native: Workaround for polling datagram sockets on z/OS

Polling datagram sockets on z/OS with an infinite timeout fails.

Use a timeout of 1s.

junixsocket-common/src/test/java/org/newsclub/net/unix/domain/ThroughputTest.java

@@ -17,9 +17,6 @@
  */
 package org.newsclub.net.unix.domain;
 
-import static org.junit.jupiter.api.Assumptions.assumeFalse;
-
-import org.junit.jupiter.api.Test;
 import org.newsclub.net.unix.AFSocketCapability;
 import org.newsclub.net.unix.AFSocketCapabilityRequirement;
 
@@ -37,20 +34,4 @@ public ThroughputTest() {
   protected String stbTestType() {
     return "AF_UNIX";
   }
-
-  @Override
-  @Test
-  public void testDatagramChannelNonBlocking() throws Exception {
-    assumeFalse("z/OS".equals(System.getProperty("os.name", "")),
-        "KNOWN ISSUE: Test may fail on z/OS");
-    super.testDatagramChannelNonBlocking();
-  }
-
-  @Override
-  @Test
-  public void testDatagramChannelNonBlockingDirect() throws Exception {
-    assumeFalse("z/OS".equals(System.getProperty("os.name", "")),
-        "KNOWN ISSUE: Test may fail on z/OS");
-    super.testDatagramChannelNonBlockingDirect();
-  }
 }

junixsocket-native/src/main/c/polling.c

@@ -380,6 +380,13 @@ JNIEXPORT jint JNICALL Java_org_newsclub_net_unix_NativeUnixSocket_poll
         }
 }
 
+#if __TOS_MVS__
+    if(timeout == -1) {
+        // polling on datagram sockets hangs if we don't set a short timeout on z/OS
+        timeout = 1000;
+    }
+#endif
+
 #if defined(_OS400)
     if(timeout == -1) {
         // unclear why, but a timeout of -1 returns EINVAL