Add support for IPv6 within VPN (#1061)

* add flake.nix with nix based dev shell
* add support for IPv6
* update thunk

---------

Co-authored-by: sijie.sun <sijie.sun@smartx.com>

easytier/src/tests/ipv6_test.rs

@@ -0,0 +1,66 @@
+use std::net::Ipv6Addr;
+
+use crate::{
+    common::config::{ConfigLoader, TomlConfigLoader},
+    common::global_ctx::tests::get_mock_global_ctx,
+    peers::peer_manager::RouteAlgoType,
+    proto::peer_rpc::RoutePeerInfo,
+};
+
+#[tokio::test]
+async fn test_ipv6_config_support() {
+    let config = TomlConfigLoader::default();
+
+    // Test IPv6 configuration setting and getting
+    let ipv6_cidr = "fd00::1/64".parse().unwrap();
+    config.set_ipv6(Some(ipv6_cidr));
+
+    assert_eq!(config.get_ipv6(), Some(ipv6_cidr));
+}
+
+#[tokio::test]
+async fn test_global_ctx_ipv6() {
+    let global_ctx = get_mock_global_ctx();
+
+    // Test setting and getting IPv6 from global context
+    let ipv6_cidr = "fd00::1/64".parse().unwrap();
+    global_ctx.set_ipv6(Some(ipv6_cidr));
+
+    assert_eq!(global_ctx.get_ipv6(), Some(ipv6_cidr));
+}
+
+#[tokio::test]
+async fn test_route_peer_info_ipv6() {
+    let global_ctx = get_mock_global_ctx();
+
+    // Set IPv6 address in global context
+    let ipv6_cidr = "fd00::1/64".parse().unwrap();
+    global_ctx.set_ipv6(Some(ipv6_cidr));
+
+    // Create RoutePeerInfo with IPv6 support
+    let peer_info = RoutePeerInfo::new();
+    let updated_info = peer_info.update_self(123, 456, &global_ctx);
+
+    // Verify IPv6 address is included
+    assert!(updated_info.ipv6_addr.is_some());
+    let ipv6_addr: Ipv6Addr = updated_info.ipv6_addr.unwrap().address.unwrap().into();
+    assert_eq!(ipv6_addr, ipv6_cidr.address());
+}
+
+#[tokio::test]
+async fn test_peer_manager_ipv6() {
+    let global_ctx = get_mock_global_ctx();
+    let (packet_sender, _packet_receiver) = tokio::sync::mpsc::channel(100);
+    let peer_mgr = crate::peers::peer_manager::PeerManager::new(
+        RouteAlgoType::Ospf,
+        global_ctx.clone(),
+        packet_sender,
+    );
+
+    // Test IPv6 address lookup for unknown address
+    let ipv6_addr = Ipv6Addr::new(0xfd00, 0, 0, 0, 0, 0, 0, 2);
+    let (peers, _is_self) = peer_mgr.get_msg_dst_peer_ipv6(&ipv6_addr).await;
+
+    // Should return empty peers list for unknown IPv6
+    assert!(peers.is_empty());
+}