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

tcpconnect(8) System Manager's Manual tcpconnect(8)

NAME

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

SYNOPSIS

tcpconnect [-h] [-t] [-p PID]

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).

EXAMPLES

Trace all active TCP connections, and show connection latency (SYN->response round trip):
# tcpconnect
Include timestamps:
# tcpconnect -t
Trace PID 181 only:
# tcpconnect -p 181

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.
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)
2016-02-19 USER COMMANDS