feat: DNS checker，自研 codec/transport，支持 system/server 双模式，UDP/TCP + TC fallback
This commit is contained in:
349
src/server/checker/runner/dns/transport.ts
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349
src/server/checker/runner/dns/transport.ts
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import type { DnsResponse } from "./codec";
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import { parseResponse } from "./codec";
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export type DnsQueryResult = DnsTransportError | DnsTransportResult;
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export interface DnsTransportError {
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error: string;
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ok: false;
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}
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export interface DnsTransportResult {
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data: Uint8Array;
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ok: true;
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protocolUsed: "tcp" | "udp";
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response: DnsResponse;
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}
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interface QueryMeta {
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id: number;
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name: string;
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qclass: number;
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qtype: number;
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}
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export async function queryDns(
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server: string,
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port: number,
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query: Uint8Array,
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options: {
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maxResponseBytes: number;
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protocol: "tcp" | "udp";
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signal: AbortSignal;
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tcpFallback: boolean;
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},
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): Promise<DnsQueryResult> {
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if (options.protocol === "tcp") {
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return queryTcp(server, port, query, options.signal, options.maxResponseBytes);
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}
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const udpResult = await queryUdp(server, port, query, options.signal, options.maxResponseBytes);
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if (!udpResult.ok) return udpResult;
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if (udpResult.response.header.flags.truncated && options.tcpFallback) {
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const tcpResult = await queryTcp(server, port, query, options.signal, options.maxResponseBytes);
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if (tcpResult.ok) {
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return { ...tcpResult, protocolUsed: "tcp" };
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}
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return udpResult;
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}
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return udpResult;
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}
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function mergeChunks(chunks: Uint8Array[], totalBytes: number): Uint8Array {
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const result = new Uint8Array(totalBytes);
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let offset = 0;
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for (const chunk of chunks) {
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result.set(chunk, offset);
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offset += chunk.byteLength;
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}
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return result;
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}
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function parseAndValidateResponse(query: Uint8Array, payload: Uint8Array, protocolUsed: "tcp" | "udp"): DnsQueryResult {
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try {
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const response = parseResponse(payload);
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const validationError = validateResponseForQuery(query, response);
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if (validationError) {
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return { error: validationError, ok: false };
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}
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return { data: payload, ok: true, protocolUsed, response };
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} catch (e) {
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return { error: `DNS 响应解析失败: ${e instanceof Error ? e.message : String(e)}`, ok: false };
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}
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}
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async function queryTcp(
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server: string,
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port: number,
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query: Uint8Array,
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signal: AbortSignal,
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maxResponseBytes: number,
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): Promise<DnsQueryResult> {
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const chunks: Uint8Array[] = [];
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let totalBytes = 0;
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let settled = false;
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let resolver: ((value: DnsQueryResult) => void) | undefined;
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const promise = new Promise<DnsQueryResult>((resolve) => {
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resolver = resolve;
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});
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const settle = (result: DnsQueryResult) => {
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if (settled) return;
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settled = true;
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resolver!(result);
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};
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const socketHandlers: Record<string, (...args: unknown[]) => void> = {
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close() {
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if (totalBytes >= 2) {
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const full = mergeChunks(chunks, totalBytes);
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const view = new DataView(full.buffer, full.byteOffset, full.byteLength);
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const respLen = view.getUint16(0);
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const payloadLen = Math.min(respLen, maxResponseBytes);
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if (totalBytes - 2 >= payloadLen) {
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if (respLen > maxResponseBytes) {
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settle({ error: `TCP 响应超过 ${maxResponseBytes} 字节限制 (${respLen} bytes)`, ok: false });
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return;
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}
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const payload = full.subarray(2, 2 + payloadLen);
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settle(parseAndValidateResponse(query, payload, "tcp"));
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} else {
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settle({ error: `TCP 响应不完整: 期望 ${respLen} 字节，收到 ${totalBytes - 2} 字节`, ok: false });
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}
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} else {
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settle({ error: "TCP 连接关闭，未收到响应", ok: false });
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}
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},
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data(_socket: unknown, data: unknown) {
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const buf = data instanceof Uint8Array ? data : new Uint8Array(data as ArrayBuffer);
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if (totalBytes + buf.byteLength > maxResponseBytes + 2) {
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const trimmed = buf.subarray(0, maxResponseBytes + 2 - totalBytes);
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if (trimmed.byteLength > 0) {
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chunks.push(new Uint8Array(trimmed));
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totalBytes += trimmed.byteLength;
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}
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} else {
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chunks.push(new Uint8Array(buf));
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totalBytes += buf.byteLength;
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}
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if (totalBytes >= 2) {
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const full = mergeChunks(chunks, totalBytes);
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const view = new DataView(full.buffer, full.byteOffset, full.byteLength);
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const respLen = view.getUint16(0);
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const payloadLen = Math.min(respLen, maxResponseBytes);
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if (totalBytes - 2 >= payloadLen) {
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try {
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(_socket as { close(): void }).close();
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} catch {
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/* best-effort */
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}
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}
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}
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},
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error(_socket: unknown, error: unknown) {
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settle({ error: error instanceof Error ? error.message : String(error), ok: false });
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},
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open() {
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// Bun socket handler 必填项，连接成功由 Bun.connect() resolve 表示
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},
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};
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const onAbort = () => {
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settle({ error: "探测超时", ok: false });
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};
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signal.addEventListener("abort", onAbort, { once: true });
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try {
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const socket = await Bun.connect({
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hostname: server,
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port,
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socket: socketHandlers,
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});
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if (signal.aborted) {
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try {
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socket.close();
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} catch {
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/* best-effort */
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}
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signal.removeEventListener("abort", onAbort);
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return promise;
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}
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const lengthBuf = new Uint8Array(2);
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new DataView(lengthBuf.buffer).setUint16(0, query.byteLength);
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socket.write(lengthBuf);
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socket.write(query);
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const result = await promise;
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signal.removeEventListener("abort", onAbort);
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try {
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socket.close();
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} catch {
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/* best-effort */
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}
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return result;
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} catch (error) {
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signal.removeEventListener("abort", onAbort);
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if (signal.aborted) {
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return { error: "探测超时", ok: false };
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}
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const message = error instanceof Error ? error.message : String(error);
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return { error: simplifyError(message), ok: false };
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}
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}
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async function queryUdp(
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server: string,
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port: number,
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query: Uint8Array,
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signal: AbortSignal,
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maxResponseBytes: number,
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): Promise<DnsQueryResult> {
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try {
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const socket = await Bun.udpSocket({
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connect: { hostname: server, port },
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socket: {
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data(socket, data) {
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if (data.byteLength > maxResponseBytes) {
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settle({ error: `UDP 响应超过 ${maxResponseBytes} 字节限制 (${data.byteLength} bytes)`, type: "error" });
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try {
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socket.close();
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} catch {
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/* best-effort */
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}
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return;
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}
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settle({ data: new Uint8Array(data.buffer, data.byteOffset, data.byteLength), type: "data" });
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try {
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socket.close();
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} catch {
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/* best-effort */
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}
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},
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drain() {
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// Bun UDP socket handler 必填项，DNS checker 不关注 drain 事件
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},
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error(_socket, error) {
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settle({ error: error.message, type: "error" });
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try {
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_socket.close();
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} catch {
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/* best-effort */
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}
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},
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},
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});
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if (signal.aborted) {
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try {
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socket.close();
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} catch {
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/* best-effort */
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}
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return { error: "探测已取消", ok: false };
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}
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let settled = false;
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let resolver: ((value: { data?: Uint8Array; error?: string; type: string }) => void) | undefined;
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const promise = new Promise<{ data?: Uint8Array; error?: string; type: string }>((resolve) => {
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resolver = resolve;
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});
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const settle = (result: { data?: Uint8Array; error?: string; type: string }) => {
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if (settled) return;
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settled = true;
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resolver!(result);
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};
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const onAbort = () => {
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settle({ type: "abort" });
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try {
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socket.close();
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} catch {
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/* best-effort */
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}
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};
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signal.addEventListener("abort", onAbort, { once: true });
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socket.send(query);
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const result = await promise;
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signal.removeEventListener("abort", onAbort);
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if (result.type === "error") {
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return { error: result.error ?? "UDP 查询失败", ok: false };
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}
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if (result.type === "abort") {
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return { error: "探测超时", ok: false };
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}
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if (!result.data) {
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return { error: "未收到 UDP 响应", ok: false };
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}
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return parseAndValidateResponse(query, result.data, "udp");
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} catch (error) {
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if (signal.aborted) {
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return { error: "探测超时", ok: false };
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}
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const message = error instanceof Error ? error.message : String(error);
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return { error: simplifyError(message), ok: false };
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}
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}
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function readQueryMeta(query: Uint8Array): null | QueryMeta {
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if (query.byteLength < 12) return null;
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const view = new DataView(query.buffer, query.byteOffset, query.byteLength);
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const id = view.getUint16(0);
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const labels: string[] = [];
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let offset = 12;
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while (true) {
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if (offset >= query.byteLength) return null;
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const len = query[offset]!;
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offset++;
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if (len === 0) break;
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if ((len & 0xc0) !== 0 || offset + len > query.byteLength) return null;
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labels.push(new TextDecoder().decode(query.subarray(offset, offset + len)));
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offset += len;
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}
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if (offset + 4 > query.byteLength) return null;
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const qtype = view.getUint16(offset);
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const qclass = view.getUint16(offset + 2);
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return { id, name: labels.join("."), qclass, qtype };
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}
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function simplifyError(message: string): string {
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const lower = message.toLowerCase();
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if (lower.includes("econnrefused") || lower.includes("connection refused")) return "connection refused";
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if (lower.includes("enoent") || lower.includes("not found")) return "host not found";
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if (lower.includes("etimedout") || lower.includes("timed out")) return "timed out";
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if (lower.includes("econnreset") || lower.includes("reset")) return "connection reset";
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if (lower.includes("enetwork") || lower.includes("network")) return "network error";
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return message;
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}
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function validateResponseForQuery(query: Uint8Array, response: DnsResponse): null | string {
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const meta = readQueryMeta(query);
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if (!meta) return "DNS 查询报文不完整";
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if (response.header.id !== meta.id) {
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return `DNS 响应 ID 不匹配: 期望 ${meta.id}，实际 ${response.header.id}`;
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}
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const question = response.questions[0];
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if (question && (question.name !== meta.name || question.qtype !== meta.qtype || question.qclass !== meta.qclass)) {
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return "DNS 响应 question 与查询不匹配";
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}
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return null;
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}
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