tcpaccept_example.txt

Demonstrations of tcpaccept, the Linux eBPF/bcc version.


This tool traces the kernel function accepting TCP socket connections (eg, a
passive connection via accept(); not connect()). Some example output (IP
addresses changed to protect the innocent):

# ./tcpaccept
PID    COMM         IP RADDR            RPORT  LADDR            LPORT
907    sshd         4  192.168.56.1     32324  192.168.56.102   22
907    sshd         4  127.0.0.1        39866  127.0.0.1        22
5389   perl         6  1234:ab12:2040:5020:2299:0:5:0 52352 1234:ab12:2040:5020:2299:0:5:0 7001

This output shows three connections, two IPv4 connections to PID 907, an "sshd"
process listening on port 22, and one IPv6 connection to a "perl" process
listening on port 7001.

The overhead of this tool should be negligible, since it is only tracing the
kernel function performing accept. It is not tracing every packet and then
filtering.

This tool only traces successful TCP accept()s. Connection attempts to closed
ports will not be shown (those can be traced via other functions).


The -t option prints a timestamp column:

# ./tcpaccept -t
TIME(s)  PID    COMM         IP RADDR            RPORT LADDR            LPORT
0.000    907    sshd         4  127.0.0.1        53700 127.0.0.1        22
0.010    5389   perl         6  1234:ab12:2040:5020:2299:0:5:0 40614 1234:ab12:2040:5020:2299:0:5:0 7001
0.992    907    sshd         4  127.0.0.1        32548 127.0.0.1        22
1.984    907    sshd         4  127.0.0.1        51250 127.0.0.1        22


USAGE message:

# ./tcpaccept -h
usage: tcpaccept [-h] [-T] [-t] [-p PID] [-P PORTS]

Trace TCP accepts

optional arguments:
  -h, --help              show this help message and exit
  -T, --time              include time column on output (HH:MM:SS)
  -t, --timestamp         include timestamp on output
  -p PID, --pid PID       trace this PID only
  -P PORTS, --port PORTS  comma-separated list of local ports to trace

examples:
    ./tcpaccept           # trace all TCP accept()s
    ./tcpaccept -t        # include timestamps
    ./tcpaccept -P 80,81  # only trace port 80 and 81
    ./tcpaccept -p 181    # only trace PID 181