Adding upstream version 5.10.209.upstream/5.10.209upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2053 insertions, 0 deletions

diff --git a/net/ipv4/nexthop.c b/net/ipv4/nexthop.c
new file mode 100644
index 000000000..7a0102a4b
--- /dev/null
+++ b/net/ipv4/nexthop.c
@@ -0,0 +1,2053 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Generic nexthop implementation
+ *
+ * Copyright (c) 2017-19 Cumulus Networks
+ * Copyright (c) 2017-19 David Ahern <dsa@cumulusnetworks.com>
+ */
+
+#include <linux/nexthop.h>
+#include <linux/rtnetlink.h>
+#include <linux/slab.h>
+#include <net/arp.h>
+#include <net/ipv6_stubs.h>
+#include <net/lwtunnel.h>
+#include <net/ndisc.h>
+#include <net/nexthop.h>
+#include <net/route.h>
+#include <net/sock.h>
+
+static void remove_nexthop(struct net *net, struct nexthop *nh,
+			   struct nl_info *nlinfo);
+
+#define NH_DEV_HASHBITS  8
+#define NH_DEV_HASHSIZE (1U << NH_DEV_HASHBITS)
+
+static const struct nla_policy rtm_nh_policy[NHA_MAX + 1] = {
+	[NHA_ID]		= { .type = NLA_U32 },
+	[NHA_GROUP]		= { .type = NLA_BINARY },
+	[NHA_GROUP_TYPE]	= { .type = NLA_U16 },
+	[NHA_BLACKHOLE]		= { .type = NLA_FLAG },
+	[NHA_OIF]		= { .type = NLA_U32 },
+	[NHA_GATEWAY]		= { .type = NLA_BINARY },
+	[NHA_ENCAP_TYPE]	= { .type = NLA_U16 },
+	[NHA_ENCAP]		= { .type = NLA_NESTED },
+	[NHA_GROUPS]		= { .type = NLA_FLAG },
+	[NHA_MASTER]		= { .type = NLA_U32 },
+	[NHA_FDB]		= { .type = NLA_FLAG },
+};
+
+static int call_nexthop_notifiers(struct net *net,
+				  enum nexthop_event_type event_type,
+				  struct nexthop *nh)
+{
+	int err;
+
+	err = blocking_notifier_call_chain(&net->nexthop.notifier_chain,
+					   event_type, nh);
+	return notifier_to_errno(err);
+}
+
+static unsigned int nh_dev_hashfn(unsigned int val)
+{
+	unsigned int mask = NH_DEV_HASHSIZE - 1;
+
+	return (val ^
+		(val >> NH_DEV_HASHBITS) ^
+		(val >> (NH_DEV_HASHBITS * 2))) & mask;
+}
+
+static void nexthop_devhash_add(struct net *net, struct nh_info *nhi)
+{
+	struct net_device *dev = nhi->fib_nhc.nhc_dev;
+	struct hlist_head *head;
+	unsigned int hash;
+
+	WARN_ON(!dev);
+
+	hash = nh_dev_hashfn(dev->ifindex);
+	head = &net->nexthop.devhash[hash];
+	hlist_add_head(&nhi->dev_hash, head);
+}
+
+static void nexthop_free_mpath(struct nexthop *nh)
+{
+	struct nh_group *nhg;
+	int i;
+
+	nhg = rcu_dereference_raw(nh->nh_grp);
+	for (i = 0; i < nhg->num_nh; ++i) {
+		struct nh_grp_entry *nhge = &nhg->nh_entries[i];
+
+		WARN_ON(!list_empty(&nhge->nh_list));
+		nexthop_put(nhge->nh);
+	}
+
+	WARN_ON(nhg->spare == nhg);
+
+	kfree(nhg->spare);
+	kfree(nhg);
+}
+
+static void nexthop_free_single(struct nexthop *nh)
+{
+	struct nh_info *nhi;
+
+	nhi = rcu_dereference_raw(nh->nh_info);
+	switch (nhi->family) {
+	case AF_INET:
+		fib_nh_release(nh->net, &nhi->fib_nh);
+		break;
+	case AF_INET6:
+		ipv6_stub->fib6_nh_release(&nhi->fib6_nh);
+		break;
+	}
+	kfree(nhi);
+}
+
+void nexthop_free_rcu(struct rcu_head *head)
+{
+	struct nexthop *nh = container_of(head, struct nexthop, rcu);
+
+	if (nh->is_group)
+		nexthop_free_mpath(nh);
+	else
+		nexthop_free_single(nh);
+
+	kfree(nh);
+}
+EXPORT_SYMBOL_GPL(nexthop_free_rcu);
+
+static struct nexthop *nexthop_alloc(void)
+{
+	struct nexthop *nh;
+
+	nh = kzalloc(sizeof(struct nexthop), GFP_KERNEL);
+	if (nh) {
+		INIT_LIST_HEAD(&nh->fi_list);
+		INIT_LIST_HEAD(&nh->f6i_list);
+		INIT_LIST_HEAD(&nh->grp_list);
+		INIT_LIST_HEAD(&nh->fdb_list);
+	}
+	return nh;
+}
+
+static struct nh_group *nexthop_grp_alloc(u16 num_nh)
+{
+	struct nh_group *nhg;
+
+	nhg = kzalloc(struct_size(nhg, nh_entries, num_nh), GFP_KERNEL);
+	if (nhg)
+		nhg->num_nh = num_nh;
+
+	return nhg;
+}
+
+static void nh_base_seq_inc(struct net *net)
+{
+	while (++net->nexthop.seq == 0)
+		;
+}
+
+/* no reference taken; rcu lock or rtnl must be held */
+struct nexthop *nexthop_find_by_id(struct net *net, u32 id)
+{
+	struct rb_node **pp, *parent = NULL, *next;
+
+	pp = &net->nexthop.rb_root.rb_node;
+	while (1) {
+		struct nexthop *nh;
+
+		next = rcu_dereference_raw(*pp);
+		if (!next)
+			break;
+		parent = next;
+
+		nh = rb_entry(parent, struct nexthop, rb_node);
+		if (id < nh->id)
+			pp = &next->rb_left;
+		else if (id > nh->id)
+			pp = &next->rb_right;
+		else
+			return nh;
+	}
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(nexthop_find_by_id);
+
+/* used for auto id allocation; called with rtnl held */
+static u32 nh_find_unused_id(struct net *net)
+{
+	u32 id_start = net->nexthop.last_id_allocated;
+
+	while (1) {
+		net->nexthop.last_id_allocated++;
+		if (net->nexthop.last_id_allocated == id_start)
+			break;
+
+		if (!nexthop_find_by_id(net, net->nexthop.last_id_allocated))
+			return net->nexthop.last_id_allocated;
+	}
+	return 0;
+}
+
+static int nla_put_nh_group(struct sk_buff *skb, struct nh_group *nhg)
+{
+	struct nexthop_grp *p;
+	size_t len = nhg->num_nh * sizeof(*p);
+	struct nlattr *nla;
+	u16 group_type = 0;
+	int i;
+
+	if (nhg->mpath)
+		group_type = NEXTHOP_GRP_TYPE_MPATH;
+
+	if (nla_put_u16(skb, NHA_GROUP_TYPE, group_type))
+		goto nla_put_failure;
+
+	nla = nla_reserve(skb, NHA_GROUP, len);
+	if (!nla)
+		goto nla_put_failure;
+
+	p = nla_data(nla);
+	for (i = 0; i < nhg->num_nh; ++i) {
+		p->id = nhg->nh_entries[i].nh->id;
+		p->weight = nhg->nh_entries[i].weight - 1;
+		p += 1;
+	}
+
+	return 0;
+
+nla_put_failure:
+	return -EMSGSIZE;
+}
+
+static int nh_fill_node(struct sk_buff *skb, struct nexthop *nh,
+			int event, u32 portid, u32 seq, unsigned int nlflags)
+{
+	struct fib6_nh *fib6_nh;
+	struct fib_nh *fib_nh;
+	struct nlmsghdr *nlh;
+	struct nh_info *nhi;
+	struct nhmsg *nhm;
+
+	nlh = nlmsg_put(skb, portid, seq, event, sizeof(*nhm), nlflags);
+	if (!nlh)
+		return -EMSGSIZE;
+
+	nhm = nlmsg_data(nlh);
+	nhm->nh_family = AF_UNSPEC;
+	nhm->nh_flags = nh->nh_flags;
+	nhm->nh_protocol = nh->protocol;
+	nhm->nh_scope = 0;
+	nhm->resvd = 0;
+
+	if (nla_put_u32(skb, NHA_ID, nh->id))
+		goto nla_put_failure;
+
+	if (nh->is_group) {
+		struct nh_group *nhg = rtnl_dereference(nh->nh_grp);
+
+		if (nhg->fdb_nh && nla_put_flag(skb, NHA_FDB))
+			goto nla_put_failure;
+		if (nla_put_nh_group(skb, nhg))
+			goto nla_put_failure;
+		goto out;
+	}
+
+	nhi = rtnl_dereference(nh->nh_info);
+	nhm->nh_family = nhi->family;
+	if (nhi->reject_nh) {
+		if (nla_put_flag(skb, NHA_BLACKHOLE))
+			goto nla_put_failure;
+		goto out;
+	} else if (nhi->fdb_nh) {
+		if (nla_put_flag(skb, NHA_FDB))
+			goto nla_put_failure;
+	} else {
+		const struct net_device *dev;
+
+		dev = nhi->fib_nhc.nhc_dev;
+		if (dev && nla_put_u32(skb, NHA_OIF, dev->ifindex))
+			goto nla_put_failure;
+	}
+
+	nhm->nh_scope = nhi->fib_nhc.nhc_scope;
+	switch (nhi->family) {
+	case AF_INET:
+		fib_nh = &nhi->fib_nh;
+		if (fib_nh->fib_nh_gw_family &&
+		    nla_put_be32(skb, NHA_GATEWAY, fib_nh->fib_nh_gw4))
+			goto nla_put_failure;
+		break;
+
+	case AF_INET6:
+		fib6_nh = &nhi->fib6_nh;
+		if (fib6_nh->fib_nh_gw_family &&
+		    nla_put_in6_addr(skb, NHA_GATEWAY, &fib6_nh->fib_nh_gw6))
+			goto nla_put_failure;
+		break;
+	}
+
+	if (nhi->fib_nhc.nhc_lwtstate &&
+	    lwtunnel_fill_encap(skb, nhi->fib_nhc.nhc_lwtstate,
+				NHA_ENCAP, NHA_ENCAP_TYPE) < 0)
+		goto nla_put_failure;
+
+out:
+	nlmsg_end(skb, nlh);
+	return 0;
+
+nla_put_failure:
+	nlmsg_cancel(skb, nlh);
+	return -EMSGSIZE;
+}
+
+static size_t nh_nlmsg_size_grp(struct nexthop *nh)
+{
+	struct nh_group *nhg = rtnl_dereference(nh->nh_grp);
+	size_t sz = sizeof(struct nexthop_grp) * nhg->num_nh;
+
+	return nla_total_size(sz) +
+	       nla_total_size(2);  /* NHA_GROUP_TYPE */
+}
+
+static size_t nh_nlmsg_size_single(struct nexthop *nh)
+{
+	struct nh_info *nhi = rtnl_dereference(nh->nh_info);
+	size_t sz;
+
+	/* covers NHA_BLACKHOLE since NHA_OIF and BLACKHOLE
+	 * are mutually exclusive
+	 */
+	sz = nla_total_size(4);  /* NHA_OIF */
+
+	switch (nhi->family) {
+	case AF_INET:
+		if (nhi->fib_nh.fib_nh_gw_family)
+			sz += nla_total_size(4);  /* NHA_GATEWAY */
+		break;
+
+	case AF_INET6:
+		/* NHA_GATEWAY */
+		if (nhi->fib6_nh.fib_nh_gw_family)
+			sz += nla_total_size(sizeof(const struct in6_addr));
+		break;
+	}
+
+	if (nhi->fib_nhc.nhc_lwtstate) {
+		sz += lwtunnel_get_encap_size(nhi->fib_nhc.nhc_lwtstate);
+		sz += nla_total_size(2);  /* NHA_ENCAP_TYPE */
+	}
+
+	return sz;
+}
+
+static size_t nh_nlmsg_size(struct nexthop *nh)
+{
+	size_t sz = NLMSG_ALIGN(sizeof(struct nhmsg));
+
+	sz += nla_total_size(4); /* NHA_ID */
+
+	if (nh->is_group)
+		sz += nh_nlmsg_size_grp(nh);
+	else
+		sz += nh_nlmsg_size_single(nh);
+
+	return sz;
+}
+
+static void nexthop_notify(int event, struct nexthop *nh, struct nl_info *info)
+{
+	unsigned int nlflags = info->nlh ? info->nlh->nlmsg_flags : 0;
+	u32 seq = info->nlh ? info->nlh->nlmsg_seq : 0;
+	struct sk_buff *skb;
+	int err = -ENOBUFS;
+
+	skb = nlmsg_new(nh_nlmsg_size(nh), gfp_any());
+	if (!skb)
+		goto errout;
+
+	err = nh_fill_node(skb, nh, event, info->portid, seq, nlflags);
+	if (err < 0) {
+		/* -EMSGSIZE implies BUG in nh_nlmsg_size() */
+		WARN_ON(err == -EMSGSIZE);
+		kfree_skb(skb);
+		goto errout;
+	}
+
+	rtnl_notify(skb, info->nl_net, info->portid, RTNLGRP_NEXTHOP,
+		    info->nlh, gfp_any());
+	return;
+errout:
+	if (err < 0)
+		rtnl_set_sk_err(info->nl_net, RTNLGRP_NEXTHOP, err);
+}
+
+static bool valid_group_nh(struct nexthop *nh, unsigned int npaths,
+			   bool *is_fdb, struct netlink_ext_ack *extack)
+{
+	if (nh->is_group) {
+		struct nh_group *nhg = rtnl_dereference(nh->nh_grp);
+
+		/* nested multipath (group within a group) is not
+		 * supported
+		 */
+		if (nhg->mpath) {
+			NL_SET_ERR_MSG(extack,
+				       "Multipath group can not be a nexthop within a group");
+			return false;
+		}
+		*is_fdb = nhg->fdb_nh;
+	} else {
+		struct nh_info *nhi = rtnl_dereference(nh->nh_info);
+
+		if (nhi->reject_nh && npaths > 1) {
+			NL_SET_ERR_MSG(extack,
+				       "Blackhole nexthop can not be used in a group with more than 1 path");
+			return false;
+		}
+		*is_fdb = nhi->fdb_nh;
+	}
+
+	return true;
+}
+
+static int nh_check_attr_fdb_group(struct nexthop *nh, u8 *nh_family,
+				   struct netlink_ext_ack *extack)
+{
+	struct nh_info *nhi;
+
+	nhi = rtnl_dereference(nh->nh_info);
+
+	if (!nhi->fdb_nh) {
+		NL_SET_ERR_MSG(extack, "FDB nexthop group can only have fdb nexthops");
+		return -EINVAL;
+	}
+
+	if (*nh_family == AF_UNSPEC) {
+		*nh_family = nhi->family;
+	} else if (*nh_family != nhi->family) {
+		NL_SET_ERR_MSG(extack, "FDB nexthop group cannot have mixed family nexthops");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int nh_check_attr_group(struct net *net, struct nlattr *tb[],
+			       struct netlink_ext_ack *extack)
+{
+	unsigned int len = nla_len(tb[NHA_GROUP]);
+	u8 nh_family = AF_UNSPEC;
+	struct nexthop_grp *nhg;
+	unsigned int i, j;
+	u8 nhg_fdb = 0;
+
+	if (!len || len & (sizeof(struct nexthop_grp) - 1)) {
+		NL_SET_ERR_MSG(extack,
+			       "Invalid length for nexthop group attribute");
+		return -EINVAL;
+	}
+
+	/* convert len to number of nexthop ids */
+	len /= sizeof(*nhg);
+
+	nhg = nla_data(tb[NHA_GROUP]);
+	for (i = 0; i < len; ++i) {
+		if (nhg[i].resvd1 || nhg[i].resvd2) {
+			NL_SET_ERR_MSG(extack, "Reserved fields in nexthop_grp must be 0");
+			return -EINVAL;
+		}
+		if (nhg[i].weight > 254) {
+			NL_SET_ERR_MSG(extack, "Invalid value for weight");
+			return -EINVAL;
+		}
+		for (j = i + 1; j < len; ++j) {
+			if (nhg[i].id == nhg[j].id) {
+				NL_SET_ERR_MSG(extack, "Nexthop id can not be used twice in a group");
+				return -EINVAL;
+			}
+		}
+	}
+
+	if (tb[NHA_FDB])
+		nhg_fdb = 1;
+	nhg = nla_data(tb[NHA_GROUP]);
+	for (i = 0; i < len; ++i) {
+		struct nexthop *nh;
+		bool is_fdb_nh;
+
+		nh = nexthop_find_by_id(net, nhg[i].id);
+		if (!nh) {
+			NL_SET_ERR_MSG(extack, "Invalid nexthop id");
+			return -EINVAL;
+		}
+		if (!valid_group_nh(nh, len, &is_fdb_nh, extack))
+			return -EINVAL;
+
+		if (nhg_fdb && nh_check_attr_fdb_group(nh, &nh_family, extack))
+			return -EINVAL;
+
+		if (!nhg_fdb && is_fdb_nh) {
+			NL_SET_ERR_MSG(extack, "Non FDB nexthop group cannot have fdb nexthops");
+			return -EINVAL;
+		}
+	}
+	for (i = NHA_GROUP_TYPE + 1; i < __NHA_MAX; ++i) {
+		if (!tb[i])
+			continue;
+		if (i == NHA_FDB)
+			continue;
+		NL_SET_ERR_MSG(extack,
+			       "No other attributes can be set in nexthop groups");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static bool ipv6_good_nh(const struct fib6_nh *nh)
+{
+	int state = NUD_REACHABLE;
+	struct neighbour *n;
+
+	rcu_read_lock_bh();
+
+	n = __ipv6_neigh_lookup_noref_stub(nh->fib_nh_dev, &nh->fib_nh_gw6);
+	if (n)
+		state = n->nud_state;
+
+	rcu_read_unlock_bh();
+
+	return !!(state & NUD_VALID);
+}
+
+static bool ipv4_good_nh(const struct fib_nh *nh)
+{
+	int state = NUD_REACHABLE;
+	struct neighbour *n;
+
+	rcu_read_lock_bh();
+
+	n = __ipv4_neigh_lookup_noref(nh->fib_nh_dev,
+				      (__force u32)nh->fib_nh_gw4);
+	if (n)
+		state = n->nud_state;
+
+	rcu_read_unlock_bh();
+
+	return !!(state & NUD_VALID);
+}
+
+struct nexthop *nexthop_select_path(struct nexthop *nh, int hash)
+{
+	struct nexthop *rc = NULL;
+	struct nh_group *nhg;
+	int i;
+
+	if (!nh->is_group)
+		return nh;
+
+	nhg = rcu_dereference(nh->nh_grp);
+	for (i = 0; i < nhg->num_nh; ++i) {
+		struct nh_grp_entry *nhge = &nhg->nh_entries[i];
+		struct nh_info *nhi;
+
+		if (hash > atomic_read(&nhge->upper_bound))
+			continue;
+
+		nhi = rcu_dereference(nhge->nh->nh_info);
+		if (nhi->fdb_nh)
+			return nhge->nh;
+
+		/* nexthops always check if it is good and does
+		 * not rely on a sysctl for this behavior
+		 */
+		switch (nhi->family) {
+		case AF_INET:
+			if (ipv4_good_nh(&nhi->fib_nh))
+				return nhge->nh;
+			break;
+		case AF_INET6:
+			if (ipv6_good_nh(&nhi->fib6_nh))
+				return nhge->nh;
+			break;
+		}
+
+		if (!rc)
+			rc = nhge->nh;
+	}
+
+	return rc;
+}
+EXPORT_SYMBOL_GPL(nexthop_select_path);
+
+int nexthop_for_each_fib6_nh(struct nexthop *nh,
+			     int (*cb)(struct fib6_nh *nh, void *arg),
+			     void *arg)
+{
+	struct nh_info *nhi;
+	int err;
+
+	if (nh->is_group) {
+		struct nh_group *nhg;
+		int i;
+
+		nhg = rcu_dereference_rtnl(nh->nh_grp);
+		for (i = 0; i < nhg->num_nh; i++) {
+			struct nh_grp_entry *nhge = &nhg->nh_entries[i];
+
+			nhi = rcu_dereference_rtnl(nhge->nh->nh_info);
+			err = cb(&nhi->fib6_nh, arg);
+			if (err)
+				return err;
+		}
+	} else {
+		nhi = rcu_dereference_rtnl(nh->nh_info);
+		err = cb(&nhi->fib6_nh, arg);
+		if (err)
+			return err;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(nexthop_for_each_fib6_nh);
+
+static int check_src_addr(const struct in6_addr *saddr,
+			  struct netlink_ext_ack *extack)
+{
+	if (!ipv6_addr_any(saddr)) {
+		NL_SET_ERR_MSG(extack, "IPv6 routes using source address can not use nexthop objects");
+		return -EINVAL;
+	}
+	return 0;
+}
+
+int fib6_check_nexthop(struct nexthop *nh, struct fib6_config *cfg,
+		       struct netlink_ext_ack *extack)
+{
+	struct nh_info *nhi;
+	bool is_fdb_nh;
+
+	/* fib6_src is unique to a fib6_info and limits the ability to cache
+	 * routes in fib6_nh within a nexthop that is potentially shared
+	 * across multiple fib entries. If the config wants to use source
+	 * routing it can not use nexthop objects. mlxsw also does not allow
+	 * fib6_src on routes.
+	 */
+	if (cfg && check_src_addr(&cfg->fc_src, extack) < 0)
+		return -EINVAL;
+
+	if (nh->is_group) {
+		struct nh_group *nhg;
+
+		nhg = rtnl_dereference(nh->nh_grp);
+		if (nhg->has_v4)
+			goto no_v4_nh;
+		is_fdb_nh = nhg->fdb_nh;
+	} else {
+		nhi = rtnl_dereference(nh->nh_info);
+		if (nhi->family == AF_INET)
+			goto no_v4_nh;
+		is_fdb_nh = nhi->fdb_nh;
+	}
+
+	if (is_fdb_nh) {
+		NL_SET_ERR_MSG(extack, "Route cannot point to a fdb nexthop");
+		return -EINVAL;
+	}
+
+	return 0;
+no_v4_nh:
+	NL_SET_ERR_MSG(extack, "IPv6 routes can not use an IPv4 nexthop");
+	return -EINVAL;
+}
+EXPORT_SYMBOL_GPL(fib6_check_nexthop);
+
+/* if existing nexthop has ipv6 routes linked to it, need
+ * to verify this new spec works with ipv6
+ */
+static int fib6_check_nh_list(struct nexthop *old, struct nexthop *new,
+			      struct netlink_ext_ack *extack)
+{
+	struct fib6_info *f6i;
+
+	if (list_empty(&old->f6i_list))
+		return 0;
+
+	list_for_each_entry(f6i, &old->f6i_list, nh_list) {
+		if (check_src_addr(&f6i->fib6_src.addr, extack) < 0)
+			return -EINVAL;
+	}
+
+	return fib6_check_nexthop(new, NULL, extack);
+}
+
+static int nexthop_check_scope(struct nh_info *nhi, u8 scope,
+			       struct netlink_ext_ack *extack)
+{
+	if (scope == RT_SCOPE_HOST && nhi->fib_nhc.nhc_gw_family) {
+		NL_SET_ERR_MSG(extack,
+			       "Route with host scope can not have a gateway");
+		return -EINVAL;
+	}
+
+	if (nhi->fib_nhc.nhc_flags & RTNH_F_ONLINK && scope >= RT_SCOPE_LINK) {
+		NL_SET_ERR_MSG(extack, "Scope mismatch with nexthop");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+/* Invoked by fib add code to verify nexthop by id is ok with
+ * config for prefix; parts of fib_check_nh not done when nexthop
+ * object is used.
+ */
+int fib_check_nexthop(struct nexthop *nh, u8 scope,
+		      struct netlink_ext_ack *extack)
+{
+	struct nh_info *nhi;
+	int err = 0;
+
+	if (nh->is_group) {
+		struct nh_group *nhg;
+
+		nhg = rtnl_dereference(nh->nh_grp);
+		if (nhg->fdb_nh) {
+			NL_SET_ERR_MSG(extack, "Route cannot point to a fdb nexthop");
+			err = -EINVAL;
+			goto out;
+		}
+
+		if (scope == RT_SCOPE_HOST) {
+			NL_SET_ERR_MSG(extack, "Route with host scope can not have multiple nexthops");
+			err = -EINVAL;
+			goto out;
+		}
+
+		/* all nexthops in a group have the same scope */
+		nhi = rtnl_dereference(nhg->nh_entries[0].nh->nh_info);
+		err = nexthop_check_scope(nhi, scope, extack);
+	} else {
+		nhi = rtnl_dereference(nh->nh_info);
+		if (nhi->fdb_nh) {
+			NL_SET_ERR_MSG(extack, "Route cannot point to a fdb nexthop");
+			err = -EINVAL;
+			goto out;
+		}
+		err = nexthop_check_scope(nhi, scope, extack);
+	}
+
+out:
+	return err;
+}
+
+static int fib_check_nh_list(struct nexthop *old, struct nexthop *new,
+			     struct netlink_ext_ack *extack)
+{
+	struct fib_info *fi;
+
+	list_for_each_entry(fi, &old->fi_list, nh_list) {
+		int err;
+
+		err = fib_check_nexthop(new, fi->fib_scope, extack);
+		if (err)
+			return err;
+	}
+	return 0;
+}
+
+static void nh_group_rebalance(struct nh_group *nhg)
+{
+	int total = 0;
+	int w = 0;
+	int i;
+
+	for (i = 0; i < nhg->num_nh; ++i)
+		total += nhg->nh_entries[i].weight;
+
+	for (i = 0; i < nhg->num_nh; ++i) {
+		struct nh_grp_entry *nhge = &nhg->nh_entries[i];
+		int upper_bound;
+
+		w += nhge->weight;
+		upper_bound = DIV_ROUND_CLOSEST_ULL((u64)w << 31, total) - 1;
+		atomic_set(&nhge->upper_bound, upper_bound);
+	}
+}
+
+static void remove_nh_grp_entry(struct net *net, struct nh_grp_entry *nhge,
+				struct nl_info *nlinfo)
+{
+	struct nh_grp_entry *nhges, *new_nhges;
+	struct nexthop *nhp = nhge->nh_parent;
+	struct nexthop *nh = nhge->nh;
+	struct nh_group *nhg, *newg;
+	int i, j;
+
+	WARN_ON(!nh);
+
+	nhg = rtnl_dereference(nhp->nh_grp);
+	newg = nhg->spare;
+
+	/* last entry, keep it visible and remove the parent */
+	if (nhg->num_nh == 1) {
+		remove_nexthop(net, nhp, nlinfo);
+		return;
+	}
+
+	newg->has_v4 = false;
+	newg->mpath = nhg->mpath;
+	newg->fdb_nh = nhg->fdb_nh;
+	newg->num_nh = nhg->num_nh;
+
+	/* copy old entries to new except the one getting removed */
+	nhges = nhg->nh_entries;
+	new_nhges = newg->nh_entries;
+	for (i = 0, j = 0; i < nhg->num_nh; ++i) {
+		struct nh_info *nhi;
+
+		/* current nexthop getting removed */
+		if (nhg->nh_entries[i].nh == nh) {
+			newg->num_nh--;
+			continue;
+		}
+
+		nhi = rtnl_dereference(nhges[i].nh->nh_info);
+		if (nhi->family == AF_INET)
+			newg->has_v4 = true;
+
+		list_del(&nhges[i].nh_list);
+		new_nhges[j].nh_parent = nhges[i].nh_parent;
+		new_nhges[j].nh = nhges[i].nh;
+		new_nhges[j].weight = nhges[i].weight;
+		list_add(&new_nhges[j].nh_list, &new_nhges[j].nh->grp_list);
+		j++;
+	}
+
+	nh_group_rebalance(newg);
+	rcu_assign_pointer(nhp->nh_grp, newg);
+
+	list_del(&nhge->nh_list);
+	nexthop_put(nhge->nh);
+
+	if (nlinfo)
+		nexthop_notify(RTM_NEWNEXTHOP, nhp, nlinfo);
+}
+
+static void remove_nexthop_from_groups(struct net *net, struct nexthop *nh,
+				       struct nl_info *nlinfo)
+{
+	struct nh_grp_entry *nhge, *tmp;
+
+	list_for_each_entry_safe(nhge, tmp, &nh->grp_list, nh_list)
+		remove_nh_grp_entry(net, nhge, nlinfo);
+
+	/* make sure all see the newly published array before releasing rtnl */
+	synchronize_net();
+}
+
+static void remove_nexthop_group(struct nexthop *nh, struct nl_info *nlinfo)
+{
+	struct nh_group *nhg = rcu_dereference_rtnl(nh->nh_grp);
+	int i, num_nh = nhg->num_nh;
+
+	for (i = 0; i < num_nh; ++i) {
+		struct nh_grp_entry *nhge = &nhg->nh_entries[i];
+
+		if (WARN_ON(!nhge->nh))
+			continue;
+
+		list_del_init(&nhge->nh_list);
+	}
+}
+
+/* not called for nexthop replace */
+static void __remove_nexthop_fib(struct net *net, struct nexthop *nh)
+{
+	struct fib6_info *f6i, *tmp;
+	bool do_flush = false;
+	struct fib_info *fi;
+
+	list_for_each_entry(fi, &nh->fi_list, nh_list) {
+		fi->fib_flags |= RTNH_F_DEAD;
+		do_flush = true;
+	}
+	if (do_flush)
+		fib_flush(net);
+
+	/* ip6_del_rt removes the entry from this list hence the _safe */
+	list_for_each_entry_safe(f6i, tmp, &nh->f6i_list, nh_list) {
+		/* __ip6_del_rt does a release, so do a hold here */
+		fib6_info_hold(f6i);
+		ipv6_stub->ip6_del_rt(net, f6i,
+				      !READ_ONCE(net->ipv4.sysctl_nexthop_compat_mode));
+	}
+}
+
+static void __remove_nexthop(struct net *net, struct nexthop *nh,
+			     struct nl_info *nlinfo)
+{
+	__remove_nexthop_fib(net, nh);
+
+	if (nh->is_group) {
+		remove_nexthop_group(nh, nlinfo);
+	} else {
+		struct nh_info *nhi;
+
+		nhi = rtnl_dereference(nh->nh_info);
+		if (nhi->fib_nhc.nhc_dev)
+			hlist_del(&nhi->dev_hash);
+
+		remove_nexthop_from_groups(net, nh, nlinfo);
+	}
+}
+
+static void remove_nexthop(struct net *net, struct nexthop *nh,
+			   struct nl_info *nlinfo)
+{
+	call_nexthop_notifiers(net, NEXTHOP_EVENT_DEL, nh);
+
+	/* remove from the tree */
+	rb_erase(&nh->rb_node, &net->nexthop.rb_root);
+
+	if (nlinfo)
+		nexthop_notify(RTM_DELNEXTHOP, nh, nlinfo);
+
+	__remove_nexthop(net, nh, nlinfo);
+	nh_base_seq_inc(net);
+
+	nexthop_put(nh);
+}
+
+/* if any FIB entries reference this nexthop, any dst entries
+ * need to be regenerated
+ */
+static void nh_rt_cache_flush(struct net *net, struct nexthop *nh,
+			      struct nexthop *replaced_nh)
+{
+	struct fib6_info *f6i;
+	struct nh_group *nhg;
+	int i;
+
+	if (!list_empty(&nh->fi_list))
+		rt_cache_flush(net);
+
+	list_for_each_entry(f6i, &nh->f6i_list, nh_list)
+		ipv6_stub->fib6_update_sernum(net, f6i);
+
+	/* if an IPv6 group was replaced, we have to release all old
+	 * dsts to make sure all refcounts are released
+	 */
+	if (!replaced_nh->is_group)
+		return;
+
+	/* new dsts must use only the new nexthop group */
+	synchronize_net();
+
+	nhg = rtnl_dereference(replaced_nh->nh_grp);
+	for (i = 0; i < nhg->num_nh; i++) {
+		struct nh_grp_entry *nhge = &nhg->nh_entries[i];
+		struct nh_info *nhi = rtnl_dereference(nhge->nh->nh_info);
+
+		if (nhi->family == AF_INET6)
+			ipv6_stub->fib6_nh_release_dsts(&nhi->fib6_nh);
+	}
+}
+
+static int replace_nexthop_grp(struct net *net, struct nexthop *old,
+			       struct nexthop *new,
+			       struct netlink_ext_ack *extack)
+{
+	struct nh_group *oldg, *newg;
+	int i;
+
+	if (!new->is_group) {
+		NL_SET_ERR_MSG(extack, "Can not replace a nexthop group with a nexthop.");
+		return -EINVAL;
+	}
+
+	oldg = rtnl_dereference(old->nh_grp);
+	newg = rtnl_dereference(new->nh_grp);
+
+	/* update parents - used by nexthop code for cleanup */
+	for (i = 0; i < newg->num_nh; i++)
+		newg->nh_entries[i].nh_parent = old;
+
+	rcu_assign_pointer(old->nh_grp, newg);
+
+	for (i = 0; i < oldg->num_nh; i++)
+		oldg->nh_entries[i].nh_parent = new;
+
+	rcu_assign_pointer(new->nh_grp, oldg);
+
+	return 0;
+}
+
+static void nh_group_v4_update(struct nh_group *nhg)
+{
+	struct nh_grp_entry *nhges;
+	bool has_v4 = false;
+	int i;
+
+	nhges = nhg->nh_entries;
+	for (i = 0; i < nhg->num_nh; i++) {
+		struct nh_info *nhi;
+
+		nhi = rtnl_dereference(nhges[i].nh->nh_info);
+		if (nhi->family == AF_INET)
+			has_v4 = true;
+	}
+	nhg->has_v4 = has_v4;
+}
+
+static int replace_nexthop_single(struct net *net, struct nexthop *old,
+				  struct nexthop *new,
+				  struct netlink_ext_ack *extack)
+{
+	struct nh_info *oldi, *newi;
+
+	if (new->is_group) {
+		NL_SET_ERR_MSG(extack, "Can not replace a nexthop with a nexthop group.");
+		return -EINVAL;
+	}
+
+	oldi = rtnl_dereference(old->nh_info);
+	newi = rtnl_dereference(new->nh_info);
+
+	newi->nh_parent = old;
+	oldi->nh_parent = new;
+
+	old->protocol = new->protocol;
+	old->nh_flags = new->nh_flags;
+
+	rcu_assign_pointer(old->nh_info, newi);
+	rcu_assign_pointer(new->nh_info, oldi);
+
+	/* When replacing an IPv4 nexthop with an IPv6 nexthop, potentially
+	 * update IPv4 indication in all the groups using the nexthop.
+	 */
+	if (oldi->family == AF_INET && newi->family == AF_INET6) {
+		struct nh_grp_entry *nhge;
+
+		list_for_each_entry(nhge, &old->grp_list, nh_list) {
+			struct nexthop *nhp = nhge->nh_parent;
+			struct nh_group *nhg;
+
+			nhg = rtnl_dereference(nhp->nh_grp);
+			nh_group_v4_update(nhg);
+		}
+	}
+
+	return 0;
+}
+
+static void __nexthop_replace_notify(struct net *net, struct nexthop *nh,
+				     struct nl_info *info)
+{
+	struct fib6_info *f6i;
+
+	if (!list_empty(&nh->fi_list)) {
+		struct fib_info *fi;
+
+		/* expectation is a few fib_info per nexthop and then
+		 * a lot of routes per fib_info. So mark the fib_info
+		 * and then walk the fib tables once
+		 */
+		list_for_each_entry(fi, &nh->fi_list, nh_list)
+			fi->nh_updated = true;
+
+		fib_info_notify_update(net, info);
+
+		list_for_each_entry(fi, &nh->fi_list, nh_list)
+			fi->nh_updated = false;
+	}
+
+	list_for_each_entry(f6i, &nh->f6i_list, nh_list)
+		ipv6_stub->fib6_rt_update(net, f6i, info);
+}
+
+/* send RTM_NEWROUTE with REPLACE flag set for all FIB entries
+ * linked to this nexthop and for all groups that the nexthop
+ * is a member of
+ */
+static void nexthop_replace_notify(struct net *net, struct nexthop *nh,
+				   struct nl_info *info)
+{
+	struct nh_grp_entry *nhge;
+
+	__nexthop_replace_notify(net, nh, info);
+
+	list_for_each_entry(nhge, &nh->grp_list, nh_list)
+		__nexthop_replace_notify(net, nhge->nh_parent, info);
+}
+
+static int replace_nexthop(struct net *net, struct nexthop *old,
+			   struct nexthop *new, struct netlink_ext_ack *extack)
+{
+	bool new_is_reject = false;
+	struct nh_grp_entry *nhge;
+	int err;
+
+	/* check that existing FIB entries are ok with the
+	 * new nexthop definition
+	 */
+	err = fib_check_nh_list(old, new, extack);
+	if (err)
+		return err;
+
+	err = fib6_check_nh_list(old, new, extack);
+	if (err)
+		return err;
+
+	if (!new->is_group) {
+		struct nh_info *nhi = rtnl_dereference(new->nh_info);
+
+		new_is_reject = nhi->reject_nh;
+	}
+
+	list_for_each_entry(nhge, &old->grp_list, nh_list) {
+		/* if new nexthop is a blackhole, any groups using this
+		 * nexthop cannot have more than 1 path
+		 */
+		if (new_is_reject &&
+		    nexthop_num_path(nhge->nh_parent) > 1) {
+			NL_SET_ERR_MSG(extack, "Blackhole nexthop can not be a member of a group with more than one path");
+			return -EINVAL;
+		}
+
+		err = fib_check_nh_list(nhge->nh_parent, new, extack);
+		if (err)
+			return err;
+
+		err = fib6_check_nh_list(nhge->nh_parent, new, extack);
+		if (err)
+			return err;
+	}
+
+	if (old->is_group)
+		err = replace_nexthop_grp(net, old, new, extack);
+	else
+		err = replace_nexthop_single(net, old, new, extack);
+
+	if (!err) {
+		nh_rt_cache_flush(net, old, new);
+
+		__remove_nexthop(net, new, NULL);
+		nexthop_put(new);
+	}
+
+	return err;
+}
+
+/* called with rtnl_lock held */
+static int insert_nexthop(struct net *net, struct nexthop *new_nh,
+			  struct nh_config *cfg, struct netlink_ext_ack *extack)
+{
+	struct rb_node **pp, *parent = NULL, *next;
+	struct rb_root *root = &net->nexthop.rb_root;
+	bool replace = !!(cfg->nlflags & NLM_F_REPLACE);
+	bool create = !!(cfg->nlflags & NLM_F_CREATE);
+	u32 new_id = new_nh->id;
+	int replace_notify = 0;
+	int rc = -EEXIST;
+
+	pp = &root->rb_node;
+	while (1) {
+		struct nexthop *nh;
+
+		next = *pp;
+		if (!next)
+			break;
+
+		parent = next;
+
+		nh = rb_entry(parent, struct nexthop, rb_node);
+		if (new_id < nh->id) {
+			pp = &next->rb_left;
+		} else if (new_id > nh->id) {
+			pp = &next->rb_right;
+		} else if (replace) {
+			rc = replace_nexthop(net, nh, new_nh, extack);
+			if (!rc) {
+				new_nh = nh; /* send notification with old nh */
+				replace_notify = 1;
+			}
+			goto out;
+		} else {
+			/* id already exists and not a replace */
+			goto out;
+		}
+	}
+
+	if (replace && !create) {
+		NL_SET_ERR_MSG(extack, "Replace specified without create and no entry exists");
+		rc = -ENOENT;
+		goto out;
+	}
+
+	rb_link_node_rcu(&new_nh->rb_node, parent, pp);
+	rb_insert_color(&new_nh->rb_node, root);
+	rc = 0;
+out:
+	if (!rc) {
+		nh_base_seq_inc(net);
+		nexthop_notify(RTM_NEWNEXTHOP, new_nh, &cfg->nlinfo);
+		if (replace_notify &&
+		    READ_ONCE(net->ipv4.sysctl_nexthop_compat_mode))
+			nexthop_replace_notify(net, new_nh, &cfg->nlinfo);
+	}
+
+	return rc;
+}
+
+/* rtnl */
+/* remove all nexthops tied to a device being deleted */
+static void nexthop_flush_dev(struct net_device *dev, unsigned long event)
+{
+	unsigned int hash = nh_dev_hashfn(dev->ifindex);
+	struct net *net = dev_net(dev);
+	struct hlist_head *head = &net->nexthop.devhash[hash];
+	struct hlist_node *n;
+	struct nh_info *nhi;
+
+	hlist_for_each_entry_safe(nhi, n, head, dev_hash) {
+		if (nhi->fib_nhc.nhc_dev != dev)
+			continue;
+
+		if (nhi->reject_nh &&
+		    (event == NETDEV_DOWN || event == NETDEV_CHANGE))
+			continue;
+
+		remove_nexthop(net, nhi->nh_parent, NULL);
+	}
+}
+
+/* rtnl; called when net namespace is deleted */
+static void flush_all_nexthops(struct net *net)
+{
+	struct rb_root *root = &net->nexthop.rb_root;
+	struct rb_node *node;
+	struct nexthop *nh;
+
+	while ((node = rb_first(root))) {
+		nh = rb_entry(node, struct nexthop, rb_node);
+		remove_nexthop(net, nh, NULL);
+		cond_resched();
+	}
+}
+
+static struct nexthop *nexthop_create_group(struct net *net,
+					    struct nh_config *cfg)
+{
+	struct nlattr *grps_attr = cfg->nh_grp;
+	struct nexthop_grp *entry = nla_data(grps_attr);
+	u16 num_nh = nla_len(grps_attr) / sizeof(*entry);
+	struct nh_group *nhg;
+	struct nexthop *nh;
+	int i;
+
+	if (WARN_ON(!num_nh))
+		return ERR_PTR(-EINVAL);
+
+	nh = nexthop_alloc();
+	if (!nh)
+		return ERR_PTR(-ENOMEM);
+
+	nh->is_group = 1;
+
+	nhg = nexthop_grp_alloc(num_nh);
+	if (!nhg) {
+		kfree(nh);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	/* spare group used for removals */
+	nhg->spare = nexthop_grp_alloc(num_nh);
+	if (!nhg->spare) {
+		kfree(nhg);
+		kfree(nh);
+		return ERR_PTR(-ENOMEM);
+	}
+	nhg->spare->spare = nhg;
+
+	for (i = 0; i < nhg->num_nh; ++i) {
+		struct nexthop *nhe;
+		struct nh_info *nhi;
+
+		nhe = nexthop_find_by_id(net, entry[i].id);
+		if (!nexthop_get(nhe))
+			goto out_no_nh;
+
+		nhi = rtnl_dereference(nhe->nh_info);
+		if (nhi->family == AF_INET)
+			nhg->has_v4 = true;
+
+		nhg->nh_entries[i].nh = nhe;
+		nhg->nh_entries[i].weight = entry[i].weight + 1;
+		list_add(&nhg->nh_entries[i].nh_list, &nhe->grp_list);
+		nhg->nh_entries[i].nh_parent = nh;
+	}
+
+	if (cfg->nh_grp_type == NEXTHOP_GRP_TYPE_MPATH) {
+		nhg->mpath = 1;
+		nh_group_rebalance(nhg);
+	}
+
+	if (cfg->nh_fdb)
+		nhg->fdb_nh = 1;
+
+	rcu_assign_pointer(nh->nh_grp, nhg);
+
+	return nh;
+
+out_no_nh:
+	for (i--; i >= 0; --i) {
+		list_del(&nhg->nh_entries[i].nh_list);
+		nexthop_put(nhg->nh_entries[i].nh);
+	}
+
+	kfree(nhg->spare);
+	kfree(nhg);
+	kfree(nh);
+
+	return ERR_PTR(-ENOENT);
+}
+
+static int nh_create_ipv4(struct net *net, struct nexthop *nh,
+			  struct nh_info *nhi, struct nh_config *cfg,
+			  struct netlink_ext_ack *extack)
+{
+	struct fib_nh *fib_nh = &nhi->fib_nh;
+	struct fib_config fib_cfg = {
+		.fc_oif   = cfg->nh_ifindex,
+		.fc_gw4   = cfg->gw.ipv4,
+		.fc_gw_family = cfg->gw.ipv4 ? AF_INET : 0,
+		.fc_flags = cfg->nh_flags,
+		.fc_nlinfo = cfg->nlinfo,
+		.fc_encap = cfg->nh_encap,
+		.fc_encap_type = cfg->nh_encap_type,
+	};
+	u32 tb_id = (cfg->dev ? l3mdev_fib_table(cfg->dev) : RT_TABLE_MAIN);
+	int err;
+
+	err = fib_nh_init(net, fib_nh, &fib_cfg, 1, extack);
+	if (err) {
+		fib_nh_release(net, fib_nh);
+		goto out;
+	}
+
+	if (nhi->fdb_nh)
+		goto out;
+
+	/* sets nh_dev if successful */
+	err = fib_check_nh(net, fib_nh, tb_id, 0, extack);
+	if (!err) {
+		nh->nh_flags = fib_nh->fib_nh_flags;
+		fib_info_update_nhc_saddr(net, &fib_nh->nh_common,
+					  !fib_nh->fib_nh_scope ? 0 : fib_nh->fib_nh_scope - 1);
+	} else {
+		fib_nh_release(net, fib_nh);
+	}
+out:
+	return err;
+}
+
+static int nh_create_ipv6(struct net *net,  struct nexthop *nh,
+			  struct nh_info *nhi, struct nh_config *cfg,
+			  struct netlink_ext_ack *extack)
+{
+	struct fib6_nh *fib6_nh = &nhi->fib6_nh;
+	struct fib6_config fib6_cfg = {
+		.fc_table = l3mdev_fib_table(cfg->dev),
+		.fc_ifindex = cfg->nh_ifindex,
+		.fc_gateway = cfg->gw.ipv6,
+		.fc_flags = cfg->nh_flags,
+		.fc_nlinfo = cfg->nlinfo,
+		.fc_encap = cfg->nh_encap,
+		.fc_encap_type = cfg->nh_encap_type,
+		.fc_is_fdb = cfg->nh_fdb,
+	};
+	int err;
+
+	if (!ipv6_addr_any(&cfg->gw.ipv6))
+		fib6_cfg.fc_flags |= RTF_GATEWAY;
+
+	/* sets nh_dev if successful */
+	err = ipv6_stub->fib6_nh_init(net, fib6_nh, &fib6_cfg, GFP_KERNEL,
+				      extack);
+	if (err) {
+		/* IPv6 is not enabled, don't call fib6_nh_release */
+		if (err == -EAFNOSUPPORT)
+			goto out;
+		ipv6_stub->fib6_nh_release(fib6_nh);
+	} else {
+		nh->nh_flags = fib6_nh->fib_nh_flags;
+	}
+out:
+	return err;
+}
+
+static struct nexthop *nexthop_create(struct net *net, struct nh_config *cfg,
+				      struct netlink_ext_ack *extack)
+{
+	struct nh_info *nhi;
+	struct nexthop *nh;
+	int err = 0;
+
+	nh = nexthop_alloc();
+	if (!nh)
+		return ERR_PTR(-ENOMEM);
+
+	nhi = kzalloc(sizeof(*nhi), GFP_KERNEL);
+	if (!nhi) {
+		kfree(nh);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	nh->nh_flags = cfg->nh_flags;
+	nh->net = net;
+
+	nhi->nh_parent = nh;
+	nhi->family = cfg->nh_family;
+	nhi->fib_nhc.nhc_scope = RT_SCOPE_LINK;
+
+	if (cfg->nh_fdb)
+		nhi->fdb_nh = 1;
+
+	if (cfg->nh_blackhole) {
+		nhi->reject_nh = 1;
+		cfg->nh_ifindex = net->loopback_dev->ifindex;
+	}
+
+	switch (cfg->nh_family) {
+	case AF_INET:
+		err = nh_create_ipv4(net, nh, nhi, cfg, extack);
+		break;
+	case AF_INET6:
+		err = nh_create_ipv6(net, nh, nhi, cfg, extack);
+		break;
+	}
+
+	if (err) {
+		kfree(nhi);
+		kfree(nh);
+		return ERR_PTR(err);
+	}
+
+	/* add the entry to the device based hash */
+	if (!nhi->fdb_nh)
+		nexthop_devhash_add(net, nhi);
+
+	rcu_assign_pointer(nh->nh_info, nhi);
+
+	return nh;
+}
+
+/* called with rtnl lock held */
+static struct nexthop *nexthop_add(struct net *net, struct nh_config *cfg,
+				   struct netlink_ext_ack *extack)
+{
+	struct nexthop *nh;
+	int err;
+
+	if (cfg->nlflags & NLM_F_REPLACE && !cfg->nh_id) {
+		NL_SET_ERR_MSG(extack, "Replace requires nexthop id");
+		return ERR_PTR(-EINVAL);
+	}
+
+	if (!cfg->nh_id) {
+		cfg->nh_id = nh_find_unused_id(net);
+		if (!cfg->nh_id) {
+			NL_SET_ERR_MSG(extack, "No unused id");
+			return ERR_PTR(-EINVAL);
+		}
+	}
+
+	if (cfg->nh_grp)
+		nh = nexthop_create_group(net, cfg);
+	else
+		nh = nexthop_create(net, cfg, extack);
+
+	if (IS_ERR(nh))
+		return nh;
+
+	refcount_set(&nh->refcnt, 1);
+	nh->id = cfg->nh_id;
+	nh->protocol = cfg->nh_protocol;
+	nh->net = net;
+
+	err = insert_nexthop(net, nh, cfg, extack);
+	if (err) {
+		__remove_nexthop(net, nh, NULL);
+		nexthop_put(nh);
+		nh = ERR_PTR(err);
+	}
+
+	return nh;
+}
+
+static int rtm_to_nh_config(struct net *net, struct sk_buff *skb,
+			    struct nlmsghdr *nlh, struct nh_config *cfg,
+			    struct netlink_ext_ack *extack)
+{
+	struct nhmsg *nhm = nlmsg_data(nlh);
+	struct nlattr *tb[NHA_MAX + 1];
+	int err;
+
+	err = nlmsg_parse(nlh, sizeof(*nhm), tb, NHA_MAX, rtm_nh_policy,
+			  extack);
+	if (err < 0)
+		return err;
+
+	err = -EINVAL;
+	if (nhm->resvd || nhm->nh_scope) {
+		NL_SET_ERR_MSG(extack, "Invalid values in ancillary header");
+		goto out;
+	}
+	if (nhm->nh_flags & ~NEXTHOP_VALID_USER_FLAGS) {
+		NL_SET_ERR_MSG(extack, "Invalid nexthop flags in ancillary header");
+		goto out;
+	}
+
+	switch (nhm->nh_family) {
+	case AF_INET:
+	case AF_INET6:
+		break;
+	case AF_UNSPEC:
+		if (tb[NHA_GROUP])
+			break;
+		fallthrough;
+	default:
+		NL_SET_ERR_MSG(extack, "Invalid address family");
+		goto out;
+	}
+
+	if (tb[NHA_GROUPS] || tb[NHA_MASTER]) {
+		NL_SET_ERR_MSG(extack, "Invalid attributes in request");
+		goto out;
+	}
+
+	memset(cfg, 0, sizeof(*cfg));
+	cfg->nlflags = nlh->nlmsg_flags;
+	cfg->nlinfo.portid = NETLINK_CB(skb).portid;
+	cfg->nlinfo.nlh = nlh;
+	cfg->nlinfo.nl_net = net;
+
+	cfg->nh_family = nhm->nh_family;
+	cfg->nh_protocol = nhm->nh_protocol;
+	cfg->nh_flags = nhm->nh_flags;
+
+	if (tb[NHA_ID])
+		cfg->nh_id = nla_get_u32(tb[NHA_ID]);
+
+	if (tb[NHA_FDB]) {
+		if (tb[NHA_OIF] || tb[NHA_BLACKHOLE] ||
+		    tb[NHA_ENCAP]   || tb[NHA_ENCAP_TYPE]) {
+			NL_SET_ERR_MSG(extack, "Fdb attribute can not be used with encap, oif or blackhole");
+			goto out;
+		}
+		if (nhm->nh_flags) {
+			NL_SET_ERR_MSG(extack, "Unsupported nexthop flags in ancillary header");
+			goto out;
+		}
+		cfg->nh_fdb = nla_get_flag(tb[NHA_FDB]);
+	}
+
+	if (tb[NHA_GROUP]) {
+		if (nhm->nh_family != AF_UNSPEC) {
+			NL_SET_ERR_MSG(extack, "Invalid family for group");
+			goto out;
+		}
+		cfg->nh_grp = tb[NHA_GROUP];
+
+		cfg->nh_grp_type = NEXTHOP_GRP_TYPE_MPATH;
+		if (tb[NHA_GROUP_TYPE])
+			cfg->nh_grp_type = nla_get_u16(tb[NHA_GROUP_TYPE]);
+
+		if (cfg->nh_grp_type > NEXTHOP_GRP_TYPE_MAX) {
+			NL_SET_ERR_MSG(extack, "Invalid group type");
+			goto out;
+		}
+		err = nh_check_attr_group(net, tb, extack);
+
+		/* no other attributes should be set */
+		goto out;
+	}
+
+	if (tb[NHA_BLACKHOLE]) {
+		if (tb[NHA_GATEWAY] || tb[NHA_OIF] ||
+		    tb[NHA_ENCAP]   || tb[NHA_ENCAP_TYPE] || tb[NHA_FDB]) {
+			NL_SET_ERR_MSG(extack, "Blackhole attribute can not be used with gateway, oif, encap or fdb");
+			goto out;
+		}
+
+		cfg->nh_blackhole = 1;
+		err = 0;
+		goto out;
+	}
+
+	if (!cfg->nh_fdb && !tb[NHA_OIF]) {
+		NL_SET_ERR_MSG(extack, "Device attribute required for non-blackhole and non-fdb nexthops");
+		goto out;
+	}
+
+	if (!cfg->nh_fdb && tb[NHA_OIF]) {
+		cfg->nh_ifindex = nla_get_u32(tb[NHA_OIF]);
+		if (cfg->nh_ifindex)
+			cfg->dev = __dev_get_by_index(net, cfg->nh_ifindex);
+
+		if (!cfg->dev) {
+			NL_SET_ERR_MSG(extack, "Invalid device index");
+			goto out;
+		} else if (!(cfg->dev->flags & IFF_UP)) {
+			NL_SET_ERR_MSG(extack, "Nexthop device is not up");
+			err = -ENETDOWN;
+			goto out;
+		} else if (!netif_carrier_ok(cfg->dev)) {
+			NL_SET_ERR_MSG(extack, "Carrier for nexthop device is down");
+			err = -ENETDOWN;
+			goto out;
+		}
+	}
+
+	err = -EINVAL;
+	if (tb[NHA_GATEWAY]) {
+		struct nlattr *gwa = tb[NHA_GATEWAY];
+
+		switch (cfg->nh_family) {
+		case AF_INET:
+			if (nla_len(gwa) != sizeof(u32)) {
+				NL_SET_ERR_MSG(extack, "Invalid gateway");
+				goto out;
+			}
+			cfg->gw.ipv4 = nla_get_be32(gwa);
+			break;
+		case AF_INET6:
+			if (nla_len(gwa) != sizeof(struct in6_addr)) {
+				NL_SET_ERR_MSG(extack, "Invalid gateway");
+				goto out;
+			}
+			cfg->gw.ipv6 = nla_get_in6_addr(gwa);
+			break;
+		default:
+			NL_SET_ERR_MSG(extack,
+				       "Unknown address family for gateway");
+			goto out;
+		}
+	} else {
+		/* device only nexthop (no gateway) */
+		if (cfg->nh_flags & RTNH_F_ONLINK) {
+			NL_SET_ERR_MSG(extack,
+				       "ONLINK flag can not be set for nexthop without a gateway");
+			goto out;
+		}
+	}
+
+	if (tb[NHA_ENCAP]) {
+		cfg->nh_encap = tb[NHA_ENCAP];
+
+		if (!tb[NHA_ENCAP_TYPE]) {
+			NL_SET_ERR_MSG(extack, "LWT encapsulation type is missing");
+			goto out;
+		}
+
+		cfg->nh_encap_type = nla_get_u16(tb[NHA_ENCAP_TYPE]);
+		err = lwtunnel_valid_encap_type(cfg->nh_encap_type, extack);
+		if (err < 0)
+			goto out;
+
+	} else if (tb[NHA_ENCAP_TYPE]) {
+		NL_SET_ERR_MSG(extack, "LWT encapsulation attribute is missing");
+		goto out;
+	}
+
+
+	err = 0;
+out:
+	return err;
+}
+
+/* rtnl */
+static int rtm_new_nexthop(struct sk_buff *skb, struct nlmsghdr *nlh,
+			   struct netlink_ext_ack *extack)
+{
+	struct net *net = sock_net(skb->sk);
+	struct nh_config cfg;
+	struct nexthop *nh;
+	int err;
+
+	err = rtm_to_nh_config(net, skb, nlh, &cfg, extack);
+	if (!err) {
+		nh = nexthop_add(net, &cfg, extack);
+		if (IS_ERR(nh))
+			err = PTR_ERR(nh);
+	}
+
+	return err;
+}
+
+static int nh_valid_get_del_req(struct nlmsghdr *nlh, u32 *id,
+				struct netlink_ext_ack *extack)
+{
+	struct nhmsg *nhm = nlmsg_data(nlh);
+	struct nlattr *tb[NHA_MAX + 1];
+	int err, i;
+
+	err = nlmsg_parse(nlh, sizeof(*nhm), tb, NHA_MAX, rtm_nh_policy,
+			  extack);
+	if (err < 0)
+		return err;
+
+	err = -EINVAL;
+	for (i = 0; i < __NHA_MAX; ++i) {
+		if (!tb[i])
+			continue;
+
+		switch (i) {
+		case NHA_ID:
+			break;
+		default:
+			NL_SET_ERR_MSG_ATTR(extack, tb[i],
+					    "Unexpected attribute in request");
+			goto out;
+		}
+	}
+	if (nhm->nh_protocol || nhm->resvd || nhm->nh_scope || nhm->nh_flags) {
+		NL_SET_ERR_MSG(extack, "Invalid values in header");
+		goto out;
+	}
+
+	if (!tb[NHA_ID]) {
+		NL_SET_ERR_MSG(extack, "Nexthop id is missing");
+		goto out;
+	}
+
+	*id = nla_get_u32(tb[NHA_ID]);
+	if (!(*id))
+		NL_SET_ERR_MSG(extack, "Invalid nexthop id");
+	else
+		err = 0;
+out:
+	return err;
+}
+
+/* rtnl */
+static int rtm_del_nexthop(struct sk_buff *skb, struct nlmsghdr *nlh,
+			   struct netlink_ext_ack *extack)
+{
+	struct net *net = sock_net(skb->sk);
+	struct nl_info nlinfo = {
+		.nlh = nlh,
+		.nl_net = net,
+		.portid = NETLINK_CB(skb).portid,
+	};
+	struct nexthop *nh;
+	int err;
+	u32 id;
+
+	err = nh_valid_get_del_req(nlh, &id, extack);
+	if (err)
+		return err;
+
+	nh = nexthop_find_by_id(net, id);
+	if (!nh)
+		return -ENOENT;
+
+	remove_nexthop(net, nh, &nlinfo);
+
+	return 0;
+}
+
+/* rtnl */
+static int rtm_get_nexthop(struct sk_buff *in_skb, struct nlmsghdr *nlh,
+			   struct netlink_ext_ack *extack)
+{
+	struct net *net = sock_net(in_skb->sk);
+	struct sk_buff *skb = NULL;
+	struct nexthop *nh;
+	int err;
+	u32 id;
+
+	err = nh_valid_get_del_req(nlh, &id, extack);
+	if (err)
+		return err;
+
+	err = -ENOBUFS;
+	skb = alloc_skb(NLMSG_GOODSIZE, GFP_KERNEL);
+	if (!skb)
+		goto out;
+
+	err = -ENOENT;
+	nh = nexthop_find_by_id(net, id);
+	if (!nh)
+		goto errout_free;
+
+	err = nh_fill_node(skb, nh, RTM_NEWNEXTHOP, NETLINK_CB(in_skb).portid,
+			   nlh->nlmsg_seq, 0);
+	if (err < 0) {
+		WARN_ON(err == -EMSGSIZE);
+		goto errout_free;
+	}
+
+	err = rtnl_unicast(skb, net, NETLINK_CB(in_skb).portid);
+out:
+	return err;
+errout_free:
+	kfree_skb(skb);
+	goto out;
+}
+
+static bool nh_dump_filtered(struct nexthop *nh, int dev_idx, int master_idx,
+			     bool group_filter, u8 family)
+{
+	const struct net_device *dev;
+	const struct nh_info *nhi;
+
+	if (group_filter && !nh->is_group)
+		return true;
+
+	if (!dev_idx && !master_idx && !family)
+		return false;
+
+	if (nh->is_group)
+		return true;
+
+	nhi = rtnl_dereference(nh->nh_info);
+	if (family && nhi->family != family)
+		return true;
+
+	dev = nhi->fib_nhc.nhc_dev;
+	if (dev_idx && (!dev || dev->ifindex != dev_idx))
+		return true;
+
+	if (master_idx) {
+		struct net_device *master;
+
+		if (!dev)
+			return true;
+
+		master = netdev_master_upper_dev_get((struct net_device *)dev);
+		if (!master || master->ifindex != master_idx)
+			return true;
+	}
+
+	return false;
+}
+
+static int nh_valid_dump_req(const struct nlmsghdr *nlh, int *dev_idx,
+			     int *master_idx, bool *group_filter,
+			     bool *fdb_filter, struct netlink_callback *cb)
+{
+	struct netlink_ext_ack *extack = cb->extack;
+	struct nlattr *tb[NHA_MAX + 1];
+	struct nhmsg *nhm;
+	int err, i;
+	u32 idx;
+
+	err = nlmsg_parse(nlh, sizeof(*nhm), tb, NHA_MAX, rtm_nh_policy,
+			  NULL);
+	if (err < 0)
+		return err;
+
+	for (i = 0; i <= NHA_MAX; ++i) {
+		if (!tb[i])
+			continue;
+
+		switch (i) {
+		case NHA_OIF:
+			idx = nla_get_u32(tb[i]);
+			if (idx > INT_MAX) {
+				NL_SET_ERR_MSG(extack, "Invalid device index");
+				return -EINVAL;
+			}
+			*dev_idx = idx;
+			break;
+		case NHA_MASTER:
+			idx = nla_get_u32(tb[i]);
+			if (idx > INT_MAX) {
+				NL_SET_ERR_MSG(extack, "Invalid master device index");
+				return -EINVAL;
+			}
+			*master_idx = idx;
+			break;
+		case NHA_GROUPS:
+			*group_filter = true;
+			break;
+		case NHA_FDB:
+			*fdb_filter = true;
+			break;
+		default:
+			NL_SET_ERR_MSG(extack, "Unsupported attribute in dump request");
+			return -EINVAL;
+		}
+	}
+
+	nhm = nlmsg_data(nlh);
+	if (nhm->nh_protocol || nhm->resvd || nhm->nh_scope || nhm->nh_flags) {
+		NL_SET_ERR_MSG(extack, "Invalid values in header for nexthop dump request");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+/* rtnl */
+static int rtm_dump_nexthop(struct sk_buff *skb, struct netlink_callback *cb)
+{
+	bool group_filter = false, fdb_filter = false;
+	struct nhmsg *nhm = nlmsg_data(cb->nlh);
+	int dev_filter_idx = 0, master_idx = 0;
+	struct net *net = sock_net(skb->sk);
+	struct rb_root *root = &net->nexthop.rb_root;
+	struct rb_node *node;
+	int idx = 0, s_idx;
+	int err;
+
+	err = nh_valid_dump_req(cb->nlh, &dev_filter_idx, &master_idx,
+				&group_filter, &fdb_filter, cb);
+	if (err < 0)
+		return err;
+
+	s_idx = cb->args[0];
+	for (node = rb_first(root); node; node = rb_next(node)) {
+		struct nexthop *nh;
+
+		if (idx < s_idx)
+			goto cont;
+
+		nh = rb_entry(node, struct nexthop, rb_node);
+		if (nh_dump_filtered(nh, dev_filter_idx, master_idx,
+				     group_filter, nhm->nh_family))
+			goto cont;
+
+		err = nh_fill_node(skb, nh, RTM_NEWNEXTHOP,
+				   NETLINK_CB(cb->skb).portid,
+				   cb->nlh->nlmsg_seq, NLM_F_MULTI);
+		if (err < 0) {
+			if (likely(skb->len))
+				goto out;
+
+			goto out_err;
+		}
+cont:
+		idx++;
+	}
+
+out:
+	err = skb->len;
+out_err:
+	cb->args[0] = idx;
+	cb->seq = net->nexthop.seq;
+	nl_dump_check_consistent(cb, nlmsg_hdr(skb));
+
+	return err;
+}
+
+static void nexthop_sync_mtu(struct net_device *dev, u32 orig_mtu)
+{
+	unsigned int hash = nh_dev_hashfn(dev->ifindex);
+	struct net *net = dev_net(dev);
+	struct hlist_head *head = &net->nexthop.devhash[hash];
+	struct hlist_node *n;
+	struct nh_info *nhi;
+
+	hlist_for_each_entry_safe(nhi, n, head, dev_hash) {
+		if (nhi->fib_nhc.nhc_dev == dev) {
+			if (nhi->family == AF_INET)
+				fib_nhc_update_mtu(&nhi->fib_nhc, dev->mtu,
+						   orig_mtu);
+		}
+	}
+}
+
+/* rtnl */
+static int nh_netdev_event(struct notifier_block *this,
+			   unsigned long event, void *ptr)
+{
+	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
+	struct netdev_notifier_info_ext *info_ext;
+
+	switch (event) {
+	case NETDEV_DOWN:
+	case NETDEV_UNREGISTER:
+		nexthop_flush_dev(dev, event);
+		break;
+	case NETDEV_CHANGE:
+		if (!(dev_get_flags(dev) & (IFF_RUNNING | IFF_LOWER_UP)))
+			nexthop_flush_dev(dev, event);
+		break;
+	case NETDEV_CHANGEMTU:
+		info_ext = ptr;
+		nexthop_sync_mtu(dev, info_ext->ext.mtu);
+		rt_cache_flush(dev_net(dev));
+		break;
+	}
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block nh_netdev_notifier = {
+	.notifier_call = nh_netdev_event,
+};
+
+int register_nexthop_notifier(struct net *net, struct notifier_block *nb)
+{
+	return blocking_notifier_chain_register(&net->nexthop.notifier_chain,
+						nb);
+}
+EXPORT_SYMBOL(register_nexthop_notifier);
+
+int unregister_nexthop_notifier(struct net *net, struct notifier_block *nb)
+{
+	return blocking_notifier_chain_unregister(&net->nexthop.notifier_chain,
+						  nb);
+}
+EXPORT_SYMBOL(unregister_nexthop_notifier);
+
+static void __net_exit nexthop_net_exit(struct net *net)
+{
+	rtnl_lock();
+	flush_all_nexthops(net);
+	rtnl_unlock();
+	kfree(net->nexthop.devhash);
+}
+
+static int __net_init nexthop_net_init(struct net *net)
+{
+	size_t sz = sizeof(struct hlist_head) * NH_DEV_HASHSIZE;
+
+	net->nexthop.rb_root = RB_ROOT;
+	net->nexthop.devhash = kzalloc(sz, GFP_KERNEL);
+	if (!net->nexthop.devhash)
+		return -ENOMEM;
+	BLOCKING_INIT_NOTIFIER_HEAD(&net->nexthop.notifier_chain);
+
+	return 0;
+}
+
+static struct pernet_operations nexthop_net_ops = {
+	.init = nexthop_net_init,
+	.exit = nexthop_net_exit,
+};
+
+static int __init nexthop_init(void)
+{
+	register_pernet_subsys(&nexthop_net_ops);
+
+	register_netdevice_notifier(&nh_netdev_notifier);
+
+	rtnl_register(PF_UNSPEC, RTM_NEWNEXTHOP, rtm_new_nexthop, NULL, 0);
+	rtnl_register(PF_UNSPEC, RTM_DELNEXTHOP, rtm_del_nexthop, NULL, 0);
+	rtnl_register(PF_UNSPEC, RTM_GETNEXTHOP, rtm_get_nexthop,
+		      rtm_dump_nexthop, 0);
+
+	rtnl_register(PF_INET, RTM_NEWNEXTHOP, rtm_new_nexthop, NULL, 0);
+	rtnl_register(PF_INET, RTM_GETNEXTHOP, NULL, rtm_dump_nexthop, 0);
+
+	rtnl_register(PF_INET6, RTM_NEWNEXTHOP, rtm_new_nexthop, NULL, 0);
+	rtnl_register(PF_INET6, RTM_GETNEXTHOP, NULL, rtm_dump_nexthop, 0);
+
+	return 0;
+}
+subsys_initcall(nexthop_init);