Recognise new IPv6 non-global range from RFC9602

This commit adds the 5f00::/16 range defined by RFC9602 to those ranges which Ipv6Addr::is_global recognises as a non-global IP. This range is used for Segment Routing (SRv6) SIDs.

Author: bardiharborow

library/core/src/net/ip_addr.rs

@@ -1581,6 +1581,8 @@ impl Ipv6Addr {
             // IANA says N/A.
             || matches!(self.segments(), [0x2002, _, _, _, _, _, _, _])
             || self.is_documentation()
+            // Segment Routing (SRv6) SIDs (`5f00::/16`)
+            || matches!(self.segments(), [0x5f00, ..])
             || self.is_unique_local()
             || self.is_unicast_link_local())
     }

library/core/tests/net/ip_addr.rs

@@ -603,6 +603,7 @@ fn ipv6_properties() {
         }
     }
 
+    let none: u32 = 0;
     let unspecified: u32 = 1 << 0;
     let loopback: u32 = 1 << 1;
     let unique_local: u32 = 1 << 2;
@@ -688,6 +689,8 @@ fn ipv6_properties() {
 
     check!("2002::", &[0x20, 0x02, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0], unicast_global);
 
+    check!("5f00::", &[0x5f, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0], none);
+
     check!("fc00::", &[0xfc, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0], unique_local);
 
     check!(