netinet tests: ensure we send IGMPv2 messages if net.inet.igmp.default_version=2

Sponsored by:	Rubicon Communications, LLC ("Netgate")
Differential Revision:	https://reviews.freebsd.org/D50072

tests/sys/netinet/igmp.py

@@ -62,6 +62,25 @@ def check_igmpv3(args, pkt):
 
     return True
 
+def check_igmpv2(args, pkt):
+    pkt.show()
+
+    igmp = pkt.getlayer(sc.igmp.IGMP)
+    if igmp is None:
+        return False
+
+    if igmp.gaddr != args["group"]:
+        return False
+
+    if args["type"] == "join":
+        if igmp.type != 0x16:
+            return False
+    if args["type"] == "leave":
+        if igmp.type != 0x17:
+            return False
+
+    return True
+
 class TestIGMP(VnetTestTemplate):
     REQUIRED_MODULES = []
     TOPOLOGY = {
@@ -82,7 +101,7 @@ class TestIGMP(VnetTestTemplate):
 
     @pytest.mark.require_progs(["scapy"])
     def test_igmp3_join_leave(self):
-        "Test that we send the expected join/leave IGMPv2 messages"
+        "Test that we send the expected join/leave IGMPv3 messages"
 
         if1 = self.vnet.iface_alias_map["if1"]
 
@@ -107,3 +126,32 @@ class TestIGMP(VnetTestTemplate):
         s.close()
         sniffer.join()
         assert(sniffer.correctPackets > 0)
+
+    @pytest.mark.require_progs(["scapy"])
+    def test_igmp2_join_leave(self):
+        "Test that we send the expected join/leave IGMPv2 messages"
+        ToolsHelper.print_output("/sbin/sysctl net.inet.igmp.default_version=2")
+
+        if1 = self.vnet.iface_alias_map["if1"]
+
+        # Start a background sniff
+        from sniffer import Sniffer
+        expected_pkt = { "type": "join", "group": "230.0.0.1" }
+        sniffer = Sniffer(expected_pkt, check_igmpv2, if1.name, timeout=10)
+
+        # Now join a multicast group, and see if we're getting the igmp packet we expect
+        s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP)
+        mreq = struct.pack("4sl", socket.inet_aton('230.0.0.1'), socket.INADDR_ANY)
+        s.setsockopt(socket.IPPROTO_IP, socket.IP_ADD_MEMBERSHIP, mreq)
+
+        # Wait for the sniffer to see the join packet
+        sniffer.join()
+        assert(sniffer.correctPackets > 0)
+
+        # Now leave, check for the packet
+        expected_pkt = { "type": "leave", "group": "230.0.0.1" }
+        sniffer = Sniffer(expected_pkt, check_igmpv2, if1.name)
+
+        s.close()
+        sniffer.join()
+        assert(sniffer.correctPackets > 0)