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Wireshark

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Wireshark is a free and open-source packet analyzer. It is used for network troubleshooting, analysis, software and communications protocol development, and education.

Installation

Install the wireshark-qt package for the Wireshark GUI or wireshark-cli for just the tshark(1) CLI.

Note The deprecated GTK interface has been removed in Wireshark 3.0.

termshark is an alternative terminal UI.

Capturing privileges

Do not run Wireshark as root; it is insecure. Wireshark has implemented privilege separation, which means that the Wireshark GUI (or the tshark CLI) can run as a normal user while the dumpcap capture utility runs as root[1].

The wireshark-cli install script sets packet capturing capabilities on the /usr/bin/dumpcap executable.

/usr/bin/dumpcap can only be executed by root and members of the wireshark group, so to use Wireshark as a normal user, you have to add your user to the wireshark user group.

A few capturing techniques

There are a number of different ways to capture exactly what you are looking for in Wireshark, by applying capture filters or display filters.

Note To learn the capture filter syntax, see pcap-filter(7). For display filters, see wireshark-filter(4).

Filtering TCP packets

If you want to see all the current TCP packets, type tcp into the Filter bar or in the CLI, enter: 

$ tshark -f "tcp"

Filtering UDP packets

If you want to see all the current UDP packets, type udp into the Filter bar or in the CLI, enter: 

$ tshark -f "udp"

Filter packets to a specific IP address

To observe traffic around a specific address, say 1.2.3.4, there are a few filter options. Note that IPv6 addresses can be filtered similarly but using ipv6 instead of ip.

  • ip.dst == 1.2.3.4 shows all traffic sent to a that address.
  • ip.src == 1.2.3.4 shows all traffic sent from that address.
  • ip.addr == 1.2.3.4 shows all traffic both sent to and sent from that address.
  • ip.addr != 1.2.3.4 shows all traffic not sent either to or from that address.

Filter packets to IPv4 LAN

To only see LAN traffic and no internet traffic use this display filter to show traffic on private network addresses. 

(ip.src==10.0.0.0/8 AND ip.dst==10.0.0.0/8) OR (ip.src==172.16.0.0/12 AND ip.dst==172.16.0.0/12) OR (ip.src==192.168.0.0/16 and ip.dst==192.168.0.0/16)

Filter packets by port

See all traffic on specific TCP or UDP ports via tcp.port or udp.port respectively. 

tcp.port == 80

Headless capturing with dumpcap

dumpcap is part of Wireshark and can be used for capturing packets without the GUI. Used in combination with tmux will allow the capture of packets in a detached session.

To see all dumpcap options, use the -h flag.

The following example will provide a ringbuffer capture. It captures twenty .pcap files of 100MB each, replacing the oldest file with the twenty-first file and so on… This allows a continuous capture without exhausting disk space. 

# dumpcap -i 1 -b filesize:100000 -b files:20 -w mycapture.pcapng
  • -i − interface number (listed from dumpcap -D)
  • -b filesize: − file size in kB before starting a new .pcap file
  • -b files: − the number of files to capture before overwriting the oldest
  • -w − write the output to the file mycaptureidentifier.pcapng