router: initial commit

Change-Id: Ief5544e58f002e8d33b72dd87295c29f93345d37
Signed-off-by: Jeff Shaw <jeffrey.b.shaw@intel.com>

7 files changed, 932 insertions, 0 deletions

diff --git a/router/.gitignore b/router/.gitignore
new file mode 100644
index 0000000..28c6672
--- /dev/null
+++ b/router/.gitignore
@@ -0,0 +1,11 @@
+Makefile.in
+aclocal.m4
+autom4te.cache
+compile
+config.guess
+config.sub
+configure
+depcomp
+install-sh
+ltmain.sh
+missing
diff --git a/router/LICENSE b/router/LICENSE
new file mode 100644
index 0000000..7a4a3ea
--- /dev/null
+++ b/router/LICENSE
@@ -0,0 +1,202 @@
+
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\ No newline at end of file
diff --git a/router/Makefile.am b/router/Makefile.am
new file mode 100644
index 0000000..2e9b38f
--- /dev/null
+++ b/router/Makefile.am
@@ -0,0 +1,14 @@
+AUTOMAKE_OPTIONS = foreign subdir-objects
+
+AM_CFLAGS = -Wall -I@TOOLKIT_INCLUDE@
+
+lib_LTLIBRARIES = router.la
+router_la_SOURCES = router/router.c
+router_la_LDFLAGS = -module
+router_la_LIBADD = -lrtnl
+
+if WITH_PLUGIN_TOOLKIT
+install-data-hook:
+	mkdir /usr/lib/vpp_plugins || true
+	cp $(prefix)/lib/router.so.*.*.* /usr/lib/vpp_plugins
+endif
diff --git a/router/README.md b/router/README.md
new file mode 100644
index 0000000..5796b83
--- /dev/null
+++ b/router/README.md
@@ -0,0 +1,74 @@
+# A plugin to help accelerate IPv4 routing
+
+This repository provides a plugin to hook up data plane interfaces, via
+tap interfaces, to a host operating system. The host operating system
+can run a route daemon referencing the tap interface(s) as if they were
+the data plane interfaces. IPv4 packet forwarding decisions are taken
+in the data path, while control traffic is sent to and handled by the host.
+
+More information can be found on the wiki page:
+- http://wiki.fd.io/view/VPP_Sandbox/router
+
+## Build/Install
+
+The router is implemented as a plugin to inject, e.g. arp, icmp4, traffic
+from data plane devices. To use it, you must build the plugin and put it
+in VPPs runtime plugin directory. The plugin depends on vpp and the netlink
+repository from the vppsb project. This README assumes familiarity with the
+build environment for both projects.
+
+Build vpp, netlink, and router all at once by creating symbolic links in the
+top level vpp directory to the netlink and router directories as well as
+symbolic links to the respective .mk files in 'build-data/packages'.
+
+```
+$ cd /git/vpp
+$ ln -sf /git/vppsb/netlink
+$ ln -sf /git/vppsb/router
+$ ln -sf ../../netlink/netlink.mk build-data/packages/
+$ ln -sf ../../router/router.mk build-data/packages/
+```
+
+Now build everything and create a link to the plugin in vpp's plugin path.
+
+```
+$ cd build-root
+$ ./bootstrap.sh
+$ make V=0 PLATFORM=vpp TAG=vpp_debug router-install
+$ ln -sf /git/vpp/build-root/install-vpp_debug-native/router/lib64/router.so.0.0.0 \
+         /usr/lib/vpp_plugins/
+```
+
+NOTE: The 'make' command above may fail twice when building netlink. If an
+error occurs, retry the make command two more times.
+
+Once VPP is running and the plugin is loaded, data plane interfaces can
+be tapped.
+
+```
+$ vppctl tap inject arp,icmp4 from TenGigabitEthernet2/0/0 as vpp0
+```
+
+The host operating system should see a tap named 'vpp0' with the same hardware
+address as 'TenGigabitEthernet2/0/0'. Adding an IPv4 interface address to 'vpp0'
+should cause the address to be added to the data plane interface as well. If
+the address is a network address, a route should be added to the data
+plane's default fib.
+
+## Administrative
+
+### Current status
+
+Currently the router plugin handles ARP, locally destined ICMPv4 and OSPF
+traffic. It supports the classifier directing packets from an ip4-table to
+the 'tap-inject-classified' node (for handling multicast OSPF and IGMP).
+
+### Objective
+
+The objective of this project is to continue to build out better integration
+with host operating system and for providing a basis to enable completely
+or partially unmodified applications to take advantage of a fast datapath.
+
+### Main contributors
+
+Jeff Shaw - LF-ID:jbshaw
diff --git a/router/configure.ac b/router/configure.ac
new file mode 100644
index 0000000..940558e
--- /dev/null
+++ b/router/configure.ac
@@ -0,0 +1,18 @@
+AC_INIT(router, 1.0)
+LT_INIT
+AM_INIT_AUTOMAKE
+
+AM_PROG_AS
+AC_PROG_CC
+AM_PROG_CC_C_O
+
+AC_ARG_WITH(plugin-toolkit,
+            AC_HELP_STRING([--with-plugin-toolkit],
+            [build using the vpp toolkit]),
+            [with_plugin_toolkit=${prefix}/include],
+            [with_plugin_toolkit=.])
+
+AC_SUBST(TOOLKIT_INCLUDE,[${with_plugin_toolkit}])
+AM_CONDITIONAL(WITH_PLUGIN_TOOLKIT, test "$with_plugin_toolkit" != ".")
+
+AC_OUTPUT([Makefile])
diff --git a/router/router.mk b/router/router.mk
new file mode 100644
index 0000000..f9bb917
--- /dev/null
+++ b/router/router.mk
@@ -0,0 +1,34 @@
+router_configure_depend =                       \
+	vppinfra-install                        \
+	dpdk-install                            \
+	svm-install                             \
+	vlib-api-install                        \
+	vlib-install                            \
+	vnet-install                            \
+	vpp-install                             \
+	netlink-install                         \
+	vpp-api-test-install
+
+router_CPPFLAGS = $(call installed_includes_fn, \
+	vppinfra                                \
+	dpdk                                    \
+	openssl                                 \
+	svm                                     \
+	vlib                                    \
+	vlib-api                                \
+	vnet                                    \
+	vpp                                     \
+	netlink                                 \
+	vpp-api-test)
+
+router_LDFLAGS = $(call installed_libs_fn,      \
+	vppinfra                                \
+	dpdk                                    \
+	openssl                                 \
+	svm                                     \
+	vlib                                    \
+	vlib-api                                \
+	vnet                                    \
+	vpp                                     \
+	netlink                                 \
+	vpp-api-test)
diff --git a/router/router/router.c b/router/router/router.c
new file mode 100644
index 0000000..571db20
--- /dev/null
+++ b/router/router/router.c
@@ -0,0 +1,579 @@
+/*
+ * Copyright 2016 Intel Corporation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#include <net/ethernet.h>
+#include <net/if_arp.h>
+#include <netinet/in.h>
+#include <sys/ioctl.h>
+#include <sys/socket.h>
+#include <vnet/vnet.h>
+#include <vnet/plugin/plugin.h>
+#include <vnet/ip/ip.h>
+#include <vnet/unix/tuntap.h>
+#include <librtnl/mapper.h>
+#include <vnet/ethernet/arp_packet.h>
+
+enum {
+	NEXT_ARP = 0,
+	NEXT_ICMP = 0,
+	NEXT_INJECT_ARP_ICMP,
+};
+
+enum {
+	NEXT_DROP,
+	NEXT_INJECT_CLASSIFIED,
+};
+
+enum {
+	ERROR_DROP = 0,
+	ERROR_INJECT_ARP,
+	ERROR_INJECT_ICMP,
+	ERROR_INJECT_CLASSIFIED,
+};
+
+static char *error_strings[] = {
+	[ERROR_DROP] = "Untapped interface",
+	[ERROR_INJECT_ARP] = "Inject ARP",
+	[ERROR_INJECT_ICMP] = "Inject ICMP",
+	[ERROR_INJECT_CLASSIFIED] = "Inject Classified",
+};
+
+vlib_node_registration_t tap_inject_arp_node;
+vlib_node_registration_t tap_inject_icmp_node;
+vlib_node_registration_t tap_inject_classified_node;
+
+struct tap_to_iface {
+	u32 tap;
+	u32 iface;
+};
+
+struct router_main {
+	vnet_main_t *vnet_main;
+	u32 *iface_to_tap;
+	struct tap_to_iface *tap_to_iface;
+	u32 ns_index;
+};
+
+static struct router_main rm;
+
+static int
+set_tap_hwaddr(vlib_main_t *m, char *name, u8 *hwaddr)
+{
+	int fd, rc;
+	struct ifreq ifr;
+
+	fd = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL));
+	if (fd < 0)
+		return -1;
+
+	memset(&ifr, 0, sizeof(ifr));
+	strncpy(ifr.ifr_name, (char *)name, sizeof(ifr.ifr_name) - 1);
+	memcpy(ifr.ifr_hwaddr.sa_data, hwaddr, ETHER_ADDR_LEN);
+	ifr.ifr_hwaddr.sa_family = ARPHRD_ETHER;
+	rc = ioctl(fd, SIOCSIFHWADDR, &ifr) < 0 ? -1 : 0;
+	close(fd);
+	return rc;
+}
+
+static clib_error_t *
+do_tap_connect(vlib_main_t *m, char *name, u32 iface, u32 *tap)
+{
+	vnet_hw_interface_t *hw = vnet_get_hw_interface(rm.vnet_main, iface);
+
+	*tap = ~0;
+	if (!hw)
+		return clib_error_return(0, "invalid interface");
+
+	if (vnet_tap_connect(m, (u8 *)name, hw->hw_address, tap))
+		return clib_error_return(0, "failed to connect tap");
+
+	if (set_tap_hwaddr(m, name, hw->hw_address))
+		return clib_error_return(0, "failed to set tap hw address");
+
+	if (set_int_l2_mode(m, rm.vnet_main, MODE_L2_XC, *tap, 0, 0, 0, iface))
+		return clib_error_return(0, "failed to xconnect to interface");
+
+	return vnet_sw_interface_set_flags(rm.vnet_main, *tap,
+	                                   VNET_SW_INTERFACE_FLAG_ADMIN_UP);
+}
+
+enum {
+	PROTO_ARP = 0,
+	PROTO_ICMP4,
+	PROTO_OSPF2,
+	PROTO_N_TOTAL,
+};
+
+enum {
+	PROTO_BIT_ARP = 1 << PROTO_ARP,
+	PROTO_BIT_ICMP4 = 1 << PROTO_ICMP4,
+	PROTO_BIT_OSPF2 = 1 << PROTO_OSPF2,
+};
+
+static char *proto_strings[PROTO_N_TOTAL] = {
+	[PROTO_ARP] = "arp",
+	[PROTO_ICMP4] = "icmp4",
+	[PROTO_OSPF2] = "ospf2",
+};
+
+static inline u32 parse_protos(char *proto_string)
+{
+	u32 protos = 0;
+	char *tok, **proto;
+
+	for (tok = strtok(proto_string, ","); tok; tok = strtok(NULL, ","))
+		for (proto = proto_strings; proto && *proto; ++proto)
+			if (!strncmp(tok, *proto, 16))
+				protos |= 1 << (proto - proto_strings);
+	return protos;
+}
+
+static uword unformat_protos(unformat_input_t *input, va_list *args)
+{
+	u32 *protos = va_arg(*args, u32 *);
+	u8 *proto_string;
+
+	if (unformat(input, "%s", &proto_string))
+		*protos = parse_protos((char *)proto_string);
+	return 1;
+}
+
+static void add_del_addr(ns_addr_t *a, int is_del)
+{
+	struct tap_to_iface *map = NULL;
+	u32 sw_if_index = ~0;
+
+	vec_foreach(map, rm.tap_to_iface) {
+		if (a->ifaddr.ifa_index == map->tap) {
+			sw_if_index = map->iface;
+			break;
+		}
+	}
+
+	if (sw_if_index == ~0)
+		return;
+
+	ip4_add_del_interface_address(vlib_get_main(),
+			sw_if_index, (ip4_address_t *)a->local,
+			a->ifaddr.ifa_prefixlen, is_del);
+}
+
+static void add_del_route(ns_route_t *r, int is_del)
+{
+	struct tap_to_iface *map = NULL;
+	u32 sw_if_index = ~0;
+
+	vec_foreach(map, rm.tap_to_iface) {
+		if (r->oif == map->tap) {
+			sw_if_index = map->iface;
+			break;
+		}
+	}
+
+	if (sw_if_index == ~0 || r->table != 254)
+		return;
+
+	ip4_add_del_route_next_hop(&ip4_main,
+			is_del ? IP4_ROUTE_FLAG_DEL : IP4_ROUTE_FLAG_ADD,
+	                (ip4_address_t *)r->dst, r->rtm.rtm_dst_len,
+	                (ip4_address_t *)r->gateway, sw_if_index, 0, ~0, 0);
+}
+
+static void
+netns_notify_cb(void *obj, netns_type_t type, u32 flags, uword opaque)
+{
+	if (type == NETNS_TYPE_ADDR)
+		add_del_addr((ns_addr_t *)obj, flags & NETNS_F_DEL);
+	else if (type == NETNS_TYPE_ROUTE)
+		add_del_route((ns_route_t *)obj, flags & NETNS_F_DEL);
+}
+
+static void insert_tap_to_iface(u32 tap, u32 iface)
+{
+	struct tap_to_iface map = {
+		.tap = tap,
+		.iface = iface,
+	};
+
+	vec_add1(rm.tap_to_iface, map);
+}
+
+static clib_error_t *
+tap_inject(vlib_main_t *m, unformat_input_t *input, vlib_cli_command_t *cmd)
+{
+	char *name = NULL;
+	u32 iface = ~0, tap = ~0, protos = 0;
+	clib_error_t *err;
+
+	while (unformat_check_input(input) != UNFORMAT_END_OF_INPUT) {
+		if (unformat(input, "from %U", unformat_vnet_sw_interface,
+		             rm.vnet_main, &iface))
+			;
+		else if (unformat(input, "as %s", &name))
+			;
+		else if (unformat(input, "%U", unformat_protos, &protos))
+			;
+		else
+			break;
+	}
+
+	if (!protos)
+		return clib_error_return(0,
+				"no protocols specified");
+	else if (iface == ~0)
+		return clib_error_return(0,
+				"interface name is missing or invalid");
+	else if (!name)
+		return clib_error_return(0,
+				"host interface name is missing or invalid");
+
+	if (protos & PROTO_BIT_OSPF2) /* Require arp and icmp4 for ospf2. */
+		if (!(protos & PROTO_BIT_ARP) || !(protos & PROTO_BIT_ICMP4))
+			return clib_error_return(0,
+				"ospf2 requires arp and icmp4");
+
+	err = do_tap_connect(m, name, iface, &tap);
+	if (err) {
+		if (tap != ~0)
+			vnet_tap_delete(m, tap);
+		return err;
+	}
+
+	if ((protos & PROTO_BIT_ARP) || (protos & PROTO_BIT_ICMP4)) {
+		if (rm.ns_index == ~0) {
+			char nsname = 0;
+			netns_sub_t sub = {
+				.notify = netns_notify_cb,
+				.opaque = 0,
+			};
+
+			rm.ns_index = netns_open(&nsname, &sub);
+			if (rm.ns_index == ~0) {
+				vnet_tap_delete(m, tap);
+				clib_error_return(0,
+					"failed to open namespace");
+			}
+		}
+	}
+
+	if (protos & PROTO_BIT_ARP)
+		ethernet_register_input_type(m, ETHERNET_TYPE_ARP,
+		                             tap_inject_arp_node.index);
+
+	if (protos & PROTO_BIT_ICMP4)
+		ip4_register_protocol(IP_PROTOCOL_ICMP,
+		                      tap_inject_icmp_node.index);
+
+	if (protos & PROTO_BIT_OSPF2)
+		ip4_register_protocol(IP_PROTOCOL_OSPF,
+		                      tap_inject_icmp_node.index);
+
+	/* Find sw_if_index of tap associated with data plane interface. */
+	rm.iface_to_tap[iface] = tap;
+
+	/* Find data plane interface associated with host tap ifindex. */
+	insert_tap_to_iface(if_nametoindex(name), iface);
+
+	return 0;
+}
+
+VLIB_CLI_COMMAND(tap_inject_command, static) = {
+	.path = "tap inject",
+	.short_help = "tap inject <protocol[,protocol...]> from <intfc-name> as <host-intfc-name>",
+	.function = tap_inject,
+};
+
+static uword
+tap_inject_arp_icmp(vlib_main_t *m, vlib_node_runtime_t *node,
+                    vlib_frame_t *f, int arp)
+{
+	u32 n_left_from = f->n_vectors;
+	u32 *from = vlib_frame_vector_args(f);
+	u32 next_index = node->cached_next_index;
+	u32 *to_next;
+	u32 me = arp ? tap_inject_arp_node.index : tap_inject_icmp_node.index;
+
+	while (n_left_from) {
+		vlib_buffer_t *b0;
+		u32 next0;
+		u32 bi0;
+		u32 n_left_to_next;
+		u32 vlib_rx, vlib_tx;
+		u32 counter;
+
+		vlib_get_next_frame(m, node, next_index, to_next,
+		                    n_left_to_next);
+
+		*(to_next++) = bi0 = *(from++);
+		--n_left_from;
+		--n_left_to_next;
+
+		b0 = vlib_get_buffer(m, bi0);
+
+		/* FIXME: What about VLAN? */
+		b0->current_data -= sizeof(ethernet_header_t);
+		b0->current_length += sizeof(ethernet_header_t);
+
+		vlib_rx = vnet_buffer(b0)->sw_if_index[VLIB_RX];
+		vlib_tx = rm.iface_to_tap[vlib_rx];
+		vnet_buffer(b0)->sw_if_index[VLIB_TX] = vlib_tx;
+
+		if (vlib_tx == 0 || vlib_tx == ~0)
+			next0 = arp ? NEXT_ARP : NEXT_ICMP;
+		else {
+			next0 = NEXT_INJECT_ARP_ICMP;
+			counter = arp ? ERROR_INJECT_ARP : ERROR_INJECT_ICMP;
+			vlib_node_increment_counter(m, me, counter, 1);
+		}
+
+		vlib_validate_buffer_enqueue_x1(m, node, next_index, to_next,
+		                                n_left_to_next, bi0, next0);
+		vlib_put_next_frame(m, node, next_index, n_left_to_next);
+	}
+	return f->n_vectors;
+}
+
+static uword
+tap_inject_icmp(vlib_main_t *m, vlib_node_runtime_t *node, vlib_frame_t *f)
+{
+	return tap_inject_arp_icmp(m, node, f, 0 /* ICMP */);
+}
+
+VLIB_REGISTER_NODE(tap_inject_icmp_node) = {
+	.function = tap_inject_icmp,
+	.name = "tap-inject-icmp",
+	.vector_size = sizeof(u32),
+	.type = VLIB_NODE_TYPE_INTERNAL,
+	.n_errors = ARRAY_LEN(error_strings),
+	.error_strings = error_strings,
+	.n_next_nodes = 2,
+	.next_nodes = {
+		[NEXT_ICMP] = "ip4-icmp-input",
+		[NEXT_INJECT_ARP_ICMP] = "interface-output",
+	},
+};
+
+static uword
+tap_inject_classified(vlib_main_t *m, vlib_node_runtime_t *node,
+                      vlib_frame_t *f)
+{
+	u32 n_left_from = f->n_vectors;
+	u32 *from = vlib_frame_vector_args(f);
+	u32 next_index = node->cached_next_index;
+	u32 *to_next;
+	u32 out = 0, drop = 0;
+
+	while (n_left_from) {
+		vlib_buffer_t *b0;
+		u32 next0;
+		u32 bi0;
+		u32 n_left_to_next;
+		u32 vlib_rx, vlib_tx;
+
+		vlib_get_next_frame(m, node, next_index, to_next,
+		                    n_left_to_next);
+
+		*(to_next++) = bi0 = *(from++);
+		--n_left_from;
+		--n_left_to_next;
+
+		b0 = vlib_get_buffer(m, bi0);
+
+		/* FIXME: What about VLAN? */
+		b0->current_data -= sizeof(ethernet_header_t);
+		b0->current_length += sizeof(ethernet_header_t);
+
+		vlib_rx = vnet_buffer(b0)->sw_if_index[VLIB_RX];
+		vlib_tx = rm.iface_to_tap[vlib_rx];
+		vnet_buffer(b0)->sw_if_index[VLIB_TX] = vlib_tx;
+
+		if (vlib_tx == 0 || vlib_tx == ~0) {
+			next0 = NEXT_DROP;
+			++drop;
+		} else {
+			next0 = NEXT_INJECT_CLASSIFIED;
+			++out;
+		}
+		vlib_validate_buffer_enqueue_x1(m, node, next_index, to_next,
+		                                n_left_to_next, bi0, next0);
+		vlib_put_next_frame(m, node, next_index, n_left_to_next);
+	}
+	vlib_node_increment_counter(m, tap_inject_classified_node.index,
+	                            ERROR_DROP, drop);
+	vlib_node_increment_counter(m, tap_inject_classified_node.index,
+	                            ERROR_INJECT_CLASSIFIED, out);
+	return f->n_vectors;
+}
+
+VLIB_REGISTER_NODE(tap_inject_classified_node) = {
+	.function = tap_inject_classified,
+	.name = "tap-inject-classified",
+	.vector_size = sizeof(u32),
+	.type = VLIB_NODE_TYPE_INTERNAL,
+	.n_errors = ARRAY_LEN(error_strings),
+	.error_strings = error_strings,
+	.n_next_nodes = 2,
+	.next_nodes = {
+		[NEXT_DROP] = "error-drop",
+		[NEXT_INJECT_CLASSIFIED] = "interface-output",
+	},
+};
+
+static clib_error_t *
+interface_add_del(struct vnet_main_t *m, u32 hw_if_index, u32 add)
+{
+	vnet_hw_interface_t *hw = vnet_get_hw_interface(m, hw_if_index);
+	vnet_sw_interface_t *sw = vnet_get_sw_interface(m, hw->sw_if_index);
+	ASSERT(hw->sw_if_index == sw->sw_if_index);
+
+	vec_validate(rm.iface_to_tap, sw->sw_if_index);
+	rm.iface_to_tap[sw->sw_if_index] = ~0;
+	return 0;
+}
+VNET_HW_INTERFACE_ADD_DEL_FUNCTION(interface_add_del);
+
+clib_error_t *
+vlib_plugin_register(vlib_main_t *m, vnet_plugin_handoff_t *h, int f)
+{
+	rm.vnet_main = h->vnet_main;
+	rm.ns_index = ~0;
+	return 0;
+}
+
+static clib_error_t *router_init(vlib_main_t *m)
+{
+	return 0;
+}
+VLIB_INIT_FUNCTION(router_init);
+
+static inline void
+update_arp_entry(vlib_buffer_t *b0, ethernet_arp_header_t *arp, u32 vlib_rx)
+{
+	ethernet_header_t *eth;
+	ip4_address_t *if_addr;
+	ip_interface_address_t *ifa;
+
+	if (arp->l2_type != ntohs(ETHERNET_ARP_HARDWARE_TYPE_ethernet) ||
+	    arp->l3_type != ntohs(ETHERNET_TYPE_IP4))
+		return;
+
+	/* Check that IP address is local and matches incoming interface. */
+	if_addr = ip4_interface_address_matching_destination(&ip4_main,
+				&arp->ip4_over_ethernet[1].ip4,
+				vlib_rx, &ifa);
+	if (!if_addr)
+		return;
+
+	/* Source must also be local to subnet of matching interface address. */
+	if (!ip4_destination_matches_interface(&ip4_main,
+				&arp->ip4_over_ethernet[0].ip4, ifa))
+		return;
+
+	/* Reject replies with our local interface address. */
+	if (if_addr->as_u32 == arp->ip4_over_ethernet[0].ip4.as_u32)
+		return;
+
+	if (if_addr->as_u32 != arp->ip4_over_ethernet[1].ip4.as_u32)
+		return;
+
+	eth = ethernet_buffer_get_header(b0);
+
+	/* Trash ARP packets whose ARP-level source addresses do not
+	 * match their L2-frame-level source addresses */
+	if (memcmp(eth->src_address, arp->ip4_over_ethernet[0].ethernet,
+	           sizeof(eth->src_address)))
+		return;
+
+	if (arp->ip4_over_ethernet[0].ip4.as_u32 == 0 ||
+	    (arp->ip4_over_ethernet[0].ip4.as_u32 ==
+	     arp->ip4_over_ethernet[1].ip4.as_u32))
+		return;
+
+	/* Learn or update sender's mapping only for requests or unicasts
+	 * that don't match local interface address. */
+	if (ethernet_address_cast(eth->dst_address) != ETHERNET_ADDRESS_UNICAST)
+		return;
+
+	vnet_arp_set_ip4_over_ethernet(rm.vnet_main, vlib_rx, ~0,
+		                       &arp->ip4_over_ethernet[0], 0);
+}
+
+static uword
+tap_inject_arp(vlib_main_t *m, vlib_node_runtime_t *node, vlib_frame_t *f)
+{
+	u32 n_left_from = f->n_vectors;
+	u32 *from = vlib_frame_vector_args(f);
+	u32 next_index = node->cached_next_index;
+	u32 *to_next;
+	u32 out = 0;
+
+	while (n_left_from) {
+		vlib_buffer_t *b0;
+		u32 next0, bi0, n_left;
+		u32 vlib_rx, vlib_tx;
+		ethernet_arp_header_t *arp;
+
+		vlib_get_next_frame(m, node, next_index, to_next, n_left);
+
+		*(to_next++) = bi0 = *(from++);
+		--n_left_from;
+		--n_left;
+
+		b0 = vlib_get_buffer(m, bi0);
+		arp = vlib_buffer_get_current(b0);
+
+		/* FIXME: What about VLAN? */
+		b0->current_data -= sizeof(ethernet_header_t);
+		b0->current_length += sizeof(ethernet_header_t);
+
+		vlib_rx = vnet_buffer(b0)->sw_if_index[VLIB_RX];
+		vlib_tx = rm.iface_to_tap[vlib_rx];
+		vnet_buffer(b0)->sw_if_index[VLIB_TX] = vlib_tx;
+
+		if (vlib_tx == 0 || vlib_tx == ~0)
+			next0 = NEXT_ARP;
+		else {
+			next0 = NEXT_INJECT_ARP_ICMP;
+			++out;
+		}
+
+		/* Add an ARP entry for injected replies. */
+		if (next0 == NEXT_INJECT_ARP_ICMP &&
+		    arp->opcode == ntohs(ETHERNET_ARP_OPCODE_reply))
+			update_arp_entry(b0, arp, vlib_rx);
+
+		vlib_validate_buffer_enqueue_x1(m, node, next_index, to_next,
+		                                n_left, bi0, next0);
+		vlib_put_next_frame(m, node, next_index, n_left);
+	}
+
+	vlib_node_increment_counter(m, tap_inject_arp_node.index,
+	                            ERROR_INJECT_ARP, out);
+	return f->n_vectors;
+}
+
+VLIB_REGISTER_NODE(tap_inject_arp_node) = {
+	.function = tap_inject_arp,
+	.name = "tap-inject-arp",
+	.vector_size = sizeof(u32),
+	.type = VLIB_NODE_TYPE_INTERNAL,
+	.n_errors = ARRAY_LEN(error_strings),
+	.error_strings = error_strings,
+	.n_next_nodes = 2,
+	.next_nodes = {
+		[NEXT_ARP] = "arp-input",
+		[NEXT_INJECT_ARP_ICMP] = "interface-output",
+	},
+};