Support connecting using link local address in hotspot.

PiperOrigin-RevId: 829634620

internal/platform/implementation/windows/wifi_hotspot_medium.cc

@@ -14,6 +14,7 @@
 #include <cstdint>
 #include <exception>
 #include <memory>
+#include <optional>
 #include <string>
 
 #include "absl/strings/str_format.h"
@@ -99,6 +100,17 @@ std::unique_ptr<api::WifiHotspotSocket> WifiHotspotMedium::ConnectToService(
     LOG(ERROR) << "no valid service address and port to connect.";
     return nullptr;
   }
+  if (server_address.IsV6LinkLocal()) {
+    // Link local address need to be scoped to the wifi interface.
+    std::optional<uint32_t> wifi_interface_index =
+        wifi_hotspot_native_.GetWifiInterfaceIndex();
+    if (!wifi_interface_index.has_value()) {
+      LOG(ERROR)
+          << "Wifi interface index is not available, skip link local address.";
+      return nullptr;
+    }
+    server_address.SetScopeId(wifi_interface_index.value());
+  }
   VLOG(1) << "ConnectToService address: " << server_address.ToString();
   LOG(INFO) << "Connecting to service.";
   auto wifi_hotspot_socket = std::make_unique<WifiHotspotSocket>();

internal/platform/implementation/windows/wifi_hotspot_native.cc

@@ -22,9 +22,11 @@
 #include <cguid.h>
 // clang-format on
 
+#include <cstdint>
 #include <cstring>
 #include <cwchar>
 #include <memory>
+#include <optional>
 #include <string>
 #include <utility>
 #include <vector>
@@ -434,4 +436,21 @@ bool WifiHotspotNative::RenewIpv4Address() const {
   return false;
 }
 
+std::optional<uint32_t> WifiHotspotNative::GetWifiInterfaceIndex() const {
+  GUID interface_guid = GetInterfaceGuid();
+  if (interface_guid == GUID_NULL) {
+    LOG(ERROR) << __func__ << ": No available WLAN Interface to use.";
+    return std::nullopt;
+  }
+  NET_LUID luid;
+  if (ConvertInterfaceGuidToLuid(&interface_guid, &luid) == NO_ERROR) {
+    NET_IFINDEX interface_index = 0;
+    if (ConvertInterfaceLuidToIndex(&luid, &interface_index) == NO_ERROR) {
+      return interface_index;
+    }
+  }
+  LOG(ERROR) << "Failed to convert interface guid to interface index.";
+  return std::nullopt;
+}
+
 }  // namespace nearby::windows

internal/platform/implementation/windows/wifi_hotspot_native.h

@@ -22,7 +22,9 @@
 #include <wlanapi.h>
 // clang-format on
 
+#include <cstdint>
 #include <memory>
+#include <optional>
 #include <string>
 
 #include "absl/base/nullability.h"
@@ -48,6 +50,10 @@ class WifiHotspotNative {
   // Returns true if the interface has a non local scoped IPv4 address.
   bool HasAssignedAddress();
   bool RenewIpv4Address() const;
+  // Return the interface index of the wifi interface used to connect to the
+  // hotspot.
+  // On error, returns std::nullopt.
+  std::optional<uint32_t> GetWifiInterfaceIndex() const;
 
  private:
   // Context for WLAN notification callback.