LibCore: Allow listening for socket errors and hang-ups

Author: https://github.com/DanShaders
Commit: 506707cc2b
Pull-request: https://github.com/SerenityOS/serenity/pull/23046
Reviewed-by: https://github.com/ADKaster

Userland/Libraries/LibCore/Event.h

@@ -83,6 +83,8 @@ enum class NotificationType {
     None = 0,
     Read = 1,
     Write = 2,
+    HangUp = 4,
+    Error = 8,
 };
 
 AK_ENUM_BITWISE_OPERATORS(NotificationType);

Userland/Libraries/LibCore/EventLoopImplementationUnix.cpp

@@ -267,6 +267,10 @@ try_select_again:
             type |= NotificationType::Read;
         if (has_flag(revents, POLLOUT))
             type |= NotificationType::Write;
+        if (has_flag(revents, POLLHUP))
+            type |= NotificationType::HangUp;
+        if (has_flag(revents, POLLERR))
+            type |= NotificationType::Error;
         type &= notifier.type();
         if (type != NotificationType::None)
             ThreadEventQueue::current().post_event(notifier, make<NotifierActivationEvent>(notifier.fd(), type));