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{{keywords>macos,unix,libpcap,sudo,permissions,dosbox,wireshark,launchdaemon,brew,homebrew,tcpdump}}
====== Using libpcap without sudo ======

===== Environment =====

  * macOS
  * [[https://brew.sh/|Homebrew]]

===== Required Homebrew Formula =====

  * ''libpcap''

===== Overview =====

In macOS, the default permissions of the **/dev/bpf*** devices allow read/write for **root**, and read-only access to the **admin** group. This means that applications that use [[https://www.tcpdump.org/|libpcap]] for ethernet access, such as [[https://dosbox-x.com/|DOSBox-X]] and [[https://www.wireshark.org/|Wireshark]], must be run with **sudo**.

While you can change the permission of the **/dev/bpf*** devices yourself to allow the **admin** group write access, this permission will be reset after a reboot.

The below instructions explain how to make this change permanent through the use of a **LaunchDaemon** which invokes a shell script to set the permissions on boot.

===== Formula Installation =====

  $ brew install libpcap

===== Download Startup Files =====

Download [[https://raw.githubusercontent.com/the-tcpdump-group/libpcap/master/chmod_bpf|chmod_bpf]] and [[https://raw.githubusercontent.com/the-tcpdump-group/libpcap/master/org.tcpdump.chmod_bpf.plist|org.tcpdump.chmod_bpf.plist]] (this guide will assume you have saved them in your **Downloads** folder).

===== Install Startup Files =====

==== chmod_bpf ====

**chmod_bpf** is a simple script that changes the permissions of the **/dev/bpf*** devices to allow the **admin** group to write to them. You can edit this file before copying if you want to give these permissions to a different group.

  $ sudo cp ~/Downloads/chmod_bpf /usr/local/bin
  $ sudo chown root:admin /usr/local/bin/chmod_bpf
  $ sudo chmod 755 /usr/local/bin/chmod_bpf
  
==== org.tcpdump.chmod_bpf.plist ====

**org.tcpdump.chmod_bpf.plist** is the **LaunchDaemon** which calls **chmod_bpf** every time macOS boots.

  $ sudo cp ~/Downloads/org.tcpdump.chmod_bpf.plist /Library/LaunchDaemons
  $ sudo chown root:admin /Library/LaunchDaemons/org.tcpdump.chmod_bpf.plist
  $ chmod 644 /Library/LaunchDaemons/org.tcpdump0.chmod_bpf.plist