From 7f27b29fd446c44a73179bd44b13ba2489c7f7c0 Mon Sep 17 00:00:00 2001
From: Christiaan Dirkx <christiaan@dirkx.email>
Date: Mon, 31 May 2021 09:56:14 +0200
Subject: [PATCH] Add `Ipv6Addr::is_unicast`

---
 library/std/src/net/ip.rs | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/library/std/src/net/ip.rs b/library/std/src/net/ip.rs
index 6c2f2eeabd6..d2fb3aac0aa 100644
--- a/library/std/src/net/ip.rs
+++ b/library/std/src/net/ip.rs
@@ -1267,6 +1267,34 @@ impl Ipv6Addr {
         (self.segments()[0] & 0xfe00) == 0xfc00
     }
 
+    /// Returns [`true`] if this is a unicast address, as defined by [IETF RFC 4291].
+    /// Any address that is not a [multicast address] (`ff00::/8`) is unicast.
+    ///
+    /// [IETF RFC 4291]: https://tools.ietf.org/html/rfc4291
+    /// [multicast address]: Ipv6Addr::is_multicast
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(ip)]
+    ///
+    /// use std::net::Ipv6Addr;
+    ///
+    /// // The unspecified and loopback addresses are unicast.
+    /// assert_eq!(Ipv6Addr::UNSPECIFIED.is_unicast(), true);
+    /// assert_eq!(Ipv6Addr::LOCALHOST.is_unicast(), true);
+    ///
+    /// // Any address that is not a multicast address (`ff00::/8`) is unicast.
+    /// assert_eq!(Ipv6Addr::new(0x2001, 0xdb8, 0, 0, 0, 0, 0, 0).is_unicast(), true);
+    /// assert_eq!(Ipv6Addr::new(0xff00, 0, 0, 0, 0, 0, 0, 0).is_unicast(), false);
+    /// ```
+    #[rustc_const_unstable(feature = "const_ipv6", issue = "76205")]
+    #[unstable(feature = "ip", issue = "27709")]
+    #[inline]
+    pub const fn is_unicast(&self) -> bool {
+        !self.is_multicast()
+    }
+
     /// Returns `true` if the address is a unicast address with link-local scope,
     /// as defined in [RFC 4291].
     ///