NAME

       tcpconnlat - Trace TCP active connection latency. Uses Linux eBPF/bcc.

SYNOPSIS

       tcpconnlat [-h] [-t] [-p PID] [-L] [-4 | -6] [-v] [min_ms]

DESCRIPTION

       This  tool  traces  active  TCP  connections  (eg, via a connect() syscall), and shows the
       latency (time) for the connection as measured locally: the  time  from  SYN  sent  to  the
       response  packet.   This is a useful performance metric that typically spans kernel TCP/IP
       processing and the network round trip time (not application runtime).

       All connection attempts are traced, even if they ultimately fail (RST packet in response).

       This tool works by use of kernel dynamic  tracing  of  TCP/IP  functions,  and  will  need
       updating  to  match  any  changes  to  these functions. This tool should be updated in the
       future to use static tracepoints, once they are available.

       Since this uses BPF, only the root user can use this tool.

REQUIREMENTS

       CONFIG_BPF and bcc.

OPTIONS

       -h     Print usage message.

       -t     Include a timestamp column.

       -p PID Trace this process ID only (filtered in-kernel).

       -L     Include a LPORT column.

       -4     Trace IPv4 family only.

       -6     Trace IPv6 family only.

       -v     Print the resulting BPF program, for debugging purposes.

       min_ms Minimum duration to trace, in milliseconds.

EXAMPLES

       Trace all active TCP connections, and show connection latency (SYN->response round trip):
              # tcpconnlat

       Include timestamps:
              # tcpconnlat -t

       Trace PID 181 only:
              # tcpconnlat -p 181

       Trace connects, and include LPORT:
              # tcpconnlat -L

       Trace IPv4 family only:
              # tcpconnlat -4

       Trace IPv6 family only:
              # tcpconnlat -6

       Trace connects with latency longer than 10 ms:
              # tcpconnlat 10

       Print the BPF program:
              # tcpconnlat -v

FIELDS

       TIME(s)
              Time of the response packet, in seconds.

       PID    Process ID that initiated the connection.

       COMM   Process name that initiated the connection.

       IP     IP address family (4 or 6).

       SADDR  Source IP address.

       DADDR  Destination IP address.

       LPORT  Source port

       DPORT  Destination port

       LAT(ms)
              The time from when a TCP connect was issued (measured in-kernel) to when a response
              packet  was  received for this connection (can be SYN,ACK, or RST, etc).  This time
              spans kernel to kernel latency, involving kernel TCP/IP processing and the  network
              round  trip  in  between.  This  typically  does  not  include  time  spent  by the
              application processing the new connection.

OVERHEAD

       This traces the kernel tcp_v[46]_connect functions and prints output for  each  event.  As
       the rate of this is generally expected to be low (< 1000/s), the overhead is also expected
       to be negligible. If you have an application that is calling a high rate  of  connects()s,
       such as a proxy server, then test and understand this overhead before use.

SOURCE

       This is from bcc.

              https://github.com/iovisor/bcc

       Also  look  in  the bcc distribution for a companion _examples.txt file containing example
       usage, output, and commentary for this tool.

OS

       Linux

STABILITY

       Unstable - in development.

AUTHOR

       Brendan Gregg

SEE ALSO

       tcpconnect(8), tcpaccept(8), funccount(8), tcpdump(8)