translation/Protocol: add packet RATE_LIMIT_SITE_REQUESTS

src/translation/Parser.cxx

@@ -1131,6 +1131,22 @@ TranslateParser::HandleAllowRemoteNetwork(std::span<const std::byte> payload)
 	response.allow_remote_networks.Add(alloc, address, prefix_length);
 }
 
+inline void
+TranslateParser::HandleTokenBucketParams(TranslateTokenBucketParams &params,
+					 const char *packet_name,
+					 std::span<const std::byte> payload)
+{
+	if (params.IsDefined())
+		throw FmtRuntimeError("duplicate {} packet", packet_name);
+
+	if (payload.size() != sizeof(params))
+		throw FmtRuntimeError("malformed {} packet", packet_name);
+
+	memcpy(&params, payload.data(), sizeof(params));
+	if (!params.IsValid())
+		throw FmtRuntimeError("malformed {} packet", packet_name);
+}
+
 #endif // TRANSLATION_ENABLE_HTTP
 
 static bool
@@ -4318,6 +4334,18 @@ TranslateParser::HandleRegularPacket(TranslationCommand command,
 #else
 		break;
 #endif
+
+case TranslationCommand::RATE_LIMIT_SITE_REQUESTS:
+#if TRANSLATION_ENABLE_HTTP
+		if (response.site == nullptr)
+			throw std::runtime_error{"misplaced RATE_LIMIT_SITE_REQUESTS packet"};
+
+		HandleTokenBucketParams(response.rate_limit_site_requests,
+					"RATE_LIMIT_SITE_REQUESTS", payload);
+		return;
+#else
+		break;
+#endif
 	}
 
 	throw FmtRuntimeError("unknown translation packet: {}", (unsigned)command);

src/translation/Parser.hxx

@@ -28,6 +28,7 @@
 #include <string_view>
 
 struct TranslateResponse;
+struct TranslateTokenBucketParams;
 struct FileAddress;
 struct CgiAddress;
 struct HttpAddress;
@@ -265,6 +266,9 @@ private:
 
 #if TRANSLATION_ENABLE_HTTP
 	void HandleAllowRemoteNetwork(std::span<const std::byte> payload);
+	void HandleTokenBucketParams(TranslateTokenBucketParams &params,
+				     const char *packet_name,
+				     std::span<const std::byte> payload);
 #endif
 
 	Result HandlePacket(TranslationCommand command,

src/translation/Protocol.hxx

@@ -1287,6 +1287,12 @@ enum class TranslationCommand : uint16_t {
 	 * This packet may be sent more than once.
 	 */
 	ALLOW_REMOTE_NETWORK = 263,
+
+	/**
+	 * Configure a rate limit for all requests of this site.
+	 * Payload is two 32-bit floats: rate and burst.
+	 */
+	RATE_LIMIT_SITE_REQUESTS = 264,
 };
 
 struct TranslationHeader {

src/translation/Response.cxx

@@ -255,6 +255,10 @@ TranslateResponse::Clear() noexcept
 
 	validate_mtime.mtime = 0;
 	validate_mtime.path = nullptr;
+
+#if TRANSLATION_ENABLE_HTTP
+	rate_limit_site_requests.Clear();
+#endif
 }
 
 static std::span<const char *const>
@@ -518,6 +522,10 @@ TranslateResponse::CopyFrom(AllocatorPtr alloc, const TranslateResponse &src) no
 
 	validate_mtime.mtime = src.validate_mtime.mtime;
 	validate_mtime.path = alloc.CheckDup(src.validate_mtime.path);
+
+#if TRANSLATION_ENABLE_HTTP
+	rate_limit_site_requests = src.rate_limit_site_requests;
+#endif
 }
 
 void

src/translation/Response.hxx

@@ -42,6 +42,23 @@ class AllocatorPtr;
 class UniqueRegex;
 class MatchData;
 
+struct TranslateTokenBucketParams {
+	float rate, burst;
+
+	void Clear() noexcept {
+		rate = -1;
+	}
+
+	bool IsDefined() const noexcept {
+		return rate > 0;
+	}
+
+	bool IsValid() const noexcept {
+		// TODO check std::isfinite()?
+		return rate > 0 && burst > 0;
+	}
+};
+
 struct TranslateResponse {
 	/**
 	 * The protocol version from the BEGIN packet.
@@ -322,6 +339,10 @@ struct TranslateResponse {
 		const char *path;
 	} validate_mtime;
 
+#if TRANSLATION_ENABLE_HTTP
+	TranslateTokenBucketParams rate_limit_site_requests;
+#endif
+
 	/**
 	 * From #TranslationCommand::TIMEOUT.  Zero if unset.
 	 */

src/translation/server/Response.hxx

@@ -378,6 +378,12 @@ public:
 				   static_cast<std::span<const std::byte>>(address));
 	}
 
+	auto &RateLimitSiteRequests(const float &rate, const float &burst) noexcept {
+		return MultiPacket(TranslationCommand::RATE_LIMIT_SITE_REQUESTS,
+				   std::span{&rate, 1},
+				   std::span{&burst, 1});
+	}
+
 	struct RedirectContext {
 		Response &response;