Reset expiry of entries in the neighbor cache on packet reception

src/iface/interface/ipv4.rs

@@ -196,6 +196,10 @@ impl InterfaceInner {
             }
         }
 
+        #[cfg(feature = "medium-ethernet")]
+        self.neighbor_cache
+            .reset_expiry_if_existing(IpAddress::Ipv4(ipv4_repr.src_addr), self.now);
+
         match ipv4_repr.next_header {
             IpProtocol::Icmp => self.process_icmpv4(sockets, ipv4_repr, ip_payload),
 

src/iface/interface/ipv6.rs

@@ -228,6 +228,10 @@ impl InterfaceInner {
         #[cfg(not(feature = "socket-raw"))]
         let handled_by_raw_socket = false;
 
+        #[cfg(any(feature = "medium-ethernet", feature = "medium-ieee802154"))]
+        self.neighbor_cache
+            .reset_expiry_if_existing(IpAddress::Ipv6(ipv6_repr.src_addr), self.now);
+
         self.process_nxt_hdr(
             sockets,
             meta,

src/iface/neighbor.rs

@@ -63,6 +63,16 @@ impl Cache {
         }
     }
 
+    pub fn reset_expiry_if_existing(&mut self, protocol_addr: IpAddress, timestamp: Instant) {
+        if let Some(Neighbor {
+            expires_at,
+            hardware_addr: _,
+        }) = self.storage.get_mut(&protocol_addr)
+        {
+            *expires_at = timestamp + Self::ENTRY_LIFETIME;
+        }
+    }
+
     pub fn fill(
         &mut self,
         protocol_addr: IpAddress,