feat: don't crash if ip:mac already exist, just skip it

harmony-rs/opnsense-config/src/modules/dhcp.rs

@@ -1,3 +1,4 @@
+use log::info;
 use opnsense_config_xml::MaybeString;
 use opnsense_config_xml::Range;
 use opnsense_config_xml::StaticMap;
@@ -93,6 +94,21 @@ impl<'a> DhcpConfig<'a> {
         //     return Err(DhcpError::IpAddressOutOfRange(ipaddr.to_string()));
         // }
 
+        if existing_mappings.iter().any(|m| {
+            m.ipaddr
+                .parse::<Ipv4Addr>()
+                .expect("Mapping contains invalid ipv4")
+                == ipaddr
+                && m.mac == mac
+        }) {
+            info!(
+                "Mapping already exists for {} [{}], skipping",
+                ipaddr.to_string(),
+                mac
+            );
+            return Ok(());
+        }
+
         if existing_mappings.iter().any(|m| {
             m.ipaddr
                 .parse::<Ipv4Addr>()