hpr2944 :: ONICS Basics Part 4: Network Flows and Connections
I try to add a bit more basic networking info while writing a quick script for Dave Morris
Hosted by Gabriel Evenfire on Thursday 2019-11-14 is flagged as Clean and is released under a CC-BY-SA license.
Tags: command line networking.
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Part of the series: Networking
This series will try and explain the basics of networking to the listener as well as introduce more detailed topics.
- connection - a bi-directional communication channel between two programs over a network
- client - the initiator of a connection
- server - the receiver of the connection
- port - a common term for the address of a program or service on a given machine
- 5-tuple - the combination of protocol, client machine network address, client port, server machine network address, server port that uniquely identifies a connection
- flow - a grouping of packets to be treated in a common way
- microflow - a flow with a fine level of granularity such as the packets from one direction of traffic in a connection
The topflow.sh Script
#!/bin/sh # Start a capture in the background that drops the packets # and just reports the flow events pktin $1 | nftrk -d -f /tmp/flows.txt & PID=$! # On CTRL-C clean kill the capture and clean up trap "kill $PID ; rm -f /tmp/flows.txt /tmp/topflows.txt /tmp/namecache.txt ; exit 0" INT TERM # Once per second do # look at the last 100 flows # sort them by 5-tuple # remove duplicates # convert ports, protocols and addresses to names # sort by data usage per flow in reverse order (highest first) # a little more pretty printing # only take the top 20 lines # clear the screen and print the result while [ 1 ] ; do tail -100 /tmp/flows.txt | sort -s -t '|' -k 3,3 | awk -f uniqflows.awk | awk -f prflow.awk | sort -s -t ',' -k 3 -r | awk -f columns.awk | head -20 > /tmp/topflows.txt clear cat /tmp/topflows.txt sleep 1 done
You can find the complete code at: https://gitlab.com/onics/onics-examples
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