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[Enhancement] Allow multicast DNS on local interfaces in killswitch mode 2 #247

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Floppy opened this issue Oct 19, 2020 · 1 comment · May be fixed by #321
Open

[Enhancement] Allow multicast DNS on local interfaces in killswitch mode 2 #247

Floppy opened this issue Oct 19, 2020 · 1 comment · May be fixed by #321

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@Floppy
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Floppy commented Oct 19, 2020

Describe the bug
The killswitch iptables config filters out multicast DNS, so hosts aren't accessible via mDNS names on local networks; i.e. I can't ssh to my machine running the VPN by name, only by IP.

Expected behavior
Multicast DNS should be allowed on the default interface as well as local network access.

Possible solution
I think the right solution is to add the mDNS IP 224.0.0.251 as a rule the same as the local network specifier at
https://github.com/ProtonVPN/linux-cli/blob/1190545a4293332824b28fe442f95f7be44b65d5/protonvpn_cli/connection.py#L849. I'll have a go and send a PR.

Concerns
I'm not sure what the security implications are of doing this... any thoughts?

@Floppy Floppy changed the title [Enhancement] Allow mulitcast DNS on local interfaces in killswitch mode 2 [Enhancement] Allow multicast DNS on local interfaces in killswitch mode 2 Oct 19, 2020
@Floppy
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Floppy commented Oct 19, 2020

It actually only needs UDP on one port:

-A OUTPUT -d 224.0.0.251/32 -o eth0 -p udp -m udp --dport 5353 -j ACCEPT
-A INPUT -s 224.0.0.251/32 -i eth0 -p udp -m udp --sport 5353 -j ACCEPT

Floppy added a commit to Floppy/linux-cli that referenced this issue Oct 19, 2020
So that we can still use mDNS hostnames for devices on the local network when the killswitch is enabled. Resolves Rafficer#247.
Floppy referenced this issue in Floppy/linux-cli Jun 26, 2021
So that we can still use mDNS hostnames for devices on the local network when the killswitch is enabled. Resolves ProtonVPN#247.
@Floppy Floppy linked a pull request Jun 26, 2021 that will close this issue
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