tcpaccept.bt - Trace TCP passive connections (accept()). Uses bpftrace/eBPF
Contents
Description
This tool traces passive TCP connections (eg, via an accept() syscall; connect() are active connections).
This can be useful for general troubleshooting to see what new connections the local server is accepting.
This uses dynamic tracing of the kernel inet_csk_accept() socket function (from tcp_prot.accept), and
will need to be modified to match kernel changes.
This tool only traces successful TCP accept()s. Connection attempts to closed ports will not be shown
(those can be traced via other functions).
Since this uses BPF, only the root user can use this tool.
Examples
Trace all passive TCP connections (accept()s):
# tcpaccept.btFIELDS
TIME(s)
Time of the call, in HH:MM:SS format.
PID Process ID
COMM Process name
RADDR Remote IP address.
RPORT Remote port.
LADDR Local IP address.
LPORT Local port
BL Current accept backlog vs maximum backlog
Name
tcpaccept.bt - Trace TCP passive connections (accept()). Uses bpftrace/eBPF
Os
Linux
Overhead
This traces the kernel inet_csk_accept function and prints output for each event. The rate of this
depends on your server application. If it is a web or proxy server accepting many tens of thousands of
connections per second, then the overhead of this tool may be measurable (although, still a lot better
than tracing every packet). If it is less than a thousand a second, then the overhead is expected to be
negligible. Test and understand this overhead before use.
Requirements
CONFIG_BPF and bpftrace.
See Also
tcpconnect.bt(8), funccount(8), tcpdump(8) USER COMMANDS 2018-10-24 tcpaccept.bt(8)
Source
This is from bpftrace
https://github.com/bpftrace/bpftrace
Also look in the bpftrace distribution for a companion _examples.txt file containing example usage,
output, and commentary for this tool.
This is a bpftrace version of the bcc tool of the same name. The bcc tool may provide more options and
customizations.
https://github.com/iovisor/bcc
Stability
Unstable - in development.
Synopsis
tcpaccept.bt
