Assert SEND_PROXY_VALUE echoed; fix agent so proxy headers are honored

- When SEND_PROXY_HEADER and SEND_PROXY_VALUE are set and we check the same
  header, test now requires the proxy response value to equal SEND_PROXY_VALUE.
- ProxyHeadersAgent: stop returning proxySocket from createConnection so the
  agent uses only the callback stream (tlsSocket). Returning the raw socket let
  the agent write the request before CONNECT completed, so the proxy sometimes
  ignored our X-ProxyMesh-IP and assigned a different IP.
- utils.buildConnectRequest: support proxyHeaders as Map for consistency.

Made-with: Cursor

Author: proxymeshai

lib/core/proxy-headers-agent.js

@@ -94,7 +94,6 @@ export class ProxyHeadersAgent extends Agent {
                 this.proxyAuth,
                 this.proxyHeaders
             );
-
             proxySocket.write(connectRequest);
         });
 
@@ -153,7 +152,8 @@ export class ProxyHeadersAgent extends Agent {
             });
         });
 
-        return proxySocket;
+        // Do not return proxySocket - the agent must use the stream from the callback
+        // (tlsSocket) so the CONNECT handshake completes before any request is written.
     }
 }
 

lib/core/utils.js

@@ -56,7 +56,10 @@ export function buildConnectRequest(targetHost, targetPort, proxyAuth, proxyHead
         lines.push(`Proxy-Authorization: Basic ${proxyAuth}`);
     }
 
-    for (const [key, value] of Object.entries(proxyHeaders)) {
+    const entries = proxyHeaders instanceof Map
+        ? [...proxyHeaders.entries()]
+        : Object.entries(proxyHeaders || {});
+    for (const [key, value] of entries) {
         lines.push(`${key}: ${value}`);
     }
 

test/test_proxy_headers.js

@@ -128,6 +128,20 @@ function checkHeader(headers, headerName) {
     return null;
 }
 
+/**
+ * When SEND_PROXY_HEADER and SEND_PROXY_VALUE are set and we're checking the same header,
+ * the proxy response must echo that value (e.g. X-ProxyMesh-IP).
+ * @returns {string|null} Error message if expectation not met, null if OK or N/A.
+ */
+function validateSentHeaderValue(config, headerValue) {
+    if (!config.sendProxyHeader || !config.sendProxyValue) return null;
+    if (config.proxyHeader.toLowerCase() !== config.sendProxyHeader.toLowerCase()) return null;
+    const expected = String(config.sendProxyValue).trim();
+    const actual = headerValue ? String(headerValue).trim() : '';
+    if (actual === expected) return null;
+    return `Expected ${config.proxyHeader} to equal ${expected} (sent in request) but got ${actual}`;
+}
+
 const AVAILABLE_TESTS = {
     async core(config) {
         try {
@@ -159,7 +173,10 @@ const AVAILABLE_TESTS = {
                             ? checkHeader(capturedHeaders, config.proxyHeader)
                             : null;
 
-                        if (headerValue) {
+                        const sentErr = validateSentHeaderValue(config, headerValue);
+                        if (sentErr) {
+                            resolve(new TestResult('core', false, null, sentErr, res.statusCode));
+                        } else if (headerValue) {
                             resolve(new TestResult('core', true, headerValue, null, res.statusCode));
                         } else {
                             resolve(new TestResult('core', false, null,
@@ -194,6 +211,8 @@ const AVAILABLE_TESTS = {
             });
             const headerValue = checkHeader(response.headers, config.proxyHeader);
 
+            const sentErr = validateSentHeaderValue(config, headerValue);
+            if (sentErr) return new TestResult('axios', false, null, sentErr);
             if (headerValue) {
                 return new TestResult('axios', true, headerValue, null, response.status);
             }
@@ -216,6 +235,8 @@ const AVAILABLE_TESTS = {
 
             const headerValue = checkHeader(response.proxyHeaders, config.proxyHeader);
 
+            const sentErr = validateSentHeaderValue(config, headerValue);
+            if (sentErr) return new TestResult('node-fetch', false, null, sentErr);
             if (headerValue) {
                 return new TestResult('node-fetch', true, headerValue, null, response.status);
             }
@@ -240,6 +261,8 @@ const AVAILABLE_TESTS = {
             const response = await client(config.testUrl);
             const headerValue = checkHeader(response.headers, config.proxyHeader);
 
+            const sentErr = validateSentHeaderValue(config, headerValue);
+            if (sentErr) return new TestResult('got', false, null, sentErr);
             if (headerValue) {
                 return new TestResult('got', true, headerValue, null, response.statusCode);
             }
@@ -262,6 +285,8 @@ const AVAILABLE_TESTS = {
 
             const headerValue = checkHeader(proxyHeaders, config.proxyHeader);
 
+            const sentErr = validateSentHeaderValue(config, headerValue);
+            if (sentErr) return new TestResult('undici', false, null, sentErr);
             if (headerValue) {
                 return new TestResult('undici', true, headerValue, null, statusCode);
             }
@@ -285,6 +310,8 @@ const AVAILABLE_TESTS = {
             const response = await client.get(config.testUrl).ok(() => true);
             const headerValue = checkHeader(response.headers, config.proxyHeader);
 
+            const sentErr = validateSentHeaderValue(config, headerValue);
+            if (sentErr) return new TestResult('superagent', false, null, sentErr);
             if (headerValue) {
                 return new TestResult('superagent', true, headerValue, null, response.status);
             }