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Keep listening after a failed accept() in ListenConnections #310

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Keep listening after a failed accept() in ListenConnections #310

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6 changes: 6 additions & 0 deletions include/mp/proxy-io.h
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Original file line number Diff line number Diff line change
Expand Up @@ -905,6 +905,12 @@ void _Listen(const std::shared_ptr<Listener>& listener, EventLoop& loop, InitImp
if (resume_accept) _Listen<InitInterface>(listener, loop, init);
});
_Listen<InitInterface>(listener, loop, init);
},
// Keep listening if a single accept() fails, so the server does not
// stop accepting future connections.
[&loop, &init, listener](const kj::Exception& e) {
MP_LOG(loop, Log::Warning) << "IPC server: accept failed:" << kj::str(e).cStr();
_Listen<InitInterface>(listener, loop, init);
}));
}

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15 changes: 15 additions & 0 deletions test/mp/test/listen_tests.cpp
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Expand Up @@ -289,6 +289,21 @@ KJ_TEST("ListenConnections accepts multiple connections")
KJ_EXPECT(client3->client->add(3, 4) == 7);
}

KJ_TEST("ListenConnections survives a client that disconnects before being accepted")
{
ListenSetup server;

// Connect and close before the server has a chance to accept() the
// connection.
int fd = server.listener.MakeConnectedSocket();
close(fd);

@ryanofsky ryanofsky Jul 17, 2026

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In commit "Keep listening after a failed accept in ListenConnections" (38391eb)

Can this be checked with KJ_SYSCALL?

@ryanofsky ryanofsky Jul 17, 2026

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In commit "Keep listening after a failed accept in ListenConnections" (d8e5395)

Would be good to add a comment here that this close is a little racy, if the socket not closed before accepted the test could appear to crash when there is still a problem.


// The server should still accept and serve later clients.
auto client = std::make_unique<ClientSetup>(server.listener.MakeConnectedSocket());
server.WaitForConnectedCount(1);
KJ_EXPECT(client->client->add(1, 2) == 3);
}

} // namespace
} // namespace test
} // namespace mp
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