netdev - Re: [PATCH net-next v2] net: core: enable SO

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Message-ID: <m37drhs1jn.fsf@bernat.ch>
Date:   Fri, 23 Oct 2020 12:02:20 +0200
From:   Vincent Bernat <vincent@...nat.ch>
To:     David Miller <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, dsahern@...il.com,
        Laurent Fasnacht <fasnacht@...tonmail.ch>
Subject: Re: [PATCH net-next v2] net: core: enable SO_BINDTODEVICE for
 non-root users

 ❦  2 avril 2020 17:47 -07, David Miller:

>> Currently, SO_BINDTODEVICE requires CAP_NET_RAW. This change allows a
>> non-root user to bind a socket to an interface if it is not already
>> bound.
>  ...
>
> Ok I'm convinced now, thanks for your patience.

I've got some user feedback about this patch. I didn't think the patch
would allow to circumvent routing policies on most common setups, but
VPN may setup a default route with a lower metric and an application may
(on purpose or by accident) use SO_BINDTODEVICE to circumvent the lower
metric route:

default via 10.81.0.1 dev tun0 proto static metric 50
default via 192.168.122.1 dev enp1s0 proto dhcp metric 100

I am wondering if we should revert the patch for 5.10 while we can,
waiting for a better solution (and breaking people relying on the new
behavior in 5.9).

Then, I can propose a patch with a sysctl to avoid breaking existing
setups.
-- 
I must have a prodigious quantity of mind; it takes me as much as a
week sometimes to make it up.
		-- Mark Twain, "The Innocents Abroad"