Ensure all tests use unique IP ports

[asomers]

What does this PR do

Checklist:

• I have read CONTRIBUTING.md
• I have written necessary tests and rustdoc comments
• A change log has been added if this PR modifies nix's API

[SteveLauC]

There still seems to be tests that are using the same port 8080 in src/sys/socket/addr.rs:

nix/src/sys/socket/addr.rs

Lines 2560 to 2597 in dbdcfed

	mod sockaddr_in6 {
	use super::*;
	use std::str::FromStr;
	#[test]
	fn display() {
	let s = "[1234:5678:90ab:cdef::1111:2222]:8080";
	let addr = SockaddrIn6::from_str(s).unwrap();
	assert_eq!(s, format!("{addr}"));
	}
	#[test]
	fn size() {
	assert_eq!(
	mem::size_of::<libc::sockaddr_in6>(),
	SockaddrIn6::size() as usize
	);
	}
	#[test]
	fn ip() {
	let s = "[1234:5678:90ab:cdef::1111:2222]:8080";
	let ip = SockaddrIn6::from_str(s).unwrap().ip();
	assert_eq!("1234:5678:90ab:cdef::1111:2222", format!("{ip}"));
	}
	#[test]
	// Ensure that we can convert to-and-from std::net variants without change.
	fn to_and_from() {
	let s = "[1234:5678:90ab:cdef::1111:2222]:8080";
	let mut nix_sin6 = SockaddrIn6::from_str(s).unwrap();
	nix_sin6.0.sin6_flowinfo = 0x12345678;
	nix_sin6.0.sin6_scope_id = 0x9abcdef0;
	let std_sin6: std::net::SocketAddrV6 = nix_sin6.into();
	assert_eq!(nix_sin6, std_sin6.into());
	}
	}

---

BTW, If we want to maintain this state, what about defining some helper type like:

/// Helper type for ensuring all ports used in tests are unique
struct PortAllocator {
    next: AtomicU16,
}

impl PortAllocator {
    pub fn allocate_port(&self) -> u16 {
         self.next.fetch_add(1, Ordering::Relaxed)
    }
}

Though it may be easier to clash (with the ports used on developer's host) comparing to manually-specified ports

[asomers]

In the case of the 8080 ports, you'll notice that none of those tests actually bind to the ports in question. So there's no real conflict. Regarding the allocator, I've wondered about that too. But I wonder if the addition of the allocator would obscure the function of some of the tests. Do you think so?

[SteveLauC]

In the case of the 8080 ports, you'll notice that none of those tests actually bind to the ports in question. So there's no real conflict.

Yeah, that's right, they are not in actual use. I saw the changes in src/sys/socket/addr.rs, which made me think we should also handle such cases, but since they are not in use, let's ignore them

Regarding the allocator, I've wondered about that too. But I wonder if the addition of the allocator would obscure the function of some of the tests. Do you think so?

Emmm, I am not sure about this:D, would you like show me a brief example demostrating your worries?

[asomers]

Regarding the allocator, I've wondered about that too. But I wonder if the addition of the allocator would obscure the function of some of the tests. Do you think so?

Emmm, I am not sure about this:D, would you like show me a brief example demostrating your worries?

I'm just thinking about readability for somebody not highly familiar with this project. Code like this:

let addr = SockaddrIn::from_str("127.0.0.1:1234");

is a lot more obvious than this:

let addr = crate::port_allocator::next();

[SteveLauC]

I'm just thinking about readability for somebody not highly familiar with this project. Code like this:

Yeah, if we do something like this, we should document it well.

I'm just thinking about readability for somebody not highly familiar with this project. Code like this:

let addr = SockaddrIn::from_str("127.0.0.1:1234");

is a lot more obvious than this:

let addr = crate::port_allocator::next();

Indeed, the old one is clearer, but will we also do this to IP address? It should be something like this if we only do this to ports:

let port = PORT_ALLOCATOR.next();
let addr = SockAddrV4::from_str(&format!("127.0.0.1:{port}")).unwrap();

[asomers]

Either way would work. What do you think is best?

[SteveLauC]

I think we should add a port allocator because manually maintaining the state is too hard, and conflicts are difficult to catch as well since tests are running concurrently.

For the readability issue, it should not be that bad if we only do this to ports:

let addr = SockAddrV4::from_str(&format!("127.0.0.1:{port}")).unwrap();

---

BTW, is there any guideline on when a test should be put in src/xxx.rs or test/test_xxx.rs, if not, we should probably make this clear, e.g.,

Tests for public Nix interfaces should all be placed under test, leaving only tests for private stuff within its own module.

[asomers]

BTW, is there any guideline on when a test should be put in src/xxx.rs or test/test_xxx.rs, if not, we should probably make this clear, e.g.,

Not really. Nix has so many contributors; it seems like each has placed tests according to his preference. For me personally I have a rule that I like to use, but it doesn't really apply to Nix.

Tests for public Nix interfaces should all be placed under test, leaving only tests for private stuff within its own module.

👍

[SteveLauC]

Should we merge this PR? I think it is ok to do that port allocator thing in the future

[asomers]

Should we merge this PR? I think it is ok to do that port allocator thing in the future

Yeah, I think so. Would you approve it please?