tcpconnect(8)

NAME
tcpconnect - Trace TCP active connections (connect()). Uses Linux eBPF/bcc.

SYNOPSIS
tcpconnect [-h] [-t] [-x] [-p PID] [-P PORT]

DESCRIPTION
This tool traces active TCP connections (eg, via a connect() syscall; accept() are passive connections). This can be useful for general troubleshooting to see what connections are initiated by the local server. All connection attempts are traced, even if they ultimately fail. This works by tracing the kernel tcp_v4_connect() and tcp_v6_connect() functions using dynamic tracing, and will need updating to match any changes to these functions. 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).

-P PORT
    Comma-separated list of destination ports to trace (filtered in-kernel).

EXAMPLES

Trace all active TCP connections:
    # tcpconnect

Trace all TCP connects, and include timestamps:
    # tcpconnect -t

Trace PID 181 only:
    # tcpconnect -p 181

Trace ports 80 and 81 only:
    # tcpconnect -P 80,81

FIELDS

TIME(s)
    Time of the call, in seconds.

PID Process ID

COMM
    Process name

IP  IP address family (4 or 6)

SADDR
    Source IP address.

DADDR
    Destination IP address.

DPORT
    Destination port

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