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[FR]: detect certain resolvconf /etc/resolv.conf files as systemd-resolved #3026

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DentonGentry opened this issue Oct 8, 2021 · 0 comments · Fixed by #3027
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[FR]: detect certain resolvconf /etc/resolv.conf files as systemd-resolved #3026

DentonGentry opened this issue Oct 8, 2021 · 0 comments · Fixed by #3027
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L1 Very few Likelihood OS-linux P2 Aggravating Priority level T5 Usability Issue type

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@DentonGentry
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We're seen /etc/resolv.conf files like these a few times:

# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
#     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
# 127.0.0.53 is the systemd-resolved stub resolver.
# run "systemd-resolve --status" to see details about the actual nameservers.

The file was created by resolvconf, and tailscaled decides to handle it using the resolvconf path, but the only nameserver in the file is systemd-resolved. The systemd-resolved handling in tailscaled allows more options, like only adding 100.100.100.100 for example.com.beta.tailscale.net and letting the system handle everything else.

I think we can detect cases like this and use systemd-resolved. It will mean making resolvOwner parse further into the file to see if a later line overrides the first match found.
@DentonGentry DentonGentry changed the title [Bug]: detect certain resolvconf /etc/resolv.conf files as systemd-resolved [FR]: detect certain resolvconf /etc/resolv.conf files as systemd-resolved Oct 8, 2021
DentonGentry added a commit that referenced this issue Oct 8, 2021
@DentonGentry
net/dns: detect when resolvconf points to systemd-resolved.
1f13cd1 
There are /etc/resolv.conf files out there where resolvconf wrote
the file but pointed to systemd-resolved as the nameserver.
We're better off handling those as systemd-resolved.

> # Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
> #     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
> # 127.0.0.53 is the systemd-resolved stub resolver.
> # run "systemd-resolve --status" to see details about the actual nameservers.

Fixes #3026
Signed-off-by: Denton Gentry <dgentry@tailscale.com>
@DentonGentry DentonGentry mentioned this issue Oct 8, 2021
Merged
@DentonGentry DentonGentry added L1 Very few Likelihood OS-linux T5 Usability Issue type P2 Aggravating Priority level and removed needs-triage labels Oct 8, 2021
DentonGentry added a commit that referenced this issue Oct 8, 2021
@DentonGentry
net/dns: detect when resolvconf points to systemd-resolved.
ac05ea8 
There are /etc/resolv.conf files out there where resolvconf wrote
the file but pointed to systemd-resolved as the nameserver.
We're better off handling those as systemd-resolved.

> # Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
> #     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
> # 127.0.0.53 is the systemd-resolved stub resolver.
> # run "systemd-resolve --status" to see details about the actual nameservers.

Fixes #3026
Signed-off-by: Denton Gentry <dgentry@tailscale.com>
DentonGentry added a commit that referenced this issue Oct 18, 2021
@DentonGentry
net/dns: detect when resolvconf points to systemd-resolved.
40b7c2e 
There are /etc/resolv.conf files out there where resolvconf wrote
the file but pointed to systemd-resolved as the nameserver.
We're better off handling those as systemd-resolved.

> # Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
> #     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
> # 127.0.0.53 is the systemd-resolved stub resolver.
> # run "systemd-resolve --status" to see details about the actual nameservers.

Fixes #3026
Signed-off-by: Denton Gentry <dgentry@tailscale.com>
DentonGentry added a commit that referenced this issue Oct 27, 2021
@DentonGentry
net/dns: detect when resolvconf points to systemd-resolved.
139a6c4 
There are /etc/resolv.conf files out there where resolvconf wrote
the file but pointed to systemd-resolved as the nameserver.
We're better off handling those as systemd-resolved.

> # Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
> #     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
> # 127.0.0.53 is the systemd-resolved stub resolver.
> # run "systemd-resolve --status" to see details about the actual nameservers.

Fixes #3026
Signed-off-by: Denton Gentry <dgentry@tailscale.com>
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net/dns: detect when resolvconf points to systemd-resolved. tailscale/tailscale
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