Define basic Linux SocketCAN constants and types

[djarek]

Add definitions from linux/can.h, which is a "base" header for remainder of SocketCAN functionality.

CAN bus (ISO-11898) is a communication standard used in automotive, automation and industrial solutions. Linux provides a socket-like interface to access raw CAN and protocols based on CAN, such as ISO-TP(ISO-15765) or SAE-J1939.

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @JohnTitor (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

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[JohnTitor]

Overall LGTM, left some comments.

[JohnTitor]

Also, it'd be great if you could squash commits into one.

[djarek]

Squashed the commits.

[JohnTitor]

Thanks!
@bors r+

[bors]

📌 Commit 5449cae has been approved by JohnTitor

[bors]

⌛ Testing commit 5449cae with merge f8fb8cd...

[bors]

💔 Test failed - checks-actions

[JohnTitor]

CI failed:

   cargo:warning=/checkout/target/mips64el-unknown-linux-gnuabi64/debug/build/libc-test-7d5e3789cf3be7ba/out/main.c:31010:59: error: 'CAN_J1939' undeclared here (not in a function)
  cargo:warning=31010 |             static const int __test_const_CAN_J1939_val = CAN_J1939;
  cargo:warning=      |                                                           ^~~~~~~~~
  cargo:warning=cc1: error: unrecognized command line option '-Wno-unknown-warning-option' [-Werror]
  cargo:warning=cc1: all warnings being treated as errors
  exit code: 1

That target's CI stuff is old (since CAN_J1939 is a new constant) or doesn't have it actually?

[djarek]

Looks like J1939 was added in Linux 5.4, not sure what version of kernel headers that target has.

[JohnTitor]

Let's skip the tests for now, we could tweak here:

libc/libc-test/build.rs

Line 2595 in 9d6d018

cfg.skip_const(move |name| {

Add this with FIXME comment:

"CAN_J1939" if mips => true,

[JohnTitor]

@bors r+

[bors]

📌 Commit 86eb6c1 has been approved by JohnTitor

[bors]

⌛ Testing commit 86eb6c1 with merge 8603b5f...

[bors]

💔 Test failed - checks-actions

[JohnTitor]

@bors r+

[bors]

📌 Commit e18dc03 has been approved by JohnTitor

[bors]

⌛ Testing commit e18dc03 with merge b5eeb45...

[bors]

💔 Test failed - checks-actions

[JohnTitor]

@bors r+

[bors]

📌 Commit a39cf0d has been approved by JohnTitor

[bors]

⌛ Testing commit a39cf0d with merge 62883d0...

[bors]

💔 Test failed - checks-actions

[JohnTitor]

@bors r+

[bors]

📌 Commit 66500ee has been approved by JohnTitor

[bors]

⌛ Testing commit 66500ee with merge f00b9a1...

[bors]

☀️ Test successful - checks-actions, checks-cirrus-freebsd-11, checks-cirrus-freebsd-12, checks-cirrus-freebsd-13
Approved by: JohnTitor
Pushing f00b9a1 to master...