netinet tests: test carp source MAC address

Ensure that (multicast) CARP packets are sent with the expected source
MAC address.

Reviewed by:	melifaro
Sponsored by:	Rubicon Communications, LLC ("Netgate")
Differential Revision:	https://reviews.freebsd.org/D39454

tests/sys/netinet/Makefile

@@ -24,6 +24,8 @@ ATF_TESTS_SH=	arp \
 		output \
 		redirect
 
+ATF_TESTS_PYTEST+=	carp.py
+
 TEST_METADATA.divert+=	required_programs="python"
 TEST_METADATA.forward+=	required_programs="python"
 TEST_METADATA.output+=	required_programs="python"

tests/sys/netinet/carp.py

@@ -0,0 +1,53 @@
+import pytest
+from atf_python.sys.net.tools import ToolsHelper
+from atf_python.sys.net.vnet import VnetTestTemplate
+
+sc = None
+
+
+def filter_f(x):
+    ip = x.getlayer(sc.IP)
+    if not ip:
+        return False
+
+    return ip.proto == 112
+
+
+class TestCarp(VnetTestTemplate):
+    REQUIRED_MODULES = ["carp"]
+    TOPOLOGY = {
+        "vnet1": {"ifaces": ["if1"]},
+        "if1": {"prefixes4": [("192.0.2.1/24", "192.0.2.2/24")]},
+    }
+
+    def setup_method(self, method):
+        global sc
+        if sc is None:
+            import scapy.all as _sc
+
+            sc = _sc
+        super().setup_method(method)
+
+    @classmethod
+    def check_carp_src_mac(self, pkts):
+        for p in pkts:
+            if not filter_f(p):
+                continue
+
+            print("Packet src mac {}".format(p.src))
+
+            if p.src != "00:00:5e:00:01:01":
+                raise
+
+    def test_source_mac(self):
+        "Test carp packets source address"
+
+        if1 = self.vnet.iface_alias_map["if1"]
+
+        ToolsHelper.print_output(
+            "ifconfig {} add vhid 1 192.0.2.203/24".format(if1.name)
+        )
+
+        carp_pkts = sc.sniff(iface=if1.name, stop_filter=filter_f, timeout=5)
+
+        self.check_carp_src_mac(carp_pkts)