refactor(core): migrate packet processing from pnet to smoltcp (#2456)

Replace pnet_packet parsing and mutation across gateway packet paths with the existing smoltcp wire APIs. Preserve length validation, fragmentation classification, TCP flags, and checksum behavior while removing the core pnet_packet feature dependency.
Reject stale non-initiator OSPF sync sessions: only initiator requests may create missing sessions, and a rejection clears the old initiator role only when the remote session generation is unchanged. This fixes an unbounded RPC storm caused by a delayed route sync recreating a session after both peers relinquished the initiator role, with regression tests for session creation and response reordering.

easytier/src/host_runtime.rs

@@ -142,7 +142,7 @@ impl ConnectorRuntime for NativeHostRuntime {
             .into_iter()
             .find(|interface| {
                 interface
-                    .ips
+                    .addr
                     .iter()
                     .any(|local| matches!(local.ip(), IpAddr::V6(local_ip) if local_ip == ip))
             })