From 350ce06f549d0ab483f6b492a5b37c2c380890ad Mon Sep 17 00:00:00 2001
From: Razvan Becheriu <razvan@isc.org>
Date: Sat, 1 Nov 2025 22:57:58 +0200
Subject: [PATCH] [#4141] addressed review comments

---
 .../util/tests/fd_event_handler_unittests.h   | 133 +++++++++++++++++-
 1 file changed, 131 insertions(+), 2 deletions(-)

diff --git a/src/lib/util/tests/fd_event_handler_unittests.h b/src/lib/util/tests/fd_event_handler_unittests.h
index 04e2ad8854..3084ebc6f5 100644
--- a/src/lib/util/tests/fd_event_handler_unittests.h
+++ b/src/lib/util/tests/fd_event_handler_unittests.h
@@ -14,7 +14,9 @@
 
 #include <thread>
 
+#include <fcntl.h>
 #include <signal.h>
+#include <sys/ioctl.h>
 
 using namespace isc;
 using namespace isc::util;
@@ -55,8 +57,8 @@ TEST_F(FDEventHandlerTest, events) {
 
     EXPECT_THROW(handler_->add(-1), BadValue);
 
-    handler_->add(pipefd[0], true, false);
-    handler_->add(pipefd[1], false, true);
+    EXPECT_NO_THROW(handler_->add(pipefd[0], true, false));
+    EXPECT_NO_THROW(handler_->add(pipefd[1], false, true));
 
     EXPECT_FALSE(handler_->readReady(pipefd[0]));
     EXPECT_FALSE(handler_->writeReady(pipefd[0]));
@@ -139,4 +141,131 @@ TEST_F(FDEventHandlerTest, events) {
     sigaction(SIGINT, &original, NULL);
 }
 
+TEST_F(FDEventHandlerTest, badFD) {
+    int fd = open("/dev/zero", O_RDONLY, 0);
+
+    ASSERT_GE(fd, 0);
+
+    EXPECT_NO_THROW(handler_->add(fd));
+
+    EXPECT_EQ(1, handler_->waitEvent(0, 1000));
+
+    EXPECT_TRUE(handler_->readReady(fd));
+
+    close(fd);
+
+    int len = 0;
+    int result = ioctl(fd, FIONREAD, &len);
+
+    EXPECT_EQ(-1, result);
+
+    EXPECT_EQ(0, len);
+
+    EXPECT_EQ(EBADF, errno);
+
+    errno = 0;
+
+    EXPECT_EQ(-1, handler_->waitEvent(0, 1000));
+
+    EXPECT_EQ(EBADF, errno);
+
+    EXPECT_TRUE(handler_->readReady(fd));
+
+    EXPECT_NO_THROW(handler_->clear());
+    errno = 0;
+
+    {
+        EXPECT_NO_THROW(handler_->add(pipefd[0], true, false));
+
+        std::thread tr([this]() {
+            usleep(500);
+            close(pipefd[1]);
+        });
+
+        EXPECT_EQ(1, handler_->waitEvent(1, 0));
+
+        EXPECT_EQ(0, errno);
+
+        EXPECT_TRUE(handler_->readReady(pipefd[0]));
+        EXPECT_FALSE(handler_->writeReady(pipefd[0]));
+
+        tr.join();
+
+        close(pipefd[0]);
+        pipe(pipefd);
+    }
+
+    EXPECT_NO_THROW(handler_->clear());
+    errno = 0;
+
+    {
+        EXPECT_NO_THROW(handler_->add(pipefd[0], true, false));
+
+        std::thread tr([this]() {
+            usleep(500);
+            close(pipefd[0]);
+        });
+
+        EXPECT_EQ(1, handler_->waitEvent(1, 0));
+
+        EXPECT_EQ(0, errno);
+
+        EXPECT_TRUE(handler_->readReady(pipefd[0]));
+        EXPECT_FALSE(handler_->writeReady(pipefd[0]));
+
+        tr.join();
+
+        close(pipefd[1]);
+        pipe(pipefd);
+    }
+
+    EXPECT_NO_THROW(handler_->clear());
+    errno = 0;
+
+    {
+        EXPECT_NO_THROW(handler_->add(pipefd[1], true, false));
+
+        std::thread tr([this]() {
+            usleep(500);
+            close(pipefd[1]);
+        });
+
+        EXPECT_EQ(1, handler_->waitEvent(1, 0));
+
+        EXPECT_EQ(0, errno);
+
+        EXPECT_TRUE(handler_->readReady(pipefd[1]));
+        EXPECT_FALSE(handler_->writeReady(pipefd[1]));
+
+        tr.join();
+
+        close(pipefd[0]);
+        pipe(pipefd);
+    }
+
+    EXPECT_NO_THROW(handler_->clear());
+    errno = 0;
+
+    {
+        EXPECT_NO_THROW(handler_->add(pipefd[1], true, false));
+
+        std::thread tr([this]() {
+            usleep(500);
+            close(pipefd[0]);
+        });
+
+        EXPECT_EQ(1, handler_->waitEvent(1, 0));
+
+        EXPECT_EQ(0, errno);
+
+        EXPECT_TRUE(handler_->readReady(pipefd[1]));
+        EXPECT_FALSE(handler_->writeReady(pipefd[1]));
+
+        tr.join();
+
+        close(pipefd[1]);
+        pipe(pipefd);
+    }
+}
+
 } // end of anonymous namespace
-- 
2.47.3