_metrics flush 192.168.0.0/24 |
| .RS 4 |
| Removes entries for destinations from subnet |
| .RE |
| .PP |
| ip tcp_metrics flush all |
| .RS 4 |
| Removes all entries from cache |
| .RE |
| .PP |
| ip -6 tcp_metrics flush all |
| .RS 4 |
| Removes all IPv6 entries from cache keeping the IPv4 entries. |
| .RE |
| |
| .SH SEE ALSO |
| .br |
| .BR ip (8) |
| |
| .SH AUTHOR |
| Original Manpage by Julian Anastasov <ja@ssi.bg> |
