fix(webrtc): fix GStreamer WHEP interop (#4720)

## Summary

This PR fixes GStreamer interoperability issues during WebRTC/WHEP
negotiation with ZLMediaServer.

GStreamer could fail to establish the connection for two separate
reasons:

1. ZLMediaServer generated a non-compliant ICE `ufrag`. The generated
value contained `_`, which is not a valid ICE character, so GStreamer
rejected the SDP.
2. ZLMediaServer did not correctly handle `bundle-only` offers and could
answer an accepted bundled m-line with `port=0`, which caused the later
WHEP negotiation to fail.

## Changes

- Generate ICE `ufrag` values using ICE-compliant characters only.
- Preserve and handle `a=bundle-only` correctly during SDP parsing and
answer generation.
- Return `port=9` instead of `port=0` for accepted bundled m-lines.
- Add regression coverage for `bundle-only` SDP handling.
- URL-encode `delete_webrtc` query parameters in the returned `Location`
header so ICE-safe identifiers remain round-trippable over HTTP.

## Validation

- Built with WebRTC and SCTP enabled.
- Added regression test: `test_webrtc_regression`
- Verified:
  - ICE-safe identifier round-trip through `delete_webrtc`
  - `bundle-only` SDP answer generation

tests/CMakeLists.txt

@@ -34,10 +34,10 @@ foreach(TEST_SRC ${TEST_SRC_LIST})
       continue()
     endif()
   endif()
-  
+
   if(NOT TARGET ZLMediaKit::WebRTC)
     # 暂时过滤掉依赖 WebRTC 的测试模块
-    if("${TEST_EXE_NAME}" MATCHES "test_rtcp_nack")
+    if("${TEST_EXE_NAME}" MATCHES "test_rtcp_nack|test_webrtc_regression")
       continue()
     endif()
   endif()

tests/test_webrtc_regression.cpp

@@ -0,0 +1,115 @@
+/*
+ * Copyright (c) 2016-present The ZLMediaKit project authors. All Rights Reserved.
+ *
+ * This file is part of ZLMediaKit(https://github.com/ZLMediaKit/ZLMediaKit).
+ *
+ * Use of this source code is governed by MIT-like license that can be found in the
+ * LICENSE file in the root of the source tree. All contributing project authors
+ * may be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include <cstdlib>
+#include <iostream>
+#include <stdexcept>
+#include <string>
+
+#include "Common/Parser.h"
+#include "Common/strCoding.h"
+#include "Http/HttpClient.h"
+#include "../webrtc/Sdp.h"
+
+using namespace std;
+using namespace mediakit;
+
+namespace {
+
+void expect(bool cond, const string &msg) {
+    if (!cond) {
+        throw runtime_error(msg);
+    }
+}
+
+string makeBundleOnlyDatachannelOffer() {
+    return
+        "v=0\r\n"
+        "o=- 0 0 IN IP4 127.0.0.1\r\n"
+        "s=-\r\n"
+        "t=0 0\r\n"
+        "a=group:BUNDLE 0\r\n"
+        "a=msid-semantic: WMS\r\n"
+        "m=application 0 UDP/DTLS/SCTP webrtc-datachannel\r\n"
+        "c=IN IP4 0.0.0.0\r\n"
+        "a=ice-ufrag:remoteUfrag\r\n"
+        "a=ice-pwd:remotePassword1234567890\r\n"
+        "a=fingerprint:sha-256 "
+        "00:11:22:33:44:55:66:77:88:99:AA:BB:CC:DD:EE:FF:"
+        "00:11:22:33:44:55:66:77:88:99:AA:BB:CC:DD:EE:FF\r\n"
+        "a=setup:actpass\r\n"
+        "a=mid:0\r\n"
+        "a=bundle-only\r\n"
+        "a=sctp-port:5000\r\n";
+}
+
+void testBundleOnlyDatachannelAnswer() {
+    RtcSession offer;
+    offer.loadFrom(makeBundleOnlyDatachannelOffer());
+    offer.checkValid();
+
+    expect(offer.media.size() == 1, "offer should contain a single application m-line");
+    expect(offer.media[0].bundle_only, "offer application m-line should preserve a=bundle-only");
+
+    SdpAttrFingerprint local_fingerprint;
+    local_fingerprint.algorithm = "sha-256";
+    local_fingerprint.hash =
+        "FF:EE:DD:CC:BB:AA:99:88:77:66:55:44:33:22:11:00:"
+        "FF:EE:DD:CC:BB:AA:99:88:77:66:55:44:33:22:11:00";
+
+    RtcConfigure configure;
+    configure.setDefaultSetting("localUfrag", "localPassword1234567890", RtpDirection::sendrecv, local_fingerprint);
+
+    auto answer = configure.createAnswer(offer);
+    expect(answer != nullptr, "createAnswer should return a session");
+    expect(answer->media.size() == 1, "answer should contain a single application m-line");
+
+#ifdef ENABLE_SCTP
+    answer->checkValid();
+    expect(answer->media[0].port == 9, "bundle-only application m-line should use port 9 in answer");
+    expect(answer->group.mids.size() == 1 && answer->group.mids[0] == "0",
+           "accepted bundle-only application m-line should remain in group:BUNDLE");
+#else
+    expect(answer->media[0].port == 0, "application m-line should stay rejected when SCTP is disabled");
+#endif
+}
+
+void testDeleteWebrtcLocationQueryRoundTrip() {
+    const string raw_id = "Ab+/9";
+    const string raw_token = "token+/9";
+
+    HttpArgs args;
+    args["id"] = raw_id;
+    args["token"] = raw_token;
+    auto query = args.make();
+
+    expect(query.find("id=Ab%2B%2F9") != string::npos, "id should be URL-encoded in delete_webrtc query");
+    expect(query.find("token=token%2B%2F9") != string::npos,
+           "token should be URL-encoded in delete_webrtc query");
+
+    auto parsed = Parser::parseArgs(query);
+    expect(strCoding::UrlDecodeComponent(parsed["id"]) == raw_id, "encoded id should round-trip through query parsing");
+    expect(strCoding::UrlDecodeComponent(parsed["token"]) == raw_token,
+           "encoded token should round-trip through query parsing");
+}
+
+} // namespace
+
+int main() {
+    try {
+        testBundleOnlyDatachannelAnswer();
+        testDeleteWebrtcLocationQueryRoundTrip();
+        cout << "test_webrtc_regression passed" << endl;
+        return 0;
+    } catch (const exception &ex) {
+        cerr << "test_webrtc_regression failed: " << ex.what() << endl;
+        return EXIT_FAILURE;
+    }
+}