# ip-tcp_metrics

## NAME



           ip-tcp_metrics - management for TCP Metrics
    


## SYNOPSIS



           **ip**[ _OPTIONS_ ] **tcp_metrics**{ _COMMAND_ | **help**}
    
           **ip tcp_metrics**{ **show** | **flush**} _SELECTOR_
    
           **ip tcp_metrics delete**[ **address**] _ADDRESS_
    
           _SELECTOR_ := [ [ **address**] _PREFIX_ ]
    


## DESCRIPTION



           **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.
    
       **ip tcp_metrics show - show cached entries**
           **address** _PREFIX_ **(default)**
                  IPv4/IPv6 prefix or address. If no prefix is provided all
                  entries are shown.
    
           The output may contain the following information:
    
           **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.
    
           **cwnd** _< N>_ - CWND metric value
    
           **fo_cookie** _< HEX-STRING>_ - Cookie value received in SYN-ACK to be
           used by Fast Open for next SYNs
    
           **fo_mss** _< N>_ - 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** _< N>_ - Reordering metric value
    
           **rtt** _< N>_**us** - RTT metric value
    
           **rttvar** _< N>_**us** - RTTVAR metric value
    
           **ssthresh** _< SSTHRESH>_ - SSTHRESH metric value
    
           **tw_ts** _< TSVAL>/<SEC>_**sec ago** - recent TSVAL and the seconds after
           saving it into TIME-WAIT socket
    
       **ip tcp_metrics delete - delete single entry**
           **address** _ADDRESS_ **(default)**
                  IPv4/IPv6 address. The address is a required argument.
    
       **ip tcp_metrics flush - flush entries**
           This command flushes the entries selected by some criteria.
    
           This command has the same arguments as **show.**
    


## EXAMPLES



           ip tcp_metrics show address 192.168.0.0/24
               Shows the entries for destinations from subnet
    
           ip tcp_metrics show 192.168.0.0/24
               The same but address keyword is optional
    
           ip tcp_metrics
               Show all is the default action
    
           ip tcp_metrics delete 192.168.0.1
               Removes the entry for 192.168.0.1 from cache.
    
           ip tcp_metrics flush 192.168.0.0/24
               Removes entries for destinations from subnet
    
           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.
    


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