From 49fe9592a47e7819179c2de4fd6068e897e944c7 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <eelco.dolstra@logicblox.com>
Date: Wed, 23 Jul 2014 19:21:00 +0200
Subject: nix-daemon: Use a thread instead of SIGPOLL to catch client
 disconnects

The thread calls poll() to wait until a HUP (or other error event)
happens on the client connection. If so, it sends SIGINT to the main
thread, which is then cleaned up normally. This is much nicer than
messing around with SIGPOLL.
---
 src/libutil/monitor-fd.hh | 43 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)
 create mode 100644 src/libutil/monitor-fd.hh

(limited to 'src/libutil/monitor-fd.hh')

diff --git a/src/libutil/monitor-fd.hh b/src/libutil/monitor-fd.hh
new file mode 100644
index 000000000000..d8db6508aede
--- /dev/null
+++ b/src/libutil/monitor-fd.hh
@@ -0,0 +1,43 @@
+#pragma once
+
+#include <thread>
+
+#include <poll.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <signal.h>
+
+namespace nix {
+
+
+class MonitorFdHup
+{
+private:
+    std::thread thread;
+
+public:
+    MonitorFdHup(int fd)
+    {
+        thread = std::thread([&]() {
+            /* Wait indefinitely until a POLLHUP occurs. */
+            struct pollfd fds[1];
+            fds[0].fd = fd;
+            fds[0].events = 0;
+            if (poll(fds, 1, -1) == -1) {
+                if (errno != EINTR) abort(); // can't happen
+                return; // destructor is asking us to exit
+            }
+            /* We got POLLHUP, so send an INT signal to the main thread. */
+            kill(getpid(), SIGINT);
+        });
+    };
+
+    ~MonitorFdHup()
+    {
+        pthread_kill(thread.native_handle(), SIGINT);
+        thread.join();
+    }
+};
+
+
+}
-- 
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