Merge branch 'vxlan-support-user-defined-reserved-bits'

Petr Machata says:

====================
vxlan: Support user-defined reserved bits

Currently the VXLAN header validation works by vxlan_rcv() going feature
by feature, each feature clearing the bits that it consumes. If anything
is left unparsed at the end, the packet is rejected.

Unfortunately there are machines out there that send VXLAN packets with
reserved bits set, even if they are configured to not use the
corresponding features. One such report is here[1], and we have heard
similar complaints from our customers as well.

This patchset adds an attribute that makes it configurable which bits
the user wishes to tolerate and which they consider reserved. This was
recommended in [1] as well.

A knob like that inevitably allows users to set as reserved bits that
are in fact required for the features enabled by the netdevice, such as
GPE. This is detected, and such configurations are rejected.

In patches #1..#7, the reserved bits validation code is gradually moved
away from the unparsed approach described above, to one where a given
set of valid bits is precomputed and then the packet is validated
against that.

In patch #8, this precomputed set is made configurable through a new
attribute IFLA_VXLAN_RESERVED_BITS.

Patches #9 and #10 massage the testsuite a bit, so that patch #11 can
introduce a selftest for the resreved bits feature.

The corresponding iproute2 support is available in [2].

[1] https://lore.kernel.org/netdev/db8b9e19-ad75-44d3-bfb2-46590d426ff5@proxmox.com/
[2] https://github.com/pmachata/iproute2/commits/vxlan_reserved_bits/
====================

Link: https://patch.msgid.link/cover.1733412063.git.petrm@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

8 files changed, 497 insertions, 62 deletions

diff --git a/drivers/net/vxlan/vxlan_core.c b/drivers/net/vxlan/vxlan_core.c
index b46a799bd390..43cf672b7b9f 100644
--- a/drivers/net/vxlan/vxlan_core.c
+++ b/drivers/net/vxlan/vxlan_core.c
@@ -622,9 +622,9 @@ static int vxlan_fdb_append(struct vxlan_fdb *f,
 	return 1;
 }
 
-static bool vxlan_parse_gpe_proto(struct vxlanhdr *hdr, __be16 *protocol)
+static bool vxlan_parse_gpe_proto(const struct vxlanhdr *hdr, __be16 *protocol)
 {
-	struct vxlanhdr_gpe *gpe = (struct vxlanhdr_gpe *)hdr;
+	const struct vxlanhdr_gpe *gpe = (const struct vxlanhdr_gpe *)hdr;
 
 	/* Need to have Next Protocol set for interfaces in GPE mode. */
 	if (!gpe->np_applied)
@@ -1554,18 +1554,17 @@ static void vxlan_sock_release(struct vxlan_dev *vxlan)
 #endif
 }
 
-static enum skb_drop_reason vxlan_remcsum(struct vxlanhdr *unparsed,
-					  struct sk_buff *skb,
-					  u32 vxflags)
+static enum skb_drop_reason vxlan_remcsum(struct sk_buff *skb, u32 vxflags)
 {
+	const struct vxlanhdr *vh = vxlan_hdr(skb);
 	enum skb_drop_reason reason;
 	size_t start, offset;
 
-	if (!(unparsed->vx_flags & VXLAN_HF_RCO) || skb->remcsum_offload)
-		goto out;
+	if (!(vh->vx_flags & VXLAN_HF_RCO) || skb->remcsum_offload)
+		return SKB_NOT_DROPPED_YET;
 
-	start = vxlan_rco_start(unparsed->vx_vni);
-	offset = start + vxlan_rco_offset(unparsed->vx_vni);
+	start = vxlan_rco_start(vh->vx_vni);
+	offset = start + vxlan_rco_offset(vh->vx_vni);
 
 	reason = pskb_may_pull_reason(skb, offset + sizeof(u16));
 	if (reason)
@@ -1573,22 +1572,20 @@ static enum skb_drop_reason vxlan_remcsum(struct vxlanhdr *unparsed,
 
 	skb_remcsum_process(skb, (void *)(vxlan_hdr(skb) + 1), start, offset,
 			    !!(vxflags & VXLAN_F_REMCSUM_NOPARTIAL));
-out:
-	unparsed->vx_flags &= ~VXLAN_HF_RCO;
-	unparsed->vx_vni &= VXLAN_VNI_MASK;
-
 	return SKB_NOT_DROPPED_YET;
 }
 
-static void vxlan_parse_gbp_hdr(struct vxlanhdr *unparsed,
-				struct sk_buff *skb, u32 vxflags,
+static void vxlan_parse_gbp_hdr(struct sk_buff *skb, u32 vxflags,
 				struct vxlan_metadata *md)
 {
-	struct vxlanhdr_gbp *gbp = (struct vxlanhdr_gbp *)unparsed;
+	const struct vxlanhdr *vh = vxlan_hdr(skb);
+	const struct vxlanhdr_gbp *gbp;
 	struct metadata_dst *tun_dst;
 
-	if (!(unparsed->vx_flags & VXLAN_HF_GBP))
-		goto out;
+	gbp = (const struct vxlanhdr_gbp *)vh;
+
+	if (!(vh->vx_flags & VXLAN_HF_GBP))
+		return;
 
 	md->gbp = ntohs(gbp->policy_id);
 
@@ -1607,8 +1604,6 @@ static void vxlan_parse_gbp_hdr(struct vxlanhdr *unparsed,
 	/* In flow-based mode, GBP is carried in dst_metadata */
 	if (!(vxflags & VXLAN_F_COLLECT_METADATA))
 		skb->mark = md->gbp;
-out:
-	unparsed->vx_flags &= ~VXLAN_GBP_USED_BITS;
 }
 
 static enum skb_drop_reason vxlan_set_mac(struct vxlan_dev *vxlan,
@@ -1672,9 +1667,9 @@ static bool vxlan_ecn_decapsulate(struct vxlan_sock *vs, void *oiph,
 static int vxlan_rcv(struct sock *sk, struct sk_buff *skb)
 {
 	struct vxlan_vni_node *vninode = NULL;
+	const struct vxlanhdr *vh;
 	struct vxlan_dev *vxlan;
 	struct vxlan_sock *vs;
-	struct vxlanhdr unparsed;
 	struct vxlan_metadata _md;
 	struct vxlan_metadata *md = &_md;
 	__be16 protocol = htons(ETH_P_TEB);
@@ -1689,24 +1684,21 @@ static int vxlan_rcv(struct sock *sk, struct sk_buff *skb)
 	if (reason)
 		goto drop;
 
-	unparsed = *vxlan_hdr(skb);
+	vh = vxlan_hdr(skb);
 	/* VNI flag always required to be set */
-	if (!(unparsed.vx_flags & VXLAN_HF_VNI)) {
+	if (!(vh->vx_flags & VXLAN_HF_VNI)) {
 		netdev_dbg(skb->dev, "invalid vxlan flags=%#x vni=%#x\n",
-			   ntohl(vxlan_hdr(skb)->vx_flags),
-			   ntohl(vxlan_hdr(skb)->vx_vni));
+			   ntohl(vh->vx_flags), ntohl(vh->vx_vni));
 		reason = SKB_DROP_REASON_VXLAN_INVALID_HDR;
 		/* Return non vxlan pkt */
 		goto drop;
 	}
-	unparsed.vx_flags &= ~VXLAN_HF_VNI;
-	unparsed.vx_vni &= ~VXLAN_VNI_MASK;
 
 	vs = rcu_dereference_sk_user_data(sk);
 	if (!vs)
 		goto drop;
 
-	vni = vxlan_vni(vxlan_hdr(skb)->vx_vni);
+	vni = vxlan_vni(vh->vx_vni);
 
 	vxlan = vxlan_vs_find_vni(vs, skb->dev->ifindex, vni, &vninode);
 	if (!vxlan) {
@@ -1714,13 +1706,27 @@ static int vxlan_rcv(struct sock *sk, struct sk_buff *skb)
 		goto drop;
 	}
 
-	/* For backwards compatibility, only allow reserved fields to be
-	 * used by VXLAN extensions if explicitly requested.
-	 */
-	if (vs->flags & VXLAN_F_GPE) {
-		if (!vxlan_parse_gpe_proto(&unparsed, &protocol))
+	if (vh->vx_flags & vxlan->cfg.reserved_bits.vx_flags ||
+	    vh->vx_vni & vxlan->cfg.reserved_bits.vx_vni) {
+		/* If the header uses bits besides those enabled by the
+		 * netdevice configuration, treat this as a malformed packet.
+		 * This behavior diverges from VXLAN RFC (RFC7348) which
+		 * stipulates that bits in reserved in reserved fields are to be
+		 * ignored. The approach here maintains compatibility with
+		 * previous stack code, and also is more robust and provides a
+		 * little more security in adding extensions to VXLAN.
+		 */
+		reason = SKB_DROP_REASON_VXLAN_INVALID_HDR;
+		DEV_STATS_INC(vxlan->dev, rx_frame_errors);
+		DEV_STATS_INC(vxlan->dev, rx_errors);
+		vxlan_vnifilter_count(vxlan, vni, vninode,
+				      VXLAN_VNI_STATS_RX_ERRORS, 0);
+		goto drop;
+	}
+
+	if (vxlan->cfg.flags & VXLAN_F_GPE) {
+		if (!vxlan_parse_gpe_proto(vh, &protocol))
 			goto drop;
-		unparsed.vx_flags &= ~VXLAN_GPE_USED_BITS;
 		raw_proto = true;
 	}
 
@@ -1730,8 +1736,8 @@ static int vxlan_rcv(struct sock *sk, struct sk_buff *skb)
 		goto drop;
 	}
 
-	if (vs->flags & VXLAN_F_REMCSUM_RX) {
-		reason = vxlan_remcsum(&unparsed, skb, vs->flags);
+	if (vxlan->cfg.flags & VXLAN_F_REMCSUM_RX) {
+		reason = vxlan_remcsum(skb, vxlan->cfg.flags);
 		if (unlikely(reason))
 			goto drop;
 	}
@@ -1756,25 +1762,12 @@ static int vxlan_rcv(struct sock *sk, struct sk_buff *skb)
 		memset(md, 0, sizeof(*md));
 	}
 
-	if (vs->flags & VXLAN_F_GBP)
-		vxlan_parse_gbp_hdr(&unparsed, skb, vs->flags, md);
+	if (vxlan->cfg.flags & VXLAN_F_GBP)
+		vxlan_parse_gbp_hdr(skb, vxlan->cfg.flags, md);
 	/* Note that GBP and GPE can never be active together. This is
 	 * ensured in vxlan_dev_configure.
 	 */
 
-	if (unparsed.vx_flags || unparsed.vx_vni) {
-		/* If there are any unprocessed flags remaining treat
-		 * this as a malformed packet. This behavior diverges from
-		 * VXLAN RFC (RFC7348) which stipulates that bits in reserved
-		 * in reserved fields are to be ignored. The approach here
-		 * maintains compatibility with previous stack code, and also
-		 * is more robust and provides a little more security in
-		 * adding extensions to VXLAN.
-		 */
-		reason = SKB_DROP_REASON_VXLAN_INVALID_HDR;
-		goto drop;
-	}
-
 	if (!raw_proto) {
 		reason = vxlan_set_mac(vxlan, vs, skb, vni);
 		if (reason)
@@ -3435,6 +3428,7 @@ static const struct nla_policy vxlan_policy[IFLA_VXLAN_MAX + 1] = {
 	[IFLA_VXLAN_VNIFILTER]	= { .type = NLA_U8 },
 	[IFLA_VXLAN_LOCALBYPASS]	= NLA_POLICY_MAX(NLA_U8, 1),
 	[IFLA_VXLAN_LABEL_POLICY]       = NLA_POLICY_MAX(NLA_U32, VXLAN_LABEL_MAX),
+	[IFLA_VXLAN_RESERVED_BITS] = NLA_POLICY_EXACT_LEN(sizeof(struct vxlanhdr)),
 };
 
 static int vxlan_validate(struct nlattr *tb[], struct nlattr *data[],
@@ -4070,6 +4064,10 @@ static int vxlan_nl2conf(struct nlattr *tb[], struct nlattr *data[],
 			 struct net_device *dev, struct vxlan_config *conf,
 			 bool changelink, struct netlink_ext_ack *extack)
 {
+	struct vxlanhdr used_bits = {
+		.vx_flags = VXLAN_HF_VNI,
+		.vx_vni = VXLAN_VNI_MASK,
+	};
 	struct vxlan_dev *vxlan = netdev_priv(dev);
 	int err = 0;
 
@@ -4296,6 +4294,8 @@ static int vxlan_nl2conf(struct nlattr *tb[], struct nlattr *data[],
 				    extack);
 		if (err)
 			return err;
+		used_bits.vx_flags |= VXLAN_HF_RCO;
+		used_bits.vx_vni |= ~VXLAN_VNI_MASK;
 	}
 
 	if (data[IFLA_VXLAN_GBP]) {
@@ -4303,6 +4303,7 @@ static int vxlan_nl2conf(struct nlattr *tb[], struct nlattr *data[],
 				    VXLAN_F_GBP, changelink, false, extack);
 		if (err)
 			return err;
+		used_bits.vx_flags |= VXLAN_GBP_USED_BITS;
 	}
 
 	if (data[IFLA_VXLAN_GPE]) {
@@ -4311,6 +4312,46 @@ static int vxlan_nl2conf(struct nlattr *tb[], struct nlattr *data[],
 				    extack);
 		if (err)
 			return err;
+
+		used_bits.vx_flags |= VXLAN_GPE_USED_BITS;
+	}
+
+	if (data[IFLA_VXLAN_RESERVED_BITS]) {
+		struct vxlanhdr reserved_bits;
+
+		if (changelink) {
+			NL_SET_ERR_MSG_ATTR(extack,
+					    data[IFLA_VXLAN_RESERVED_BITS],
+					    "Cannot change reserved_bits");
+			return -EOPNOTSUPP;
+		}
+
+		nla_memcpy(&reserved_bits, data[IFLA_VXLAN_RESERVED_BITS],
+			   sizeof(reserved_bits));
+		if (used_bits.vx_flags & reserved_bits.vx_flags ||
+		    used_bits.vx_vni & reserved_bits.vx_vni) {
+			__be64 ub_be64, rb_be64;
+
+			memcpy(&ub_be64, &used_bits, sizeof(ub_be64));
+			memcpy(&rb_be64, &reserved_bits, sizeof(rb_be64));
+
+			NL_SET_ERR_MSG_ATTR_FMT(extack,
+						data[IFLA_VXLAN_RESERVED_BITS],
+						"Used bits %#018llx cannot overlap reserved bits %#018llx",
+						be64_to_cpu(ub_be64),
+						be64_to_cpu(rb_be64));
+			return -EINVAL;
+		}
+
+		conf->reserved_bits = reserved_bits;
+	} else {
+		/* For backwards compatibility, only allow reserved fields to be
+		 * used by VXLAN extensions if explicitly requested.
+		 */
+		conf->reserved_bits = (struct vxlanhdr) {
+			.vx_flags = ~used_bits.vx_flags,
+			.vx_vni = ~used_bits.vx_vni,
+		};
 	}
 
 	if (data[IFLA_VXLAN_REMCSUM_NOPARTIAL]) {
@@ -4497,6 +4538,8 @@ static size_t vxlan_get_size(const struct net_device *dev)
 		nla_total_size(0) + /* IFLA_VXLAN_GPE */
 		nla_total_size(0) + /* IFLA_VXLAN_REMCSUM_NOPARTIAL */
 		nla_total_size(sizeof(__u8)) + /* IFLA_VXLAN_VNIFILTER */
+		/* IFLA_VXLAN_RESERVED_BITS */
+		nla_total_size(sizeof(struct vxlanhdr)) +
 		0;
 }
 
@@ -4599,6 +4642,11 @@ static int vxlan_fill_info(struct sk_buff *skb, const struct net_device *dev)
 		       !!(vxlan->cfg.flags & VXLAN_F_VNIFILTER)))
 		goto nla_put_failure;
 
+	if (nla_put(skb, IFLA_VXLAN_RESERVED_BITS,
+		    sizeof(vxlan->cfg.reserved_bits),
+		    &vxlan->cfg.reserved_bits))
+		goto nla_put_failure;
+
 	return 0;
 
 nla_put_failure:
diff --git a/include/net/vxlan.h b/include/net/vxlan.h
index 33ba6fc151cf..2dd23ee2bacd 100644
--- a/include/net/vxlan.h
+++ b/include/net/vxlan.h
@@ -227,6 +227,7 @@ struct vxlan_config {
 	unsigned int			addrmax;
 	bool				no_share;
 	enum ifla_vxlan_df		df;
+	struct vxlanhdr			reserved_bits;
 };
 
 enum {
diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
index 2575e0cd9b48..77730c340c8f 100644
--- a/include/uapi/linux/if_link.h
+++ b/include/uapi/linux/if_link.h
@@ -1394,6 +1394,7 @@ enum {
 	IFLA_VXLAN_VNIFILTER, /* only applicable with COLLECT_METADATA mode */
 	IFLA_VXLAN_LOCALBYPASS,
 	IFLA_VXLAN_LABEL_POLICY, /* IPv6 flow label policy; ifla_vxlan_label_policy */
+	IFLA_VXLAN_RESERVED_BITS,
 	__IFLA_VXLAN_MAX
 };
 #define IFLA_VXLAN_MAX	(__IFLA_VXLAN_MAX - 1)
diff --git a/tools/testing/selftests/net/fdb_notify.sh b/tools/testing/selftests/net/fdb_notify.sh
index c03151e7791c..c159230c9b62 100755
--- a/tools/testing/selftests/net/fdb_notify.sh
+++ b/tools/testing/selftests/net/fdb_notify.sh
@@ -49,7 +49,7 @@ test_dup_vxlan_self()
 {
 	ip_link_add br up type bridge vlan_filtering 1
 	ip_link_add vx up type vxlan id 2000 dstport 4789
-	ip_link_master vx br
+	ip_link_set_master vx br
 
 	do_test_dup add "vxlan" dev vx self dst 192.0.2.1
 	do_test_dup del "vxlan" dev vx self dst 192.0.2.1
@@ -59,7 +59,7 @@ test_dup_vxlan_master()
 {
 	ip_link_add br up type bridge vlan_filtering 1
 	ip_link_add vx up type vxlan id 2000 dstport 4789
-	ip_link_master vx br
+	ip_link_set_master vx br
 
 	do_test_dup add "vxlan master" dev vx master
 	do_test_dup del "vxlan master" dev vx master
@@ -79,7 +79,7 @@ test_dup_macvlan_master()
 	ip_link_add br up type bridge vlan_filtering 1
 	ip_link_add dd up type dummy
 	ip_link_add mv up link dd type macvlan mode passthru
-	ip_link_master mv br
+	ip_link_set_master mv br
 
 	do_test_dup add "macvlan master" dev mv self
 	do_test_dup del "macvlan master" dev mv self
diff --git a/tools/testing/selftests/net/forwarding/Makefile b/tools/testing/selftests/net/forwarding/Makefile
index 7d885cff8d79..00bde7b6f39e 100644
--- a/tools/testing/selftests/net/forwarding/Makefile
+++ b/tools/testing/selftests/net/forwarding/Makefile
@@ -105,6 +105,7 @@ TEST_PROGS = bridge_fdb_learning_limit.sh \
 	vxlan_bridge_1q_port_8472_ipv6.sh \
 	vxlan_bridge_1q_port_8472.sh \
 	vxlan_bridge_1q.sh \
+	vxlan_reserved.sh \
 	vxlan_symmetric_ipv6.sh \
 	vxlan_symmetric.sh
 
diff --git a/tools/testing/selftests/net/forwarding/lib.sh b/tools/testing/selftests/net/forwarding/lib.sh
index 7337f398f9cc..1fd40bada694 100644
--- a/tools/testing/selftests/net/forwarding/lib.sh
+++ b/tools/testing/selftests/net/forwarding/lib.sh
@@ -932,13 +932,6 @@ packets_rate()
 	echo $(((t1 - t0) / interval))
 }
 
-mac_get()
-{
-	local if_name=$1
-
-	ip -j link show dev $if_name | jq -r '.[]["address"]'
-}
-
 ether_addr_to_u64()
 {
 	local addr="$1"
diff --git a/tools/testing/selftests/net/forwarding/vxlan_reserved.sh b/tools/testing/selftests/net/forwarding/vxlan_reserved.sh
new file mode 100755
index 000000000000..46c31794b91b
--- /dev/null
+++ b/tools/testing/selftests/net/forwarding/vxlan_reserved.sh
@@ -0,0 +1,352 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+# +--------------------+
+# | H1 (vrf)           |
+# |    + $h1           |
+# |    | 192.0.2.1/28  |
+# +----|---------------+
+#      |
+# +----|--------------------------------+
+# | SW |                                |
+# | +--|------------------------------+ |
+# | |  + $swp1           BR1 (802.1d) | |
+# | |                                 | |
+# | |  + vx1 (vxlan)                  | |
+# | |    local 192.0.2.17             | |
+# | |    id 1000 dstport $VXPORT      | |
+# | +---------------------------------+ |
+# |                                     |
+# |  192.0.2.32/28 via 192.0.2.18       |
+# |                                     |
+# |  + $rp1                             |
+# |  | 192.0.2.17/28                    |
+# +--|----------------------------------+
+#    |
+# +--|----------------------------------+
+# |  |                                  |
+# |  + $rp2                             |
+# |    192.0.2.18/28                    |
+# |                                     |
+# | VRP2 (vrf)                          |
+# +-------------------------------------+
+
+: ${VXPORT:=4789}
+: ${ALL_TESTS:="
+	default_test
+	plain_test
+	reserved_0_test
+	reserved_10_test
+	reserved_31_test
+	reserved_56_test
+	reserved_63_test
+    "}
+
+NUM_NETIFS=4
+source lib.sh
+
+h1_create()
+{
+	simple_if_init $h1 192.0.2.1/28
+	defer simple_if_fini $h1 192.0.2.1/28
+
+	tc qdisc add dev $h1 clsact
+	defer tc qdisc del dev $h1 clsact
+
+	tc filter add dev $h1 ingress pref 77 \
+	   prot ip flower skip_hw ip_proto icmp action drop
+	defer tc filter del dev $h1 ingress pref 77
+}
+
+switch_create()
+{
+	ip_link_add br1 type bridge vlan_filtering 0 mcast_snooping 0
+	# Make sure the bridge uses the MAC address of the local port and not
+	# that of the VxLAN's device.
+	ip_link_set_addr br1 $(mac_get $swp1)
+	ip_link_set_up br1
+
+	ip_link_set_up $rp1
+	ip_addr_add $rp1 192.0.2.17/28
+	ip_route_add 192.0.2.32/28 nexthop via 192.0.2.18
+
+	ip_link_set_master $swp1 br1
+	ip_link_set_up $swp1
+}
+
+vrp2_create()
+{
+	simple_if_init $rp2 192.0.2.18/28
+	defer simple_if_fini $rp2 192.0.2.18/28
+}
+
+setup_prepare()
+{
+	h1=${NETIFS[p1]}
+	swp1=${NETIFS[p2]}
+
+	rp1=${NETIFS[p3]}
+	rp2=${NETIFS[p4]}
+
+	vrf_prepare
+	defer vrf_cleanup
+
+	forwarding_enable
+	defer forwarding_restore
+
+	h1_create
+	switch_create
+
+	vrp2_create
+}
+
+vxlan_header_bytes()
+{
+	local vni=$1; shift
+	local -a extra_bits=("$@")
+	local -a bits
+	local i
+
+	for ((i=0; i < 64; i++)); do
+		bits[i]=0
+	done
+
+	# Bit 4 is the I flag and is always on.
+	bits[4]=1
+
+	for i in ${extra_bits[@]}; do
+		bits[i]=1
+	done
+
+	# Bits 32..55 carry the VNI
+	local mask=0x800000
+	for ((i=0; i < 24; i++)); do
+		bits[$((i + 32))]=$(((vni & mask) != 0))
+		((mask >>= 1))
+	done
+
+	local bytes
+	for ((i=0; i < 8; i++)); do
+		local byte=0
+		local j
+		for ((j=0; j < 8; j++)); do
+			local bit=${bits[8 * i + j]}
+			((byte += bit << (7 - j)))
+		done
+		bytes+=$(printf %02x $byte):
+	done
+
+	echo ${bytes%:}
+}
+
+neg_bytes()
+{
+	local bytes=$1; shift
+
+	local -A neg=([0]=f [1]=e [2]=d [3]=c [4]=b [5]=a [6]=9 [7]=8
+		      [8]=7 [9]=6 [a]=5 [b]=4 [c]=3 [d]=2 [e]=1 [f]=0 [:]=:)
+	local out
+	local i
+
+	for ((i=0; i < ${#bytes}; i++)); do
+		local c=${bytes:$i:1}
+		out+=${neg[$c]}
+	done
+	echo $out
+}
+
+vxlan_ping_do()
+{
+	local count=$1; shift
+	local dev=$1; shift
+	local next_hop_mac=$1; shift
+	local dest_ip=$1; shift
+	local dest_mac=$1; shift
+	local vni=$1; shift
+	local reserved_bits=$1; shift
+
+	local vxlan_header=$(vxlan_header_bytes $vni $reserved_bits)
+
+	$MZ $dev -c $count -d 100msec -q \
+		-b $next_hop_mac -B $dest_ip \
+		-t udp sp=23456,dp=$VXPORT,p=$(:
+		    )"$vxlan_header:"$(              : VXLAN
+		    )"$dest_mac:"$(                  : ETH daddr
+		    )"00:11:22:33:44:55:"$(          : ETH saddr
+		    )"08:00:"$(                      : ETH type
+		    )"45:"$(                         : IP version + IHL
+		    )"00:"$(                         : IP TOS
+		    )"00:54:"$(                      : IP total length
+		    )"99:83:"$(                      : IP identification
+		    )"40:00:"$(                      : IP flags + frag off
+		    )"40:"$(                         : IP TTL
+		    )"01:"$(                         : IP proto
+		    )"00:00:"$(                      : IP header csum
+		    )"$(ipv4_to_bytes 192.0.2.3):"$( : IP saddr
+		    )"$(ipv4_to_bytes 192.0.2.1):"$( : IP daddr
+		    )"08:"$(                         : ICMP type
+		    )"00:"$(                         : ICMP code
+		    )"8b:f2:"$(                      : ICMP csum
+		    )"1f:6a:"$(                      : ICMP request identifier
+		    )"00:01:"$(                      : ICMP request seq. number
+		    )"4f:ff:c5:5b:00:00:00:00:"$(    : ICMP payload
+		    )"6d:74:0b:00:00:00:00:00:"$(    :
+		    )"10:11:12:13:14:15:16:17:"$(    :
+		    )"18:19:1a:1b:1c:1d:1e:1f:"$(    :
+		    )"20:21:22:23:24:25:26:27:"$(    :
+		    )"28:29:2a:2b:2c:2d:2e:2f:"$(    :
+		    )"30:31:32:33:34:35:36:37"
+}
+
+vxlan_device_add()
+{
+	ip_link_add vx1 up type vxlan id 1000		\
+		local 192.0.2.17 dstport "$VXPORT"	\
+		nolearning noudpcsum tos inherit ttl 100 "$@"
+	ip_link_set_master vx1 br1
+}
+
+vxlan_all_reserved_bits()
+{
+	local i
+
+	for ((i=0; i < 64; i++)); do
+		if ((i == 4 || i >= 32 && i < 56)); then
+			continue
+		fi
+		echo $i
+	done
+}
+
+vxlan_ping_vanilla()
+{
+	vxlan_ping_do 10 $rp2 $(mac_get $rp1) 192.0.2.17 $(mac_get $h1) 1000
+}
+
+vxlan_ping_reserved()
+{
+	for bit in $(vxlan_all_reserved_bits); do
+		vxlan_ping_do 1 $rp2 $(mac_get $rp1) \
+			      192.0.2.17 $(mac_get $h1) 1000 "$bit"
+		((n++))
+	done
+}
+
+vxlan_ping_test()
+{
+	local what=$1; shift
+	local get_stat=$1; shift
+	local expect=$1; shift
+
+	RET=0
+
+	local t0=$($get_stat)
+
+	"$@"
+	check_err $? "Failure when running $@"
+
+	local t1=$($get_stat)
+	local delta=$((t1 - t0))
+
+	((expect == delta))
+	check_err $? "Expected to capture $expect packets, got $delta."
+
+	log_test "$what"
+}
+
+__default_test_do()
+{
+	local n_allowed_bits=$1; shift
+	local what=$1; shift
+
+	vxlan_ping_test "$what: clean packets" \
+		"tc_rule_stats_get $h1 77 ingress" \
+		10 vxlan_ping_vanilla
+
+	local t0=$(link_stats_get vx1 rx errors)
+	vxlan_ping_test "$what: mangled packets" \
+		"tc_rule_stats_get $h1 77 ingress" \
+		$n_allowed_bits vxlan_ping_reserved
+	local t1=$(link_stats_get vx1 rx errors)
+
+	RET=0
+	local expect=$((39 - n_allowed_bits))
+	local delta=$((t1 - t0))
+	((expect == delta))
+	check_err $? "Expected $expect error packets, got $delta."
+	log_test "$what: drops reported"
+}
+
+default_test_do()
+{
+	vxlan_device_add
+	__default_test_do 0 "Default"
+}
+
+default_test()
+{
+	in_defer_scope \
+	    default_test_do
+}
+
+plain_test_do()
+{
+	vxlan_device_add reserved_bits 0xf7ffffff000000ff
+	__default_test_do 0 "reserved_bits 0xf7ffffff000000ff"
+}
+
+plain_test()
+{
+	in_defer_scope \
+	    plain_test_do
+}
+
+reserved_test()
+{
+	local bit=$1; shift
+
+	local allowed_bytes=$(vxlan_header_bytes 0xffffff $bit)
+	local reserved_bytes=$(neg_bytes $allowed_bytes)
+	local reserved_bits=${reserved_bytes//:/}
+
+	vxlan_device_add reserved_bits 0x$reserved_bits
+	__default_test_do 1 "reserved_bits 0x$reserved_bits"
+}
+
+reserved_0_test()
+{
+	in_defer_scope \
+	    reserved_test 0
+}
+
+reserved_10_test()
+{
+	in_defer_scope \
+	    reserved_test 10
+}
+
+reserved_31_test()
+{
+	in_defer_scope \
+	    reserved_test 31
+}
+
+reserved_56_test()
+{
+	in_defer_scope \
+	    reserved_test 56
+}
+
+reserved_63_test()
+{
+	in_defer_scope \
+	    reserved_test 63
+}
+
+trap cleanup EXIT
+
+setup_prepare
+setup_wait
+tests_run
+
+exit $EXIT_STATUS
diff --git a/tools/testing/selftests/net/lib.sh b/tools/testing/selftests/net/lib.sh
index 8994fec1c38f..2cd5c743b2d9 100644
--- a/tools/testing/selftests/net/lib.sh
+++ b/tools/testing/selftests/net/lib.sh
@@ -435,6 +435,13 @@ xfail_on_veth()
 	fi
 }
 
+mac_get()
+{
+	local if_name=$1
+
+	ip -j link show dev $if_name | jq -r '.[]["address"]'
+}
+
 kill_process()
 {
 	local pid=$1; shift
@@ -451,7 +458,7 @@ ip_link_add()
 	defer ip link del dev "$name"
 }
 
-ip_link_master()
+ip_link_set_master()
 {
 	local member=$1; shift
 	local master=$1; shift
@@ -459,3 +466,35 @@ ip_link_master()
 	ip link set dev "$member" master "$master"
 	defer ip link set dev "$member" nomaster
 }
+
+ip_link_set_addr()
+{
+	local name=$1; shift
+	local addr=$1; shift
+
+	local old_addr=$(mac_get "$name")
+	ip link set dev "$name" address "$addr"
+	defer ip link set dev "$name" address "$old_addr"
+}
+
+ip_link_set_up()
+{
+	local name=$1; shift
+
+	ip link set dev "$name" up
+	defer ip link set dev "$name" down
+}
+
+ip_addr_add()
+{
+	local name=$1; shift
+
+	ip addr add dev "$name" "$@"
+	defer ip addr del dev "$name" "$@"
+}
+
+ip_route_add()
+{
+	ip route add "$@"
+	defer ip route del "$@"
+}