Add daita as a Cargo feature

[MarkusPettersson98]

This PR adds support for gating DAITA behind a cfg option. It also bundles libwg as a shared object, which unifies the process across platforms which use Wireguard-Go.

This fixes DES-937.

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This change is 

[linear]

DES-937 Make sure `wireguard-go` build correctly on all platforms

[Serock3]

One big concern with making DAITA a feature is that you would not be able to use --all-features (on platforms without DAITA) anymore. The DAITA feature would have to be enabled on Windows and Linux and disabled on other platforms, and it would be up to the developer to know which platforms have the feature, otherwise the app will not build.

It seems that features simply cannot be specified per platform, it is a fundamental limitation of cargo. You cannot specify which features exists or are enabled by default per platform. It is not possible to get around this using build.rs either, as feature resolution is done before the build scripts are run. You can set cfg variables like we do with wireguard_go in talpid-wireguard, but this can't affect which features are enabled in dependencies.

I have thought a lot about how to get around this, but it may be the case that the only proper solution is to simply abandon this PR and keep the raw #[cfg(any(target_os = "windows", target_os = "linux"))] gates, unfortunately.

[hulthe]

Reviewed 64 of 64 files at r1, all commit messages.
Reviewable status: all files reviewed, 5 unresolved discussions (waiting on @MarkusPettersson98)

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mullvad-management-interface/build.rs line 7 at r1 (raw file):

    // Enable Daita by default on Linux and Windows.
    println!("cargo:rustc-check-cfg=cfg(daita)");

should be double :s, i thought it would reject the single-color syntax since check-cfg is a newly added thing 🤔

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mullvad-relay-selector/build.rs line 5 at r1 (raw file):

    // Enable Daita by default on Linux and Windows.
    println!("cargo:rustc-check-cfg=cfg(daita)");

scobido doubleido, etc
maybe do a search replace

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talpid-wireguard/src/lib.rs line 70 at r1 (raw file):

/// TODO: Document
/// TODO: Rename

👁️ 👄 👁️

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wireguard-go-rs/Cargo.lock line 1 at r1 (raw file):

# This file is automatically @generated by Cargo.

wgrs is part of the workspace, this file should be deleted

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wireguard-go-rs/libwg/wireguard-go line 1 at r1 (raw file):

Subproject commit 1e3bc447c174e243df151cf668ba8eab36739ce0

I guess update this after the other PR is merged

[MarkusPettersson98]

Reviewable status: all files reviewed, 5 unresolved discussions (waiting on @hulthe)

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mullvad-management-interface/build.rs line 7 at r1 (raw file):

Previously, hulthe (Joakim Hulthe) wrote…

should be double :s, i thought it would reject the single-color syntax since check-cfg is a newly added thing 🤔

Done. That's a bit weird aye, but good catch!

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mullvad-relay-selector/build.rs line 5 at r1 (raw file):

Previously, hulthe (Joakim Hulthe) wrote…

scobido doubleido, etc
maybe do a search replace

Done.

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talpid-wireguard/src/lib.rs line 70 at r1 (raw file):

Previously, hulthe (Joakim Hulthe) wrote…

👁️ 👄 👁️

Lmao, reverting this

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wireguard-go-rs/Cargo.lock line 1 at r1 (raw file):

Previously, hulthe (Joakim Hulthe) wrote…

wgrs is part of the workspace, this file should be deleted

🤦

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wireguard-go-rs/libwg/wireguard-go line 1 at r1 (raw file):

Previously, hulthe (Joakim Hulthe) wrote…

I guess update this after the other PR is merged

Yup

[Serock3]

Reviewed 4 of 6 files at r2, 21 of 22 files at r3, 1 of 1 files at r5, all commit messages.
Reviewable status: all files reviewed, 9 unresolved discussions (waiting on @hulthe and @MarkusPettersson98)

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mullvad-daemon/build.rs line 40 at r5 (raw file):

    }

    // when development, configure rpath to facilitate linking with libwg.so

"when development"?

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wireguard-go-rs/build.rs line 43 at r5 (raw file):

    // NOTE: Link to libwg dynamically on all platforms.
    //
    // LTO breaks when statically linking to libwg & Go programs does not

Great that you documented this. Perhaps we could even be more specific about the double symbol issue, to make it easier for future devs to find other solutions.

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wireguard-go-rs/build-wireguard-go.sh line 51 at r5 (raw file):

function build_unix {
    # TODO: consider using `log_header` here

I left this comment, though it's a very inconsequential style issue. We should remove the comment or implement it.

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wireguard-go-rs/build-wireguard-go.sh line 97 at r5 (raw file):

        go build -v -o "$BUILD_DIR/lib/$TARGET/libwg.so" -buildmode c-shared
    fi
    # Copy libwg to `OUT_DIR` so that we may refer to it via `OUT_DIR` in `build.rs`, which might be handy.

Do we need two copies of the object file? Is it not ok to just move it instead?

[MarkusPettersson98]

Reviewable status: 66 of 67 files reviewed, 8 unresolved discussions (waiting on @hulthe and @Serock3)

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mullvad-daemon/build.rs line 40 at r5 (raw file):

Previously, Serock3 (Sebastian Holmin) wrote…

"when development"?

Done Updated the text

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wireguard-go-rs/build.rs line 43 at r5 (raw file):

Previously, Serock3 (Sebastian Holmin) wrote…

Great that you documented this. Perhaps we could even be more specific about the double symbol issue, to make it easier for future devs to find other solutions.

Done clarified that part 😊

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wireguard-go-rs/build-wireguard-go.sh line 51 at r5 (raw file):

Previously, Serock3 (Sebastian Holmin) wrote…

I left this comment, though it's a very inconsequential style issue. We should remove the comment or implement it.

Since the output most likely will be consumed by cargo, and would seldom be seen by a human, I think it's fine to just not implement it here. At least for now 😊

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wireguard-go-rs/build-wireguard-go.sh line 97 at r5 (raw file):

Previously, Serock3 (Sebastian Holmin) wrote…

Do we need two copies of the object file? Is it not ok to just move it instead?

Kind of, yes. 😢 cargo won't look outside of target for stuff that we want to link against, which we let cargo know about via the rustc-link-search instruction. This is needed to do to make debug builds / cargo test work as expected. However, OUT_DIR changes between compilations, which means that rebuilding the project becomes kind of expensive (since we have to build wireguard-go each time we hit cargo check/build/test. Thus, it is cheaper to dump it into a known location build/lib/<arch> and copy it from there to OUT_DIR as needed.