Use neighbour lookup for RoCE UD QPs Eth L2 resolution

In order to implement RoCE IP based addressing for UD QPs, without introducing
uverbs changes, we need a way to resolve the L2 Ethernet addresses from user-space.

This is done with netlink through libnl, and in libibverbs such that multiple
vendor provider libraries can use the code.

This is implemented as a helper function ibv_resolve_eth_l2_from_gid.
If the GID is IP based, the provider shall call this utility function,
which resolves the IP to MAC and vlan.

The steps for resolution:

1. get sgid

2. from sgid, get the interface

3. query route from interface to the destination

4. query the neigh table, if the MAC for the destination is already known, done.

5. if not, loop until timeout:
    a. send a UDP packet to that IP targeted to the "discard" port
    b. listen to events from the neigh table
    c. query neigh table in order to know if the neigh has shown up between
       query until we started monitoring it

6. query vlan id from the interface

This solution depends on libnl-3 with backports to libnl-1.

Change-Id: I5c36145f8eaa46ab3890cc06da00d04686d68a1e
Signed-off-by: Matan Barak <matanb@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

8 files changed, 1152 insertions, 10 deletions

diff --git a/Makefile.am b/Makefile.am
index a6767de..ef4df03 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -5,13 +5,17 @@ lib_LTLIBRARIES = src/libibverbs.la
 ACLOCAL_AMFLAGS = -I config
 AM_CFLAGS = -g -Wall
 
-src_libibverbs_la_CFLAGS = $(AM_CFLAGS) -DIBV_CONFIG_DIR=\"$(sysconfdir)/libibverbs.d\"
-
+src_libibverbs_la_CFLAGS = $(AM_CFLAGS) -DIBV_CONFIG_DIR=\"$(sysconfdir)/libibverbs.d\" \
+			   $(LIBNL_CFLAGS)
 libibverbs_version_script = @LIBIBVERBS_VERSION_SCRIPT@
+src_libibverbs_la_LIBADD = $(LIBNL_LIBS)
 
 src_libibverbs_la_SOURCES = src/cmd.c src/compat-1_0.c src/device.c src/init.c \
 			    src/marshall.c src/memory.c src/sysfs.c src/verbs.c \
 			    src/enum_strs.c
+if ! NO_RESOLVE_NEIGH
+src_libibverbs_la_SOURCES += src/neigh.c
+endif
 src_libibverbs_la_LDFLAGS = -version-info 1 -export-dynamic \
     $(libibverbs_version_script)
 src_libibverbs_la_DEPENDENCIES = $(srcdir)/src/libibverbs.map
@@ -20,21 +24,21 @@ bin_PROGRAMS = examples/ibv_devices examples/ibv_devinfo \
     examples/ibv_asyncwatch examples/ibv_rc_pingpong examples/ibv_uc_pingpong \
     examples/ibv_ud_pingpong examples/ibv_srq_pingpong examples/ibv_xsrq_pingpong
 examples_ibv_devices_SOURCES = examples/device_list.c
-examples_ibv_devices_LDADD = $(top_builddir)/src/libibverbs.la
+examples_ibv_devices_LDADD = $(top_builddir)/src/libibverbs.la $(LIBNL_LIBS)
 examples_ibv_devinfo_SOURCES = examples/devinfo.c
-examples_ibv_devinfo_LDADD = $(top_builddir)/src/libibverbs.la
+examples_ibv_devinfo_LDADD = $(top_builddir)/src/libibverbs.la $(LIBNL_LIBS)
 examples_ibv_rc_pingpong_SOURCES = examples/rc_pingpong.c examples/pingpong.c
-examples_ibv_rc_pingpong_LDADD = $(top_builddir)/src/libibverbs.la
+examples_ibv_rc_pingpong_LDADD = $(top_builddir)/src/libibverbs.la $(LIBNL_LIBS)
 examples_ibv_uc_pingpong_SOURCES = examples/uc_pingpong.c examples/pingpong.c
-examples_ibv_uc_pingpong_LDADD = $(top_builddir)/src/libibverbs.la
+examples_ibv_uc_pingpong_LDADD = $(top_builddir)/src/libibverbs.la $(LIBNL_LIBS)
 examples_ibv_ud_pingpong_SOURCES = examples/ud_pingpong.c examples/pingpong.c
-examples_ibv_ud_pingpong_LDADD = $(top_builddir)/src/libibverbs.la
+examples_ibv_ud_pingpong_LDADD = $(top_builddir)/src/libibverbs.la $(LIBNL_LIBS)
 examples_ibv_srq_pingpong_SOURCES = examples/srq_pingpong.c examples/pingpong.c
-examples_ibv_srq_pingpong_LDADD = $(top_builddir)/src/libibverbs.la
+examples_ibv_srq_pingpong_LDADD = $(top_builddir)/src/libibverbs.la $(LIBNL_LIBS)
 examples_ibv_xsrq_pingpong_SOURCES = examples/xsrq_pingpong.c examples/pingpong.c
-examples_ibv_xsrq_pingpong_LDADD = $(top_builddir)/src/libibverbs.la
+examples_ibv_xsrq_pingpong_LDADD = $(top_builddir)/src/libibverbs.la $(LIBNL_LIBS)
 examples_ibv_asyncwatch_SOURCES = examples/asyncwatch.c
-examples_ibv_asyncwatch_LDADD = $(top_builddir)/src/libibverbs.la
+examples_ibv_asyncwatch_LDADD = $(top_builddir)/src/libibverbs.la $(LIBNL_LIBS)
 
 libibverbsincludedir = $(includedir)/infiniband
 
diff --git a/configure.ac b/configure.ac
index b5f6dfc..bef0e35 100644
--- a/configure.ac
+++ b/configure.ac
@@ -28,6 +28,37 @@ else
     fi
 fi
 
+AC_ARG_WITH([resolve-neigh],
+    AC_HELP_STRING([--with-resolve-neigh],
+        [Enable neighbour resolution in Ethernet (default YES)]))
+have_libnl=no
+if  test x$with_resolve_neigh = x || test x$with_resolve_neigh = xyes; then
+	PKG_CHECK_MODULES([LIBNL],[libnl-3.0],[
+			   have_libnl=yes
+			   AC_DEFINE([HAVE_LIBNL3], [1], [Use libnl-3.0])
+			   AC_DEFINE([HAVE_LIBNL], [1],  [Use libnl])
+			   PKG_CHECK_MODULES([LIBNL_ROUTE3], [libnl-route-3.0])
+			   LIBNL_CFLAGS="$LIBNL_CFLAGS $LIBNL_ROUTE3_CFLAGS"
+			   LIBNL_LIBS="$LIBNL_LIBS $LIBNL_ROUTE3_LIBS"], [:]
+			  );
+	if test "$have_libnl" = no; then
+		PKG_CHECK_MODULES([LIBNL], [libnl-1], [have_libnl=yes
+				  AC_DEFINE([HAVE_LIBNL1], [1], [Use libnl-1])
+				  AC_DEFINE([HAVE_LIBNL], [1],  [Use libnl])
+				  AC_CHECK_LIB(nl, rtnl_link_vlan_get_id, [],
+					AC_MSG_ERROR([rtnl_link_vlan_get_id not found.  libibverbs requires libnl.]))
+				 ],[
+					AC_MSG_ERROR([libibverbs requires libnl.])
+				 ])
+	fi
+else
+    AC_DEFINE([NRESOLVE_NEIGH], 1, [Define to 1 to disable resovle neigh annotations.])
+fi
+AM_CONDITIONAL([HAVE_LIBNL], [test "$have_libnl" = "yes"])
+AC_SUBST([LIBNL_CFLAGS])
+AC_SUBST([LIBNL_LIBS])
+AM_CONDITIONAL(NO_RESOLVE_NEIGH, test x$with_resolve_neigh = xno)
+
 dnl Checks for libraries
 AC_CHECK_LIB(dl, dlsym, [],
     AC_MSG_ERROR([dlsym() not found.  libibverbs requires libdl.]))
diff --git a/include/infiniband/verbs.h b/include/infiniband/verbs.h
index 2d302a4..28e1586 100644
--- a/include/infiniband/verbs.h
+++ b/include/infiniband/verbs.h
@@ -1544,6 +1544,11 @@ const char *ibv_port_state_str(enum ibv_port_state port_state);
  */
 const char *ibv_event_type_str(enum ibv_event_type event);
 
+#define ETHERNET_LL_SIZE 6
+int ibv_resolve_eth_l2_from_gid(struct ibv_context *context,
+				struct ibv_ah_attr *attr,
+				uint8_t eth_mac[ETHERNET_LL_SIZE],
+				uint16_t *vid);
 END_C_DECLS
 
 #  undef __attribute_const
diff --git a/src/libibverbs.map b/src/libibverbs.map
index 30212f3..9f0ec69 100644
--- a/src/libibverbs.map
+++ b/src/libibverbs.map
@@ -103,6 +103,8 @@ IBVERBS_1.1 {
 		ibv_rate_to_mbps;
 		mbps_to_ibv_rate;
 
+		ibv_resolve_eth_l2_from_gid;
+
 		ibv_cmd_open_xrcd;
 		ibv_cmd_close_xrcd;
 		ibv_cmd_create_srq_ex;
diff --git a/src/neigh.c b/src/neigh.c
new file mode 100644
index 0000000..799b810
--- /dev/null
+++ b/src/neigh.c
@@ -0,0 +1,853 @@
+
+#include "config.h"
+#include <net/if_packet.h>
+#include <linux/netlink.h>
+#include <linux/rtnetlink.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <netlink/route/rtnl.h>
+#include <netlink/route/link.h>
+#include <netlink/route/route.h>
+#include <netlink/route/neighbour.h>
+
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/timerfd.h>
+#include <netinet/in.h>
+#include <errno.h>
+#include <unistd.h>
+#include <ifaddrs.h>
+#include <netdb.h>
+#ifndef _LINUX_IF_H
+#include <net/if.h>
+#else
+/*Workaround when there's a collision between the includes */
+extern unsigned int if_nametoindex(__const char *__ifname) __THROW;
+#endif
+
+/* for PFX */
+#include "ibverbs.h"
+
+#include "neigh.h"
+
+#define MAX(a, b) ((a) > (b) ? (a) : (b))
+#define MIN(a, b) ((a) < (b) ? (a) : (b))
+
+/* Workaround - declaration missing */
+extern int		rtnl_link_vlan_get_id(struct rtnl_link *);
+
+#ifndef HAVE_LIBNL1
+#include <netlink/route/link/vlan.h>
+#endif
+
+static pthread_once_t device_neigh_alloc = PTHREAD_ONCE_INIT;
+static struct nl_sock *zero_socket;
+
+union sktaddr {
+	struct sockaddr s;
+	struct sockaddr_in s4;
+	struct sockaddr_in6 s6;
+};
+
+struct skt {
+	union sktaddr sktaddr;
+	socklen_t len;
+};
+
+static int set_link_port(union sktaddr *s, int port, int oif)
+{
+	switch (s->s.sa_family) {
+	case AF_INET:
+		s->s4.sin_port = port;
+		break;
+	case AF_INET6:
+		s->s6.sin6_port = port;
+		s->s6.sin6_scope_id = oif;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static bool cmp_address(const struct sockaddr *s1,
+			const struct sockaddr *s2)
+{
+	if (s1->sa_family != s2->sa_family)
+		return false;
+
+	switch (s1->sa_family) {
+	case AF_INET:
+		return ((struct sockaddr_in *)s1)->sin_addr.s_addr ==
+		       ((struct sockaddr_in *)s2)->sin_addr.s_addr;
+	case AF_INET6:
+		return !memcmp(
+			((struct sockaddr_in6 *)s1)->sin6_addr.s6_addr,
+			((struct sockaddr_in6 *)s2)->sin6_addr.s6_addr,
+			sizeof(((struct sockaddr_in6 *)s1)->sin6_addr.s6_addr));
+	default:
+		return false;
+	}
+}
+
+static int get_ifindex(const struct sockaddr *s)
+{
+	struct ifaddrs *ifaddr, *ifa;
+	int name2index = -ENODEV;
+
+	if (-1 == getifaddrs(&ifaddr))
+		return errno;
+
+	for (ifa = ifaddr; ifa != NULL; ifa = ifa->ifa_next) {
+		if (ifa->ifa_addr == NULL)
+			continue;
+
+		if (cmp_address(ifa->ifa_addr, s)) {
+			name2index = if_nametoindex(ifa->ifa_name);
+			break;
+		}
+	}
+
+	freeifaddrs(ifaddr);
+
+	return name2index;
+}
+
+static struct nl_addr *get_neigh_mac(struct get_neigh_handler *neigh_handler)
+{
+	struct rtnl_neigh *neigh;
+	struct nl_addr *ll_addr = NULL;
+
+	/* future optimization - if link local address - parse address and
+	 * return mac now instead of doing so after the routing CB. This
+	 * is of course referred to GIDs */
+	neigh = rtnl_neigh_get(neigh_handler->neigh_cache,
+			       neigh_handler->oif,
+			       neigh_handler->dst);
+	if (neigh == NULL)
+		return NULL;
+
+	ll_addr = rtnl_neigh_get_lladdr(neigh);
+	if (NULL != ll_addr)
+		ll_addr = nl_addr_clone(ll_addr);
+
+	rtnl_neigh_put(neigh);
+	return ll_addr;
+}
+
+static void get_neigh_cb_event(struct nl_object *obj, void *arg)
+{
+	struct get_neigh_handler *neigh_handler =
+		(struct get_neigh_handler *)arg;
+	/* assumed serilized callback (no parallel execution of function) */
+	if (nl_object_match_filter(
+		obj,
+		(struct nl_object *)neigh_handler->filter_neigh)) {
+		struct rtnl_neigh *neigh = (struct rtnl_neigh *)obj;
+		/* check that we didn't set it already */
+		if (neigh_handler->found_ll_addr == NULL) {
+			if (rtnl_neigh_get_lladdr(neigh) == NULL)
+				return;
+
+			neigh_handler->found_ll_addr =
+				nl_addr_clone(rtnl_neigh_get_lladdr(neigh));
+		}
+	}
+}
+
+static int get_neigh_cb(struct nl_msg *msg, void *arg)
+{
+	struct get_neigh_handler *neigh_handler =
+		(struct get_neigh_handler *)arg;
+
+	if (nl_msg_parse(msg, &get_neigh_cb_event, neigh_handler) < 0)
+		errno = ENOMSG;
+
+	return NL_OK;
+}
+
+static void set_neigh_filter(struct get_neigh_handler *neigh_handler,
+			     struct rtnl_neigh *filter) {
+	neigh_handler->filter_neigh = filter;
+}
+
+static struct rtnl_neigh *create_filter_neigh_for_dst(struct nl_addr *dst_addr,
+						      int oif)
+{
+	struct rtnl_neigh *filter_neigh;
+
+	filter_neigh = rtnl_neigh_alloc();
+	if (filter_neigh == NULL)
+		return NULL;
+
+	rtnl_neigh_set_ifindex(filter_neigh, oif);
+	rtnl_neigh_set_dst(filter_neigh, dst_addr);
+
+	return filter_neigh;
+}
+
+#define PORT_DISCARD htons(9)
+#define SEND_PAYLOAD "H"
+
+static int create_socket(struct get_neigh_handler *neigh_handler,
+			 struct skt *addr_dst, int *psock_fd)
+{
+	int err;
+	struct skt addr_src;
+	int sock_fd;
+
+	memset(addr_dst, 0, sizeof(*addr_dst));
+	memset(&addr_src, 0, sizeof(addr_src));
+	addr_src.len = sizeof(addr_src.sktaddr);
+
+	err = nl_addr_fill_sockaddr(neigh_handler->src,
+				    &addr_src.sktaddr.s,
+				    &addr_src.len);
+	if (err) {
+		errno = EADDRNOTAVAIL;
+		return err;
+	}
+
+	addr_dst->len = sizeof(addr_dst->sktaddr);
+	err = nl_addr_fill_sockaddr(neigh_handler->dst,
+				    &addr_dst->sktaddr.s,
+				    &addr_dst->len);
+	if (err) {
+		errno = EADDRNOTAVAIL;
+		return err;
+	}
+
+	err = set_link_port(&addr_dst->sktaddr, PORT_DISCARD,
+			    neigh_handler->oif);
+	if (err)
+		return err;
+
+	sock_fd = socket(addr_dst->sktaddr.s.sa_family,
+			 SOCK_DGRAM | SOCK_CLOEXEC, 0);
+	if (sock_fd == -1)
+		return errno ? -errno : -1;
+	err = bind(sock_fd, &addr_src.sktaddr.s, addr_src.len);
+	if (err) {
+		int bind_err = -errno;
+
+		close(sock_fd);
+		return bind_err ?: EADDRNOTAVAIL;
+	}
+
+	*psock_fd = sock_fd;
+
+	return 0;
+}
+
+#define NUM_OF_RETRIES 10
+#define NUM_OF_TRIES ((NUM_OF_RETRIES) + 1)
+#if NUM_OF_TRIES < 1
+#error "neigh: invalid value of NUM_OF_RETRIES"
+#endif
+static int create_timer(struct get_neigh_handler *neigh_handler)
+{
+	int user_timeout = neigh_handler->timeout/NUM_OF_TRIES;
+	struct timespec timeout = {
+		.tv_sec = user_timeout / 1000,
+		.tv_nsec = (user_timeout % 1000) * 1000000
+	};
+	struct itimerspec timer_time = {.it_value = timeout};
+	int timer_fd;
+
+	timer_fd = timerfd_create(CLOCK_MONOTONIC, TFD_NONBLOCK | TFD_CLOEXEC);
+	if (timer_fd == -1)
+		return timer_fd;
+
+	if (neigh_handler->timeout) {
+		if (NUM_OF_TRIES <= 1)
+			bzero(&timer_time.it_interval,
+			      sizeof(timer_time.it_interval));
+		else
+			timer_time.it_interval = timeout;
+		if (timerfd_settime(timer_fd, 0, &timer_time, NULL)) {
+			close(timer_fd);
+			return -1;
+		}
+	}
+
+	return timer_fd;
+}
+
+#define UDP_SOCKET_MAX_SENDTO 100000ULL
+static int try_send_to(int sock_fd, void *buff, size_t buf_size,
+		       struct skt *addr_dst)
+{
+	uint64_t max_count = UDP_SOCKET_MAX_SENDTO;
+	int err;
+
+	do {
+		err = sendto(sock_fd, buff, buf_size, 0,
+			     &addr_dst->sktaddr.s,
+			     addr_dst->len);
+		if (err > 0)
+			err = 0;
+	} while (-1 == err && EADDRNOTAVAIL == errno && --max_count);
+
+	return err;
+}
+
+static struct nl_addr *process_get_neigh_mac(
+		struct get_neigh_handler *neigh_handler)
+{
+	int err;
+	struct nl_addr *ll_addr = get_neigh_mac(neigh_handler);
+	struct rtnl_neigh *neigh_filter;
+	fd_set fdset;
+	int sock_fd;
+	int fd;
+	int nfds;
+	int timer_fd;
+	int ret;
+	struct skt addr_dst;
+	char buff[sizeof(SEND_PAYLOAD)] = SEND_PAYLOAD;
+	int retries = 0;
+
+	if (NULL != ll_addr)
+		return ll_addr;
+
+	err = nl_socket_add_membership(neigh_handler->sock,
+				       RTNLGRP_NEIGH);
+	if (err < 0)
+		return NULL;
+
+	neigh_filter = create_filter_neigh_for_dst(neigh_handler->dst,
+						   neigh_handler->oif);
+	if (neigh_filter == NULL)
+		return NULL;
+
+	set_neigh_filter(neigh_handler, neigh_filter);
+
+	nl_socket_disable_seq_check(neigh_handler->sock);
+	nl_socket_modify_cb(neigh_handler->sock, NL_CB_VALID, NL_CB_CUSTOM,
+			    &get_neigh_cb, neigh_handler);
+
+	fd = nl_socket_get_fd(neigh_handler->sock);
+
+	err = create_socket(neigh_handler, &addr_dst, &sock_fd);
+
+	if (err)
+		return NULL;
+
+	err = try_send_to(sock_fd, buff, sizeof(buff), &addr_dst);
+	if (err)
+		goto close_socket;
+
+	timer_fd = create_timer(neigh_handler);
+	if (timer_fd < 0)
+		goto close_socket;
+
+	nfds = MAX(fd, timer_fd) + 1;
+
+	while (1) {
+		FD_ZERO(&fdset);
+		FD_SET(fd, &fdset);
+		FD_SET(timer_fd, &fdset);
+
+		/* wait for an incoming message on the netlink socket */
+		ret = select(nfds, &fdset, NULL, NULL, NULL);
+		if (ret == -1) {
+			goto select_err;
+		} else if (ret) {
+			if (FD_ISSET(fd, &fdset)) {
+				nl_recvmsgs_default(neigh_handler->sock);
+				if (neigh_handler->found_ll_addr)
+					break;
+			} else {
+				nl_cache_refill(neigh_handler->sock,
+						neigh_handler->neigh_cache);
+				ll_addr = get_neigh_mac(neigh_handler);
+				if (NULL != ll_addr) {
+					break;
+				} else if (FD_ISSET(timer_fd, &fdset) &&
+					   retries < NUM_OF_RETRIES) {
+					try_send_to(sock_fd, buff, sizeof(buff),
+						    &addr_dst);
+				}
+			}
+
+			if (FD_ISSET(timer_fd, &fdset)) {
+				uint64_t read_val;
+
+				(void)read(timer_fd, &read_val,
+					   sizeof(read_val));
+				if (++retries >=  NUM_OF_TRIES) {
+					if (!errno)
+						errno = EDESTADDRREQ;
+					break;
+				}
+			}
+		}
+	}
+select_err:
+	close(timer_fd);
+close_socket:
+	close(sock_fd);
+	return ll_addr ? ll_addr : neigh_handler->found_ll_addr;
+}
+
+static int get_mcast_mac_ipv4(struct nl_addr *dst, struct nl_addr **ll_addr)
+{
+	uint8_t mac_addr[6] = {0x01, 0x00, 0x5E};
+	uint32_t addr = ntohl(*(uint32_t *)nl_addr_get_binary_addr(dst));
+
+	mac_addr[5] = addr & 0xFF;
+	addr >>= 8;
+	mac_addr[4] = addr & 0xFF;
+	addr >>= 8;
+	mac_addr[3] = addr & 0x7F;
+
+	*ll_addr = nl_addr_build(AF_LLC, mac_addr, sizeof(mac_addr));
+
+	return *ll_addr == NULL ? -EINVAL : 0;
+}
+
+static int get_mcast_mac_ipv6(struct nl_addr *dst, struct nl_addr **ll_addr)
+{
+	uint8_t mac_addr[6] = {0x33, 0x33};
+
+	memcpy(mac_addr + 2, (uint8_t *)nl_addr_get_binary_addr(dst) + 12, 4);
+
+	*ll_addr = nl_addr_build(AF_LLC, mac_addr, sizeof(mac_addr));
+
+	return *ll_addr == NULL ? -EINVAL : 0;
+}
+
+static int get_link_local_mac_ipv6(struct nl_addr *dst,
+				   struct nl_addr **ll_addr)
+{
+	uint8_t mac_addr[6];
+
+	memcpy(mac_addr + 3, (uint8_t *)nl_addr_get_binary_addr(dst) + 13, 3);
+	memcpy(mac_addr, (uint8_t *)nl_addr_get_binary_addr(dst) + 8, 3);
+	mac_addr[0] ^= 2;
+
+	*ll_addr = nl_addr_build(AF_LLC, mac_addr, sizeof(mac_addr));
+	return *ll_addr == NULL ? -EINVAL : 0;
+}
+
+static const struct encoded_l3_addr {
+	short family;
+	uint8_t prefix_bits;
+	const uint8_t data[16];
+	int (*getter)(struct nl_addr *dst, struct nl_addr **ll_addr);
+} encoded_prefixes[] = {
+	{.family = AF_INET,
+	 .prefix_bits = 4,
+	 .data = {0xe0},
+	 .getter = &get_mcast_mac_ipv4},
+	{.family = AF_INET6,
+	 .prefix_bits = 8,
+	 .data = {0xff},
+	 .getter = &get_mcast_mac_ipv6},
+	{.family = AF_INET6,
+	 .prefix_bits = 64,
+	 .data = {0xfe, 0x80},
+	 .getter = get_link_local_mac_ipv6},
+};
+
+static int nl_addr_cmp_prefix_msb(void *addr1, int len1, void *addr2, int len2)
+{
+	int len = MIN(len1, len2);
+	int bytes = len / 8;
+	int d = memcmp(addr1, addr2, bytes);
+
+	if (d == 0) {
+		int mask = ((1UL << (len % 8)) - 1UL) << (8 - len);
+
+		d = (((uint8_t *)addr1)[bytes] & mask) -
+		    (((uint8_t *)addr2)[bytes] & mask);
+	}
+
+	return d;
+}
+
+static int handle_encoded_mac(struct nl_addr *dst, struct nl_addr **ll_addr)
+{
+	uint32_t family = nl_addr_get_family(dst);
+	struct nl_addr *prefix = NULL;
+	int i;
+	int ret = 1;
+
+	for (i = 0;
+	     i < sizeof(encoded_prefixes)/sizeof(encoded_prefixes[0]) &&
+	     ret; prefix = NULL, i++) {
+		if (encoded_prefixes[i].family != family)
+			continue;
+
+		prefix = nl_addr_build(
+				family,
+				(void *)encoded_prefixes[i].data,
+				MIN(encoded_prefixes[i].prefix_bits/8 +
+				    !!(encoded_prefixes[i].prefix_bits % 8),
+				    sizeof(encoded_prefixes[i].data)));
+
+		if (prefix == NULL)
+			return -ENOMEM;
+		nl_addr_set_prefixlen(prefix,
+				      encoded_prefixes[i].prefix_bits);
+
+		if (nl_addr_cmp_prefix_msb(nl_addr_get_binary_addr(dst),
+					   nl_addr_get_prefixlen(dst),
+					   nl_addr_get_binary_addr(prefix),
+					   nl_addr_get_prefixlen(prefix)))
+			continue;
+
+		ret = encoded_prefixes[i].getter(dst, ll_addr);
+		nl_addr_put(prefix);
+	}
+
+	return ret;
+}
+
+static void get_route_cb_parser(struct nl_object *obj, void *arg)
+{
+	struct get_neigh_handler *neigh_handler =
+		(struct get_neigh_handler *)arg;
+
+	struct rtnl_route *route = (struct rtnl_route *)obj;
+	struct nl_addr *gateway = NULL;
+	struct nl_addr *src = rtnl_route_get_pref_src(route);
+	int oif;
+	int type = rtnl_route_get_type(route);
+	struct rtnl_link *link;
+
+	struct rtnl_nexthop *nh = rtnl_route_nexthop_n(route, 0);
+
+	if (nh != NULL)
+		gateway = rtnl_route_nh_get_gateway(nh);
+	oif = rtnl_route_nh_get_ifindex(nh);
+
+	if (gateway) {
+		nl_addr_put(neigh_handler->dst);
+		neigh_handler->dst = nl_addr_clone(gateway);
+	}
+
+	if (RTN_BLACKHOLE == type ||
+	    RTN_UNREACHABLE == type ||
+	    RTN_PROHIBIT == type ||
+	    RTN_THROW == type) {
+		errno = ENETUNREACH;
+		goto err;
+	}
+
+	if (!neigh_handler->src && src)
+		neigh_handler->src = nl_addr_clone(src);
+
+	if (neigh_handler->oif < 0 && oif > 0)
+		neigh_handler->oif = oif;
+
+	/* Link Local */
+	if (RTN_LOCAL == type) {
+		struct nl_addr *lladdr;
+
+		link = rtnl_link_get(neigh_handler->link_cache,
+				     neigh_handler->oif);
+
+		if (link == NULL)
+			goto err;
+
+		lladdr = rtnl_link_get_addr(link);
+
+		if (lladdr == NULL)
+			goto err_link;
+
+		neigh_handler->found_ll_addr = nl_addr_clone(lladdr);
+		rtnl_link_put(link);
+	} else {
+		handle_encoded_mac(
+			neigh_handler->dst,
+			&neigh_handler->found_ll_addr);
+	}
+
+	return;
+
+err_link:
+	rtnl_link_put(link);
+err:
+	if (neigh_handler->src) {
+		nl_addr_put(neigh_handler->src);
+		neigh_handler->src = NULL;
+	}
+}
+
+static int get_route_cb(struct nl_msg *msg, void *arg)
+{
+	struct get_neigh_handler *neigh_handler =
+		(struct get_neigh_handler *)arg;
+	int err;
+
+	err = nl_msg_parse(msg, &get_route_cb_parser, neigh_handler);
+	if (err < 0) {
+		errno = ENOMSG;
+		return err;
+	}
+
+	if (!neigh_handler->dst || !neigh_handler->src ||
+	    neigh_handler->oif <= 0) {
+		errno = EINVAL;
+		return -1;
+	}
+
+	if (NULL != neigh_handler->found_ll_addr)
+		goto found;
+
+	neigh_handler->found_ll_addr =
+		process_get_neigh_mac(neigh_handler);
+
+found:
+	return neigh_handler->found_ll_addr ? 0 : -1;
+}
+
+int neigh_get_oif_from_src(struct get_neigh_handler *neigh_handler)
+{
+	int oif = -ENODEV;
+	struct addrinfo *src_info;
+	int err;
+
+	err = nl_addr_info(neigh_handler->src, &src_info);
+	if (err) {
+		if (!errno)
+			errno = ENXIO;
+		return oif;
+	}
+
+	oif = get_ifindex(src_info->ai_addr);
+	if (oif <= 0)
+		goto free;
+
+free:
+	freeaddrinfo(src_info);
+	return oif;
+}
+
+static void destroy_zero_based_socket(void)
+{
+	if (zero_socket != NULL)
+		nl_socket_free(zero_socket);
+}
+
+static void alloc_zero_based_socket(void)
+{
+	zero_socket = nl_socket_alloc();
+	atexit(&destroy_zero_based_socket);
+}
+
+int neigh_init_resources(struct get_neigh_handler *neigh_handler, int timeout)
+{
+	int err;
+
+	pthread_once(&device_neigh_alloc, &alloc_zero_based_socket);
+	neigh_handler->sock = nl_socket_alloc();
+	if (neigh_handler->sock == NULL) {
+		errno = ENOMEM;
+		return -1;
+	}
+
+	err = nl_connect(neigh_handler->sock, NETLINK_ROUTE);
+	if (err < 0)
+		goto free_socket;
+
+	err = rtnl_link_alloc_cache(neigh_handler->sock, AF_UNSPEC,
+				    &neigh_handler->link_cache);
+	if (err) {
+		err = -1;
+		errno = ENOMEM;
+		goto close_connection;
+	}
+
+	nl_cache_mngt_provide(neigh_handler->link_cache);
+
+	err = rtnl_route_alloc_cache(neigh_handler->sock, AF_UNSPEC, 0,
+				     &neigh_handler->route_cache);
+	if (err) {
+		err = -1;
+		errno = ENOMEM;
+		goto free_link_cache;
+	}
+
+	nl_cache_mngt_provide(neigh_handler->route_cache);
+
+	err = rtnl_neigh_alloc_cache(neigh_handler->sock,
+				     &neigh_handler->neigh_cache);
+	if (err) {
+		err = -ENOMEM;
+		goto free_route_cache;
+	}
+
+	nl_cache_mngt_provide(neigh_handler->neigh_cache);
+
+	/* init structure */
+	neigh_handler->timeout = timeout;
+	neigh_handler->oif = -1;
+	neigh_handler->filter_neigh = NULL;
+	neigh_handler->found_ll_addr = NULL;
+	neigh_handler->dst = NULL;
+	neigh_handler->src = NULL;
+	neigh_handler->vid = -1;
+
+	return 0;
+
+free_route_cache:
+	nl_cache_mngt_unprovide(neigh_handler->route_cache);
+	nl_cache_free(neigh_handler->route_cache);
+	neigh_handler->route_cache = NULL;
+free_link_cache:
+	nl_cache_mngt_unprovide(neigh_handler->link_cache);
+	nl_cache_free(neigh_handler->link_cache);
+	neigh_handler->link_cache = NULL;
+close_connection:
+	nl_close(neigh_handler->sock);
+free_socket:
+	nl_socket_free(neigh_handler->sock);
+	neigh_handler->sock = NULL;
+	return err;
+}
+
+uint16_t neigh_get_vlan_id_from_dev(struct get_neigh_handler *neigh_handler)
+{
+	struct rtnl_link *link;
+	int vid = 0xffff;
+
+	link = rtnl_link_get(neigh_handler->link_cache, neigh_handler->oif);
+	if (link == NULL) {
+		errno = EINVAL;
+		return vid;
+	}
+
+	if (rtnl_link_is_vlan(link))
+		vid = rtnl_link_vlan_get_id(link);
+	rtnl_link_put(link);
+	return vid >= 0 && vid <= 0xfff ? vid : 0xffff;
+}
+
+void neigh_set_vlan_id(struct get_neigh_handler *neigh_handler, uint16_t vid)
+{
+	if (vid >= 0 && vid <= 0xfff)
+		neigh_handler->vid = vid;
+}
+
+int neigh_set_dst(struct get_neigh_handler *neigh_handler,
+		  int family, void *buf, size_t size)
+{
+	neigh_handler->dst = nl_addr_build(family, buf, size);
+	return neigh_handler->dst == NULL;
+}
+
+int neigh_set_src(struct get_neigh_handler *neigh_handler,
+		  int family, void *buf, size_t size)
+{
+	neigh_handler->src = nl_addr_build(family, buf, size);
+	return neigh_handler->src == NULL;
+}
+
+void neigh_set_oif(struct get_neigh_handler *neigh_handler, int oif)
+{
+	neigh_handler->oif = oif;
+}
+
+int neigh_get_ll(struct get_neigh_handler *neigh_handler, void *addr_buff,
+		 int addr_size) {
+	int neigh_len;
+
+	if (neigh_handler->found_ll_addr == NULL)
+		return -EINVAL;
+
+	 neigh_len = nl_addr_get_len(neigh_handler->found_ll_addr);
+
+	if (neigh_len > addr_size)
+		return -EINVAL;
+
+	memcpy(addr_buff, nl_addr_get_binary_addr(neigh_handler->found_ll_addr),
+	       neigh_len);
+
+	return neigh_len;
+}
+
+void neigh_free_resources(struct get_neigh_handler *neigh_handler)
+{
+	/* Should be released first because it's holding a reference to dst */
+	if (neigh_handler->filter_neigh != NULL) {
+		rtnl_neigh_put(neigh_handler->filter_neigh);
+		neigh_handler->filter_neigh = NULL;
+	}
+
+	if (neigh_handler->src != NULL) {
+		nl_addr_put(neigh_handler->src);
+		neigh_handler->src = NULL;
+	}
+
+	if (neigh_handler->dst != NULL) {
+		nl_addr_put(neigh_handler->dst);
+		neigh_handler->dst = NULL;
+	}
+
+	if (neigh_handler->found_ll_addr != NULL) {
+		nl_addr_put(neigh_handler->found_ll_addr);
+		neigh_handler->found_ll_addr = NULL;
+	}
+
+	if (neigh_handler->neigh_cache != NULL) {
+		nl_cache_mngt_unprovide(neigh_handler->neigh_cache);
+		nl_cache_free(neigh_handler->neigh_cache);
+		neigh_handler->neigh_cache = NULL;
+	}
+
+	if (neigh_handler->route_cache != NULL) {
+		nl_cache_mngt_unprovide(neigh_handler->route_cache);
+		nl_cache_free(neigh_handler->route_cache);
+		neigh_handler->route_cache = NULL;
+	}
+
+	if (neigh_handler->link_cache != NULL) {
+		nl_cache_mngt_unprovide(neigh_handler->link_cache);
+		nl_cache_free(neigh_handler->link_cache);
+		neigh_handler->link_cache = NULL;
+	}
+
+	if (neigh_handler->sock != NULL) {
+		nl_close(neigh_handler->sock);
+		nl_socket_free(neigh_handler->sock);
+		neigh_handler->sock = NULL;
+	}
+}
+
+int process_get_neigh(struct get_neigh_handler *neigh_handler)
+{
+	struct nl_msg *m;
+	struct rtmsg rmsg = {
+		.rtm_family = nl_addr_get_family(neigh_handler->dst),
+		.rtm_dst_len = nl_addr_get_prefixlen(neigh_handler->dst),
+	};
+	int err;
+
+	m = nlmsg_alloc_simple(RTM_GETROUTE, 0);
+
+	if (m == NULL)
+		return -ENOMEM;
+
+	nlmsg_append(m, &rmsg, sizeof(rmsg), NLMSG_ALIGNTO);
+
+	nla_put_addr(m, RTA_DST, neigh_handler->dst);
+
+	if (neigh_handler->oif > 0)
+		nla_put_u32(m, RTA_OIF, neigh_handler->oif);
+
+	err = nl_send_auto_complete(neigh_handler->sock, m);
+	nlmsg_free(m);
+	if (err < 0)
+		return err;
+
+	nl_socket_modify_cb(neigh_handler->sock, NL_CB_VALID,
+			    NL_CB_CUSTOM, &get_route_cb, neigh_handler);
+
+	err = nl_recvmsgs_default(neigh_handler->sock);
+
+	return err;
+}
diff --git a/src/neigh.h b/src/neigh.h
new file mode 100644
index 0000000..61dfd85
--- /dev/null
+++ b/src/neigh.h
@@ -0,0 +1,47 @@
+#ifndef _NEIGH_H_
+#define _NEIGH_H_
+
+#include <stddef.h>
+#include <stdint.h>
+#include "config.h"
+#ifdef HAVE_LIBNL1
+#include <netlink/object.h>
+#include "nl1_compat.h"
+#else
+#include <netlink/object-api.h>
+#endif
+
+struct get_neigh_handler {
+#ifdef HAVE_LIBNL1
+	struct nl_handle *sock;
+#else
+	struct nl_sock *sock;
+#endif
+	struct nl_cache *link_cache;
+	struct nl_cache	*neigh_cache;
+	struct nl_cache *route_cache;
+	int32_t oif;
+	int vid;
+	struct rtnl_neigh *filter_neigh;
+	struct nl_addr *found_ll_addr;
+	struct nl_addr *dst;
+	struct nl_addr *src;
+	uint64_t timeout;
+};
+
+int process_get_neigh(struct get_neigh_handler *neigh_handler);
+void neigh_free_resources(struct get_neigh_handler *neigh_handler);
+void neigh_set_vlan_id(struct get_neigh_handler *neigh_handler, uint16_t vid);
+uint16_t neigh_get_vlan_id_from_dev(struct get_neigh_handler *neigh_handler);
+int neigh_init_resources(struct get_neigh_handler *neigh_handler, int timeout);
+
+int neigh_set_src(struct get_neigh_handler *neigh_handler,
+		  int family, void *buf, size_t size);
+void neigh_set_oif(struct get_neigh_handler *neigh_handler, int oif);
+int neigh_set_dst(struct get_neigh_handler *neigh_handler,
+		  int family, void *buf, size_t size);
+int neigh_get_oif_from_src(struct get_neigh_handler *neigh_handler);
+int neigh_get_ll(struct get_neigh_handler *neigh_handler, void *addr_buf,
+		 int addr_size);
+
+#endif
diff --git a/src/nl1_compat.h b/src/nl1_compat.h
new file mode 100644
index 0000000..809259d
--- /dev/null
+++ b/src/nl1_compat.h
@@ -0,0 +1,73 @@
+#ifndef _NL1_COMPAT_H_
+#define _NL1_COMPAT_H_
+
+#include <netlink/route/rtnl.h>
+#include <netlink/route/link.h>
+#include <netlink/route/route.h>
+#include <netlink/route/neighbour.h>
+
+/* Workaround - declaration missing */
+extern int		rtnl_link_vlan_get_id(struct rtnl_link *);
+
+#define nl_geterror(x) nl_geterror()
+#define nl_sock nl_handle
+
+static inline void nl_socket_disable_seq_check(struct nl_sock *sock)
+{
+	nl_disable_sequence_check(sock);
+}
+
+struct rtnl_nexthop {};
+
+static inline struct rtnl_nexthop *rtnl_route_nexthop_n(
+	struct rtnl_route *r, int n)
+{
+	return (struct rtnl_nexthop *)r;
+}
+
+static inline struct nl_addr *rtnl_route_nh_get_gateway(struct rtnl_nexthop *nh)
+{
+	return rtnl_route_get_gateway((struct rtnl_route *)nh);
+}
+
+static inline int rtnl_route_nh_get_ifindex(struct rtnl_nexthop *nh)
+{
+	return rtnl_route_get_oif((struct rtnl_route *)nh);
+}
+
+#define nl_addr_info(addr, result)	(		\
+	*(result) = nl_addr_info(addr),			\
+	(*(result) == NULL) ? nl_get_errno() : 0		\
+)
+
+static inline void nl_socket_free(struct nl_sock *sock)
+{
+	nl_close(sock);
+}
+
+static inline struct nl_sock *nl_socket_alloc(void)
+{
+	return nl_handle_alloc();
+}
+
+#define rtnl_link_alloc_cache(sock, family, result) (	\
+	*result = rtnl_link_alloc_cache(sock),		\
+	(*result == NULL) ? nl_get_errno() : 0		\
+)
+
+#define rtnl_route_alloc_cache(sock, family, flags, result) (	\
+	*result = rtnl_route_alloc_cache(sock),			\
+	(*result == NULL) ? nl_get_errno() : 0			\
+)
+
+#define rtnl_neigh_alloc_cache(sock, result) (			\
+	*result = rtnl_neigh_alloc_cache(sock),			\
+	(*result == NULL) ? nl_get_errno() : 0			\
+)
+
+static inline int rtnl_link_is_vlan(struct rtnl_link *link)
+{
+	return rtnl_link_vlan_get_id(link) <= 0;
+}
+
+#endif
diff --git a/src/verbs.c b/src/verbs.c
index a6aae70..ada3515 100644
--- a/src/verbs.c
+++ b/src/verbs.c
@@ -43,6 +43,11 @@
 #include <string.h>
 
 #include "ibverbs.h"
+#ifndef NRESOLVE_NEIGH
+#include <net/if.h>
+#include <net/if_arp.h>
+#include "neigh.h"
+#endif
 
 int ibv_rate_to_mult(enum ibv_rate rate)
 {
@@ -591,3 +596,125 @@ int __ibv_detach_mcast(struct ibv_qp *qp, const union ibv_gid *gid, uint16_t lid
 	return qp->context->ops.detach_mcast(qp, gid, lid);
 }
 default_symver(__ibv_detach_mcast, ibv_detach_mcast);
+
+static inline int ipv6_addr_v4mapped(const struct in6_addr *a)
+{
+	return IN6_IS_ADDR_V4MAPPED(&a->s6_addr32) ||
+		/* IPv4 encoded multicast addresses */
+		(a->s6_addr32[0]  == htonl(0xff0e0000) &&
+		((a->s6_addr32[1] |
+		 (a->s6_addr32[2] ^ htonl(0x0000ffff))) == 0UL));
+}
+
+struct peer_address {
+	void *address;
+	uint32_t size;
+};
+
+static inline int create_peer_from_gid(int family, void *raw_gid,
+				       struct peer_address *peer_address)
+{
+	switch (family) {
+	case AF_INET:
+		peer_address->address = raw_gid + 12;
+		peer_address->size = 4;
+		break;
+	case AF_INET6:
+		peer_address->address = raw_gid;
+		peer_address->size = 16;
+		break;
+	default:
+		return -1;
+	}
+
+	return 0;
+}
+
+#define NEIGH_GET_DEFAULT_TIMEOUT_MS 3000
+int ibv_resolve_eth_l2_from_gid(struct ibv_context *context,
+				struct ibv_ah_attr *attr,
+				uint8_t eth_mac[ETHERNET_LL_SIZE],
+				uint16_t *vid)
+{
+#ifndef NRESOLVE_NEIGH
+	int dst_family;
+	int src_family;
+	int oif;
+	struct get_neigh_handler neigh_handler;
+	union ibv_gid sgid;
+	int ether_len;
+	struct peer_address src;
+	struct peer_address dst;
+	uint16_t ret_vid;
+	int ret = -EINVAL;
+	int err;
+
+	err = ibv_query_gid(context, attr->port_num,
+			    attr->grh.sgid_index, &sgid);
+
+	if (err)
+		return err;
+
+	err = neigh_init_resources(&neigh_handler,
+				   NEIGH_GET_DEFAULT_TIMEOUT_MS);
+
+	if (err)
+		return err;
+
+	dst_family = ipv6_addr_v4mapped((struct in6_addr *)attr->grh.dgid.raw) ?
+			AF_INET : AF_INET6;
+	src_family = ipv6_addr_v4mapped((struct in6_addr *)sgid.raw) ?
+			AF_INET : AF_INET6;
+
+	if (create_peer_from_gid(dst_family, attr->grh.dgid.raw, &dst))
+		goto free_resources;
+
+	if (create_peer_from_gid(src_family, &sgid.raw, &src))
+		goto free_resources;
+
+	if (neigh_set_dst(&neigh_handler, dst_family, dst.address,
+			  dst.size))
+		goto free_resources;
+
+	if (neigh_set_src(&neigh_handler, src_family, src.address,
+			  src.size))
+		goto free_resources;
+
+	oif = neigh_get_oif_from_src(&neigh_handler);
+
+	if (oif > 0)
+		neigh_set_oif(&neigh_handler, oif);
+	else
+		goto free_resources;
+
+	ret = -EHOSTUNREACH;
+
+	/* blocking call */
+	if (process_get_neigh(&neigh_handler))
+		goto free_resources;
+
+	ret_vid = neigh_get_vlan_id_from_dev(&neigh_handler);
+
+	if (ret_vid <= 0xfff)
+		neigh_set_vlan_id(&neigh_handler, ret_vid);
+
+	/* We are using only Ethernet here */
+	ether_len = neigh_get_ll(&neigh_handler,
+				 eth_mac,
+				 sizeof(uint8_t) * ETHERNET_LL_SIZE);
+
+	if (ether_len <= 0)
+		goto free_resources;
+
+	*vid = ret_vid;
+
+	ret = 0;
+
+free_resources:
+	neigh_free_resources(&neigh_handler);
+
+	return ret;
+#else
+	return -ENOSYS;
+#endif
+}