diff --git a/include/linux/netfilter/nf_conntrack_proto_gre.h b/include/linux/netfilter/nf_conntrack_proto_gre.h
index 9ee7014400e8..ad5563f0f864 100644
--- a/include/linux/netfilter/nf_conntrack_proto_gre.h
+++ b/include/linux/netfilter/nf_conntrack_proto_gre.h
@@ -18,9 +18,10 @@ struct nf_ct_gre_keymap {
 	struct rcu_head rcu;
 };
 
-/* add new tuple->key_reply pair to keymap */
-int nf_ct_gre_keymap_add(struct nf_conn *ct, enum ip_conntrack_dir dir,
-			 struct nf_conntrack_tuple *t);
+/* add tuple->key_reply pairs to keymap */
+bool nf_ct_gre_keymap_add(struct nf_conn *ct,
+			  const struct nf_conntrack_tuple *orig,
+			  const struct nf_conntrack_tuple *repl);
 
 /* delete keymap entries */
 void nf_ct_gre_keymap_destroy(struct nf_conn *ct);
diff --git a/include/net/netfilter/nf_tables.h b/include/net/netfilter/nf_tables.h
index cff7b773e972..9d844354c4d9 100644
--- a/include/net/netfilter/nf_tables.h
+++ b/include/net/netfilter/nf_tables.h
@@ -180,6 +180,13 @@ static inline u64 nft_reg_load64(const u32 *sreg)
 	return get_unaligned((u64 *)sreg);
 }
 
+static inline bool nft_reg_overlap(u8 src, u8 dst, u32 len)
+{
+	unsigned int n = DIV_ROUND_UP(len, sizeof(u32));
+
+	return src != dst && src < dst + n && dst < src + n;
+}
+
 static inline void nft_data_copy(u32 *dst, const struct nft_data *src,
 				 unsigned int len)
 {
diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c
index b9f4daac09af..8a6a069329d2 100644
--- a/net/bridge/netfilter/ebtables.c
+++ b/net/bridge/netfilter/ebtables.c
@@ -1956,6 +1956,25 @@ enum compat_mwt {
 	EBT_COMPAT_TARGET,
 };
 
+static bool match_size_ok(const struct xt_match *match, unsigned int match_size)
+{
+	u16 csize;
+
+	if (match->matchsize == -1) /* cannot validate ebt_among */
+		return true;
+
+	csize = match->compatsize ? : match->matchsize;
+
+	return match_size >= csize;
+}
+
+static bool tgt_size_ok(const struct xt_target *tgt, unsigned int tgt_size)
+{
+	u16 csize = tgt->compatsize ? : tgt->targetsize;
+
+	return tgt_size >= csize;
+}
+
 static int compat_mtw_from_user(const struct compat_ebt_entry_mwt *mwt,
 				enum compat_mwt compat_mwt,
 				struct ebt_entries_buf_state *state,
@@ -1981,6 +2000,11 @@ static int compat_mtw_from_user(const struct compat_ebt_entry_mwt *mwt,
 		if (IS_ERR(match))
 			return PTR_ERR(match);
 
+		if (!match_size_ok(match, match_size)) {
+			module_put(match->me);
+			return -EINVAL;
+		}
+
 		off = ebt_compat_match_offset(match, match_size);
 		if (dst) {
 			if (match->compat_from_user)
@@ -2000,6 +2024,12 @@ static int compat_mtw_from_user(const struct compat_ebt_entry_mwt *mwt,
 					    mwt->u.revision);
 		if (IS_ERR(wt))
 			return PTR_ERR(wt);
+
+		if (!tgt_size_ok(wt, match_size)) {
+			module_put(wt->me);
+			return -EINVAL;
+		}
+
 		off = xt_compat_target_offset(wt);
 
 		if (dst) {
diff --git a/net/ipv6/netfilter/nft_fib_ipv6.c b/net/ipv6/netfilter/nft_fib_ipv6.c
index 8b2dba88ee96..c0a0075e2590 100644
--- a/net/ipv6/netfilter/nft_fib_ipv6.c
+++ b/net/ipv6/netfilter/nft_fib_ipv6.c
@@ -160,17 +160,33 @@ static bool nft_fib6_info_nh_dev_match(const struct net_device *nh_dev,
 	       l3mdev_master_ifindex_rcu(nh_dev) == dev->ifindex;
 }
 
+static int nft_fib6_nh_match_dev_cb(struct fib6_nh *nh, void *arg)
+{
+	const struct net_device *dev = arg;
+
+	return nft_fib6_info_nh_dev_match(nh->fib_nh_dev, dev);
+}
+
 static bool nft_fib6_info_nh_uses_dev(struct fib6_info *rt,
 				      const struct net_device *dev)
 {
 	const struct net_device *nh_dev;
 	struct fib6_info *iter;
 
+	/* External nexthop: fib6_siblings slot aliases nh_list, walk via nh. */
+	if (rt->nh)
+		return nexthop_for_each_fib6_nh(rt->nh,
+						nft_fib6_nh_match_dev_cb,
+						(void *)dev);
+
 	nh_dev = fib6_info_nh_dev(rt);
 	if (nft_fib6_info_nh_dev_match(nh_dev, dev))
 		return true;
 
-	list_for_each_entry(iter, &rt->fib6_siblings, fib6_siblings) {
+	if (!READ_ONCE(rt->fib6_nsiblings))
+		return false;
+
+	list_for_each_entry_rcu(iter, &rt->fib6_siblings, fib6_siblings) {
 		nh_dev = fib6_info_nh_dev(iter);
 
 		if (nft_fib6_info_nh_dev_match(nh_dev, dev))
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 8ba5b22a1eef..b521b5ebd664 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -568,6 +568,13 @@ static void destroy_gre_conntrack(struct nf_conn *ct)
 #endif
 }
 
+static void warn_on_keymap_list_leak(const struct net *net)
+{
+#ifdef CONFIG_NF_CT_PROTO_GRE
+	WARN_ON_ONCE(!list_empty(&net->ct.nf_ct_proto.gre.keymap_list));
+#endif
+}
+
 void nf_ct_destroy(struct nf_conntrack *nfct)
 {
 	struct nf_conn *ct = (struct nf_conn *)nfct;
@@ -2510,6 +2517,7 @@ void nf_conntrack_cleanup_net_list(struct list_head *net_exit_list)
 	}
 
 	list_for_each_entry(net, net_exit_list, exit_list) {
+		warn_on_keymap_list_leak(net);
 		nf_conntrack_ecache_pernet_fini(net);
 		nf_conntrack_expect_pernet_fini(net);
 		free_percpu(net->ct.stat);
diff --git a/net/netfilter/nf_conntrack_pptp.c b/net/netfilter/nf_conntrack_pptp.c
index 4c679638df06..dc23e4181618 100644
--- a/net/netfilter/nf_conntrack_pptp.c
+++ b/net/netfilter/nf_conntrack_pptp.c
@@ -225,13 +225,9 @@ static int exp_gre(struct nf_conn *ct, __be16 callid, __be16 peer_callid)
 	if (nf_ct_expect_related(exp_reply, 0) != 0)
 		goto out_unexpect_orig;
 
-	/* Add GRE keymap entries */
-	if (nf_ct_gre_keymap_add(ct, IP_CT_DIR_ORIGINAL, &exp_orig->tuple) != 0)
+	if (!nf_ct_gre_keymap_add(ct, &exp_orig->tuple,
+				  &exp_reply->tuple))
 		goto out_unexpect_both;
-	if (nf_ct_gre_keymap_add(ct, IP_CT_DIR_REPLY, &exp_reply->tuple) != 0) {
-		nf_ct_gre_keymap_destroy(ct);
-		goto out_unexpect_both;
-	}
 	ret = 0;
 
 out_put_both:
diff --git a/net/netfilter/nf_conntrack_proto_gre.c b/net/netfilter/nf_conntrack_proto_gre.c
index 94c19bc4edc5..35e22082d65a 100644
--- a/net/netfilter/nf_conntrack_proto_gre.c
+++ b/net/netfilter/nf_conntrack_proto_gre.c
@@ -87,41 +87,97 @@ static __be16 gre_keymap_lookup(struct net *net, struct nf_conntrack_tuple *t)
 	return key;
 }
 
-/* add a single keymap entry, associate with specified master ct */
-int nf_ct_gre_keymap_add(struct nf_conn *ct, enum ip_conntrack_dir dir,
-			 struct nf_conntrack_tuple *t)
+enum nf_ct_gre_km_act {
+	NF_CT_GRE_KM_NEW,
+	NF_CT_GRE_KM_BAD,
+	NF_CT_GRE_KM_DUP
+};
+
+static enum nf_ct_gre_km_act
+nf_ct_gre_km_acceptable(const struct nf_ct_pptp_master *ct_pptp_info,
+			const struct nf_conntrack_tuple *orig,
+			const struct nf_conntrack_tuple *repl)
+{
+	struct nf_ct_gre_keymap *km_orig, *km_repl;
+
+	lockdep_assert_held(&keymap_lock);
+
+	km_orig = ct_pptp_info->keymap[IP_CT_DIR_ORIGINAL];
+	km_repl = ct_pptp_info->keymap[IP_CT_DIR_REPLY];
+
+	if (km_orig && km_repl) {
+		if (!gre_key_cmpfn(km_orig, orig))
+			return NF_CT_GRE_KM_BAD;
+
+		if (!gre_key_cmpfn(km_repl, repl))
+			return NF_CT_GRE_KM_BAD;
+
+		return NF_CT_GRE_KM_DUP;
+	}
+
+	DEBUG_NET_WARN_ON_ONCE(km_orig);
+	DEBUG_NET_WARN_ON_ONCE(km_repl);
+	return NF_CT_GRE_KM_NEW;
+}
+
+/* add keymap entries, associate with specified master ct */
+bool nf_ct_gre_keymap_add(struct nf_conn *ct,
+			  const struct nf_conntrack_tuple *orig,
+			  const struct nf_conntrack_tuple *repl)
 {
 	struct net *net = nf_ct_net(ct);
 	struct nf_gre_net *net_gre = gre_pernet(net);
 	struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct);
-	struct nf_ct_gre_keymap **kmp, *km;
+	struct nf_ct_gre_keymap *km_orig, *km_repl;
+	bool ret = false;
 
-	kmp = &ct_pptp_info->keymap[dir];
-	if (*kmp) {
-		/* check whether it's a retransmission */
-		list_for_each_entry_rcu(km, &net_gre->keymap_list, list) {
-			if (gre_key_cmpfn(km, t) && km == *kmp)
-				return 0;
-		}
-		pr_debug("trying to override keymap_%s for ct %p\n",
-			 dir == IP_CT_DIR_REPLY ? "reply" : "orig", ct);
-		return -EEXIST;
-	}
+	km_orig = kmalloc_obj(*km_orig, GFP_ATOMIC);
+	if (!km_orig)
+		return false;
+	km_repl = kmalloc_obj(*km_repl, GFP_ATOMIC);
+	if (!km_repl)
+		goto km_free;
 
-	km = kmalloc_obj(*km, GFP_ATOMIC);
-	if (!km)
-		return -ENOMEM;
-	memcpy(&km->tuple, t, sizeof(*t));
-	*kmp = km;
-
-	pr_debug("adding new entry %p: ", km);
-	nf_ct_dump_tuple(&km->tuple);
+	memcpy(&km_orig->tuple, orig, sizeof(*orig));
+	memcpy(&km_repl->tuple, repl, sizeof(*repl));
 
 	spin_lock_bh(&keymap_lock);
-	list_add_tail(&km->list, &net_gre->keymap_list);
+	if (nf_ct_is_dying(ct))
+		goto unlock_free;
+
+	switch (nf_ct_gre_km_acceptable(ct_pptp_info, orig, repl)) {
+	case NF_CT_GRE_KM_NEW:
+		break;
+	case NF_CT_GRE_KM_DUP:
+		ret = true;
+		goto unlock_free;
+	case NF_CT_GRE_KM_BAD:
+		pr_debug("trying to override keymap for ct %p\n", ct);
+		goto unlock_free;
+	}
+
+	if (ct_pptp_info->keymap[IP_CT_DIR_ORIGINAL] ||
+	    ct_pptp_info->keymap[IP_CT_DIR_REPLY])
+		goto unlock_free;
+
+	pr_debug("adding new entries %p,%p: ", km_orig, km_repl);
+	nf_ct_dump_tuple(&km_orig->tuple);
+	nf_ct_dump_tuple(&km_repl->tuple);
+
+	list_add_tail_rcu(&km_orig->list, &net_gre->keymap_list);
+	list_add_tail_rcu(&km_repl->list, &net_gre->keymap_list);
+	ct_pptp_info->keymap[IP_CT_DIR_ORIGINAL] = km_orig;
+	ct_pptp_info->keymap[IP_CT_DIR_REPLY] = km_repl;
 	spin_unlock_bh(&keymap_lock);
 
-	return 0;
+	return true;
+
+unlock_free:
+	spin_unlock_bh(&keymap_lock);
+km_free:
+	kfree(km_orig);
+	kfree(km_repl);
+	return ret;
 }
 EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_add);
 
diff --git a/net/netfilter/nf_conntrack_proto_tcp.c b/net/netfilter/nf_conntrack_proto_tcp.c
index b67426c2189b..e99ab1e88e9f 100644
--- a/net/netfilter/nf_conntrack_proto_tcp.c
+++ b/net/netfilter/nf_conntrack_proto_tcp.c
@@ -1221,7 +1221,8 @@ int nf_conntrack_tcp_packet(struct nf_conn *ct,
 			new_state = old_state;
 		}
 		if (((test_bit(IPS_SEEN_REPLY_BIT, &ct->status)
-			 && ct->proto.tcp.last_index == TCP_SYN_SET)
+			 && ct->proto.tcp.last_index == TCP_SYN_SET
+			 && ct->proto.tcp.last_dir != dir)
 			|| (!test_bit(IPS_ASSURED_BIT, &ct->status)
 			    && ct->proto.tcp.last_index == TCP_ACK_SET))
 		    && ntohl(th->ack_seq) == ct->proto.tcp.last_end) {
diff --git a/net/netfilter/nf_synproxy_core.c b/net/netfilter/nf_synproxy_core.c
index 57f57e2fc80a..036c8586f49b 100644
--- a/net/netfilter/nf_synproxy_core.c
+++ b/net/netfilter/nf_synproxy_core.c
@@ -200,6 +200,8 @@ synproxy_tstamp_adjust(struct sk_buff *skb, unsigned int protoff,
 	if (skb_ensure_writable(skb, optend))
 		return 0;
 
+	th = (struct tcphdr *)(skb->data + protoff);
+
 	while (optoff < optend) {
 		unsigned char *op = skb->data + optoff;
 
diff --git a/net/netfilter/nfnetlink_queue.c b/net/netfilter/nfnetlink_queue.c
index 984a0eb9e149..60ab88d45096 100644
--- a/net/netfilter/nfnetlink_queue.c
+++ b/net/netfilter/nfnetlink_queue.c
@@ -1141,6 +1141,9 @@ nfqnl_mangle(void *data, unsigned int data_len, struct nf_queue_entry *e, int di
 {
 	struct sk_buff *nskb;
 
+	if (e->state.net->user_ns != &init_user_ns)
+		return -EPERM;
+
 	if (diff < 0) {
 		unsigned int min_len = skb_transport_offset(e->skb);
 
@@ -1537,8 +1540,7 @@ static int nfqnl_recv_verdict(struct sk_buff *skb, const struct nfnl_info *info,
 		if (nfqnl_mangle(nla_data(nfqa[NFQA_PAYLOAD]),
 				 payload_len, entry, diff) < 0)
 			verdict = NF_DROP;
-
-		if (ct && diff)
+		else if (ct && diff)
 			nfnl_ct->seq_adjust(entry->skb, ct, ctinfo, diff);
 	}
 
diff --git a/net/netfilter/nft_bitwise.c b/net/netfilter/nft_bitwise.c
index 94dccdcfa06b..785b8e9731d1 100644
--- a/net/netfilter/nft_bitwise.c
+++ b/net/netfilter/nft_bitwise.c
@@ -43,8 +43,10 @@ static void nft_bitwise_eval_lshift(u32 *dst, const u32 *src,
 	u32 carry = 0;
 
 	for (i = DIV_ROUND_UP(priv->len, sizeof(u32)); i > 0; i--) {
-		dst[i - 1] = (src[i - 1] << shift) | carry;
-		carry = src[i - 1] >> (BITS_PER_TYPE(u32) - shift);
+		u32 tmp_src = src[i - 1];
+
+		dst[i - 1] = (tmp_src << shift) | carry;
+		carry = tmp_src >> (BITS_PER_TYPE(u32) - shift);
 	}
 }
 
@@ -56,8 +58,10 @@ static void nft_bitwise_eval_rshift(u32 *dst, const u32 *src,
 	u32 carry = 0;
 
 	for (i = 0; i < DIV_ROUND_UP(priv->len, sizeof(u32)); i++) {
-		dst[i] = carry | (src[i] >> shift);
-		carry = src[i] << (BITS_PER_TYPE(u32) - shift);
+		u32 tmp_src = src[i];
+
+		dst[i] = carry | (tmp_src >> shift);
+		carry = tmp_src << (BITS_PER_TYPE(u32) - shift);
 	}
 }
 
@@ -235,6 +239,9 @@ static int nft_bitwise_init_bool(const struct nft_ctx *ctx,
 					      &priv->sreg2, priv->len);
 		if (err < 0)
 			return err;
+
+		if (nft_reg_overlap(priv->sreg2, priv->dreg, priv->len))
+			return -EINVAL;
 	}
 
 	return 0;
@@ -265,6 +272,9 @@ static int nft_bitwise_init(const struct nft_ctx *ctx,
 	if (err < 0)
 		return err;
 
+	if (nft_reg_overlap(priv->sreg, priv->dreg, priv->len))
+		return -EINVAL;
+
 	if (tb[NFTA_BITWISE_OP]) {
 		priv->op = ntohl(nla_get_be32(tb[NFTA_BITWISE_OP]));
 		switch (priv->op) {
diff --git a/net/netfilter/nft_byteorder.c b/net/netfilter/nft_byteorder.c
index e00dddfa2fc0..2316c77f4228 100644
--- a/net/netfilter/nft_byteorder.c
+++ b/net/netfilter/nft_byteorder.c
@@ -144,9 +144,16 @@ static int nft_byteorder_init(const struct nft_ctx *ctx,
 	if (err < 0)
 		return err;
 
-	return nft_parse_register_store(ctx, tb[NFTA_BYTEORDER_DREG],
-					&priv->dreg, NULL, NFT_DATA_VALUE,
-					priv->len);
+	err = nft_parse_register_store(ctx, tb[NFTA_BYTEORDER_DREG],
+				       &priv->dreg, NULL, NFT_DATA_VALUE,
+				       priv->len);
+	if (err < 0)
+		return err;
+
+	if (nft_reg_overlap(priv->sreg, priv->dreg, priv->len))
+		return -EINVAL;
+
+	return 0;
 }
 
 static int nft_byteorder_dump(struct sk_buff *skb,
diff --git a/net/netfilter/nft_payload.c b/net/netfilter/nft_payload.c
index 01e13e5255a9..484a5490832e 100644
--- a/net/netfilter/nft_payload.c
+++ b/net/netfilter/nft_payload.c
@@ -917,6 +917,9 @@ static int nft_payload_set_init(const struct nft_ctx *ctx,
 	struct nft_payload_set *priv = nft_expr_priv(expr);
 	int err;
 
+	if (ctx->net->user_ns != &init_user_ns)
+		return -EPERM;
+
 	priv->base        = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_BASE]));
 	priv->len         = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_LEN]));
 
diff --git a/net/netfilter/xt_cpu.c b/net/netfilter/xt_cpu.c
index 3bdc302a0f91..9cb259902a58 100644
--- a/net/netfilter/xt_cpu.c
+++ b/net/netfilter/xt_cpu.c
@@ -34,7 +34,7 @@ static bool cpu_mt(const struct sk_buff *skb, struct xt_action_param *par)
 {
 	const struct xt_cpu_info *info = par->matchinfo;
 
-	return (info->cpu == smp_processor_id()) ^ info->invert;
+	return (info->cpu == raw_smp_processor_id()) ^ info->invert;
 }
 
 static struct xt_match cpu_mt_reg __read_mostly = {
diff --git a/tools/testing/selftests/net/netfilter/Makefile b/tools/testing/selftests/net/netfilter/Makefile
index ee2d1a5254f8..d953ee218c0f 100644
--- a/tools/testing/selftests/net/netfilter/Makefile
+++ b/tools/testing/selftests/net/netfilter/Makefile
@@ -26,6 +26,7 @@ TEST_PROGS := \
 	nft_concat_range.sh \
 	nft_conntrack_helper.sh \
 	nft_fib.sh \
+	nft_fib_nexthop.sh \
 	nft_flowtable.sh \
 	nft_interface_stress.sh \
 	nft_meta.sh \
diff --git a/tools/testing/selftests/net/netfilter/nft_fib_nexthop.sh b/tools/testing/selftests/net/netfilter/nft_fib_nexthop.sh
new file mode 100755
index 000000000000..c4f203057382
--- /dev/null
+++ b/tools/testing/selftests/net/netfilter/nft_fib_nexthop.sh
@@ -0,0 +1,152 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# shellcheck disable=SC2154
+#
+# Exercise nft_fib6_eval()'s sibling/nh enumeration on three route shapes:
+#   1) route via a single external nexthop (nhid)
+#   2) route via an external nexthop group (nhid -> group, two members)
+#   3) route via old-style multipath (nexthop ... nexthop ...)
+#
+# In each scenario the route's nexthop set contains veth0 (the iif of the
+# test packet). nft_fib6_info_nh_uses_dev() must walk the set and report
+# veth0 as a valid oif. For (2) and (3) the matching nexthop is the second
+# member, so the walk has to traverse beyond the primary nh.
+#
+# After sending $PKTS ICMPv6 echo requests from ns1, check two counters on
+# nsrouter:
+#   nf_ok  -- `fib daddr . iif oif eq "veth0"`  must equal $PKTS
+#   nf_bad -- `fib daddr . iif oif missing`     must stay at 0
+# Both rules also match on iif veth0 and ip6 daddr dead:dead::/64 so that
+# kernel-generated ND/MLD/RA traffic cannot pollute the counters.
+#
+# Topology similar to nft_fib.sh, without ns2; two dummy interfaces on
+# nsrouter host extra nh devices:
+#
+#   dead:1::99             dead:1::1
+#       ns1 <----veth----> nsrouter --- dummy0 dead:2::1
+#                                   \-- dummy1 dead:9::1
+
+source lib.sh
+
+ret=0
+PKTS=3
+
+checktool "nft --version" "run test without nft"
+checktool "ip -V"         "run test without iproute2"
+
+setup_ns nsrouter ns1
+trap cleanup_all_ns EXIT
+
+if ! ip link add veth0 netns "$nsrouter" type veth peer name eth0 netns "$ns1" \
+	> /dev/null 2>&1; then
+	echo "SKIP: No virtual ethernet pair device support in kernel"
+	exit $ksft_skip
+fi
+
+ip -net "$ns1" link set lo up
+ip -net "$ns1" link set eth0 up
+ip -net "$ns1" -6 addr add dead:1::99/64 dev eth0 nodad
+ip -net "$ns1" -6 route add default via dead:1::1
+
+ip -net "$nsrouter" link set lo up
+ip -net "$nsrouter" link set veth0 up
+ip -net "$nsrouter" -6 addr add dead:1::1/64 dev veth0 nodad
+
+if ! ip -net "$nsrouter" link add dummy0 type dummy 2>/dev/null; then
+	echo "SKIP: dummy netdev not available"
+	exit $ksft_skip
+fi
+ip -net "$nsrouter" link set dummy0 up
+ip -net "$nsrouter" -6 addr add dead:2::1/64 dev dummy0 nodad
+
+ip -net "$nsrouter" link add dummy1 type dummy
+ip -net "$nsrouter" link set dummy1 up
+ip -net "$nsrouter" -6 addr add dead:9::1/64 dev dummy1 nodad
+
+ip netns exec "$nsrouter" sysctl -q net.ipv6.conf.all.forwarding=1
+
+load_fib_rule() {
+	# filter on iif + daddr so the counters only see our test packets
+	ip netns exec "$nsrouter" nft -f /dev/stdin <<EOF
+flush ruleset
+table ip6 t {
+	counter nf_ok  { }
+	counter nf_bad { }
+	chain c {
+		type filter hook prerouting priority 0; policy accept;
+		iif "veth0" ip6 daddr dead:dead::/64 fib daddr . iif oif eq "veth0" counter name nf_ok
+		iif "veth0" ip6 daddr dead:dead::/64 fib daddr . iif oif missing    counter name nf_bad
+	}
+}
+EOF
+}
+
+bad_counter() {
+	local counter=$1
+	local expect=$2
+	local tag=$3
+
+	echo "FAIL ($tag): counter $counter has unexpected value (expected \"$expect\")" 1>&2
+	ip netns exec "$nsrouter" nft list counter ip6 t "$counter" 1>&2
+}
+
+run_scenario() {
+	local what="$1"; shift
+	# counter output format is "packets PACKET_NUM bytes BYTES_NUM";
+	# we only care about the packet count
+	local expect_ok="packets $PKTS bytes"
+	local expect_bad="packets 0 bytes"
+	local lret=0
+
+	# reset route + nexthop state between scenarios
+	ip -net "$nsrouter" -6 route del dead:dead::/64 > /dev/null 2>&1 || true
+	ip -net "$nsrouter" nexthop flush               > /dev/null 2>&1 || true
+
+	# run the scenario function passed by the caller
+	"$@" || echo "WARN ($what): scenario setup returned non-zero"
+
+	load_fib_rule || { echo "FAIL ($what): nft load"; ret=1; return; }
+
+	# ping a daddr inside dead:dead::/64 so fib has to walk the nh set
+	ip netns exec "$ns1" ping -6 -c "$PKTS" -i 0.1 -W 1 dead:dead::1 \
+		> /dev/null 2>&1 || true
+
+	# verify the packets went through the expected fib path
+	if ! ip netns exec "$nsrouter" nft list counter ip6 t nf_ok | grep -q "$expect_ok"; then
+		bad_counter nf_ok "$expect_ok" "$what"
+		lret=1
+	fi
+	if ! ip netns exec "$nsrouter" nft list counter ip6 t nf_bad | grep -q "$expect_bad"; then
+		bad_counter nf_bad "$expect_bad" "$what"
+		lret=1
+	fi
+
+	if [ $lret -eq 0 ]; then
+		echo "PASS: $what"
+	else
+		ret=1
+	fi
+}
+
+scenario_single_nh() {
+	ip -net "$nsrouter" nexthop add id 1 via dead:1::99 dev veth0
+	ip -net "$nsrouter" -6 route add dead:dead::/64 nhid 1
+}
+run_scenario "single external nexthop (nhid -> veth0)" scenario_single_nh
+
+scenario_nh_group() {
+	ip -net "$nsrouter" nexthop add id 1   via dead:2::2  dev dummy0
+	ip -net "$nsrouter" nexthop add id 2   via dead:1::99 dev veth0
+	ip -net "$nsrouter" nexthop add id 100 group 1/2
+	ip -net "$nsrouter" -6 route   add dead:dead::/64 nhid 100
+}
+run_scenario "nexthop group (dummy0 + veth0)" scenario_nh_group
+
+scenario_old_multipath() {
+	ip -net "$nsrouter" -6 route add dead:dead::/64 \
+		nexthop via dead:2::2  dev dummy0 \
+		nexthop via dead:1::99 dev veth0
+}
+run_scenario "old-style multipath (sibling on veth0)" scenario_old_multipath
+
+exit $ret