avoid packets sending to non-exist peer causing route loop (#1378)

easytier/src/common/global_ctx.rs

@@ -1,4 +1,5 @@
 use std::collections::hash_map::DefaultHasher;
+use std::net::IpAddr;
 use std::{
     hash::Hasher,
     sync::{Arc, Mutex},
@@ -239,6 +240,13 @@ impl GlobalCtx {
         self.config.get_id()
     }
 
+    pub fn is_ip_in_same_network(&self, ip: &IpAddr) -> bool {
+        match ip {
+            IpAddr::V4(v4) => self.get_ipv4().map(|x| x.contains(v4)).unwrap_or(false),
+            IpAddr::V6(v6) => self.get_ipv6().map(|x| x.contains(v6)).unwrap_or(false),
+        }
+    }
+
     pub fn get_network_identity(&self) -> NetworkIdentity {
         self.config.get_network_identity()
     }