Conversation

Jonathan Corbet

Once upon a time, if I enabled tethering on an Android phone, it would take the phone off the local WiFi network and route traffic over the cellular link

Now, if the phone is on a WiFi network, tethering will route packets from the tethered device over that WiFi network.

I'm guessing that improvements in WiFi interfaces and drivers have enabled this change. But it misses an important point: if I'm tethering a device in an environment where a WiFi network exists, it is almost certainly because said WiFi network sucks and I want to circumvent it. Having the phone continue to use it silently thwarts that purpose.

It's easy enough to work around — just turn off WiFi on the phone — but for slow folks like me that only happens after wondering for a while why the performance is still bad. Does anybody know of a way to disable this behavior permanently?
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Edited 3 months ago
@corbet I don't think stock unrooted Android can do this, it can't even tether through VPN.
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@corbet
> But it misses an important point

My use case used to be quite the opposite when not in my mobile network (travelling): some sketchy WiFi avail. which I was desperate to connect my laptop to but only could do through my phone. Fancy auth my phone could do (but not the laptop) easily worked-around by using phone's MAC, but in some situations it used to be more than that. So always wished to be able to tether to the WiFi.

Sorry for not answering your question blob0w0

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@corbet I don't think you can. Remember when teathering you're simply using the phone's global default route, which is preprogrammed to prefer WiFi over mobile. The phone could run a new network ns with a different default route and teather you to it, but that feature doesn't exist in AOSP.

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@corbet Another usecase would be to give access to the second wifi without exposing the credentials. It's easier to renew the settings on the tethering device without affecting all those clients connected to the wifi.

But yes - sounds silly.

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@corbet fwiw, I've found this feature useful when either my laptop's wifi antenna was insufficient or there was some strange incompatability with a wifi network

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