fix(desktop): handle proxy response resets (#1050, #1056)

desktop/electron/services/systemProxyBridge.test.ts

@@ -83,6 +83,28 @@ describe('SystemProxyBridge', () => {
       .toBe('request-fallback')
   })
 
+  it('terminates the downstream response when a selected proxy resets after sending headers', async () => {
+    const resettingProxy = net.createServer(socket => {
+      socket.once('data', () => {
+        socket.write(
+          'HTTP/1.1 200 OK\r\nContent-Length: 100\r\nConnection: close\r\n\r\npartial',
+          () => setTimeout(() => socket.resetAndDestroy(), 25),
+        )
+      })
+    })
+    servers.push(resettingProxy)
+    const resettingPort = await listen(resettingProxy)
+    const bridge = await startBridge(async () => `PROXY 127.0.0.1:${resettingPort}`)
+
+    const outcome = await Promise.race([
+      requestOutcomeThroughProxy(bridge, 'http://foreign.example/after-reset'),
+      new Promise<'timed-out'>(resolve => setTimeout(() => resolve('timed-out'), 500)),
+    ])
+
+    expect(outcome).not.toBe('timed-out')
+    expect(outcome).not.toBe('end')
+  })
+
   it('does not replay a non-idempotent request after its selected proxy drops it', async () => {
     let firstProxyRequests = 0
     const droppingProxy = net.createServer(socket => {
@@ -314,6 +336,28 @@ function requestThroughProxy(
   })
 }
 
+function requestOutcomeThroughProxy(
+  proxyUrl: string,
+  targetUrl: string,
+): Promise<'aborted' | 'response-error' | 'request-error' | 'end'> {
+  const proxy = new URL(proxyUrl)
+  return new Promise(resolve => {
+    const request = http.request({
+      host: proxy.hostname,
+      port: Number(proxy.port),
+      path: targetUrl,
+      headers: { Host: new URL(targetUrl).host },
+    }, response => {
+      response.resume()
+      response.once('aborted', () => resolve('aborted'))
+      response.once('error', () => resolve('response-error'))
+      response.once('end', () => resolve('end'))
+    })
+    request.once('error', () => resolve('request-error'))
+    request.end()
+  })
+}
+
 function connectAndEcho(
   proxyUrl: string,
   authority: string,

desktop/electron/services/systemProxyBridge.ts

@@ -4,6 +4,7 @@ import net from 'node:net'
 import tls from 'node:tls'
 import { lookup } from 'node:dns/promises'
 import type { Duplex } from 'node:stream'
+import { pipeline } from 'node:stream/promises'
 
 export const SYSTEM_PROXY_BRIDGE_HOST = '127.0.0.1'
 const CONNECT_TIMEOUT_MS = 10_000
@@ -163,9 +164,13 @@ export class SystemProxyBridge implements SystemProxyBridgeLike {
             onSocket,
           )
       response.writeHead(upstreamResponse.statusCode ?? 502, upstreamResponse.statusMessage, upstreamResponse.headers)
-      upstreamResponse.pipe(response)
+      await pipeline(upstreamResponse, response)
     } catch (error) {
-      if (!response.headersSent) response.writeHead(502, { Connection: 'close' })
+      if (response.headersSent) {
+        response.destroy()
+        return
+      }
+      response.writeHead(502, { Connection: 'close' })
       response.end(`System proxy bridge failed: ${error instanceof Error ? error.message : String(error)}`)
     }
   }