http.server (command) fails to bind dual-stack on Windows

[zkonge]

BPO	38907
Nosy	@jaraco, @zkonge
PRs	bpo-38907: Add IPv6 Dual-Stack control for http.server #17378 bpo-38907: In http.server script, restore binding to IPv4 on Windows. #17851 [3.8] bpo-38907: In http.server script, restore binding to IPv4 on Windows. (GH-17851) #17854 bpo-38907: Suppress any exception when attempting to set V6ONLY. #17864 [3.8] bpo-38907: Suppress any exception when attempting to set V6ONLY. (GH-17864) #17865

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2020-01-06.13:30:04.604>
created_at = <Date 2019-11-24.17:04:10.875>
labels = ['3.8', 'type-feature', 'library', '3.9']
title = 'http.server (command) fails to bind dual-stack on Windows'
updated_at = <Date 2020-01-06.13:30:04.603>
user = 'https://github.com/zkonge'

bugs.python.org fields:

activity = <Date 2020-01-06.13:30:04.603>
actor = 'jaraco'
assignee = 'none'
closed = True
closed_date = <Date 2020-01-06.13:30:04.604>
closer = 'jaraco'
components = ['Library (Lib)']
creation = <Date 2019-11-24.17:04:10.875>
creator = 'zkonge'
dependencies = []
files = []
hgrepos = []
issue_num = 38907
keywords = ['patch']
message_count = 8.0
messages = ['357399', '357401', '359378', '359399', '359419', '359422', '359424', '359425']
nosy_count = 2.0
nosy_names = ['jaraco', 'zkonge']
pr_nums = ['17378', '17851', '17854', '17864', '17865']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue38907'
versions = ['Python 3.8', 'Python 3.9']

[zkonge]

In Python 3.8+, when we run the http.server in a PC that support IPv6, it will bind IPv6 socket normally. On Linux or some other platforms, it also bind IPv4, that's pretty good, but on Windows, it doesn't work and "--bind 0.0.0.0" have to be provided to make it works in IPv4 environment.
In another case, once someone only want the http.server provide service in IPv6 environment, but linux will still bind IPv4 socket automatically.

Could we add a argument such as "--ipv6-only" for http.server and open the support of Dual-Stack socket by default?

[zkonge]

"--no-dual-stack" seems to be a better argument name. "--ipv6-only" lead to ambiguity in a IPv4 only environment.

[jaraco]

In bpo-39211, I've done a good deal of investigation on this issue and confirmed your findings - on Windows, the server fails to bind dual stack on Windows, but instead binds IPV6ONLY. That needs to be fixed such that the default is to bind dual-stack. Adding dual-stack control is a new feature and should be considered separately.

[jaraco]

New changeset ee94bdb by Jason R. Coombs in branch 'master':
bpo-38907: In http.server script, restore binding to IPv4 on Windows. (GH-17851)
ee94bdb

[jaraco]

New changeset 5ed9d60 by Jason R. Coombs (Miss Islington (bot)) in branch '3.8':
bpo-38907: In http.server script, restore binding to IPv4 on Windows. (GH-17851) (bpo-17854)
5ed9d60

[jaraco]

New changeset 7cdc31a by Jason R. Coombs in branch 'master':
bpo-38907: Suppress any exception when attempting to set V6ONLY. (GH-17864)
7cdc31a

[jaraco]

New changeset 33cb4a6 by Jason R. Coombs (Miss Islington (bot)) in branch '3.8':
bpo-38907: Suppress any exception when attempting to set V6ONLY. (GH-17864) (GH-17865)
33cb4a6

[jaraco]

In PR 17378, we discussed and I believe the conclusion is that the fix in the other PR(s) is sufficient to address the deficiency.