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+These days, for various reason, I'm using USB tethering very often.
+Enabling it it's not difficult at all, it as simple as
+
+    doas dhclient urndis0
+
+But it's tedious.  Especially if you need to do it multiple times per
+day.  I needed something to save me from filling my shell history of
+`dhclient urndis0`.
+
+Enter [`hotplugd(8)`](https://man.openbsd.org/hotplugd)!
+
+`hotplugd` is a daemon that will listen for the attach/detach of
+various devices and execute a script.  It's that simple, and at the
+same time really useful.
+
+Disclaimer: I don't like to write *howtos* because the man pages are
+generally better, and the information in blog like this tends to rot
+sooner or later.  I encourage you to go read the
+[`hotplugd(8)`](https://man.openbsd.org/hotplugd) man page (it's
+really short, simple and understandable -- it even has some examples!)
+and consider this post as a "did you know?"-sort of thing.
+
+With the disclaimer in place, let's continue.  The idea is that
+`hotplugd` will execute `/etc/hotplug/attach` and `detach` script when
+a device is attached or detached.  It doesn't need to be a shell
+script, any executable file will do, but will stick with a plain old
+sh script.
+
+When you enable your phone USB tethering, a new device called
+`urndisN` is created.  So, knowing this, we just need to execute
+`dhclient` inside the `attach` script on the correct `urndis(4)`
+devices.  Easy peasy:
+
+```sh
+#!/bin/sh
+# /etc/hotplug/attach
+
+DEVCLASS=$1
+DEVNAME=$2
+
+case $DEVCLASS in
+# network devices
+3)
+	case $2 in
+        # USB tethering
+        urndis*) dhclient $2 ;;
+    esac
+esac
+```
+
+Remember to make the script executable and to enable `hotplugd(8)`:
+
+    # chmod +x /etc/hotplug/attach
+    # rcctl enable hotplugd
+    # rcctl start hotplugd
+
+Every time you enable the tethering on your phone your computer will
+automatically connect to it.  In theory the same principle can also be
+used to automatically mount discs when plugged, but I haven't tried
+yet.
+
+NB: I'm not paranoid enough to worry about accidentally connect to a
+stranger's phone.  You have been warned.
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-[{:title "EMMS"
+[{:title "Automatic USB Tethering on OpenBSD"
+  :slug "openbsd-tethering"
+  :date "2020/09/21"
+  :tags #{:OpenBSD}
+  :short "hotplug my lazyness"
+  :xkcd 1319}
+ {:title "EMMS"
   :slug  "emms"
   :date  "2020/09/20"
   :tags  #{:emacs :elisp}