ip-tcp_metrics - management for TCP Metrics
ip tcp_metrics delete
:= [ [ address
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.
- address PREFIX (default)
- IPv4/IPv6 prefix or address. If no prefix is provided all
entries are shown.
The output may contain the following information:
- 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.
- CWND metric value
- Cookie value received in SYN-ACK to
be used by Fast Open for next SYNs
- MSS value received in SYN-ACK to be used by
Fast Open for next SYNs
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.
- Reordering metric value
- RTT metric value
- RTTVAR metric value
- SSTHRESH metric value
tw_ts <TSVAL>/<SEC>sec ago
- recent TSVAL and
the seconds after saving it into TIME-WAIT socket
- address ADDRESS (default)
- IPv4/IPv6 address. The address is a required argument.
This command flushes the entries selected by some criteria.
This command has the same arguments as show.
ip tcp_metrics show address 192.168.0.0/24
Shows the entries for destinations from
ip tcp_metrics show 192.168.0.0/24
The same but address keyword is optional
Show all is the default action
ip tcp_metrics delete 192.168.0.1
Removes the entry for 192.168.0.1 from
ip tcp_metrics flush 192.168.0.0/24
Removes entries for destinations from
ip tcp_metrics flush all
Removes all entries from cache
ip -6 tcp_metrics flush all
Removes all IPv6 entries from cache keeping
the IPv4 entries.
Original Manpage by Julian Anastasov <firstname.lastname@example.org>