Add GetDynamicPortRange api for Wifilan medium

PiperOrigin-RevId: 416669312

cpp/core/internal/mediums/wifi_lan.cc

@@ -227,9 +227,16 @@ bool WifiLan::StartAcceptingConnections(const std::string& service_id,
     return false;
   }
 
-  // We can generate an exact port here on server socket; now we just assign 0
-  // to let platform medium decide it.
+  auto port_range = medium_.GetDynamicPortRange();
+  // Generate an exact port here on server socket; if platform doesn't provide
+  // range of port then assign 0 to let platform decide it.
   int port = 0;
+  if (port_range.has_value() &&
+      (port_range->first > 0 && port_range->first <= 65535 &&
+       port_range->second > 0 && port_range->second <= 65535 &&
+       port_range->first <= port_range->second)) {
+    port = GeneratePort(service_id, port_range.value());
+  }
   WifiLanServerSocket server_socket = medium_.ListenForService(port);
   if (!server_socket.IsValid()) {
     NEARBY_LOGS(INFO)
@@ -404,6 +411,19 @@ std::string WifiLan::GenerateServiceType(const std::string& service_id) {
                          service_id_hash_string);
 }
 
+int WifiLan::GeneratePort(const std::string& service_id,
+                          std::pair<std::int32_t, std::int32_t> port_range) {
+  const std::string service_id_hash =
+      std::string(Utils::Sha256Hash(service_id, 4));
+
+  std::uint32_t uint_of_service_id_hash =
+      service_id_hash[0] << 24 | service_id_hash[1] << 16 |
+      service_id_hash[2] << 8 | service_id_hash[3];
+
+  return port_range.first +
+         (uint_of_service_id_hash % (port_range.second - port_range.first));
+}
+
 }  // namespace connections
 }  // namespace nearby
 }  // namespace location

cpp/core/internal/mediums/wifi_lan.h

@@ -170,6 +170,10 @@ class WifiLan {
   // Generates mDNS type.
   std::string GenerateServiceType(const std::string& service_id);
 
+  // Generates port number based on port_range_.
+  int GeneratePort(const std::string& service_id,
+                   std::pair<std::int32_t, std::int32_t> port_range);
+
   mutable Mutex mutex_;
   WifiLanMedium medium_ ABSL_GUARDED_BY(mutex_);
   AdvertisingInfo advertising_info_ ABSL_GUARDED_BY(mutex_);

cpp/platform/api/wifi_lan.h

@@ -144,6 +144,10 @@ class WifiLanMedium {
   // On error, returns nullptr.
   virtual std::unique_ptr<WifiLanServerSocket> ListenForService(
       int port = 0) = 0;
+
+  // Returns the port range as a pair of min and max port.
+  virtual absl::optional<std::pair<std::int32_t, std::int32_t>>
+  GetDynamicPortRange() = 0;
 };
 
 }  // namespace api

cpp/platform/impl/g3/wifi_lan.h

@@ -233,6 +233,12 @@ class WifiLanMedium : public api::WifiLanMedium {
   std::unique_ptr<api::WifiLanServerSocket> ListenForService(int port) override
       ABSL_LOCKS_EXCLUDED(mutex_);
 
+  // Returns the port range as a pair of min and max port.
+  absl::optional<std::pair<std::int32_t, std::int32_t>> GetDynamicPortRange()
+      override {
+    return std::make_pair(49152, 65535);
+  }
+
  private:
   struct AdvertisingInfo {
     bool Empty() const { return service_types.empty(); }

cpp/platform/impl/ios/Source/Platform/wifi_lan.h

@@ -155,6 +155,10 @@ class WifiLanMedium : public api::WifiLanMedium {
   std::unique_ptr<api::WifiLanServerSocket> ListenForService(int port) override
       ABSL_LOCKS_EXCLUDED(mutex_);
 
+  absl::optional<std::pair<std::int32_t, std::int32_t>> GetDynamicPortRange() override {
+    return absl::nullopt;
+  }
+
  private:
   struct AdvertisingInfo {
     bool Empty() const { return services.empty(); }

cpp/platform/impl/windows/wifi_lan.h

@@ -30,6 +30,7 @@
 #include "absl/container/flat_hash_map.h"
 #include "absl/container/flat_hash_set.h"
 #include "absl/synchronization/mutex.h"
+#include "absl/types/optional.h"
 #include "platform/api/wifi_lan.h"
 #include "platform/base/exception.h"
 #include "platform/base/input_stream.h"
@@ -247,6 +248,11 @@ class WifiLanMedium : public api::WifiLanMedium {
   // continue.
   void NotifyDnsServiceUnregistered(DWORD status);
 
+  absl::optional<std::pair<std::int32_t, std::int32_t>> GetDynamicPortRange()
+      override {
+    return absl::nullopt;
+  }
+
  private:
   // mDNS text attributes
   static constexpr std::string_view KEY_ENDPOINT_INFO = "n";

cpp/platform/public/wifi_lan.h

@@ -187,6 +187,11 @@ class WifiLanMedium {
     return WifiLanServerSocket(impl_->ListenForService(port));
   }
 
+  // Returns the port range as a pair of min and max port.
+  absl::optional<std::pair<std::int32_t, std::int32_t>> GetDynamicPortRange() {
+    return impl_->GetDynamicPortRange();
+  }
+
   bool IsValid() const { return impl_ != nullptr; }
 
   api::WifiLanMedium& GetImpl() { return *impl_; }