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Update comment regarding SO_REUSEADDR on Windows - #71785

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reitermarkus:cfg-attribute
May 3, 2020
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Update comment regarding SO_REUSEADDR on Windows#71785
bors merged 1 commit into
rust-lang:masterfrom
reitermarkus:cfg-attribute

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@reitermarkus

@reitermarkusreitermarkus commented May 2, 2020

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@rust-highfive

rust-highfive commented May 2, 2020

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r? @Mark-Simulacrum

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@rust-highfiverust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label May 2, 2020
@reitermarkus

reitermarkus commented May 2, 2020•
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Seems like SO_REUSEADDR actually exists on Windows: https://docs.microsoft.com/en-us/windows/win32/winsock/using-so-reuseaddr-and-so-exclusiveaddruse

@reitermarkusreitermarkus changed the title Replace cfg macro with attribute.Remove cfg attribute.May 2, 2020
@jonas-schievinkjonas-schievink added T-libs Relevant to the library team, which will review and decide on the PR/issue. O-windows Operating system: Windows labels May 2, 2020
@Mark-Simulacrum

Mark-Simulacrum commented May 2, 2020

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Hm, so some rough searching online suggests that Windows may not actually want this set (e.g. this random github thread).

I myself don't have much windows experience so I'm not willing to approve this just yet. I'll leave myself assigned as I don't know if we have anyone better at this time.

cc @retep998

@reitermarkus

reitermarkus commented May 2, 2020

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I also don't really have any Windows experience, just stumbled upon this while implementing libstd for another target.

So either this should be used or the constant removed.

@retep998

retep998 commented May 2, 2020•
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From the very MSDN article that you linked:

The SO_REUSEADDR option has very few uses in normal applications aside from multicast sockets where data is delivered to all of the sockets bound on the same port. Otherwise, any application that sets this socket option should be redesigned to remove the dependency since it is eminently vulnerable to "socket hijacking". As long as SO_REUSEADDR socket option can be used to potentially hijack a port in a server application, the application must be considered to be not secure.

While on non-windows platforms SO_REUSEADDR allows you to bind to sockets that are still in TIME_WAIT, on Windows SO_REUSEADDR allows you to bind to sockets that are actively being used resulting in undefined behavior.

So no, we do not want this change. A change which we should consider though is setting SO_EXCLUSIVEADDRUSE for all our sockets on Windows.

@Mark-Simulacrum

Mark-Simulacrum commented May 2, 2020

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Okay, yeah, that's what I suspected based on the GitHub thread. My skimming must have missed that on the MSDN page.

I would appreciate an update to this PR which includes a note that links to the MSDN page and summarizes why we don't want it.

@tesuji

tesuji commented May 2, 2020•
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This PR could be changed to document that for Windows.

@reitermarkusreitermarkus changed the title Remove cfg attribute.Replace cfg macro with attribute.May 2, 2020
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reitermarkus commented May 2, 2020

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Ok, I reverted the change and added an explanation as to why we don't set it on Windows.

@Mark-SimulacrumMark-Simulacrum changed the title Replace cfg macro with attribute.Update comment regarding SO_REUSEADDR on WindowsMay 2, 2020
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Mark-Simulacrum commented May 2, 2020

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@bors r+ rollup

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bors commented May 2, 2020

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📌 Commit 39a9790 has been approved by Mark-Simulacrum

@borsbors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels May 2, 2020
@Dylan-DPC-zzDylan-DPC-zz mentioned this pull request May 2, 2020
Merged
bors added a commit to rust-lang-ci/rust that referenced this pull request May 2, 2020
@bors
Auto merge ofrust-lang#71807- Dylan-DPC:rollup-jvb8sd9, r=Dylan-DPC
c1e0552
Rollup of 7 pull requests
Successful merges:
- rust-lang#69274 (Implement RFC 2396: `#[target_feature]` 1.1)
- rust-lang#71767 (doc: make Stack and StackElement a little pretty)
- rust-lang#71772 (Mark query function as must_use.)
- rust-lang#71777 (cleanup: `config::CrateType` -> `CrateType`)
- rust-lang#71784 (Remove recommendation for unmaintained dirs crate)
- rust-lang#71785 (Update comment regarding SO_REUSEADDR on Windows)
- rust-lang#71787 (fix rustdoc warnings)
Failed merges:
r? @ghost
@bors
bors merged commit 5a7b21f into rust-lang:masterMay 3, 2020
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