libp2p: public means global routable

2 files changed, 45 insertions, 7 deletions

diff --git a/src/transport/libp2p/book.rs b/src/transport/libp2p/book.rs
index 02a6b49..c2296d3 100644
--- a/src/transport/libp2p/book.rs
+++ b/src/transport/libp2p/book.rs
@@ -611,24 +611,38 @@ pub(super) fn ip_of(address: &Multiaddr) -> Option<std::net::IpAddr> {
     }
 }
 
-/// Whether `ip` can be reached from the internet, as far as its range tells.
+/// Whether `ip` can be reached from the internet, as far as its range tells. For IPv6,
+/// only global unicast (`2000::/3`) is: other ranges in use are an overlay's
+/// (Mycelium's `400::/7`), a translator's (`64:ff9b::/96`) or local, and, ranked as
+/// public, would be preferred over the LAN (`preference`).
 pub(super) fn is_public(ip: std::net::IpAddr) -> bool {
     use std::net::IpAddr;
     match ip {
         IpAddr::V4(ip) => {
+            let [a, b, c, _] = ip.octets();
             // 100.64.0.0/10: carrier-grade NAT.
-            let shared = ip.octets()[0] == 100 && (ip.octets()[1] & 0xc0) == 64;
+            let shared = a == 100 && (b & 0xc0) == 64;
+            // 198.18.0.0/15: benchmarking; 240.0.0.0/4: reserved (and broadcast).
+            let benchmarking = a == 198 && (b & 0xfe) == 18;
+            let reserved = a >= 240;
+            // 192.0.0.0/24: protocol assignments.
+            let protocol = a == 192 && b == 0 && c == 0;
             !(ip.is_private()
                 || ip.is_loopback()
                 || ip.is_link_local()
                 || ip.is_unspecified()
-                || shared)
+                || ip.is_documentation()
+                || ip.is_multicast()
+                || shared
+                || benchmarking
+                || reserved
+                || protocol)
         }
         IpAddr::V6(ip) => {
-            !(ip.is_loopback()
-                || ip.is_unspecified()
-                || ip.is_unique_local()
-                || ip.is_unicast_link_local())
+            let [first, second, ..] = ip.segments();
+            // 2001:db8::/32: documentation.
+            let documentation = first == 0x2001 && second == 0x0db8;
+            (first & 0xe000) == 0x2000 && !documentation
         }
     }
 }
diff --git a/src/transport/libp2p/tests.rs b/src/transport/libp2p/tests.rs
index 801dfd3..fd607fe 100644
--- a/src/transport/libp2p/tests.rs
+++ b/src/transport/libp2p/tests.rs
@@ -539,6 +539,30 @@ async fn a_member_that_relays_is_picked() {
 
 /// A peer on the LAN that speaks continuum becomes a seed once, at its address.
 #[test]
+fn public_ranges() {
+    let public = |ip: &str| book::is_public(ip.parse().unwrap());
+    assert!(public("203.0.114.5"));
+    assert!(public("2a01:4f8::1"));
+    for not in [
+        "10.1.2.3",
+        "100.64.0.1",
+        "192.0.2.1",
+        "198.18.0.1",
+        "224.0.0.1",
+        "255.255.255.255",
+        "::1",
+        "fd00::1",
+        "fe80::1",
+        "2001:db8::1",
+        "64:ff9b::1",
+        // Mycelium's overlay.
+        "45f:fa21:4bdd::1",
+    ] {
+        assert!(!public(not), "{not}");
+    }
+}
+
+#[test]
 fn lan_peers_become_seeds_once() {
     let mut book = Book::default();
     let lan = peer();