tcpcong - Measure tcp congestion state duration. Uses Linux eBPF/bcc. tcpcong [-h] [-T] [-L] [-R] [-u] [-d] [interval] [outputs] this tool measures tcp sockets congestion control status duration, and prints a summary of tcp congestion state durations along with the number of total state changes. It uses dynamic tracing of kernel tcp congestion control status updating functions, and will need to be updated to match kernel changes. The traced functions are only called when there is congestion state update, and therefore have low overhead. we also use BPF map to store traced data to reduce overhead. See the OVERHEAD section for more details. Since this uses BPF, only the root user can use this tool. CONFIG_BPF and bcc.

-h Print usage message.

-T Include a timestamp column.

-L Specify local tcp port range.

-R Specify remote tcp port range.

-u Output in microseconds.

-d Show congestion status duration distribution as histograms.

Show all tcp sockets congestion status duration until Ctrl-C: # tcpcongestdura

Show all tcp sockets congestion status duration every 1 second and 10 times: # tcpcong 1 10

Show only local port 3000-3006 congestion status duration every 1 second: # tcpcong -L 3000-3006 1

Show only remote port 5000-5005 congestion status duration every 1 second: # tcpcong -R 5000-5005 1

Show 1 second summaries, printed in microseconds, with timestamps: # tcpcong -uT 1

Show all tcp sockets congestion status duration as histograms: # tcpcong -d

LAddrPort local ip address and tcp socket port.

RAddrPort remote ip address and tcp socket port.

Open_us Total duration in open status for microseconds.

Dod_us Total duration in disorder status for microseconds.

Rcov_us Total duration in recovery status for microseconds.

Cwr_us Total duration in cwr status for microseconds.

Los_us Total duration in loss status for microseconds.

Open_ms Total duration in open status for milliseconds.

Dod_ms Total duration in disorder status for milliseconds.

Rcov_ms Total duration in recovery status for milliseconds.

Cwr_ms Total duration in cwr status for milliseconds.

Loss_ms Total duration in loss status for milliseconds.

Chgs Total number of status change.

usecs Range of microseconds for this bucket.

msecs Range of milliseconds for this bucket.

count Number of congestion status in this time range.

distribution ASCII representation of the distribution (the count column).

This traces the kernel tcp congestion status change functions. As called rate per second of these functions per socket is low(<10000), the overhead is also expected to be negligible. If you have an application that will create thousands of tcp connections, then test and understand overhead before use. 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.

Linux Unstable - in development. jacky gan tcpretrans(8), tcpconnect(8), tcptop(8), tcpdrop(8)