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Expose a global switch to disable IPV6 to overcome DualMode socket issues in environments that do not support IPV6 #47583

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antonfirsov opened this issue Jan 28, 2021 · 5 comments · Fixed by #55012
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Expose a global switch to disable IPV6 to overcome DualMode socket issues in environments that do not support IPV6 #47583

antonfirsov opened this issue Jan 28, 2021 · 5 comments · Fixed by #55012
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area-System.Net enhancement Product code improvement that does NOT require public API changes/additions
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@antonfirsov
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antonfirsov commented Jan 28, 2021 •
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BCL as well as external libraries tend to shift towards dual-stack sockets in their networking code. This conforms to best practices defined in RFC1933, but can lead to issues when connections are established through VPN tunnels which do not support IPv6 and/or dual-stack properly.

A custom ConnectCallback can help in HttpClient use cases where users have direct control over their HttpClient instances (#47267), but in cases where the Socket connections are carried out by an external component, users may get blocked (#45462).

This cases are rare, but the fix is simple, and easy to communicate (see #45893), therefore we should consider implementing it in .NET 6.
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Issue Details

BCL and external libraries tend to shift towards dual-stack sockets in their networking code. This conforms to best practices defined in RFC1933, but can lead to issues when connections are established through VPN tunnels which do not support IPv6 and/or dual-stack properly.

A custom ConnectCallback can help in HttpClient use cases where users have direct control over their HttpClient instances (#47267), but in cases where the Socket connections are carried out by an external component, users may get blocked (#45462).

This cases are rare, but the fix is simple, and easy to communicate (see #45893), therefore we should consider implementing it in .NET 6.

Author: antonfirsov
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@antonfirsov antonfirsov mentioned this issue Jan 28, 2021
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@karelz
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karelz commented Feb 2, 2021

Would it make sense to generalize it to global switch to disable either IPv4 or IPv6?

@karelz karelz added this to the 6.0.0 milestone Feb 2, 2021
@karelz karelz added the enhancement Product code improvement that does NOT require public API changes/additions label Feb 2, 2021
@geoffkizer
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Would it make sense to generalize it to global switch to disable either IPv4 or IPv6?

I doubt it. I haven't heard any issues re IPv4.

Even if we wanted to do this, I think it would be a separate switch.

@antonfirsov antonfirsov mentioned this issue Feb 9, 2021
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@karelz karelz removed the untriaged New issue has not been triaged by the area owner label Feb 16, 2021
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karelz commented Feb 16, 2021

Triage: We cannot do today IPv6 only, so let's add DisableIPv6 switch.

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karelz commented May 5, 2021

Another case in #52287

@karelz karelz mentioned this issue Jun 30, 2021
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@antonfirsov antonfirsov mentioned this issue Jul 1, 2021
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@ghost ghost added the in-pr There is an active PR which will close this issue when it is merged label Jul 1, 2021
@ManickaP ManickaP mentioned this issue Jul 9, 2021
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alnikola pushed a commit that referenced this issue Jul 12, 2021
@antonfirsov
Expose a global switch to disable IPV6 (#55012)
067aa16 
Fixes #47583. Resolves #52287, #54807 and similar issues, without changing customer application code.

Introduces an AppContext switch `System.Net.DisableIPv6` and environment variable `DOTNET_SYSTEM_NET_DISABLEIPV6` to emulate the lack of OS-level IPv6 support. This is useful to workaround dual-stack socket issues when the OS reports support of IPv6, but some other underlying infrastructure element (typically VPN) doesn't function well with IPv6 request.

For consistency, this switch also impacts NameResolution and Ping, not only Sockets.
@ghost ghost removed the in-pr There is an active PR which will close this issue when it is merged label Jul 12, 2021
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Expose a global switch to disable IPV6 antonfirsov/runtime
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@karelz @antonfirsov @geoffkizer