Netlink: Add option to specify netlink socket receive buffer size

Add option 'netlink rx buffer' to specify netlink socket receive buffer
size. Uses SO_RCVBUFFORCE, so it can override rmem_max limit.

Thanks to Trisha Biswas and Michal for the original patches.

1 files changed, 2179 insertions, 0 deletions

diff --git a/sysdep/linux/netlink.c.orig b/sysdep/linux/netlink.c.orig
new file mode 100644
index 00000000..7cea5322
--- /dev/null
+++ b/sysdep/linux/netlink.c.orig
@@ -0,0 +1,2179 @@
+/*
+ *	BIRD -- Linux Netlink Interface
+ *
+ *	(c) 1999--2000 Martin Mares <mj@ucw.cz>
+ *
+ *	Can be freely distributed and used under the terms of the GNU GPL.
+ */
+
+#include <alloca.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/socket.h>
+#include <sys/uio.h>
+#include <errno.h>
+
+#undef LOCAL_DEBUG
+
+#include "nest/bird.h"
+#include "nest/route.h"
+#include "nest/protocol.h"
+#include "nest/iface.h"
+#include "lib/alloca.h"
+#include "sysdep/unix/unix.h"
+#include "sysdep/unix/krt.h"
+#include "lib/socket.h"
+#include "lib/string.h"
+#include "lib/hash.h"
+#include "conf/conf.h"
+
+#include <asm/types.h>
+#include <linux/if.h>
+#include <linux/netlink.h>
+#include <linux/rtnetlink.h>
+
+#ifdef HAVE_MPLS_KERNEL
+#include <linux/lwtunnel.h>
+#endif
+
+#ifndef MSG_TRUNC			/* Hack: Several versions of glibc miss this one :( */
+#define MSG_TRUNC 0x20
+#endif
+
+#ifndef IFA_FLAGS
+#define IFA_FLAGS 8
+#endif
+
+#ifndef IFF_LOWER_UP
+#define IFF_LOWER_UP 0x10000
+#endif
+
+#ifndef RTA_TABLE
+#define RTA_TABLE  15
+#endif
+
+#ifndef RTA_VIA
+#define RTA_VIA	 18
+#endif
+
+#ifndef RTA_NEWDST
+#define RTA_NEWDST  19
+#endif
+
+#ifndef RTA_ENCAP_TYPE
+#define RTA_ENCAP_TYPE	21
+#endif
+
+#ifndef RTA_ENCAP
+#define RTA_ENCAP  22
+#endif
+
+#define krt_ipv4(p) ((p)->af == AF_INET)
+#define krt_ecmp6(p) ((p)->af == AF_INET6)
+
+const int rt_default_ecmp = 16;
+
+/*
+ * Structure nl_parse_state keeps state of received route processing. Ideally,
+ * we could just independently parse received Netlink messages and immediately
+ * propagate received routes to the rest of BIRD, but older Linux kernel (before
+ * version 4.11) represents and announces IPv6 ECMP routes not as one route with
+ * multiple next hops (like RTA_MULTIPATH in IPv4 ECMP), but as a sequence of
+ * routes with the same prefix. More recent kernels work as with IPv4.
+ *
+ * Therefore, BIRD keeps currently processed route in nl_parse_state structure
+ * and postpones its propagation until we expect it to be final; i.e., when
+ * non-matching route is received or when the scan ends. When another matching
+ * route is received, it is merged with the already processed route to form an
+ * ECMP route. Note that merging is done only for IPv6 (merge == 1), but the
+ * postponing is done in both cases (for simplicity). All IPv4 routes or IPv6
+ * routes with RTA_MULTIPATH set are just considered non-matching.
+ *
+ * This is ignored for asynchronous notifications (every notification is handled
+ * as a separate route). It is not an issue for our routes, as we ignore such
+ * notifications anyways. But importing alien IPv6 ECMP routes does not work
+ * properly with older kernels.
+ *
+ * Whatever the kernel version is, IPv6 ECMP routes are sent as multiple routes
+ * for the same prefix.
+ */
+
+struct nl_parse_state
+{
+  struct linpool *pool;
+  int scan;
+  int merge;
+
+  net *net;
+  rta *attrs;
+  struct krt_proto *proto;
+  s8 new;
+  s8 krt_src;
+  u8 krt_type;
+  u8 krt_proto;
+  u32 krt_metric;
+
+  u32 rta_flow;		/* Used during parsing */
+};
+
+/*
+ *	Synchronous Netlink interface
+ */
+
+struct nl_sock
+{
+  int fd;
+  u32 seq;
+  byte *rx_buffer;			/* Receive buffer */
+  struct nlmsghdr *last_hdr;		/* Recently received packet */
+  uint last_size;
+};
+
+#define NL_RX_SIZE 8192
+
+#define NL_OP_DELETE	0
+#define NL_OP_ADD	(NLM_F_CREATE|NLM_F_EXCL)
+#define NL_OP_REPLACE	(NLM_F_CREATE|NLM_F_REPLACE)
+#define NL_OP_APPEND	(NLM_F_CREATE|NLM_F_APPEND)
+
+static linpool *nl_linpool;
+
+static struct nl_sock nl_scan = {.fd = -1};	/* Netlink socket for synchronous scan */
+static struct nl_sock nl_req  = {.fd = -1};	/* Netlink socket for requests */
+
+static void
+nl_open_sock(struct nl_sock *nl)
+{
+  if (nl->fd < 0)
+    {
+      nl->fd = socket(PF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
+      if (nl->fd < 0)
+	die("Unable to open rtnetlink socket: %m");
+      nl->seq = (u32) (current_time() TO_S); /* Or perhaps random_u32() ? */
+      nl->rx_buffer = xmalloc(NL_RX_SIZE);
+      nl->last_hdr = NULL;
+      nl->last_size = 0;
+    }
+}
+
+static void
+nl_open(void)
+{
+  nl_open_sock(&nl_scan);
+  nl_open_sock(&nl_req);
+}
+
+static void
+nl_send(struct nl_sock *nl, struct nlmsghdr *nh)
+{
+  struct sockaddr_nl sa;
+
+  memset(&sa, 0, sizeof(sa));
+  sa.nl_family = AF_NETLINK;
+  nh->nlmsg_pid = 0;
+  nh->nlmsg_seq = ++(nl->seq);
+  nh->nlmsg_len = NLMSG_ALIGN(nh->nlmsg_len);
+  if (sendto(nl->fd, nh, nh->nlmsg_len, 0, (struct sockaddr *)&sa, sizeof(sa)) < 0)
+    die("rtnetlink sendto: %m");
+  nl->last_hdr = NULL;
+}
+
+static void
+nl_request_dump(int af, int cmd)
+{
+  struct {
+    struct nlmsghdr nh;
+    struct rtgenmsg g;
+  } req = {
+    .nh.nlmsg_type = cmd,
+    .nh.nlmsg_len = sizeof(req),
+    .nh.nlmsg_flags = NLM_F_REQUEST | NLM_F_DUMP,
+    .g.rtgen_family = af
+  };
+  nl_send(&nl_scan, &req.nh);
+}
+
+static struct nlmsghdr *
+nl_get_reply(struct nl_sock *nl)
+{
+  for(;;)
+    {
+      if (!nl->last_hdr)
+	{
+	  struct iovec iov = { nl->rx_buffer, NL_RX_SIZE };
+	  struct sockaddr_nl sa;
+	  struct msghdr m = {
+	    .msg_name = &sa,
+	    .msg_namelen = sizeof(sa),
+	    .msg_iov = &iov,
+	    .msg_iovlen = 1,
+	  };
+	  int x = recvmsg(nl->fd, &m, 0);
+	  if (x < 0)
+	    die("nl_get_reply: %m");
+	  if (sa.nl_pid)		/* It isn't from the kernel */
+	    {
+	      DBG("Non-kernel packet\n");
+	      continue;
+	    }
+	  nl->last_size = x;
+	  nl->last_hdr = (void *) nl->rx_buffer;
+	  if (m.msg_flags & MSG_TRUNC)
+	    bug("nl_get_reply: got truncated reply which should be impossible");
+	}
+      if (NLMSG_OK(nl->last_hdr, nl->last_size))
+	{
+	  struct nlmsghdr *h = nl->last_hdr;
+	  nl->last_hdr = NLMSG_NEXT(h, nl->last_size);
+	  if (h->nlmsg_seq != nl->seq)
+	    {
+	      log(L_WARN "nl_get_reply: Ignoring out of sequence netlink packet (%x != %x)",
+		  h->nlmsg_seq, nl->seq);
+	      continue;
+	    }
+	  return h;
+	}
+      if (nl->last_size)
+	log(L_WARN "nl_get_reply: Found packet remnant of size %d", nl->last_size);
+      nl->last_hdr = NULL;
+    }
+}
+
+static struct tbf rl_netlink_err = TBF_DEFAULT_LOG_LIMITS;
+
+static int
+nl_error(struct nlmsghdr *h, int ignore_esrch)
+{
+  struct nlmsgerr *e;
+  int ec;
+
+  if (h->nlmsg_len < NLMSG_LENGTH(sizeof(struct nlmsgerr)))
+    {
+      log(L_WARN "Netlink: Truncated error message received");
+      return ENOBUFS;
+    }
+  e = (struct nlmsgerr *) NLMSG_DATA(h);
+  ec = -e->error;
+  if (ec && !(ignore_esrch && (ec == ESRCH)))
+    log_rl(&rl_netlink_err, L_WARN "Netlink: %s", strerror(ec));
+  return ec;
+}
+
+static struct nlmsghdr *
+nl_get_scan(void)
+{
+  struct nlmsghdr *h = nl_get_reply(&nl_scan);
+
+  if (h->nlmsg_type == NLMSG_DONE)
+    return NULL;
+  if (h->nlmsg_type == NLMSG_ERROR)
+    {
+      nl_error(h, 0);
+      return NULL;
+    }
+  return h;
+}
+
+static int
+nl_exchange(struct nlmsghdr *pkt, int ignore_esrch)
+{
+  struct nlmsghdr *h;
+
+  nl_send(&nl_req, pkt);
+  for(;;)
+    {
+      h = nl_get_reply(&nl_req);
+      if (h->nlmsg_type == NLMSG_ERROR)
+	break;
+      log(L_WARN "nl_exchange: Unexpected reply received");
+    }
+  return nl_error(h, ignore_esrch) ? -1 : 0;
+}
+
+/*
+ *	Netlink attributes
+ */
+
+static int nl_attr_len;
+
+static void *
+nl_checkin(struct nlmsghdr *h, int lsize)
+{
+  nl_attr_len = h->nlmsg_len - NLMSG_LENGTH(lsize);
+  if (nl_attr_len < 0)
+    {
+      log(L_ERR "nl_checkin: underrun by %d bytes", -nl_attr_len);
+      return NULL;
+    }
+  return NLMSG_DATA(h);
+}
+
+struct nl_want_attrs {
+  u8 defined:1;
+  u8 checksize:1;
+  u8 size;
+};
+
+
+#define BIRD_IFLA_MAX (IFLA_WIRELESS+1)
+
+static struct nl_want_attrs ifla_attr_want[BIRD_IFLA_MAX] = {
+  [IFLA_IFNAME]	  = { 1, 0, 0 },
+  [IFLA_MTU]	  = { 1, 1, sizeof(u32) },
+  [IFLA_MASTER]	  = { 1, 1, sizeof(u32) },
+  [IFLA_WIRELESS] = { 1, 0, 0 },
+};
+
+
+#define BIRD_IFA_MAX  (IFA_FLAGS+1)
+
+static struct nl_want_attrs ifa_attr_want4[BIRD_IFA_MAX] = {
+  [IFA_ADDRESS]	  = { 1, 1, sizeof(ip4_addr) },
+  [IFA_LOCAL]	  = { 1, 1, sizeof(ip4_addr) },
+  [IFA_BROADCAST] = { 1, 1, sizeof(ip4_addr) },
+  [IFA_FLAGS]     = { 1, 1, sizeof(u32) },
+};
+
+static struct nl_want_attrs ifa_attr_want6[BIRD_IFA_MAX] = {
+  [IFA_ADDRESS]	  = { 1, 1, sizeof(ip6_addr) },
+  [IFA_LOCAL]	  = { 1, 1, sizeof(ip6_addr) },
+  [IFA_FLAGS]	  = { 1, 1, sizeof(u32) },
+};
+
+
+#define BIRD_RTA_MAX  (RTA_ENCAP+1)
+
+static struct nl_want_attrs nexthop_attr_want4[BIRD_RTA_MAX] = {
+  [RTA_GATEWAY]	  = { 1, 1, sizeof(ip4_addr) },
+  [RTA_VIA]	  = { 1, 0, 0 },
+  [RTA_FLOW]	  = { 1, 1, sizeof(u32) },
+  [RTA_ENCAP_TYPE]= { 1, 1, sizeof(u16) },
+  [RTA_ENCAP]	  = { 1, 0, 0 },
+};
+
+static struct nl_want_attrs nexthop_attr_want6[BIRD_RTA_MAX] = {
+  [RTA_GATEWAY]	  = { 1, 1, sizeof(ip6_addr) },
+  [RTA_VIA]	  = { 1, 0, 0 },
+  [RTA_FLOW]	  = { 1, 1, sizeof(u32) },
+  [RTA_ENCAP_TYPE]= { 1, 1, sizeof(u16) },
+  [RTA_ENCAP]	  = { 1, 0, 0 },
+};
+
+#ifdef HAVE_MPLS_KERNEL
+static struct nl_want_attrs nexthop_attr_want_mpls[BIRD_RTA_MAX] = {
+  [RTA_VIA]	  = { 1, 0, 0 },
+  [RTA_NEWDST]	  = { 1, 0, 0 },
+};
+
+static struct nl_want_attrs encap_mpls_want[BIRD_RTA_MAX] = {
+  [RTA_DST]       = { 1, 0, 0 },
+};
+#endif
+
+static struct nl_want_attrs rtm_attr_want4[BIRD_RTA_MAX] = {
+  [RTA_DST]	  = { 1, 1, sizeof(ip4_addr) },
+  [RTA_OIF]	  = { 1, 1, sizeof(u32) },
+  [RTA_GATEWAY]	  = { 1, 1, sizeof(ip4_addr) },
+  [RTA_PRIORITY]  = { 1, 1, sizeof(u32) },
+  [RTA_PREFSRC]	  = { 1, 1, sizeof(ip4_addr) },
+  [RTA_METRICS]	  = { 1, 0, 0 },
+  [RTA_MULTIPATH] = { 1, 0, 0 },
+  [RTA_FLOW]	  = { 1, 1, sizeof(u32) },
+  [RTA_TABLE]	  = { 1, 1, sizeof(u32) },
+  [RTA_VIA]	  = { 1, 0, 0 },
+  [RTA_ENCAP_TYPE]= { 1, 1, sizeof(u16) },
+  [RTA_ENCAP]	  = { 1, 0, 0 },
+};
+
+static struct nl_want_attrs rtm_attr_want6[BIRD_RTA_MAX] = {
+  [RTA_DST]	  = { 1, 1, sizeof(ip6_addr) },
+  [RTA_SRC]	  = { 1, 1, sizeof(ip6_addr) },
+  [RTA_IIF]	  = { 1, 1, sizeof(u32) },
+  [RTA_OIF]	  = { 1, 1, sizeof(u32) },
+  [RTA_GATEWAY]	  = { 1, 1, sizeof(ip6_addr) },
+  [RTA_PRIORITY]  = { 1, 1, sizeof(u32) },
+  [RTA_PREFSRC]	  = { 1, 1, sizeof(ip6_addr) },
+  [RTA_METRICS]	  = { 1, 0, 0 },
+  [RTA_MULTIPATH] = { 1, 0, 0 },
+  [RTA_FLOW]	  = { 1, 1, sizeof(u32) },
+  [RTA_TABLE]	  = { 1, 1, sizeof(u32) },
+  [RTA_VIA]	  = { 1, 0, 0 },
+  [RTA_ENCAP_TYPE]= { 1, 1, sizeof(u16) },
+  [RTA_ENCAP]	  = { 1, 0, 0 },
+};
+
+#ifdef HAVE_MPLS_KERNEL
+static struct nl_want_attrs rtm_attr_want_mpls[BIRD_RTA_MAX] = {
+  [RTA_DST]	  = { 1, 1, sizeof(u32) },
+  [RTA_IIF]	  = { 1, 1, sizeof(u32) },
+  [RTA_OIF]	  = { 1, 1, sizeof(u32) },
+  [RTA_PRIORITY]  = { 1, 1, sizeof(u32) },
+  [RTA_METRICS]	  = { 1, 0, 0 },
+  [RTA_MULTIPATH] = { 1, 0, 0 },
+  [RTA_FLOW]	  = { 1, 1, sizeof(u32) },
+  [RTA_TABLE]	  = { 1, 1, sizeof(u32) },
+  [RTA_VIA]	  = { 1, 0, 0 },
+  [RTA_NEWDST]	  = { 1, 0, 0 },
+};
+#endif
+
+
+static int
+nl_parse_attrs(struct rtattr *a, struct nl_want_attrs *want, struct rtattr **k, int ksize)
+{
+  int max = ksize / sizeof(struct rtattr *);
+  bzero(k, ksize);
+
+  for ( ; RTA_OK(a, nl_attr_len); a = RTA_NEXT(a, nl_attr_len))
+    {
+      if ((a->rta_type >= max) || !want[a->rta_type].defined)
+	continue;
+
+      if (want[a->rta_type].checksize && (RTA_PAYLOAD(a) != want[a->rta_type].size))
+	{
+	  log(L_ERR "nl_parse_attrs: Malformed attribute received");
+	  return 0;
+	}
+
+      k[a->rta_type] = a;
+    }
+
+  if (nl_attr_len)
+    {
+      log(L_ERR "nl_parse_attrs: remnant of size %d", nl_attr_len);
+      return 0;
+    }
+
+  return 1;
+}
+
+static inline u16 rta_get_u16(struct rtattr *a)
+{ return *(u16 *) RTA_DATA(a); }
+
+static inline u32 rta_get_u32(struct rtattr *a)
+{ return *(u32 *) RTA_DATA(a); }
+
+static inline ip4_addr rta_get_ip4(struct rtattr *a)
+{ return ip4_ntoh(*(ip4_addr *) RTA_DATA(a)); }
+
+static inline ip6_addr rta_get_ip6(struct rtattr *a)
+{ return ip6_ntoh(*(ip6_addr *) RTA_DATA(a)); }
+
+static inline ip_addr rta_get_ipa(struct rtattr *a)
+{
+  if (RTA_PAYLOAD(a) == sizeof(ip4_addr))
+    return ipa_from_ip4(rta_get_ip4(a));
+  else
+    return ipa_from_ip6(rta_get_ip6(a));
+}
+
+#ifdef HAVE_MPLS_KERNEL
+static inline ip_addr rta_get_via(struct rtattr *a)
+{
+  struct rtvia *v = RTA_DATA(a);
+  switch(v->rtvia_family) {
+    case AF_INET:  return ipa_from_ip4(ip4_ntoh(*(ip4_addr *) v->rtvia_addr));
+    case AF_INET6: return ipa_from_ip6(ip6_ntoh(*(ip6_addr *) v->rtvia_addr));
+  }
+  return IPA_NONE;
+}
+
+static u32 rta_mpls_stack[MPLS_MAX_LABEL_STACK];
+static inline int rta_get_mpls(struct rtattr *a, u32 *stack)
+{
+  if (!a)
+    return 0;
+
+  if (RTA_PAYLOAD(a) % 4)
+    log(L_WARN "KRT: Strange length of received MPLS stack: %u", RTA_PAYLOAD(a));
+
+  int labels = mpls_get(RTA_DATA(a), RTA_PAYLOAD(a) & ~0x3, stack);
+
+  if (labels < 0)
+  {
+    log(L_WARN "KRT: Too long MPLS stack received, ignoring");
+    labels = 0;
+  }
+
+  return labels;
+}
+#endif
+
+struct rtattr *
+nl_add_attr(struct nlmsghdr *h, uint bufsize, uint code, const void *data, uint dlen)
+{
+  uint pos = NLMSG_ALIGN(h->nlmsg_len);
+  uint len = RTA_LENGTH(dlen);
+
+  if (pos + len > bufsize)
+    bug("nl_add_attr: packet buffer overflow");
+
+  struct rtattr *a = (struct rtattr *)((char *)h + pos);
+  a->rta_type = code;
+  a->rta_len = len;
+  h->nlmsg_len = pos + len;
+
+  if (dlen > 0)
+    memcpy(RTA_DATA(a), data, dlen);
+
+  return a;
+}
+
+static inline struct rtattr *
+nl_open_attr(struct nlmsghdr *h, uint bufsize, uint code)
+{
+  return nl_add_attr(h, bufsize, code, NULL, 0);
+}
+
+static inline void
+nl_close_attr(struct nlmsghdr *h, struct rtattr *a)
+{
+  a->rta_len = (void *)h + NLMSG_ALIGN(h->nlmsg_len) - (void *)a;
+}
+
+static inline void
+nl_add_attr_u16(struct nlmsghdr *h, uint bufsize, int code, u16 data)
+{
+  nl_add_attr(h, bufsize, code, &data, 2);
+}
+
+static inline void
+nl_add_attr_u32(struct nlmsghdr *h, uint bufsize, int code, u32 data)
+{
+  nl_add_attr(h, bufsize, code, &data, 4);
+}
+
+static inline void
+nl_add_attr_ip4(struct nlmsghdr *h, uint bufsize, int code, ip4_addr ip4)
+{
+  ip4 = ip4_hton(ip4);
+  nl_add_attr(h, bufsize, code, &ip4, sizeof(ip4));
+}
+
+static inline void
+nl_add_attr_ip6(struct nlmsghdr *h, uint bufsize, int code, ip6_addr ip6)
+{
+  ip6 = ip6_hton(ip6);
+  nl_add_attr(h, bufsize, code, &ip6, sizeof(ip6));
+}
+
+static inline void
+nl_add_attr_ipa(struct nlmsghdr *h, uint bufsize, int code, ip_addr ipa)
+{
+  if (ipa_is_ip4(ipa))
+    nl_add_attr_ip4(h, bufsize, code, ipa_to_ip4(ipa));
+  else
+    nl_add_attr_ip6(h, bufsize, code, ipa_to_ip6(ipa));
+}
+
+#ifdef HAVE_MPLS_KERNEL
+static inline void
+nl_add_attr_mpls(struct nlmsghdr *h, uint bufsize, int code, int len, u32 *stack)
+{
+  char buf[len*4];
+  mpls_put(buf, len, stack);
+  nl_add_attr(h, bufsize, code, buf, len*4);
+}
+
+static inline void
+nl_add_attr_mpls_encap(struct nlmsghdr *h, uint bufsize, int len, u32 *stack)
+{
+  nl_add_attr_u16(h, bufsize, RTA_ENCAP_TYPE, LWTUNNEL_ENCAP_MPLS);
+
+  struct rtattr *nest = nl_open_attr(h, bufsize, RTA_ENCAP);
+  nl_add_attr_mpls(h, bufsize, RTA_DST, len, stack);
+  nl_close_attr(h, nest);
+}
+
+static inline void
+nl_add_attr_via(struct nlmsghdr *h, uint bufsize, ip_addr ipa)
+{
+  struct rtvia *via = alloca(sizeof(struct rtvia) + 16);
+
+  if (ipa_is_ip4(ipa))
+  {
+    via->rtvia_family = AF_INET;
+    put_ip4(via->rtvia_addr, ipa_to_ip4(ipa));
+    nl_add_attr(h, bufsize, RTA_VIA, via, sizeof(struct rtvia) + 4);
+  }
+  else
+  {
+    via->rtvia_family = AF_INET6;
+    put_ip6(via->rtvia_addr, ipa_to_ip6(ipa));
+    nl_add_attr(h, bufsize, RTA_VIA, via, sizeof(struct rtvia) + 16);
+  }
+}
+#endif
+
+static inline struct rtnexthop *
+nl_open_nexthop(struct nlmsghdr *h, uint bufsize)
+{
+  uint pos = NLMSG_ALIGN(h->nlmsg_len);
+  uint len = RTNH_LENGTH(0);
+
+  if (pos + len > bufsize)
+    bug("nl_open_nexthop: packet buffer overflow");
+
+  h->nlmsg_len = pos + len;
+
+  return (void *)h + pos;
+}
+
+static inline void
+nl_close_nexthop(struct nlmsghdr *h, struct rtnexthop *nh)
+{
+  nh->rtnh_len = (void *)h + NLMSG_ALIGN(h->nlmsg_len) - (void *)nh;
+}
+
+static inline void
+nl_add_nexthop(struct nlmsghdr *h, uint bufsize, struct nexthop *nh, int af UNUSED)
+{
+#ifdef HAVE_MPLS_KERNEL
+  if (nh->labels > 0)
+    if (af == AF_MPLS)
+      nl_add_attr_mpls(h, bufsize, RTA_NEWDST, nh->labels, nh->label);
+    else
+      nl_add_attr_mpls_encap(h, bufsize, nh->labels, nh->label);
+
+  if (ipa_nonzero(nh->gw))
+  {
+    if (af == (ipa_is_ip4(nh->gw) ? AF_INET : AF_INET6))
+      nl_add_attr_ipa(h, bufsize, RTA_GATEWAY, nh->gw);
+    else
+      nl_add_attr_via(h, bufsize, nh->gw);
+  }
+#else
+
+  if (ipa_nonzero(nh->gw))
+    nl_add_attr_ipa(h, bufsize, RTA_GATEWAY, nh->gw);
+#endif
+}
+
+static void
+nl_add_multipath(struct nlmsghdr *h, uint bufsize, struct nexthop *nh, int af, ea_list *eattrs)
+{
+  struct rtattr *a = nl_open_attr(h, bufsize, RTA_MULTIPATH);
+  eattr *flow = ea_find(eattrs, EA_KRT_REALM);
+
+  for (; nh; nh = nh->next)
+  {
+    struct rtnexthop *rtnh = nl_open_nexthop(h, bufsize);
+
+    rtnh->rtnh_flags = 0;
+    rtnh->rtnh_hops = nh->weight;
+    rtnh->rtnh_ifindex = nh->iface->index;
+
+    nl_add_nexthop(h, bufsize, nh, af);
+
+    if (nh->flags & RNF_ONLINK)
+      rtnh->rtnh_flags |= RTNH_F_ONLINK;
+
+    /* Our KRT_REALM is per-route, but kernel RTA_FLOW is per-nexthop.
+       Therefore, we need to attach the same attribute to each nexthop. */
+    if (flow)
+      nl_add_attr_u32(h, bufsize, RTA_FLOW, flow->u.data);
+
+    nl_close_nexthop(h, rtnh);
+  }
+
+  nl_close_attr(h, a);
+}
+
+static struct nexthop *
+nl_parse_multipath(struct nl_parse_state *s, struct krt_proto *p, const net_addr *n, struct rtattr *ra, int af, int krt_src)
+{
+  struct rtattr *a[BIRD_RTA_MAX];
+  struct rtnexthop *nh = RTA_DATA(ra);
+  struct nexthop *rv, *first, **last;
+  unsigned len = RTA_PAYLOAD(ra);
+
+  first = NULL;
+  last = &first;
+
+  while (len)
+    {
+      /* Use RTNH_OK(nh,len) ?? */
+      if ((len < sizeof(*nh)) || (len < nh->rtnh_len))
+	goto err;
+
+      if ((nh->rtnh_flags & RTNH_F_DEAD) && (krt_src != KRT_SRC_BIRD))
+	goto next;
+
+      *last = rv = lp_allocz(s->pool, NEXTHOP_MAX_SIZE);
+      last = &(rv->next);
+
+      rv->weight = nh->rtnh_hops;
+      rv->iface = if_find_by_index(nh->rtnh_ifindex);
+      if (!rv->iface)
+	{
+	  log(L_ERR "KRT: Received route %N with unknown ifindex %u", n, nh->rtnh_ifindex);
+	  return NULL;
+	}
+
+      /* Nonexistent RTNH_PAYLOAD ?? */
+      nl_attr_len = nh->rtnh_len - RTNH_LENGTH(0);
+      switch (af)
+        {
+	case AF_INET:
+	  if (!nl_parse_attrs(RTNH_DATA(nh), nexthop_attr_want4, a, sizeof(a)))
+	    goto err;
+	  break;
+
+	case AF_INET6:
+	  if (!nl_parse_attrs(RTNH_DATA(nh), nexthop_attr_want6, a, sizeof(a)))
+	    goto err;
+	  break;
+
+#ifdef HAVE_MPLS_KERNEL
+	case AF_MPLS:
+	  if (!nl_parse_attrs(RTNH_DATA(nh), nexthop_attr_want_mpls, a, sizeof(a)))
+	    goto err;
+
+	  if (a[RTA_NEWDST])
+	    rv->labels = rta_get_mpls(a[RTA_NEWDST], rv->label);
+
+	  break;
+#endif
+
+	default:
+	  goto err;
+	}
+
+      if (a[RTA_GATEWAY])
+	rv->gw = rta_get_ipa(a[RTA_GATEWAY]);
+
+      if (a[RTA_FLOW])
+	s->rta_flow = rta_get_u32(a[RTA_FLOW]);
+
+#ifdef HAVE_MPLS_KERNEL
+      if (a[RTA_VIA])
+	rv->gw = rta_get_via(a[RTA_VIA]);
+#endif
+
+      if (ipa_nonzero(rv->gw))
+	{
+	  if (nh->rtnh_flags & RTNH_F_ONLINK)
+	    rv->flags |= RNF_ONLINK;
+
+	  neighbor *nbr;
+	  nbr = neigh_find(&p->p, rv->gw, rv->iface,
+			   (rv->flags & RNF_ONLINK) ? NEF_ONLINK : 0);
+	  if (!nbr || (nbr->scope == SCOPE_HOST))
+	    {
+	        log(L_ERR "KRT: Received route %N with strange next-hop %I", n, rv->gw);
+	        return NULL;
+	    }
+	}
+
+#ifdef HAVE_MPLS_KERNEL
+      if (a[RTA_ENCAP] && a[RTA_ENCAP_TYPE])
+      {
+	if (rta_get_u16(a[RTA_ENCAP_TYPE]) != LWTUNNEL_ENCAP_MPLS)
+	{
+	  log(L_WARN "KRT: Received route %N with unknown encapsulation method %d",
+	      n, rta_get_u16(a[RTA_ENCAP_TYPE]));
+	  return NULL;
+	}
+
+	struct rtattr *enca[BIRD_RTA_MAX];
+	nl_attr_len = RTA_PAYLOAD(a[RTA_ENCAP]);
+	nl_parse_attrs(RTA_DATA(a[RTA_ENCAP]), encap_mpls_want, enca, sizeof(enca));
+	rv->labels = rta_get_mpls(enca[RTA_DST], rv->label);
+      }
+#endif
+
+    next:
+      len -= NLMSG_ALIGN(nh->rtnh_len);
+      nh = RTNH_NEXT(nh);
+    }
+
+  /* Ensure nexthops are sorted to satisfy nest invariant */
+  if (!nexthop_is_sorted(first))
+    first = nexthop_sort(first);
+
+  return first;
+
+err:
+  log(L_ERR "KRT: Received strange multipath route %N", n);
+  return NULL;
+}
+
+static void
+nl_add_metrics(struct nlmsghdr *h, uint bufsize, u32 *metrics, int max)
+{
+  struct rtattr *a = nl_open_attr(h, bufsize, RTA_METRICS);
+  int t;
+
+  for (t = 1; t < max; t++)
+    if (metrics[0] & (1 << t))
+      nl_add_attr_u32(h, bufsize, t, metrics[t]);
+
+  nl_close_attr(h, a);
+}
+
+static int
+nl_parse_metrics(struct rtattr *hdr, u32 *metrics, int max)
+{
+  struct rtattr *a = RTA_DATA(hdr);
+  int len = RTA_PAYLOAD(hdr);
+
+  metrics[0] = 0;
+  for (; RTA_OK(a, len); a = RTA_NEXT(a, len))
+  {
+    if (a->rta_type == RTA_UNSPEC)
+      continue;
+
+    if (a->rta_type >= max)
+      continue;
+
+    if (RTA_PAYLOAD(a) != 4)
+      return -1;
+
+    metrics[0] |= 1 << a->rta_type;
+    metrics[a->rta_type] = rta_get_u32(a);
+  }
+
+  if (len > 0)
+    return -1;
+
+  return 0;
+}
+
+
+/*
+ *	Scanning of interfaces
+ */
+
+static void
+nl_parse_link(struct nlmsghdr *h, int scan)
+{
+  struct ifinfomsg *i;
+  struct rtattr *a[BIRD_IFLA_MAX];
+  int new = h->nlmsg_type == RTM_NEWLINK;
+  struct iface f = {};
+  struct iface *ifi;
+  char *name;
+  u32 mtu, master = 0;
+  uint fl;
+
+  if (!(i = nl_checkin(h, sizeof(*i))) || !nl_parse_attrs(IFLA_RTA(i), ifla_attr_want, a, sizeof(a)))
+    return;
+  if (!a[IFLA_IFNAME] || (RTA_PAYLOAD(a[IFLA_IFNAME]) < 2) || !a[IFLA_MTU])
+    {
+      /*
+       * IFLA_IFNAME and IFLA_MTU are required, in fact, but there may also come
+       * a message with IFLA_WIRELESS set, where (e.g.) no IFLA_IFNAME exists.
+       * We simply ignore all such messages with IFLA_WIRELESS without notice.
+       */
+
+      if (a[IFLA_WIRELESS])
+	return;
+
+      log(L_ERR "KIF: Malformed message received");
+      return;
+    }
+
+  name = RTA_DATA(a[IFLA_IFNAME]);
+  mtu = rta_get_u32(a[IFLA_MTU]);
+
+  if (a[IFLA_MASTER])
+    master = rta_get_u32(a[IFLA_MASTER]);
+
+  ifi = if_find_by_index(i->ifi_index);
+  if (!new)
+    {
+      DBG("KIF: IF%d(%s) goes down\n", i->ifi_index, name);
+      if (!ifi)
+	return;
+
+      if_delete(ifi);
+    }
+  else
+    {
+      DBG("KIF: IF%d(%s) goes up (mtu=%d,flg=%x)\n", i->ifi_index, name, mtu, i->ifi_flags);
+      if (ifi && strncmp(ifi->name, name, sizeof(ifi->name)-1))
+	if_delete(ifi);
+
+      strncpy(f.name, name, sizeof(f.name)-1);
+      f.index = i->ifi_index;
+      f.mtu = mtu;
+
+      f.master_index = master;
+      f.master = if_find_by_index(master);
+
+      fl = i->ifi_flags;
+      if (fl & IFF_UP)
+	f.flags |= IF_ADMIN_UP;
+      if (fl & IFF_LOWER_UP)
+	f.flags |= IF_LINK_UP;
+      if (fl & IFF_LOOPBACK)		/* Loopback */
+	f.flags |= IF_MULTIACCESS | IF_LOOPBACK | IF_IGNORE;
+      else if (fl & IFF_POINTOPOINT)	/* PtP */
+	f.flags |= IF_MULTICAST;
+      else if (fl & IFF_BROADCAST)	/* Broadcast */
+	f.flags |= IF_MULTIACCESS | IF_BROADCAST | IF_MULTICAST;
+      else
+	f.flags |= IF_MULTIACCESS;	/* NBMA */
+
+      if (fl & IFF_MULTICAST)
+	f.flags |= IF_MULTICAST;
+
+      ifi = if_update(&f);
+
+      if (!scan)
+	if_end_partial_update(ifi);
+    }
+}
+
+static void
+nl_parse_addr4(struct ifaddrmsg *i, int scan, int new)
+{
+  struct rtattr *a[BIRD_IFA_MAX];
+  struct iface *ifi;
+  u32 ifa_flags;
+  int scope;
+
+  if (!nl_parse_attrs(IFA_RTA(i), ifa_attr_want4, a, sizeof(a)))
+    return;
+
+  if (!a[IFA_LOCAL])
+    {
+      log(L_ERR "KIF: Malformed message received (missing IFA_LOCAL)");
+      return;
+    }
+  if (!a[IFA_ADDRESS])
+    {
+      log(L_ERR "KIF: Malformed message received (missing IFA_ADDRESS)");
+      return;
+    }
+
+  ifi = if_find_by_index(i->ifa_index);
+  if (!ifi)
+    {
+      log(L_ERR "KIF: Received address message for unknown interface %d", i->ifa_index);
+      return;
+    }
+
+  if (a[IFA_FLAGS])
+    ifa_flags = rta_get_u32(a[IFA_FLAGS]);
+  else
+    ifa_flags = i->ifa_flags;
+
+  struct ifa ifa;
+  bzero(&ifa, sizeof(ifa));
+  ifa.iface = ifi;
+  if (ifa_flags & IFA_F_SECONDARY)
+    ifa.flags |= IA_SECONDARY;
+
+  ifa.ip = rta_get_ipa(a[IFA_LOCAL]);
+
+  if (i->ifa_prefixlen > IP4_MAX_PREFIX_LENGTH)
+    {
+      log(L_ERR "KIF: Invalid prefix length for interface %s: %d", ifi->name, i->ifa_prefixlen);
+      new = 0;
+    }
+  if (i->ifa_prefixlen == IP4_MAX_PREFIX_LENGTH)
+    {
+      ifa.brd = rta_get_ipa(a[IFA_ADDRESS]);
+      net_fill_ip4(&ifa.prefix, rta_get_ip4(a[IFA_ADDRESS]), i->ifa_prefixlen);
+
+      /* It is either a host address or a peer address */
+      if (ipa_equal(ifa.ip, ifa.brd))
+	ifa.flags |= IA_HOST;
+      else
+	{
+	  ifa.flags |= IA_PEER;
+	  ifa.opposite = ifa.brd;
+	}
+    }
+  else
+    {
+      net_fill_ip4(&ifa.prefix, ipa_to_ip4(ifa.ip), i->ifa_prefixlen);
+      net_normalize(&ifa.prefix);
+
+      if (i->ifa_prefixlen == IP4_MAX_PREFIX_LENGTH - 1)
+	ifa.opposite = ipa_opposite_m1(ifa.ip);
+
+      if (i->ifa_prefixlen == IP4_MAX_PREFIX_LENGTH - 2)
+	ifa.opposite = ipa_opposite_m2(ifa.ip);
+
+      if (ifi->flags & IF_BROADCAST)
+        {
+	  /* If kernel offers us a broadcast address, we trust it */
+	  if (a[IFA_BROADCAST])
+	    ifa.brd = ipa_from_ip4(rta_get_ip4(a[IFA_BROADCAST]));
+	  /* Otherwise we create one (except for /31) */
+	  else if (i->ifa_prefixlen < (IP4_MAX_PREFIX_LENGTH - 1))
+	    ifa.brd = ipa_from_ip4(ip4_or(ipa_to_ip4(ifa.ip),
+					  ip4_not(ip4_mkmask(i->ifa_prefixlen))));
+	}
+    }
+
+  scope = ipa_classify(ifa.ip);
+  if (scope < 0)
+    {
+      log(L_ERR "KIF: Invalid interface address %I for %s", ifa.ip, ifi->name);
+      return;
+    }
+  ifa.scope = scope & IADDR_SCOPE_MASK;
+
+  DBG("KIF: IF%d(%s): %s IPA %I, flg %x, net %N, brd %I, opp %I\n",
+      ifi->index, ifi->name,
+      new ? "added" : "removed",
+      ifa.ip, ifa.flags, &ifa.prefix, ifa.brd, ifa.opposite);
+
+  if (new)
+    ifa_update(&ifa);
+  else
+    ifa_delete(&ifa);
+
+  if (!scan)
+    if_end_partial_update(ifi);
+}
+
+static void
+nl_parse_addr6(struct ifaddrmsg *i, int scan, int new)
+{
+  struct rtattr *a[BIRD_IFA_MAX];
+  struct iface *ifi;
+  u32 ifa_flags;
+  int scope;
+
+  if (!nl_parse_attrs(IFA_RTA(i), ifa_attr_want6, a, sizeof(a)))
+    return;
+
+  if (!a[IFA_ADDRESS])
+    {
+      log(L_ERR "KIF: Malformed message received (missing IFA_ADDRESS)");
+      return;
+    }
+
+  ifi = if_find_by_index(i->ifa_index);
+  if (!ifi)
+    {
+      log(L_ERR "KIF: Received address message for unknown interface %d", i->ifa_index);
+      return;
+    }
+
+  if (a[IFA_FLAGS])
+    ifa_flags = rta_get_u32(a[IFA_FLAGS]);
+  else
+    ifa_flags = i->ifa_flags;
+
+  struct ifa ifa;
+  bzero(&ifa, sizeof(ifa));
+  ifa.iface = ifi;
+  if (ifa_flags & IFA_F_SECONDARY)
+    ifa.flags |= IA_SECONDARY;
+
+  /* Ignore tentative addresses silently */
+  if (ifa_flags & IFA_F_TENTATIVE)
+    return;
+
+  /* IFA_LOCAL can be unset for IPv6 interfaces */
+  ifa.ip = rta_get_ipa(a[IFA_LOCAL] ? : a[IFA_ADDRESS]);
+
+  if (i->ifa_prefixlen > IP6_MAX_PREFIX_LENGTH)
+    {
+      log(L_ERR "KIF: Invalid prefix length for interface %s: %d", ifi->name, i->ifa_prefixlen);
+      new = 0;
+    }
+  if (i->ifa_prefixlen == IP6_MAX_PREFIX_LENGTH)
+    {
+      ifa.brd = rta_get_ipa(a[IFA_ADDRESS]);
+      net_fill_ip6(&ifa.prefix, rta_get_ip6(a[IFA_ADDRESS]), i->ifa_prefixlen);
+
+      /* It is either a host address or a peer address */
+      if (ipa_equal(ifa.ip, ifa.brd))
+	ifa.flags |= IA_HOST;
+      else
+	{
+	  ifa.flags |= IA_PEER;
+	  ifa.opposite = ifa.brd;
+	}
+    }
+  else
+    {
+      net_fill_ip6(&ifa.prefix, ipa_to_ip6(ifa.ip), i->ifa_prefixlen);
+      net_normalize(&ifa.prefix);
+
+      if (i->ifa_prefixlen == IP6_MAX_PREFIX_LENGTH - 1)
+	ifa.opposite = ipa_opposite_m1(ifa.ip);
+    }
+
+  scope = ipa_classify(ifa.ip);
+  if (scope < 0)
+    {
+      log(L_ERR "KIF: Invalid interface address %I for %s", ifa.ip, ifi->name);
+      return;
+    }
+  ifa.scope = scope & IADDR_SCOPE_MASK;
+
+  DBG("KIF: IF%d(%s): %s IPA %I, flg %x, net %N, brd %I, opp %I\n",
+      ifi->index, ifi->name,
+      new ? "added" : "removed",
+      ifa.ip, ifa.flags, &ifa.prefix, ifa.brd, ifa.opposite);
+
+  if (new)
+    ifa_update(&ifa);
+  else
+    ifa_delete(&ifa);
+
+  if (!scan)
+    if_end_partial_update(ifi);
+}
+
+static void
+nl_parse_addr(struct nlmsghdr *h, int scan)
+{
+  struct ifaddrmsg *i;
+
+  if (!(i = nl_checkin(h, sizeof(*i))))
+    return;
+
+  int new = (h->nlmsg_type == RTM_NEWADDR);
+
+  switch (i->ifa_family)
+    {
+      case AF_INET:
+	return nl_parse_addr4(i, scan, new);
+
+      case AF_INET6:
+	return nl_parse_addr6(i, scan, new);
+    }
+}
+
+void
+kif_do_scan(struct kif_proto *p UNUSED)
+{
+  struct nlmsghdr *h;
+
+  if_start_update();
+
+  nl_request_dump(AF_UNSPEC, RTM_GETLINK);
+  while (h = nl_get_scan())
+    if (h->nlmsg_type == RTM_NEWLINK || h->nlmsg_type == RTM_DELLINK)
+      nl_parse_link(h, 1);
+    else
+      log(L_DEBUG "nl_scan_ifaces: Unknown packet received (type=%d)", h->nlmsg_type);
+
+  /* Re-resolve master interface for slaves */
+  struct iface *i;
+  WALK_LIST(i, iface_list)
+    if (i->master_index)
+    {
+      struct iface f = {
+	.flags = i->flags,
+	.mtu = i->mtu,
+	.index = i->index,
+	.master_index = i->master_index,
+	.master = if_find_by_index(i->master_index)
+      };
+
+      if (f.master != i->master)
+      {
+	memcpy(f.name, i->name, sizeof(f.name));
+	if_update(&f);
+      }
+    }
+
+  nl_request_dump(AF_INET, RTM_GETADDR);
+  while (h = nl_get_scan())
+    if (h->nlmsg_type == RTM_NEWADDR || h->nlmsg_type == RTM_DELADDR)
+      nl_parse_addr(h, 1);
+    else
+      log(L_DEBUG "nl_scan_ifaces: Unknown packet received (type=%d)", h->nlmsg_type);
+
+  nl_request_dump(AF_INET6, RTM_GETADDR);
+  while (h = nl_get_scan())
+    if (h->nlmsg_type == RTM_NEWADDR || h->nlmsg_type == RTM_DELADDR)
+      nl_parse_addr(h, 1);
+    else
+      log(L_DEBUG "nl_scan_ifaces: Unknown packet received (type=%d)", h->nlmsg_type);
+
+  if_end_update();
+}
+
+/*
+ *	Routes
+ */
+
+static inline u32
+krt_table_id(struct krt_proto *p)
+{
+  return KRT_CF->sys.table_id;
+}
+
+static HASH(struct krt_proto) nl_table_map;
+
+#define RTH_KEY(p)		p->af, krt_table_id(p)
+#define RTH_NEXT(p)		p->sys.hash_next
+#define RTH_EQ(a1,i1,a2,i2)	a1 == a2 && i1 == i2
+#define RTH_FN(a,i)		a ^ u32_hash(i)
+
+#define RTH_REHASH		rth_rehash
+#define RTH_PARAMS		/8, *2, 2, 2, 6, 20
+
+HASH_DEFINE_REHASH_FN(RTH, struct krt_proto)
+
+int
+krt_capable(rte *e)
+{
+  rta *a = e->attrs;
+
+  switch (a->dest)
+  {
+    case RTD_UNICAST:
+    case RTD_BLACKHOLE:
+    case RTD_UNREACHABLE:
+    case RTD_PROHIBIT:
+      return 1;
+
+    default:
+      return 0;
+  }
+}
+
+static inline int
+nh_bufsize(struct nexthop *nh)
+{
+  int rv = 0;
+  for (; nh != NULL; nh = nh->next)
+    rv += RTNH_LENGTH(RTA_LENGTH(sizeof(ip_addr)));
+  return rv;
+}
+
+static int
+nl_send_route(struct krt_proto *p, rte *e, int op, int dest, struct nexthop *nh)
+{
+  eattr *ea;
+  net *net = e->net;
+  rta *a = e->attrs;
+  ea_list *eattrs = a->eattrs;
+  int bufsize = 128 + KRT_METRICS_MAX*8 + nh_bufsize(&(a->nh));
+  u32 priority = 0;
+
+  struct {
+    struct nlmsghdr h;
+    struct rtmsg r;
+    char buf[0];
+  } *r;
+
+  int rsize = sizeof(*r) + bufsize;
+  r = alloca(rsize);
+
+  DBG("nl_send_route(%N,op=%x)\n", net->n.addr, op);
+
+  bzero(&r->h, sizeof(r->h));
+  bzero(&r->r, sizeof(r->r));
+  r->h.nlmsg_type = op ? RTM_NEWROUTE : RTM_DELROUTE;
+  r->h.nlmsg_len = NLMSG_LENGTH(sizeof(struct rtmsg));
+  r->h.nlmsg_flags = op | NLM_F_REQUEST | NLM_F_ACK;
+
+  r->r.rtm_family = p->af;
+  r->r.rtm_dst_len = net_pxlen(net->n.addr);
+  r->r.rtm_protocol = RTPROT_BIRD;
+  r->r.rtm_scope = RT_SCOPE_NOWHERE;
+#ifdef HAVE_MPLS_KERNEL
+  if (p->af == AF_MPLS)
+  {
+    /*
+     * Kernel MPLS code is a bit picky. We must:
+     * 1) Always set RT_SCOPE_UNIVERSE and RTN_UNICAST (even for RTM_DELROUTE)
+     * 2) Never use RTA_PRIORITY
+     */
+
+    u32 label = net_mpls(net->n.addr);
+    nl_add_attr_mpls(&r->h, rsize, RTA_DST, 1, &label);
+    r->r.rtm_scope = RT_SCOPE_UNIVERSE;
+    r->r.rtm_type = RTN_UNICAST;
+  }
+  else
+#endif
+  {
+    nl_add_attr_ipa(&r->h, rsize, RTA_DST, net_prefix(net->n.addr));
+
+    /* Add source address for IPv6 SADR routes */
+    if (net->n.addr->type == NET_IP6_SADR)
+    {
+      net_addr_ip6_sadr *a = (void *) &net->n.addr;
+      nl_add_attr_ip6(&r->h, rsize, RTA_SRC, a->src_prefix);
+      r->r.rtm_src_len = a->src_pxlen;
+    }
+  }
+
+  /*
+   * Strange behavior for RTM_DELROUTE:
+   * 1) rtm_family is ignored in IPv6, works for IPv4
+   * 2) not setting RTA_PRIORITY is different from setting default value (on IPv6)
+   * 3) not setting RTA_PRIORITY is equivalent to setting 0, which is wildcard
+   */
+
+  if (krt_table_id(p) < 256)
+    r->r.rtm_table = krt_table_id(p);
+  else
+    nl_add_attr_u32(&r->h, rsize, RTA_TABLE, krt_table_id(p));
+
+  if (p->af == AF_MPLS)
+    priority = 0;
+  else if (a->source == RTS_DUMMY)
+    priority = e->u.krt.metric;
+  else if (KRT_CF->sys.metric)
+    priority = KRT_CF->sys.metric;
+  else if ((op != NL_OP_DELETE) && (ea = ea_find(eattrs, EA_KRT_METRIC)))
+    priority = ea->u.data;
+
+  if (priority)
+    nl_add_attr_u32(&r->h, rsize, RTA_PRIORITY, priority);
+
+  /* For route delete, we do not specify remaining route attributes */
+  if (op == NL_OP_DELETE)
+    goto dest;
+
+  /* Default scope is LINK for device routes, UNIVERSE otherwise */
+  if (p->af == AF_MPLS)
+    r->r.rtm_scope = RT_SCOPE_UNIVERSE;
+  else if (ea = ea_find(eattrs, EA_KRT_SCOPE))
+    r->r.rtm_scope = ea->u.data;
+  else
+    r->r.rtm_scope = (dest == RTD_UNICAST && ipa_zero(nh->gw)) ? RT_SCOPE_LINK : RT_SCOPE_UNIVERSE;
+
+  if (ea = ea_find(eattrs, EA_KRT_PREFSRC))
+    nl_add_attr_ipa(&r->h, rsize, RTA_PREFSRC, *(ip_addr *)ea->u.ptr->data);
+
+  if (ea = ea_find(eattrs, EA_KRT_REALM))
+    nl_add_attr_u32(&r->h, rsize, RTA_FLOW, ea->u.data);
+
+
+  u32 metrics[KRT_METRICS_MAX];
+  metrics[0] = 0;
+
+  struct ea_walk_state ews = { .eattrs = eattrs };
+  while (ea = ea_walk(&ews, EA_KRT_METRICS, KRT_METRICS_MAX))
+  {
+    int id = ea->id - EA_KRT_METRICS;
+    metrics[0] |= 1 << id;
+    metrics[id] = ea->u.data;
+  }
+
+  if (metrics[0])
+    nl_add_metrics(&r->h, rsize, metrics, KRT_METRICS_MAX);
+
+
+dest:
+  switch (dest)
+    {
+    case RTD_UNICAST:
+      r->r.rtm_type = RTN_UNICAST;
+      if (nh->next && !krt_ecmp6(p))
+	nl_add_multipath(&r->h, rsize, nh, p->af, eattrs);
+      else
+      {
+	nl_add_attr_u32(&r->h, rsize, RTA_OIF, nh->iface->index);
+	nl_add_nexthop(&r->h, rsize, nh, p->af);
+
+	if (nh->flags & RNF_ONLINK)
+	  r->r.rtm_flags |= RTNH_F_ONLINK;
+      }
+      break;
+    case RTD_BLACKHOLE:
+      r->r.rtm_type = RTN_BLACKHOLE;
+      break;
+    case RTD_UNREACHABLE:
+      r->r.rtm_type = RTN_UNREACHABLE;
+      break;
+    case RTD_PROHIBIT:
+      r->r.rtm_type = RTN_PROHIBIT;
+      break;
+    case RTD_NONE:
+      break;
+    default:
+      bug("krt_capable inconsistent with nl_send_route");
+    }
+
+  /* Ignore missing for DELETE */
+  return nl_exchange(&r->h, (op == NL_OP_DELETE));
+}
+
+static inline int
+nl_add_rte(struct krt_proto *p, rte *e)
+{
+  rta *a = e->attrs;
+  int err = 0;
+
+  if (krt_ecmp6(p) && a->nh.next)
+  {
+    struct nexthop *nh = &(a->nh);
+
+    err = nl_send_route(p, e, NL_OP_ADD, RTD_UNICAST, nh);
+    if (err < 0)
+      return err;
+
+    for (nh = nh->next; nh; nh = nh->next)
+      err += nl_send_route(p, e, NL_OP_APPEND, RTD_UNICAST, nh);
+
+    return err;
+  }
+
+  return nl_send_route(p, e, NL_OP_ADD, a->dest, &(a->nh));
+}
+
+static inline int
+nl_delete_rte(struct krt_proto *p, rte *e)
+{
+  int err = 0;
+
+  /* For IPv6, we just repeatedly request DELETE until we get error */
+  do
+    err = nl_send_route(p, e, NL_OP_DELETE, RTD_NONE, NULL);
+  while (krt_ecmp6(p) && !err);
+
+  return err;
+}
+
+static inline int
+nl_replace_rte(struct krt_proto *p, rte *e)
+{
+  rta *a = e->attrs;
+  return nl_send_route(p, e, NL_OP_REPLACE, a->dest, &(a->nh));
+}
+
+
+void
+krt_replace_rte(struct krt_proto *p, net *n UNUSED, rte *new, rte *old)
+{
+  int err = 0;
+
+  /*
+   * We use NL_OP_REPLACE for IPv4, it has an issue with not checking for
+   * matching rtm_protocol, but that is OK when dedicated priority is used.
+   *
+   * We do not use NL_OP_REPLACE for IPv6, as it has broken semantics for ECMP
+   * and with some kernel versions ECMP replace crashes kernel. Would need more
+   * testing and checks for kernel versions.
+   *
+   * For IPv6, we use NL_OP_DELETE and then NL_OP_ADD. We also do not trust the
+   * old route value, so we do not try to optimize IPv6 ECMP reconfigurations.
+   */
+
+  if (krt_ipv4(p) && old && new)
+  {
+    err = nl_replace_rte(p, new);
+  }
+  else
+  {
+    if (old)
+      nl_delete_rte(p, old);
+
+    if (new)
+      err = nl_add_rte(p, new);
+  }
+
+  if (new)
+  {
+    if (err < 0)
+      bmap_clear(&p->sync_map, new->id);
+    else
+      bmap_set(&p->sync_map, new->id);
+  }
+}
+
+static int
+nl_mergable_route(struct nl_parse_state *s, net *net, struct krt_proto *p, uint priority, uint krt_type, uint rtm_family)
+{
+  /* Route merging is used for IPv6 scans */
+  if (!s->scan || (rtm_family != AF_INET6))
+    return 0;
+
+  /* Saved and new route must have same network, proto/table, and priority */
+  if ((s->net != net) || (s->proto != p) || (s->krt_metric != priority))
+    return 0;
+
+  /* Both must be regular unicast routes */
+  if ((s->krt_type != RTN_UNICAST) || (krt_type != RTN_UNICAST))
+    return 0;
+
+  return 1;
+}
+
+static void
+nl_announce_route(struct nl_parse_state *s)
+{
+  rte *e = rte_get_temp(s->attrs);
+  e->net = s->net;
+  e->u.krt.src = s->krt_src;
+  e->u.krt.proto = s->krt_proto;
+  e->u.krt.seen = 0;
+  e->u.krt.best = 0;
+  e->u.krt.metric = s->krt_metric;
+
+  if (s->scan)
+    krt_got_route(s->proto, e);
+  else
+    krt_got_route_async(s->proto, e, s->new);
+
+  s->net = NULL;
+  s->attrs = NULL;
+  s->proto = NULL;
+  lp_flush(s->pool);
+}
+
+static inline void
+nl_parse_begin(struct nl_parse_state *s, int scan)
+{
+  memset(s, 0, sizeof (struct nl_parse_state));
+  s->pool = nl_linpool;
+  s->scan = scan;
+}
+
+static inline void
+nl_parse_end(struct nl_parse_state *s)
+{
+  if (s->net)
+    nl_announce_route(s);
+}
+
+
+#define SKIP0(ARG, ...) do { DBG("KRT: Ignoring route - " ARG, ##__VA_ARGS__); return; } while(0)
+#define SKIP(ARG, ...)  do { DBG("KRT: Ignoring route %N - " ARG, &dst, ##__VA_ARGS__); return; } while(0)
+
+static void
+nl_parse_route(struct nl_parse_state *s, struct nlmsghdr *h)
+{
+  struct krt_proto *p;
+  struct rtmsg *i;
+  struct rtattr *a[BIRD_RTA_MAX];
+  int new = h->nlmsg_type == RTM_NEWROUTE;
+
+  net_addr dst, src = {};
+  u32 oif = ~0;
+  u32 table_id;
+  u32 priority = 0;
+  u32 def_scope = RT_SCOPE_UNIVERSE;
+  int krt_src;
+
+  if (!(i = nl_checkin(h, sizeof(*i))))
+    return;
+
+  switch (i->rtm_family)
+    {
+    case AF_INET:
+      if (!nl_parse_attrs(RTM_RTA(i), rtm_attr_want4, a, sizeof(a)))
+	return;
+
+      if (a[RTA_DST])
+	net_fill_ip4(&dst, rta_get_ip4(a[RTA_DST]), i->rtm_dst_len);
+      else
+	net_fill_ip4(&dst, IP4_NONE, 0);
+      break;
+
+    case AF_INET6:
+      if (!nl_parse_attrs(RTM_RTA(i), rtm_attr_want6, a, sizeof(a)))
+	return;
+
+      if (a[RTA_DST])
+	net_fill_ip6(&dst, rta_get_ip6(a[RTA_DST]), i->rtm_dst_len);
+      else
+	net_fill_ip6(&dst, IP6_NONE, 0);
+
+      if (a[RTA_SRC])
+	net_fill_ip6(&src, rta_get_ip6(a[RTA_SRC]), i->rtm_src_len);
+      else
+	net_fill_ip6(&src, IP6_NONE, 0);
+      break;
+
+#ifdef HAVE_MPLS_KERNEL
+    case AF_MPLS:
+      if (!nl_parse_attrs(RTM_RTA(i), rtm_attr_want_mpls, a, sizeof(a)))
+	return;
+
+      if (!a[RTA_DST])
+	SKIP0("MPLS route without RTA_DST\n");
+
+      if (rta_get_mpls(a[RTA_DST], rta_mpls_stack) != 1)
+	SKIP0("MPLS route with multi-label RTA_DST\n");
+
+      net_fill_mpls(&dst, rta_mpls_stack[0]);
+      break;
+#endif
+
+    default:
+      return;
+    }
+
+  if (a[RTA_OIF])
+    oif = rta_get_u32(a[RTA_OIF]);
+
+  if (a[RTA_TABLE])
+    table_id = rta_get_u32(a[RTA_TABLE]);
+  else
+    table_id = i->rtm_table;
+
+  if (i->rtm_flags & RTM_F_CLONED)
+    SKIP("cloned\n");
+
+  /* Do we know this table? */
+  p = HASH_FIND(nl_table_map, RTH, i->rtm_family, table_id);
+  if (!p)
+    SKIP("unknown table %u\n", table_id);
+
+  if (a[RTA_SRC] && (p->p.net_type != NET_IP6_SADR))
+    SKIP("src prefix for non-SADR channel\n");
+
+  if (a[RTA_IIF])
+    SKIP("IIF set\n");
+
+  if (i->rtm_tos != 0)			/* We don't support TOS */
+    SKIP("TOS %02x\n", i->rtm_tos);
+
+  if (s->scan && !new)
+    SKIP("RTM_DELROUTE in scan\n");
+
+  if (a[RTA_PRIORITY])
+    priority = rta_get_u32(a[RTA_PRIORITY]);
+
+  int c = net_classify(&dst);
+  if ((c < 0) || !(c & IADDR_HOST) || ((c & IADDR_SCOPE_MASK) <= SCOPE_LINK))
+    SKIP("strange class/scope\n");
+
+  switch (i->rtm_protocol)
+    {
+    case RTPROT_UNSPEC:
+      SKIP("proto unspec\n");
+
+    case RTPROT_REDIRECT:
+      krt_src = KRT_SRC_REDIRECT;
+      break;
+
+    case RTPROT_KERNEL:
+      krt_src = KRT_SRC_KERNEL;
+      return;
+
+    case RTPROT_BIRD:
+      if (!s->scan)
+	SKIP("echo\n");
+      krt_src = KRT_SRC_BIRD;
+      break;
+
+    case RTPROT_BOOT:
+    default:
+      krt_src = KRT_SRC_ALIEN;
+    }
+
+  net_addr *n = &dst;
+  if (p->p.net_type == NET_IP6_SADR)
+  {
+    n = alloca(sizeof(net_addr_ip6_sadr));
+    net_fill_ip6_sadr(n, net6_prefix(&dst), net6_pxlen(&dst),
+		      net6_prefix(&src), net6_pxlen(&src));
+  }
+
+  net *net = net_get(p->p.main_channel->table, n);
+
+  if (s->net && !nl_mergable_route(s, net, p, priority, i->rtm_type, i->rtm_family))
+    nl_announce_route(s);
+
+  rta *ra = lp_allocz(s->pool, RTA_MAX_SIZE);
+  ra->src = p->p.main_source;
+  ra->source = RTS_INHERIT;
+  ra->scope = SCOPE_UNIVERSE;
+
+  if (a[RTA_FLOW])
+    s->rta_flow = rta_get_u32(a[RTA_FLOW]);
+  else
+    s->rta_flow = 0;
+
+  switch (i->rtm_type)
+    {
+    case RTN_UNICAST:
+      ra->dest = RTD_UNICAST;
+
+      if (a[RTA_MULTIPATH])
+        {
+	  struct nexthop *nh = nl_parse_multipath(s, p, n, a[RTA_MULTIPATH], i->rtm_family, krt_src);
+	  if (!nh)
+	    SKIP("strange RTA_MULTIPATH\n");
+
+	  nexthop_link(ra, nh);
+	  break;
+	}
+
+      if ((i->rtm_flags & RTNH_F_DEAD) && (krt_src != KRT_SRC_BIRD))
+	SKIP("ignore RTNH_F_DEAD\n");
+
+      ra->nh.iface = if_find_by_index(oif);
+      if (!ra->nh.iface)
+	{
+	  log(L_ERR "KRT: Received route %N with unknown ifindex %u", net->n.addr, oif);
+	  return;
+	}
+
+      if (a[RTA_GATEWAY])
+	ra->nh.gw = rta_get_ipa(a[RTA_GATEWAY]);
+
+#ifdef HAVE_MPLS_KERNEL
+      if (a[RTA_VIA])
+	ra->nh.gw = rta_get_via(a[RTA_VIA]);
+#endif
+
+      if (ipa_nonzero(ra->nh.gw))
+	{
+	  /* Silently skip strange 6to4 routes */
+	  const net_addr_ip6 sit = NET_ADDR_IP6(IP6_NONE, 96);
+	  if ((i->rtm_family == AF_INET6) && ipa_in_netX(ra->nh.gw, (net_addr *) &sit))
+	    return;
+
+	  if (i->rtm_flags & RTNH_F_ONLINK)
+	    ra->nh.flags |= RNF_ONLINK;
+
+	  neighbor *nbr;
+	  nbr = neigh_find(&p->p, ra->nh.gw, ra->nh.iface,
+			   (ra->nh.flags & RNF_ONLINK) ? NEF_ONLINK : 0);
+	  if (!nbr || (nbr->scope == SCOPE_HOST))
+	    {
+	      log(L_ERR "KRT: Received route %N with strange next-hop %I", net->n.addr,
+                  ra->nh.gw);
+	      return;
+	    }
+	}
+
+      break;
+    case RTN_BLACKHOLE:
+      ra->dest = RTD_BLACKHOLE;
+      break;
+    case RTN_UNREACHABLE:
+      ra->dest = RTD_UNREACHABLE;
+      break;
+    case RTN_PROHIBIT:
+      ra->dest = RTD_PROHIBIT;
+      break;
+    /* FIXME: What about RTN_THROW? */
+    default:
+      SKIP("type %d\n", i->rtm_type);
+      return;
+    }
+
+#ifdef HAVE_MPLS_KERNEL
+  if ((i->rtm_family == AF_MPLS) && a[RTA_NEWDST] && !ra->nh.next)
+    ra->nh.labels = rta_get_mpls(a[RTA_NEWDST], ra->nh.label);
+
+  if (a[RTA_ENCAP] && a[RTA_ENCAP_TYPE] && !ra->nh.next)
+    {
+      switch (rta_get_u16(a[RTA_ENCAP_TYPE]))
+	{
+	  case LWTUNNEL_ENCAP_MPLS:
+	    {
+	      struct rtattr *enca[BIRD_RTA_MAX];
+	      nl_attr_len = RTA_PAYLOAD(a[RTA_ENCAP]);
+	      nl_parse_attrs(RTA_DATA(a[RTA_ENCAP]), encap_mpls_want, enca, sizeof(enca));
+	      ra->nh.labels = rta_get_mpls(enca[RTA_DST], ra->nh.label);
+	      break;
+	    }
+	  default:
+	    SKIP("unknown encapsulation method %d\n", rta_get_u16(a[RTA_ENCAP_TYPE]));
+	    break;
+	}
+    }
+#endif
+
+  if (i->rtm_scope != def_scope)
+    {
+      ea_list *ea = lp_alloc(s->pool, sizeof(ea_list) + sizeof(eattr));
+      ea->next = ra->eattrs;
+      ra->eattrs = ea;
+      ea->flags = EALF_SORTED;
+      ea->count = 1;
+      ea->attrs[0].id = EA_KRT_SCOPE;
+      ea->attrs[0].flags = 0;
+      ea->attrs[0].type = EAF_TYPE_INT;
+      ea->attrs[0].u.data = i->rtm_scope;
+    }
+
+  if (a[RTA_PREFSRC])
+    {
+      ip_addr ps = rta_get_ipa(a[RTA_PREFSRC]);
+
+      ea_list *ea = lp_alloc(s->pool, sizeof(ea_list) + sizeof(eattr));
+      ea->next = ra->eattrs;
+      ra->eattrs = ea;
+      ea->flags = EALF_SORTED;
+      ea->count = 1;
+      ea->attrs[0].id = EA_KRT_PREFSRC;
+      ea->attrs[0].flags = 0;
+      ea->attrs[0].type = EAF_TYPE_IP_ADDRESS;
+
+      struct adata *ad = lp_alloc(s->pool, sizeof(struct adata) + sizeof(ps));
+      ad->length = sizeof(ps);
+      memcpy(ad->data, &ps, sizeof(ps));
+
+      ea->attrs[0].u.ptr = ad;
+    }
+
+  /* Can be set per-route or per-nexthop */
+  if (s->rta_flow)
+    {
+      ea_list *ea = lp_alloc(s->pool, sizeof(ea_list) + sizeof(eattr));
+      ea->next = ra->eattrs;
+      ra->eattrs = ea;
+      ea->flags = EALF_SORTED;
+      ea->count = 1;
+      ea->attrs[0].id = EA_KRT_REALM;
+      ea->attrs[0].flags = 0;
+      ea->attrs[0].type = EAF_TYPE_INT;
+      ea->attrs[0].u.data = s->rta_flow;
+    }
+
+  if (a[RTA_METRICS])
+    {
+      u32 metrics[KRT_METRICS_MAX];
+      ea_list *ea = lp_alloc(s->pool, sizeof(ea_list) + KRT_METRICS_MAX * sizeof(eattr));
+      int t, n = 0;
+
+      if (nl_parse_metrics(a[RTA_METRICS], metrics, ARRAY_SIZE(metrics)) < 0)
+        {
+	  log(L_ERR "KRT: Received route %N with strange RTA_METRICS attribute", net->n.addr);
+	  return;
+	}
+
+      for (t = 1; t < KRT_METRICS_MAX; t++)
+	if (metrics[0] & (1 << t))
+	  {
+	    ea->attrs[n].id = EA_CODE(PROTOCOL_KERNEL, KRT_METRICS_OFFSET + t);
+	    ea->attrs[n].flags = 0;
+	    ea->attrs[n].type = EAF_TYPE_INT; /* FIXME: Some are EAF_TYPE_BITFIELD */
+	    ea->attrs[n].u.data = metrics[t];
+	    n++;
+	  }
+
+      if (n > 0)
+        {
+	  ea->next = ra->eattrs;
+	  ea->flags = EALF_SORTED;
+	  ea->count = n;
+	  ra->eattrs = ea;
+	}
+    }
+
+  /*
+   * Ideally, now we would send the received route to the rest of kernel code.
+   * But IPv6 ECMP routes before 4.11 are sent as a sequence of routes, so we
+   * postpone it and merge next hops until the end of the sequence. Note that
+   * when doing merging of next hops, we expect the new route to be unipath.
+   * Otherwise, we ignore additional next hops in nexthop_insert().
+   */
+
+  if (!s->net)
+  {
+    /* Store the new route */
+    s->net = net;
+    s->attrs = ra;
+    s->proto = p;
+    s->new = new;
+    s->krt_src = krt_src;
+    s->krt_type = i->rtm_type;
+    s->krt_proto = i->rtm_protocol;
+    s->krt_metric = priority;
+  }
+  else
+  {
+    /* Merge next hops with the stored route */
+    rta *oa = s->attrs;
+
+    struct nexthop *nhs = &oa->nh;
+    nexthop_insert(&nhs, &ra->nh);
+
+    /* Perhaps new nexthop is inserted at the first position */
+    if (nhs == &ra->nh)
+    {
+      /* Swap rtas */
+      s->attrs = ra;
+
+      /* Keep old eattrs */
+      ra->eattrs = oa->eattrs;
+    }
+  }
+}
+
+void
+krt_do_scan(struct krt_proto *p UNUSED)	/* CONFIG_ALL_TABLES_AT_ONCE => p is NULL */
+{
+  struct nlmsghdr *h;
+  struct nl_parse_state s;
+
+  nl_parse_begin(&s, 1);
+  nl_request_dump(AF_UNSPEC, RTM_GETROUTE);
+  while (h = nl_get_scan())
+    if (h->nlmsg_type == RTM_NEWROUTE || h->nlmsg_type == RTM_DELROUTE)
+      nl_parse_route(&s, h);
+    else
+      log(L_DEBUG "nl_scan_fire: Unknown packet received (type=%d)", h->nlmsg_type);
+  nl_parse_end(&s);
+}
+
+/*
+ *	Asynchronous Netlink interface
+ */
+
+static sock *nl_async_sk;		/* BIRD socket for asynchronous notifications */
+static byte *nl_async_rx_buffer;	/* Receive buffer */
+
+static void
+nl_async_msg(struct nlmsghdr *h)
+{
+  struct nl_parse_state s;
+
+  switch (h->nlmsg_type)
+    {
+    case RTM_NEWROUTE:
+    case RTM_DELROUTE:
+      DBG("KRT: Received async route notification (%d)\n", h->nlmsg_type);
+      nl_parse_begin(&s, 0);
+      nl_parse_route(&s, h);
+      nl_parse_end(&s);
+      break;
+    case RTM_NEWLINK:
+    case RTM_DELLINK:
+      DBG("KRT: Received async link notification (%d)\n", h->nlmsg_type);
+      if (kif_proto)
+	nl_parse_link(h, 0);
+      break;
+    case RTM_NEWADDR:
+    case RTM_DELADDR:
+      DBG("KRT: Received async address notification (%d)\n", h->nlmsg_type);
+      if (kif_proto)
+	nl_parse_addr(h, 0);
+      break;
+    default:
+      DBG("KRT: Received unknown async notification (%d)\n", h->nlmsg_type);
+    }
+}
+
+static int
+nl_async_hook(sock *sk, uint size UNUSED)
+{
+  struct iovec iov = { nl_async_rx_buffer, NL_RX_SIZE };
+  struct sockaddr_nl sa;
+  struct msghdr m = {
+    .msg_name = &sa,
+    .msg_namelen = sizeof(sa),
+    .msg_iov = &iov,
+    .msg_iovlen = 1,
+  };
+  struct nlmsghdr *h;
+  int x;
+  uint len;
+
+  x = recvmsg(sk->fd, &m, 0);
+  if (x < 0)
+    {
+      if (errno == ENOBUFS)
+	{
+	  /*
+	   *  Netlink reports some packets have been thrown away.
+	   *  One day we might react to it by asking for route table
+	   *  scan in near future.
+	   */
+	  log(L_WARN "Kernel dropped some netlink messages, will resync on next scan.");
+	  return 1;	/* More data are likely to be ready */
+	}
+      else if (errno != EWOULDBLOCK)
+	log(L_ERR "Netlink recvmsg: %m");
+      return 0;
+    }
+  if (sa.nl_pid)		/* It isn't from the kernel */
+    {
+      DBG("Non-kernel packet\n");
+      return 1;
+    }
+  h = (void *) nl_async_rx_buffer;
+  len = x;
+  if (m.msg_flags & MSG_TRUNC)
+    {
+      log(L_WARN "Netlink got truncated asynchronous message");
+      return 1;
+    }
+  while (NLMSG_OK(h, len))
+    {
+      nl_async_msg(h);
+      h = NLMSG_NEXT(h, len);
+    }
+  if (len)
+    log(L_WARN "nl_async_hook: Found packet remnant of size %d", len);
+  return 1;
+}
+
+static void
+nl_async_err_hook(sock *sk, int e UNUSED)
+{
+  nl_async_hook(sk, 0);
+}
+
+static void
+nl_open_async(void)
+{
+  sock *sk;
+  struct sockaddr_nl sa;
+  int fd;
+
+  if (nl_async_sk)
+    return;
+
+  DBG("KRT: Opening async netlink socket\n");
+
+  fd = socket(PF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
+  if (fd < 0)
+    {
+      log(L_ERR "Unable to open asynchronous rtnetlink socket: %m");
+      return;
+    }
+
+  bzero(&sa, sizeof(sa));
+  sa.nl_family = AF_NETLINK;
+  sa.nl_groups = RTMGRP_LINK |
+    RTMGRP_IPV4_IFADDR | RTMGRP_IPV4_ROUTE |
+    RTMGRP_IPV6_IFADDR | RTMGRP_IPV6_ROUTE;
+
+  if (bind(fd, (struct sockaddr *) &sa, sizeof(sa)) < 0)
+    {
+      log(L_ERR "Unable to bind asynchronous rtnetlink socket: %m");
+      close(fd);
+      return;
+    }
+
+  nl_async_rx_buffer = xmalloc(NL_RX_SIZE);
+
+  sk = nl_async_sk = sk_new(krt_pool);
+  sk->type = SK_MAGIC;
+  sk->rx_hook = nl_async_hook;
+  sk->err_hook = nl_async_err_hook;
+  sk->fd = fd;
+  if (sk_open(sk) < 0)
+    bug("Netlink: sk_open failed");
+}
+
+
+/*
+ *	Interface to the UNIX krt module
+ */
+
+void
+krt_sys_io_init(void)
+{
+  nl_linpool = lp_new_default(krt_pool);
+  HASH_INIT(nl_table_map, krt_pool, 6);
+}
+
+int
+krt_sys_start(struct krt_proto *p)
+{
+  struct krt_proto *old = HASH_FIND(nl_table_map, RTH, p->af, krt_table_id(p));
+
+  if (old)
+    {
+      log(L_ERR "%s: Kernel table %u already registered by %s",
+	  p->p.name, krt_table_id(p), old->p.name);
+      return 0;
+    }
+
+  HASH_INSERT2(nl_table_map, RTH, krt_pool, p);
+
+  nl_open();
+  nl_open_async();
+
+  return 1;
+}
+
+void
+krt_sys_shutdown(struct krt_proto *p)
+{
+  HASH_REMOVE2(nl_table_map, RTH, krt_pool, p);
+}
+
+int
+krt_sys_reconfigure(struct krt_proto *p UNUSED, struct krt_config *n, struct krt_config *o)
+{
+  return (n->sys.table_id == o->sys.table_id) && (n->sys.metric == o->sys.metric);
+}
+
+void
+krt_sys_init_config(struct krt_config *cf)
+{
+  cf->sys.table_id = RT_TABLE_MAIN;
+  cf->sys.metric = 32;
+}
+
+void
+krt_sys_copy_config(struct krt_config *d, struct krt_config *s)
+{
+  d->sys.table_id = s->sys.table_id;
+  d->sys.metric = s->sys.metric;
+}
+
+static const char *krt_metrics_names[KRT_METRICS_MAX] = {
+  NULL, "lock", "mtu", "window", "rtt", "rttvar", "sstresh", "cwnd", "advmss",
+  "reordering", "hoplimit", "initcwnd", "features", "rto_min", "initrwnd", "quickack"
+};
+
+static const char *krt_features_names[KRT_FEATURES_MAX] = {
+  "ecn", NULL, NULL, "allfrag"
+};
+
+int
+krt_sys_get_attr(const eattr *a, byte *buf, int buflen UNUSED)
+{
+  switch (a->id)
+  {
+  case EA_KRT_PREFSRC:
+    bsprintf(buf, "prefsrc");
+    return GA_NAME;
+
+  case EA_KRT_REALM:
+    bsprintf(buf, "realm");
+    return GA_NAME;
+
+  case EA_KRT_SCOPE:
+    bsprintf(buf, "scope");
+    return GA_NAME;
+
+  case EA_KRT_LOCK:
+    buf += bsprintf(buf, "lock:");
+    ea_format_bitfield(a, buf, buflen, krt_metrics_names, 2, KRT_METRICS_MAX);
+    return GA_FULL;
+
+  case EA_KRT_FEATURES:
+    buf += bsprintf(buf, "features:");
+    ea_format_bitfield(a, buf, buflen, krt_features_names, 0, KRT_FEATURES_MAX);
+    return GA_FULL;
+
+  default:;
+    int id = (int)EA_ID(a->id) - KRT_METRICS_OFFSET;
+    if (id > 0 && id < KRT_METRICS_MAX)
+    {
+      bsprintf(buf, "%s", krt_metrics_names[id]);
+      return GA_NAME;
+    }
+
+    return GA_UNKNOWN;
+  }
+}
+
+
+
+void
+kif_sys_start(struct kif_proto *p UNUSED)
+{
+  nl_open();
+  nl_open_async();
+}
+
+void
+kif_sys_shutdown(struct kif_proto *p UNUSED)
+{
+}
+
+int
+kif_update_sysdep_addr(struct iface *i UNUSED)
+{
+  return 0;
+}