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wslrelay KD: stay open after first disconnect #13441

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wslrelay KD: stay open after first disconnect #13441

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wslrelay KD: stay open after first disconnect
asweet-confluent Sep 1, 2025
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asweet-confluent Sep 3, 2025
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37 changes: 28 additions & 9 deletions src/windows/wslrelay/main.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -101,7 +101,7 @@ try
// Ensure that the other end of the pipe has connected.
wsl::windows::common::helpers::ConnectPipe(pipe.get(), (15 * 1000), {exitEvent.get()});

// Bind, listen, and accept a connection on the specified port.
// Bind and listen on the specified port (once)
const wil::unique_socket listenSocket(WSASocket(AF_INET, SOCK_STREAM, IPPROTO_TCP, nullptr, 0, WSA_FLAG_OVERLAPPED));
THROW_LAST_ERROR_IF(!listenSocket);

Expand All @@ -113,14 +113,33 @@ try

THROW_LAST_ERROR_IF(listen(listenSocket.get(), 1) == SOCKET_ERROR);

const wil::unique_socket socket(WSASocket(AF_INET, SOCK_STREAM, IPPROTO_TCP, nullptr, 0, WSA_FLAG_OVERLAPPED));
THROW_LAST_ERROR_IF(!socket);

wsl::windows::common::socket::Accept(listenSocket.get(), socket.get(), INFINITE, exitEvent.get());

// Begin the relay.
wsl::windows::common::relay::BidirectionalRelay(
reinterpret_cast<HANDLE>(socket.get()), pipe.get(), 0x1000, wsl::windows::common::relay::RelayFlags::LeftIsSocket);
for (;;)
{
if (exitEvent && WaitForSingleObject(exitEvent.get(), 0) == WAIT_OBJECT_0)
{
break;
}

const wil::unique_socket socket(WSASocket(AF_INET, SOCK_STREAM, IPPROTO_TCP, nullptr, 0, WSA_FLAG_OVERLAPPED));
THROW_LAST_ERROR_IF(!socket);

try
{
wsl::windows::common::socket::Accept(listenSocket.get(), socket.get(), INFINITE, exitEvent.get());

// Begin the relay for this connection
wsl::windows::common::relay::BidirectionalRelay(
reinterpret_cast<HANDLE>(socket.get()), pipe.get(), 0x1000,
wsl::windows::common::relay::RelayFlags::LeftIsSocket);
}
catch (...)
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Copilot AI Sep 1, 2025

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The catch-all exception handler may mask specific error conditions that should cause the relay to exit (e.g., pipe closure, critical system errors). Consider catching specific exceptions or checking for terminal error conditions.

Suggested change
catch (...)
catch (const wil::ResultException& ex)

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{
LOG_CAUGHT_EXCEPTION();

// Small delay to prevent tight loop on persistent errors
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@benhillis benhillis Sep 3, 2025

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What kind of persistent errors were you seeing?

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@asweet-confluent asweet-confluent Sep 3, 2025

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Oh, I didn't see any errors... Copilot added that and I figured it knew something I didn't. I can remove the sleep if you think it isn't needed.

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@benhillis benhillis Sep 4, 2025

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Yes I'd suggest removing this try / catch entirely.

Sleep(100);
Comment on lines +135 to +136
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Copilot AI Sep 1, 2025

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The fixed 100ms delay may be too aggressive for rapid reconnections in kernel debugging scenarios. Consider implementing exponential backoff or making the delay configurable to balance between responsiveness and resource usage.

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}
}

break;
}
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