libp2p: autoignore unroutable address ranges

1 files changed, 25 insertions, 1 deletions

diff --git a/src/transport/libp2p/ignore.rs b/src/transport/libp2p/ignore.rs
index ab59a3e..2fcbd6f 100644
--- a/src/transport/libp2p/ignore.rs
+++ b/src/transport/libp2p/ignore.rs
@@ -2,11 +2,13 @@
 //! (`Ignoring`, a behaviour that denies connections there), nor told peers by identify
 //! (`Identifying`).
 
+use std::fmt;
+
 use super::*;
 
 /// An address range (`10.244.0.0/16`, `42::/16`; a bare address is a range of one), for
 /// `Libp2pConfig::ignore`.
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub(crate) struct IpRange {
     pub(super) network: std::net::IpAddr,
     pub(super) prefix: u8,
@@ -36,7 +38,29 @@ impl FromStr for IpRange {
     }
 }
 
+impl fmt::Display for IpRange {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{}/{}", self.network, self.prefix)
+    }
+}
+
 impl IpRange {
+    /// The range of the `prefix` bits of `ip` (the rest zero).
+    pub(super) fn masked(ip: std::net::IpAddr, prefix: u8) -> Self {
+        use std::net::IpAddr;
+        let network = match ip {
+            IpAddr::V4(ip) => {
+                let mask = u32::MAX.checked_shl(32 - u32::from(prefix)).unwrap_or(0);
+                IpAddr::V4((u32::from(ip) & mask).into())
+            }
+            IpAddr::V6(ip) => {
+                let mask = u128::MAX.checked_shl(128 - u32::from(prefix)).unwrap_or(0);
+                IpAddr::V6((u128::from(ip) & mask).into())
+            }
+        };
+        Self { network, prefix }
+    }
+
     /// Whether every address of `other` is in this range too.
     pub(super) fn covers(&self, other: &IpRange) -> bool {
         self.network.is_ipv4() == other.network.is_ipv4()