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Auto merge of #85820 - CDirkx:is_unicast_site_local, r=joshtriplett

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Remove `Ipv6Addr::is_unicast_site_local`

Removes the unstable method `Ipv6Addr::is_unicast_site_local`, see also #85604 where I have tried to summarize related discussion so far.

Unicast site-local addresses (`fec0::/10`) were deprecated in [IETF RFC #3879](https://datatracker.ietf.org/doc/html/rfc3879), see also [RFC #4291 Section 2.5.7](https://datatracker.ietf.org/doc/html/rfc4291#section-2.5.7). Any new implementation must no longer support the special behaviour of site-local addresses. This is mentioned in the docs of `is_unicast_site_local` and already implemented in `is_unicast_global`, which considers addresses in `fec0::/10` to have global scope, thus overlapping with `is_unicast_site_local`.

Given that RFC #3879 was published in 2004, long before Rust existed, and it is specified that any new implementation must no longer support the special behaviour of site-local addresses, I don't see how a user would ever have a need for `is_unicast_site_local`. It is also confusing that currently both `is_unicast_site_local` and `is_unicast_global` can be `true` for an address, but an address can actually only have a single scope. The deprecating RFC mentions that Site-Local scope was confusing to work with and that the classification of an address as either Link-Local or Global better matches the mental model of users.

There has been earlier discussion of removing `is_unicast_site_local` (https://github.com/rust-lang/rust/pull/60145#issuecomment-485970669) which decided against it, but that had the incorrect assumption that the method was already stable; it is not. (This confusion arose from the placement of the unstable attribute on the entire module, instead of on individual methods, resolved in #85672)

r? `@joshtriplett` as reviewer of all the related PRs
This commit is contained in:
bors 2021-06-16 01:46:08 +00:00
commit d192c80d22
2 changed files with 1 additions and 52 deletions
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41
library/std/src/net/ip.rs
View File

@ -1346,47 +1346,6 @@ impl Ipv6Addr {
(self.segments()[0] & 0xffc0) == 0xfe80
}
/// Returns [`true`] if this is a deprecated unicast site-local address (`fec0::/10`). The
/// unicast site-local address format is defined in [RFC 4291 section 2.5.7] as:
///
/// ```no_rust
/// | 10 |
/// | bits | 54 bits | 64 bits |
/// +----------+-------------------------+----------------------------+
/// |1111111011| subnet ID | interface ID |
/// +----------+-------------------------+----------------------------+
/// ```
///
/// [RFC 4291 section 2.5.7]: https://tools.ietf.org/html/rfc4291#section-2.5.7
///
/// # Examples
///
/// ```
/// #![feature(ip)]
///
/// use std::net::Ipv6Addr;
///
/// assert_eq!(
/// Ipv6Addr::new(0, 0, 0, 0, 0, 0xffff, 0xc00a, 0x2ff).is_unicast_site_local(),
/// false
/// );
/// assert_eq!(Ipv6Addr::new(0xfec2, 0, 0, 0, 0, 0, 0, 0).is_unicast_site_local(), true);
/// ```
///
/// # Warning
///
/// As per [RFC 3879], the whole `fec0::/10` prefix is
/// deprecated. New software must not support site-local
/// addresses.
///
/// [RFC 3879]: https://tools.ietf.org/html/rfc3879
#[rustc_const_unstable(feature = "const_ipv6", issue = "76205")]
#[unstable(feature = "ip", issue = "27709")]
#[inline]
pub const fn is_unicast_site_local(&self) -> bool {
(self.segments()[0] & 0xffc0) == 0xfec0
}
/// Returns [`true`] if this is an address reserved for documentation
/// (`2001:db8::/32`).
///

12
library/std/src/net/ip/tests.rs
View File

@ -480,7 +480,6 @@ fn ipv6_properties() {
let unique_local: u16 = 1 << 2;
let global: u16 = 1 << 3;
let unicast_link_local: u16 = 1 << 4;
let unicast_site_local: u16 = 1 << 6;
let unicast_global: u16 = 1 << 7;
let documentation: u16 = 1 << 8;
let multicast_interface_local: u16 = 1 << 9;
@ -523,11 +522,6 @@ fn ipv6_properties() {
} else {
assert!(!ip!($s).is_unicast_link_local());
}
if ($mask & unicast_site_local) == unicast_site_local {
assert!(ip!($s).is_unicast_site_local());
} else {
assert!(!ip!($s).is_unicast_site_local());
}
if ($mask & unicast_global) == unicast_global {
assert!(ip!($s).is_unicast_global());
} else {
@ -581,7 +575,6 @@ fn ipv6_properties() {
let unique_local: u16 = 1 << 2;
let global: u16 = 1 << 3;
let unicast_link_local: u16 = 1 << 4;
let unicast_site_local: u16 = 1 << 6;
let unicast_global: u16 = 1 << 7;
let documentation: u16 = 1 << 8;
let multicast_interface_local: u16 = 1 << 9;
@ -651,7 +644,7 @@ fn ipv6_properties() {
check!(
"fec0::",
&[0xfe, 0xc0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
unicast_site_local | unicast_global | global
unicast_global | global
);
check!(
@ -889,9 +882,6 @@ fn ipv6_const() {
const IS_UNICAST_LINK_LOCAL: bool = IP_ADDRESS.is_unicast_link_local();
assert!(!IS_UNICAST_LINK_LOCAL);
const IS_UNICAST_SITE_LOCAL: bool = IP_ADDRESS.is_unicast_site_local();
assert!(!IS_UNICAST_SITE_LOCAL);
const IS_DOCUMENTATION: bool = IP_ADDRESS.is_documentation();
assert!(!IS_DOCUMENTATION);