ip: punt socket - take the tags in Ethernet header into consideration

The punt socket code rewinds the current_data pointer by sizeof (ethernet_header_t),
which is incorrect if the header is tagged - resulting in truncated destination MAC
address. Use ethernet_buffer_header_size() instead, which takes tags into account.

Also add the unittest that verifies the issue and the fix.

Type: fix
Change-Id: I6352a174df144ca1e4230390c126f4b698724ebc
Signed-off-by: Andrew Yourtchenko <ayourtch@gmail.com>

src/vnet/ip/punt_node.c

@@ -23,6 +23,7 @@
  */
 
 #include <vnet/ip/ip.h>
+#include <vnet/ethernet/ethernet.h>
 #include <vlib/vlib.h>
 #include <vnet/ip/punt.h>
 #include <vlib/unix/unix.h>
@@ -339,7 +340,7 @@ punt_socket_inline (vlib_main_t * vm,
       iov->iov_len = sizeof (packetdesc);
 
       /** VLIB buffer chain -> Unix iovec(s). */
-      vlib_buffer_advance (b, -(sizeof (ethernet_header_t)));
+      vlib_buffer_advance (b, -ethernet_buffer_header_size (b));
       vec_add2 (ptd->iovecs, iov, 1);
       iov->iov_base = b->data + b->current_data;
       iov->iov_len = l = b->current_length;

test/test_punt.py

@@ -21,6 +21,7 @@ from re import compile
 import scapy.compat
 from scapy.packet import Raw
 from scapy.layers.l2 import Ether
+from scapy.layers.l2 import Dot1Q
 from scapy.layers.inet import IP, UDP, ICMP
 from scapy.layers.ipsec import ESP
 import scapy.layers.inet6 as inet6
@@ -28,6 +29,7 @@ from scapy.layers.inet6 import IPv6, ICMPv6DestUnreach
 from scapy.contrib.ospf import OSPF_Hdr, OSPFv3_Hello
 from framework import tag_fixme_vpp_workers
 from framework import VppTestCase, VppTestRunner
+from vpp_sub_interface import VppSubInterface, VppDot1QSubint
 
 from vpp_ip import DpoProto
 from vpp_ip_route import VppIpRoute, VppRoutePath
@@ -1015,6 +1017,86 @@ class TestIpProtoPuntSocket(TestPuntSocket):
         self.vapi.punt_socket_deregister(punt_ospf)
 
 
+class TestDot1QPuntSocket(TestPuntSocket):
+    """Punt Socket for 802.1Q (dot1q)"""
+
+    def setUp(self):
+        super(TestDot1QPuntSocket, self).setUp()
+
+        for i in self.pg_interfaces:
+            i.admin_up()
+            i.config_ip4()
+            i.resolve_arp()
+
+    def tearDown(self):
+        super(TestDot1QPuntSocket, self).tearDown()
+        for i in self.pg_interfaces:
+            i.unconfig_ip4()
+            i.admin_down()
+
+    def test_dot1q_header_punt(self):
+        """Punt socket traffic with Dot1q header"""
+
+        port = self.ports[0]
+        pt_l4 = VppEnum.vl_api_punt_type_t.PUNT_API_TYPE_L4
+        punt_l4 = set_port(mk_vpp_cfg4(), port)
+
+        # VLAN ID
+        vlan_id = 100
+
+        # Create a subinterface with the VLAN ID
+        subif = VppDot1QSubint(self, self.pg0, vlan_id)
+        subif.admin_up()
+        subif.config_ip4()
+
+        # Configure an IP address on the subinterface
+        subif_ip4 = subif.local_ip4
+
+        p = (
+            Ether(src=self.pg0.remote_mac, dst=self.pg0.local_mac)
+            / Dot1Q(vlan=vlan_id)
+            / IP(src=self.pg0.remote_ip4, dst=subif_ip4)
+            / UDP(sport=9876, dport=port)
+            / Raw(b"\xa5" * 100)
+        )
+
+        pkts = p * self.nr_packets
+
+        # Expect ICMP - port unreachable for all packets
+        rx = self.send_and_expect_some(self.pg0, pkts, self.pg0)
+
+        for p in rx:
+            self.assertEqual(int(p[IP].proto), 1)  # ICMP
+            self.assertEqual(int(p[ICMP].code), 3)  # unreachable
+
+        # Configure a punt socket
+        self.socket_client_create("%s/socket_%d" % (self.tempdir, port))
+        self.vapi.punt_socket_register(punt_l4, "%s/socket_%d" % (self.tempdir, port))
+        punts = self.vapi.punt_socket_dump(type=pt_l4)
+        self.assertEqual(len(punts), 1)
+
+        # Expect punt socket and no packets on pg0
+        self.send_and_assert_no_replies(self.pg0, pkts)
+        rx = self.socket_client_close()
+        self.logger.info("RXPKT")
+        self.logger.info(rx)
+        self.verify_udp_pkts(rx, len(pkts), port)
+        for pkt in rx:
+            self.assertEqual(pkt[Ether].src, self.pg0.remote_mac)
+            self.assertEqual(pkt[Ether].dst, self.pg0.local_mac)
+            self.assertEqual(pkt[Dot1Q].vlan, 100)
+
+        # Remove punt socket. Expect ICMP - port unreachable for all packets
+        self.vapi.punt_socket_deregister(punt_l4)
+        punts = self.vapi.punt_socket_dump(type=pt_l4)
+        self.assertEqual(len(punts), 0)
+
+        rx = self.send_and_expect_some(self.pg0, pkts, self.pg0)
+        for p in rx:
+            self.assertEqual(int(p[IP].proto), 1)  # ICMP
+            self.assertEqual(int(p[ICMP].code), 3)  # unreachable
+
+
 @tag_fixme_vpp_workers
 class TestPunt(VppTestCase):
     """Exception Punt Test Case"""