Autodetect if the remote nc command supports the -q option

Based on a patch by Marc Deslauriers <marc.deslauriers@ubuntu.com>

RH: https://bugzilla.redhat.com/show_bug.cgi?id=562176
Ubuntu: https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/517478
Debian: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=573172

src/rpc/virnetsocket.c

@@ -634,9 +634,29 @@ int virNetSocketNewConnectSSH(const char *nodename,
                              "-e", "none", NULL);
     if (noVerify)
         virCommandAddArgList(cmd, "-o", "StrictHostKeyChecking=no", NULL);
-    virCommandAddArgList(cmd, nodename,
-                         netcat ? netcat : "nc",
-                         "-U", path, NULL);
+
+    if (!netcat)
+        netcat = "nc";
+
+    virCommandAddArgList(cmd, nodename, "sh", "-c", NULL);
+    /*
+     * This ugly thing is a shell script to detect availability of
+     * the -q option for 'nc': debian and suse based distros need this
+     * flag to ensure the remote nc will exit on EOF, so it will go away
+     * when we close the connection tunnel. If it doesn't go away, subsequent
+     * connection attempts will hang.
+     *
+     * Fedora's 'nc' doesn't have this option, and defaults to the desired
+     * behavior.
+     */
+    virCommandAddArgFormat(cmd,
+         "'if %s -q 2>&1 | grep \"requires an argument\" >/dev/null 2>&1; then "
+             "ARG=-q0;"
+         "else "
+             "ARG=;"
+         "fi;"
+         "%s $ARG -U %s'",
+         netcat, netcat, path);
 
     return virNetSocketNewConnectCommand(cmd, retsock);
 }

tests/virnetsockettest.c

@@ -496,7 +496,12 @@ mymain(void)
     struct testSSHData sshData1 = {
         .nodename = "somehost",
         .path = "/tmp/socket",
-        .expectOut = "somehost nc -U /tmp/socket\n",
+        .expectOut = "somehost sh -c 'if nc -q 2>&1 | grep \"requires an argument\" >/dev/null 2>&1; then "
+                                         "ARG=-q0;"
+                                     "else "
+                                         "ARG=;"
+                                     "fi;"
+                                     "nc $ARG -U /tmp/socket'\n",
     };
     if (virtTestRun("SSH test 1", 1, testSocketSSH, &sshData1) < 0)
         ret = -1;
@@ -509,7 +514,13 @@ mymain(void)
         .noTTY = true,
         .noVerify = false,
         .path = "/tmp/socket",
-        .expectOut = "-p 9000 -l fred -T -o BatchMode=yes -e none somehost netcat -U /tmp/socket\n",
+        .expectOut = "-p 9000 -l fred -T -o BatchMode=yes -e none somehost sh -c '"
+                     "if netcat -q 2>&1 | grep \"requires an argument\" >/dev/null 2>&1; then "
+                         "ARG=-q0;"
+                     "else "
+                         "ARG=;"
+                     "fi;"
+                     "netcat $ARG -U /tmp/socket'\n",
     };
     if (virtTestRun("SSH test 2", 1, testSocketSSH, &sshData2) < 0)
         ret = -1;
@@ -522,7 +533,13 @@ mymain(void)
         .noTTY = false,
         .noVerify = true,
         .path = "/tmp/socket",
-        .expectOut = "-p 9000 -l fred -o StrictHostKeyChecking=no somehost netcat -U /tmp/socket\n",
+        .expectOut = "-p 9000 -l fred -o StrictHostKeyChecking=no somehost sh -c '"
+                     "if netcat -q 2>&1 | grep \"requires an argument\" >/dev/null 2>&1; then "
+                         "ARG=-q0;"
+                     "else "
+                         "ARG=;"
+                     "fi;"
+                     "netcat $ARG -U /tmp/socket'\n",
     };
     if (virtTestRun("SSH test 3", 1, testSocketSSH, &sshData3) < 0)
         ret = -1;
@@ -538,7 +555,13 @@ mymain(void)
     struct testSSHData sshData5 = {
         .nodename = "crashyhost",
         .path = "/tmp/socket",
-        .expectOut = "crashyhost nc -U /tmp/socket\n",
+        .expectOut = "crashyhost sh -c "
+                     "'if nc -q 2>&1 | grep \"requires an argument\" >/dev/null 2>&1; then "
+                         "ARG=-q0;"
+                     "else "
+                         "ARG=;"
+                     "fi;"
+                     "nc $ARG -U /tmp/socket'\n",
         .dieEarly = true,
     };
     if (virtTestRun("SSH test 5", 1, testSocketSSH, &sshData5) < 0)
@@ -549,7 +572,13 @@ mymain(void)
         .path = "/tmp/socket",
         .keyfile = "/root/.ssh/example_key",
         .noVerify = true,
-        .expectOut = "-i /root/.ssh/example_key -o StrictHostKeyChecking=no example.com nc -U /tmp/socket\n",
+        .expectOut = "-i /root/.ssh/example_key -o StrictHostKeyChecking=no example.com sh -c '"
+                     "if nc -q 2>&1 | grep \"requires an argument\" >/dev/null 2>&1; then "
+                         "ARG=-q0;"
+                     "else "
+                         "ARG=;"
+                     "fi;"
+                     "nc $ARG -U /tmp/socket'\n",
     };
     if (virtTestRun("SSH test 6", 1, testSocketSSH, &sshData6) < 0)
         ret = -1;