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Wifi on OpenBSD

Connect to a wireless SSID with password, independent from any 'join' entries in /etc/hostname.iwm0.

# ifconfig iwm0 nwid <SSID-name> wpakey <password>

Disconnect from the SSID that you joined using nwid above.

# ifconfig iwm0 -nwid

It will return to scanning for any preconfigured SSIDs in /etc/hostname.iwm0.

https://www.reddit.com/r/openbsd/comments/p8ml4g/switch_openbsd_laptop_from_preferred_wifi_to

Thanks guys. I was already using 'join SSID wpakey KEY' in hostname.if(5) for all my SSIDs and had just switched successfully from 'dhcp' to 'inet autoconf' to get faster boot time with dhcpleased(8). Roaming between access points at home, at work, and on my hotspot has continued to work well.

To the one who pointed out the manpages, I had already read through those (even the long ifconfig(8) manpage) and still didn't get how to switch among multiple in-range wifi's. That's why I asked in this thread.

But you guys did point me in the right direction. Here's what I found worked.

Use ifconfig(8) to find out your wifi driver. This guide assumes you use the iwm(4) driver for Intel chipsets and have all your SSIDs in /etc/hostname.iwm0 as described above.

Start with all the SSIDs and wpakeys in /etc/hostname.iwm0 (if you have a wifi card supported by the iwm driver).

ifconfig will do a scan and auto-join the SSID, and channel of that SSID, on the list (cached) which has the best signal. Then dhcpleased will auto-obtain an IP address (much faster than dhclient). You can check which SSID that is with:

# ifconfig iwm0 scan

In this guide, we call that SSID1. It is not necessarily the first SSID listed in hostname.if.

You can check the IP address and additional info ifconfig doesn't tell you with dhcpleasectl. Below includes output while connected to an iOS hotspot.

# dhcpleasectl show interface iwm0
iwm0 [Bound]: 
	server: 172.20.10.1
		IP: 172.20.10.4/255.255.255.240 
	routes: 0.0.0.0/0.0.0.0 - 172.20.10.1
	   DNS: 172.20.10.1 
	 lease: 22h 57m 26s

To switch to another cached SSID, unjoin from the currently-connected one.

# ifconfig iwm0 -join SSID1

ifconfig should automatically associate with the next best signal SSID cached in hostname.if. Then dhcpleased should auto-obtain an IP address lease for that connection.

To switch to a third in-range SSID, unjoin from the second one.

# ifconfig iwm0 -join SSID2

If you later decide to re-join SSID1 or SSID2, you need to re-join with the full wpakey.

# ifconfig iwm0 join SSID1 wpakey KEY

But if SSID3 has sufficient signal strength, ifconfig won't switch back to SSID1 or 2 just because you re-cached 1's or 2's credentials. You'll likely need to unjoin from SSID3.

# ifconfig iwm0 -join SSID3

If it's SSID1 you want to go back to, you could just restart /etc/netstart, which reloads the values from hostname.if afresh.

# sh /etc/netstart

One thing I noticed is that when I join the iOS hotspot, switch to another SSID, and back to the hotspot later, ifconfig doesn't get the IP address it had before, or any at all, not unless I turn off the hotspot and back on in the iOS settings.

This issue does not occur when reconnecting to a Comcast gateway or OpenBSD router (which sits on the LAN side of the Comcast gateway), and to my Android hotspot. All three servers seem to readily resume the prior dhcp lease my OpenBSD laptop had before, and (unlike the iOS hotspot) advertise the IP info again to ifconfig and dhcpleasectl.

I remember seeing comments on undeadly.org that dhcpleased does not record obtained leases in a file but needs to be queried by dhcpleasectl, or (according to the manpage) through the unix socket file.

I don't recall if dhclient also failed to re-obtain IP address info in this case.