ccan/io: test read after hangup.

In particular, make sure that idle connections don't get closed.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

ccan/io/poll.c

@@ -31,8 +31,12 @@ static bool add_fd(struct fd *fd, short events)
 		max_fds = num;
 	}
 
-	pollfds[num_fds].fd = fd->fd;
 	pollfds[num_fds].events = events;
+	/* In case it's idle. */
+	if (!events)
+		pollfds[num_fds].fd = -fd->fd;
+	else
+		pollfds[num_fds].fd = fd->fd;
 	pollfds[num_fds].revents = 0; /* In case we're iterating now */
 	fds[num_fds] = fd;
 	fd->backend_info = num_fds;
@@ -91,8 +95,11 @@ void backend_plan_changed(struct io_conn *conn)
 		assert(!mask || pfd->events != mask);
 		pfd->events |= mask;
 	}
-	if (pfd->events)
+	if (pfd->events) {
 		num_waiting++;
+		pfd->fd = conn->fd.fd;
+	} else
+		pfd->fd = -conn->fd.fd;
 
 	if (!conn->plan.next)
 		num_closing++;

ccan/io/test/run-08-hangup-on-idle.c

+#include <ccan/io/io.h>
+/* Include the C files directly. */
+#include <ccan/io/poll.c>
+#include <ccan/io/io.c>
+#include <ccan/tap/tap.h>
+#include <sys/wait.h>
+#include <stdio.h>
+
+static int fds2[2];
+
+static struct io_plan timeout_wakeup(struct io_conn *conn, char *buf)
+{
+	/* This kills the dummy connection. */
+	close(fds2[1]);
+	return io_read(buf, 16, io_close, NULL);
+}
+
+int main(void)
+{
+	int fds[2];
+	struct io_conn *conn;
+	char buf[16];
+
+	plan_tests(4);
+
+	ok1(pipe(fds) == 0);
+
+	/* Write then close. */
+	io_new_conn(fds[1], io_write("hello there world", 16, io_close, NULL),
+		    NULL, NULL);
+	conn = io_new_conn(fds[0], io_idle(), NULL, NULL);
+
+	/* To avoid assert(num_waiting) */
+	ok1(pipe(fds2) == 0);
+	io_new_conn(fds2[0], io_read(buf, 16, io_close, NULL), NULL, NULL);
+
+	/* After half a second, it will read. */
+	io_timeout(conn, time_from_msec(500), timeout_wakeup, buf);
+
+	ok1(io_loop() == NULL);
+	ok1(memcmp(buf, "hello there world", 16) == 0);
+
+	/* This exits depending on whether all tests passed */
+	return exit_status();
+}

ccan/io/test/run-08-read-after-hangup.c

+#include <ccan/io/io.h>
+/* Include the C files directly. */
+#include <ccan/io/poll.c>
+#include <ccan/io/io.c>
+#include <ccan/tap/tap.h>
+#include <sys/wait.h>
+#include <stdio.h>
+#include <signal.h>
+
+static char inbuf[8];
+
+static struct io_plan wake_it(struct io_conn *conn, struct io_conn *reader)
+{
+	io_wake(reader, io_read(inbuf, 8, io_close, NULL));
+	return io_close(conn, NULL);
+}
+
+int main(void)
+{
+	int fds[2];
+	struct io_conn *conn;
+
+	plan_tests(3);
+
+	ok1(pipe(fds) == 0);
+	conn = io_new_conn(fds[0], io_idle(), NULL, NULL);
+	io_new_conn(fds[1], io_write("EASYTEST", 8, wake_it, conn),
+		    NULL, NULL);
+
+	ok1(io_loop() == NULL);
+	ok1(memcmp(inbuf, "EASYTEST", sizeof(inbuf)) == 0);
+
+	/* This exits depending on whether all tests passed */
+	return exit_status();
+}