Move the platform independent part of net into core

[lygstate]

Specifically, the address manipulation part for IPV4 and IPV6 can be moved to core

rust-lang/rust/blob/master/library/std/src/net/addr.rs

So the bare-metal and network stack implementor care sharing same piece of code across library

[bascule]

Related:

RFC: Move `std::net::IpAddr` types into `core::net`.

std::net::Ipv4Addr in core?

I'm an embedded developer so I don't have access to std. Could we move std::net::Ipv4 to core?

Why are SocketAddrV4/SocketAddrV6 based on low level sockaddr_in[6]?

A port is always 16 bits (2 bytes). An IPv4 address is 4 bytes. This means the optimal size for SocketAddrV4 is 6 bytes (8 bytes with alignment 4 for Ipv4Addr). However, size_of::<SocketAddrV4>() == 16 (on Linux). This is 2x the expected size Hmm.. Yes, this is because the implementation is: pub struct SocketAddrV4 { inner: c::sockaddr_in, } And sockaddr_in has more data than just the IP and port. It's also not (currently) possible to make the new constructors for these sock…

[faern]

I'm trying to remove the blockers for doing this in Implement network primitives with ideal Rust layout, not C system layout by faern · Pull Request #78802 · rust-lang/rust · GitHub

The problem is that the current IpAddr structs are based on system representations that we can't have in core really. And we can't just merge the fix for that since a bunch of crates invalidly assumed the memory layout of the types So it's currently a waiting game. We have to find everyone who broke this API contract, patch them and wait for the usage of the broken crates to drop quite a lot.