[PATCH bpf-next v3 0/3] bpf: bidirectional VLAN support for bpf_fib_lookup()

[PATCH bpf-next v3 0/3] bpf: bidirectional VLAN support for bpf_fib_lookup()

[Avinash Duduskar]

This series adds VLAN awareness to bpf_fib_lookup() in both directions.
BPF_FIB_LOOKUP_VLAN resolves a VLAN egress to its underlying real device
plus the VLAN tag (XDP programs need this because VLAN devices have no XDP
xmit), and BPF_FIB_LOOKUP_VLAN_INPUT runs the lookup as if a tagged frame
had arrived on the matching VLAN subinterface, for iif policy routing and
VRF table selection.

The l3mdev/VRF flow-init fix that was patch 1 in v1 and v2 has been split
out and sent to bpf on its own, since it is an independent Fixes:-tagged
fix that routes to stable on its own schedule. This series is otherwise
independent of it: on the default CONFIG_INIT_STACK_ALL_ZERO the VRF
selftests pass with or without the fix. Only the one full-lookup VRF arm
("IPv4 VLAN input, tag selects VRF table") depends on it, and only on
INIT_STACK_ALL_PATTERN or NONE builds, where the uninitialized
flowi_l3mdev otherwise misses the l3mdev rule and the lookup falls
through to the main table. Applying the l3mdev fix first closes that
window.

Changes v2 -> v3 (all from Toke's review unless noted):

- Split the l3mdev/VRF flow-init fix out to a standalone bpf submission
  (it was patch 1 in v2).

- Patch 2 (VLAN_INPUT): bpf_fib_vlan_input_dev() returns a
  struct net_device * with ERR_PTR() for the -EINVAL case and NULL for
  NOT_FWDED, instead of an int return and a **dev out-parameter.

- Trim the BPF_FIB_LOOKUP_VLAN and BPF_FIB_LOOKUP_VLAN_INPUT UAPI doc
  blocks, and drop the in-function comments that restated the commit
  message or the flag doc.

- Patch 1 (VLAN egress): on the skb path without tot_len, the deferred mtu
  check now runs against the resolved egress (VLAN) device, not the parent
  params->ifindex was swapped to, so a VLAN device with a smaller mtu than
  its parent is no longer checked against, or reported as, the parent's
  larger mtu. Found by the bpf ci bot; this was an open question in v2.

- Patch 3 (selftests): re-run every case through bpf_xdp_fib_lookup() as
  well, since the feature targets XDP; and flip the no-tot_len mtu arm to
  expect the VLAN device's mtu after the fix above.

Open questions (defaults chosen, noted here in case a maintainer
prefers otherwise):

1. An unmatched, down, or foreign-netns tag returns
   BPF_FIB_LKUP_RET_NOT_FWDED, matching the DIRECT path when
   fib_get_table() finds no table, rather than a new return code.

2. BPF_FIB_LOOKUP_OUTPUT | BPF_FIB_LOOKUP_VLAN_INPUT is rejected with
   -EINVAL; restricting now keeps relaxing later backward-compatible.

3. The name BPF_FIB_LOOKUP_VLAN_INPUT reads oddly next to
   BPF_FIB_LOOKUP_OUTPUT. A pair like _VLAN_EGRESS/_VLAN_INGRESS is an
   option while nothing is merged.

4. The egress flag leaves a VLAN it cannot reduce to a physical parent
   plus one tag (QinQ, or a parent in another namespace) as SUCCESS with
   the VLAN device's ifindex and the vlan fields zero, like a plain
   lookup. The input side instead fails closed (NOT_FWDED) on the
   cross-namespace case. An XDP caller cannot xmit on a VLAN device, and
   a zero h_vlan_proto does not distinguish this result from a physical
   egress, so returning NOT_FWDED would be safer for XDP. But the two
   cases differ: a foreign-netns parent is clearly fail-worthy, while a
   QinQ egress is still a forwardable route (tc xmits on the inner VLAN
   device), so failing it closed would reject a usable route. Should
   egress signal NOT_FWDED, for both or only foreign-netns? I left it
   best-effort, but will change it if you prefer.

Taking the tag as lookup input follows the approach David Ahern
suggested in the 2021 fwmark discussion:
https://lore.kernel.org/bpf/6248c547-ad64-04d6-fcec-374893cc1ef2@gmail.com/

v2: https://lore.kernel.org/all/20260616223426.3568080-1-avinash.duduskar@gmail.com/
v1: https://lore.kernel.org/all/20260609172052.81613-1-avinash.duduskar@gmail.com/

Avinash Duduskar (3):
  bpf: Add BPF_FIB_LOOKUP_VLAN flag to bpf_fib_lookup() helper
  bpf: Add BPF_FIB_LOOKUP_VLAN_INPUT flag to bpf_fib_lookup() helper
  selftests/bpf: Add bpf_fib_lookup() VLAN flag tests

 include/uapi/linux/bpf.h                      |  41 +-
 net/core/filter.c                             | 125 +++-
 tools/include/uapi/linux/bpf.h                |  41 +-
 .../selftests/bpf/prog_tests/fib_lookup.c     | 554 +++++++++++++++++-
 .../testing/selftests/bpf/progs/fib_lookup.c  |   9 +
 5 files changed, 741 insertions(+), 29 deletions(-)


base-commit: e771677c937da5808f7b6c1f0e4a97ec1a84f8a8
-- 
2.54.0

[PATCH bpf-next v3 1/3] bpf: Add BPF_FIB_LOOKUP_VLAN flag to bpf_fib_lookup() helper

[Avinash Duduskar]

bpf_fib_lookup() returns the FIB-resolved egress ifindex straight
from the fib result. When the egress is a VLAN device, the returned
ifindex is the VLAN netdev's, which has no XDP xmit handler; XDP
programs that want to forward the frame (e.g. xdp-forward) must
instead target the underlying physical device and push the VLAN tag
themselves. Today the program has no way to learn either the
underlying ifindex or the VLAN tag without maintaining its own
VLAN-to-ifindex map in userspace and refreshing it on netlink
events.

Add BPF_FIB_LOOKUP_VLAN. When the caller sets this flag and the fib
result is a VLAN device whose immediate parent is a real (non-VLAN)
device in the same network namespace, populate the existing output
fields params->h_vlan_proto and params->h_vlan_TCI from the VLAN
device and replace params->ifindex with the parent's ifindex.
params->h_vlan_TCI carries the VID only, with PCP and DEI bits zero; a
consumer wanting to set egress priority writes PCP itself.
params->smac is the VLAN device's own address, which can differ from
the parent's.

Only the immediate parent is resolved, via vlan_dev_priv(dev)->real_dev
and not vlan_dev_real_dev(), which walks to the bottom of a stack. For a
stacked VLAN (QinQ) the immediate parent is itself a VLAN device; since
one h_vlan_proto/h_vlan_TCI pair cannot describe two tags, ifindex is
left unchanged and the vlan fields remain zero in that case. The swap
is also skipped when the parent lives in another network namespace (a
VLAN device can be moved while its parent stays), since its ifindex
would be meaningless or match an unrelated device in the caller's
namespace. The swap and the vlan fields are written only on success;
other output fields keep their existing behaviour, so a frag-needed
result still reports the route mtu in params->mtu_result.

On the skb path without tot_len the deferred mtu check is done against
the resolved egress device. To keep that the VLAN device rather than
the parent after the swap, bpf_ipv4_fib_lookup()/bpf_ipv6_fib_lookup()
hand the FIB-result device back to the caller; the XDP path always
runs the route-mtu check and passes NULL. When the flag is not set,
behaviour is unchanged: h_vlan_proto and h_vlan_TCI are zeroed and
ifindex is left at the FIB result.

The new block is compiled only under CONFIG_VLAN_8021Q since
vlan_dev_priv() is not defined otherwise; without that config
is_vlan_dev() is constant false and the flag is accepted but never
acts.

This lets an XDP redirect target the physical device and learn the
tag to push in a single lookup, which xdp-forward's optional VLAN
mode (xdp-project/xdp-tools#504) wants from the kernel side.

The helper's input semantics are unchanged; the reverse direction
(supplying a tag as lookup input) is added in the following patch.

Suggested-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Avinash Duduskar <avinash.duduskar@gmail.com>
---
 include/uapi/linux/bpf.h       | 22 +++++++++++-
 net/core/filter.c              | 61 +++++++++++++++++++++++-----------
 tools/include/uapi/linux/bpf.h | 22 +++++++++++-
 3 files changed, 84 insertions(+), 21 deletions(-)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 89b36de5fdbb..f1ac9266a2ab 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -3532,6 +3532,21 @@ union bpf_attr {
  *			Use the mark present in *params*->mark for the fib lookup.
  *			This option should not be used with BPF_FIB_LOOKUP_DIRECT,
  *			as it only has meaning for full lookups.
+ *		**BPF_FIB_LOOKUP_VLAN**
+ *			If the fib lookup resolves to a VLAN device whose
+ *			parent is a real (non-VLAN) device, set
+ *			*params*->h_vlan_proto and *params*->h_vlan_TCI from
+ *			the VLAN device and replace *params*->ifindex with the
+ *			parent's ifindex. *params*->h_vlan_TCI carries the VID
+ *			only, with PCP and DEI bits zero; a consumer wanting to
+ *			set egress priority writes PCP itself. *params*->smac is
+ *			the VLAN device's own address, which can differ from the
+ *			parent's. Only the immediate parent is resolved (QinQ is
+ *			not supported), and the swap is skipped if the parent is
+ *			in a different namespace. The swap and the vlan fields
+ *			are written only on success; other output fields keep
+ *			the helper's existing behaviour, so a frag-needed result
+ *			still reports the route mtu in *params*->mtu_result.
  *
  *		*ctx* is either **struct xdp_md** for XDP programs or
  *		**struct sk_buff** tc cls_act programs.
@@ -7327,6 +7342,7 @@ enum {
 	BPF_FIB_LOOKUP_TBID    = (1U << 3),
 	BPF_FIB_LOOKUP_SRC     = (1U << 4),
 	BPF_FIB_LOOKUP_MARK    = (1U << 5),
+	BPF_FIB_LOOKUP_VLAN    = (1U << 6),
 };
 
 enum {
@@ -7393,7 +7409,11 @@ struct bpf_fib_lookup {
 
 	union {
 		struct {
-			/* output */
+			/*
+			 * output with BPF_FIB_LOOKUP_VLAN: set from the
+			 * resolved egress VLAN device (see the flag); zeroed
+			 * on other successful lookups.
+			 */
 			__be16	h_vlan_proto;
 			__be16	h_vlan_TCI;
 		};
diff --git a/net/core/filter.c b/net/core/filter.c
index 2e96b4b847ce..27e4792f11e9 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -6201,10 +6201,26 @@ static const struct bpf_func_proto bpf_skb_get_xfrm_state_proto = {
 #endif
 
 #if IS_ENABLED(CONFIG_INET) || IS_ENABLED(CONFIG_IPV6)
-static int bpf_fib_set_fwd_params(struct bpf_fib_lookup *params, u32 mtu)
+static int bpf_fib_set_fwd_params(struct net_device *dev,
+				  struct bpf_fib_lookup *params,
+				  u32 flags, u32 mtu)
 {
 	params->h_vlan_TCI = 0;
 	params->h_vlan_proto = 0;
+
+#if IS_ENABLED(CONFIG_VLAN_8021Q)
+	if ((flags & BPF_FIB_LOOKUP_VLAN) && is_vlan_dev(dev)) {
+		struct net_device *real_dev = vlan_dev_priv(dev)->real_dev;
+
+		if (!is_vlan_dev(real_dev) &&
+		    net_eq(dev_net(real_dev), dev_net(dev))) {
+			params->h_vlan_proto = vlan_dev_vlan_proto(dev);
+			params->h_vlan_TCI = htons(vlan_dev_vlan_id(dev));
+			params->ifindex = real_dev->ifindex;
+		}
+	}
+#endif
+
 	if (mtu)
 		params->mtu_result = mtu; /* union with tot_len */
 
@@ -6214,7 +6230,8 @@ static int bpf_fib_set_fwd_params(struct bpf_fib_lookup *params, u32 mtu)
 
 #if IS_ENABLED(CONFIG_INET)
 static int bpf_ipv4_fib_lookup(struct net *net, struct bpf_fib_lookup *params,
-			       u32 flags, bool check_mtu)
+			       u32 flags, bool check_mtu,
+			       struct net_device **fwd_dev)
 {
 	struct neighbour *neigh = NULL;
 	struct fib_nh_common *nhc;
@@ -6347,13 +6364,16 @@ static int bpf_ipv4_fib_lookup(struct net *net, struct bpf_fib_lookup *params,
 	memcpy(params->smac, dev->dev_addr, ETH_ALEN);
 
 set_fwd_params:
-	return bpf_fib_set_fwd_params(params, mtu);
+	if (fwd_dev)
+		*fwd_dev = dev;
+	return bpf_fib_set_fwd_params(dev, params, flags, mtu);
 }
 #endif
 
 #if IS_ENABLED(CONFIG_IPV6)
 static int bpf_ipv6_fib_lookup(struct net *net, struct bpf_fib_lookup *params,
-			       u32 flags, bool check_mtu)
+			       u32 flags, bool check_mtu,
+			       struct net_device **fwd_dev)
 {
 	struct in6_addr *src = (struct in6_addr *) params->ipv6_src;
 	struct in6_addr *dst = (struct in6_addr *) params->ipv6_dst;
@@ -6486,13 +6506,16 @@ static int bpf_ipv6_fib_lookup(struct net *net, struct bpf_fib_lookup *params,
 	memcpy(params->smac, dev->dev_addr, ETH_ALEN);
 
 set_fwd_params:
-	return bpf_fib_set_fwd_params(params, mtu);
+	if (fwd_dev)
+		*fwd_dev = dev;
+	return bpf_fib_set_fwd_params(dev, params, flags, mtu);
 }
 #endif
 
 #define BPF_FIB_LOOKUP_MASK (BPF_FIB_LOOKUP_DIRECT | BPF_FIB_LOOKUP_OUTPUT | \
 			     BPF_FIB_LOOKUP_SKIP_NEIGH | BPF_FIB_LOOKUP_TBID | \
-			     BPF_FIB_LOOKUP_SRC | BPF_FIB_LOOKUP_MARK)
+			     BPF_FIB_LOOKUP_SRC | BPF_FIB_LOOKUP_MARK | \
+			     BPF_FIB_LOOKUP_VLAN)
 
 BPF_CALL_4(bpf_xdp_fib_lookup, struct xdp_buff *, ctx,
 	   struct bpf_fib_lookup *, params, int, plen, u32, flags)
@@ -6507,12 +6530,12 @@ BPF_CALL_4(bpf_xdp_fib_lookup, struct xdp_buff *, ctx,
 #if IS_ENABLED(CONFIG_INET)
 	case AF_INET:
 		return bpf_ipv4_fib_lookup(dev_net(ctx->rxq->dev), params,
-					   flags, true);
+					   flags, true, NULL);
 #endif
 #if IS_ENABLED(CONFIG_IPV6)
 	case AF_INET6:
 		return bpf_ipv6_fib_lookup(dev_net(ctx->rxq->dev), params,
-					   flags, true);
+					   flags, true, NULL);
 #endif
 	}
 	return -EAFNOSUPPORT;
@@ -6532,6 +6555,7 @@ BPF_CALL_4(bpf_skb_fib_lookup, struct sk_buff *, skb,
 	   struct bpf_fib_lookup *, params, int, plen, u32, flags)
 {
 	struct net *net = dev_net(skb->dev);
+	struct net_device *fwd_dev = NULL;
 	int rc = -EAFNOSUPPORT;
 	bool check_mtu = false;
 
@@ -6547,29 +6571,28 @@ BPF_CALL_4(bpf_skb_fib_lookup, struct sk_buff *, skb,
 	switch (params->family) {
 #if IS_ENABLED(CONFIG_INET)
 	case AF_INET:
-		rc = bpf_ipv4_fib_lookup(net, params, flags, check_mtu);
+		rc = bpf_ipv4_fib_lookup(net, params, flags, check_mtu,
+					 &fwd_dev);
 		break;
 #endif
 #if IS_ENABLED(CONFIG_IPV6)
 	case AF_INET6:
-		rc = bpf_ipv6_fib_lookup(net, params, flags, check_mtu);
+		rc = bpf_ipv6_fib_lookup(net, params, flags, check_mtu,
+					 &fwd_dev);
 		break;
 #endif
 	}
 
 	if (rc == BPF_FIB_LKUP_RET_SUCCESS && !check_mtu) {
-		struct net_device *dev;
-
-		/* When tot_len isn't provided by user, check skb
-		 * against MTU of FIB lookup resulting net_device
+		/*
+		 * Without tot_len, check the skb against the FIB result
+		 * device's MTU, which BPF_FIB_LOOKUP_VLAN keeps as the VLAN
+		 * device even though params->ifindex was swapped to the parent.
 		 */
-		dev = dev_get_by_index_rcu(net, params->ifindex);
-		if (unlikely(!dev))
-			return -ENODEV;
-		if (!is_skb_forwardable(dev, skb))
+		if (!is_skb_forwardable(fwd_dev, skb))
 			rc = BPF_FIB_LKUP_RET_FRAG_NEEDED;
 
-		params->mtu_result = dev->mtu; /* union with tot_len */
+		params->mtu_result = fwd_dev->mtu; /* union with tot_len */
 	}
 
 	return rc;
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 89b36de5fdbb..f1ac9266a2ab 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -3532,6 +3532,21 @@ union bpf_attr {
  *			Use the mark present in *params*->mark for the fib lookup.
  *			This option should not be used with BPF_FIB_LOOKUP_DIRECT,
  *			as it only has meaning for full lookups.
+ *		**BPF_FIB_LOOKUP_VLAN**
+ *			If the fib lookup resolves to a VLAN device whose
+ *			parent is a real (non-VLAN) device, set
+ *			*params*->h_vlan_proto and *params*->h_vlan_TCI from
+ *			the VLAN device and replace *params*->ifindex with the
+ *			parent's ifindex. *params*->h_vlan_TCI carries the VID
+ *			only, with PCP and DEI bits zero; a consumer wanting to
+ *			set egress priority writes PCP itself. *params*->smac is
+ *			the VLAN device's own address, which can differ from the
+ *			parent's. Only the immediate parent is resolved (QinQ is
+ *			not supported), and the swap is skipped if the parent is
+ *			in a different namespace. The swap and the vlan fields
+ *			are written only on success; other output fields keep
+ *			the helper's existing behaviour, so a frag-needed result
+ *			still reports the route mtu in *params*->mtu_result.
  *
  *		*ctx* is either **struct xdp_md** for XDP programs or
  *		**struct sk_buff** tc cls_act programs.
@@ -7327,6 +7342,7 @@ enum {
 	BPF_FIB_LOOKUP_TBID    = (1U << 3),
 	BPF_FIB_LOOKUP_SRC     = (1U << 4),
 	BPF_FIB_LOOKUP_MARK    = (1U << 5),
+	BPF_FIB_LOOKUP_VLAN    = (1U << 6),
 };
 
 enum {
@@ -7393,7 +7409,11 @@ struct bpf_fib_lookup {
 
 	union {
 		struct {
-			/* output */
+			/*
+			 * output with BPF_FIB_LOOKUP_VLAN: set from the
+			 * resolved egress VLAN device (see the flag); zeroed
+			 * on other successful lookups.
+			 */
 			__be16	h_vlan_proto;
 			__be16	h_vlan_TCI;
 		};
-- 
2.54.0

[PATCH bpf-next v3 2/3] bpf: Add BPF_FIB_LOOKUP_VLAN_INPUT flag to bpf_fib_lookup() helper

[Avinash Duduskar]

BPF_FIB_LOOKUP_VLAN resolves a VLAN egress. The reverse is also
useful: an XDP program receiving a VLAN-tagged frame on a physical
device wants the lookup to behave as if the packet had arrived on the
corresponding VLAN subinterface, so iif-based policy routing and VRF
table selection use the right ingress.

Add BPF_FIB_LOOKUP_VLAN_INPUT. When set, params->h_vlan_proto and
params->h_vlan_TCI are read as an input VLAN tag and the matching VLAN
device of params->ifindex is resolved with __vlan_find_dev_deep_rcu().
The device must be up and in the same network namespace as
params->ifindex (a VLAN device can be moved to another netns while
registered on its parent; receive would deliver into that other
namespace, which a lookup here cannot represent). If params->ifindex
is itself a VLAN device, its inner (QinQ) subinterface is matched.
For a bond or team, a tag on a port matches no device and returns
NOT_FWDED; pass the master's ifindex.
The lookup then runs with the resolved device as the ingress;
params->ifindex itself is not modified on the input side. When the
resolved device is enslaved to a VRF, both the full lookup (via the
l3mdev rule) and BPF_FIB_LOOKUP_DIRECT (via l3mdev_fib_table_rcu())
select the VRF's table from the resolved ingress. That follows from
feeding the resolved device to the flow as the ingress
(fl4.flowi4_iif = dev->ifindex), which is what makes l3mdev resolve
the VRF master from the subinterface rather than from
params->ifindex.

The two failure classes get different treatment on purpose. A
h_vlan_proto other than 802.1Q/802.1ad is API misuse and returns
-EINVAL, since it would otherwise reach the WARN in vlan_proto_idx()
with a program-controlled value. An unmatched VID, a device that is
down, or one in another namespace is a data outcome and returns
BPF_FIB_LKUP_RET_NOT_FWDED, matching the DIRECT path when
fib_get_table() finds no table and mirroring real ingress, where the
receive path drops such frames. A VID of 0 (a priority tag) is looked
up literally and normally fails the same way; receive instead
processes such frames untagged, so callers should not set the flag for
priority tags. Proceeding on the physical device for any of these
would be fail-open for the policy-routing cases above.

The h_vlan fields share a union with tbid, so the flag cannot be
combined with BPF_FIB_LOOKUP_TBID. It describes ingress, so it also
cannot be combined with BPF_FIB_LOOKUP_OUTPUT. Both combinations
return -EINVAL; restricting now keeps a later relaxation backward
compatible. Combining with BPF_FIB_LOOKUP_VLAN is allowed: the tag is
consumed on the ingress side and the egress tag is written on
success.

Under !CONFIG_VLAN_8021Q the __vlan_find_dev_deep_rcu() stub returns
NULL, so every lookup with the flag returns NOT_FWDED, which is
correct since no VLAN device can exist.

Suggested-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Avinash Duduskar <avinash.duduskar@gmail.com>
---
 include/uapi/linux/bpf.h       | 21 ++++++++++-
 net/core/filter.c              | 66 +++++++++++++++++++++++++++++++---
 tools/include/uapi/linux/bpf.h | 21 ++++++++++-
 3 files changed, 101 insertions(+), 7 deletions(-)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index f1ac9266a2ab..23bc3109619d 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -3547,6 +3547,22 @@ union bpf_attr {
  *			are written only on success; other output fields keep
  *			the helper's existing behaviour, so a frag-needed result
  *			still reports the route mtu in *params*->mtu_result.
+ *		**BPF_FIB_LOOKUP_VLAN_INPUT**
+ *			Treat *params*->h_vlan_proto and *params*->h_vlan_TCI
+ *			as an input VLAN tag and run the lookup as if ingress
+ *			had happened on the VLAN subinterface carrying that tag
+ *			on *params*->ifindex. The VID is the low 12 bits of
+ *			*params*->h_vlan_TCI; *params*->h_vlan_proto must be
+ *			ETH_P_8021Q or ETH_P_8021AD in network byte order, else
+ *			**-EINVAL**. If *params*->ifindex is itself a VLAN
+ *			device, its inner (QinQ) subinterface is matched; for a
+ *			bond or team, pass the master's ifindex. An unmatched
+ *			tag, a down device, or one in another namespace returns
+ *			**BPF_FIB_LKUP_RET_NOT_FWDED**, mirroring real ingress.
+ *			A VID of 0 is looked up literally, so do not set this
+ *			flag for priority-tagged frames. Cannot be combined with
+ *			**BPF_FIB_LOOKUP_TBID** or **BPF_FIB_LOOKUP_OUTPUT**
+ *			(returns **-EINVAL**).
  *
  *		*ctx* is either **struct xdp_md** for XDP programs or
  *		**struct sk_buff** tc cls_act programs.
@@ -7343,6 +7359,7 @@ enum {
 	BPF_FIB_LOOKUP_SRC     = (1U << 4),
 	BPF_FIB_LOOKUP_MARK    = (1U << 5),
 	BPF_FIB_LOOKUP_VLAN    = (1U << 6),
+	BPF_FIB_LOOKUP_VLAN_INPUT = (1U << 7),
 };
 
 enum {
@@ -7412,7 +7429,9 @@ struct bpf_fib_lookup {
 			/*
 			 * output with BPF_FIB_LOOKUP_VLAN: set from the
 			 * resolved egress VLAN device (see the flag); zeroed
-			 * on other successful lookups.
+			 * on other successful lookups. input with
+			 * BPF_FIB_LOOKUP_VLAN_INPUT: the VLAN tag to scope
+			 * the lookup by.
 			 */
 			__be16	h_vlan_proto;
 			__be16	h_vlan_TCI;
diff --git a/net/core/filter.c b/net/core/filter.c
index 27e4792f11e9..399adf2a824a 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -6226,6 +6226,25 @@ static int bpf_fib_set_fwd_params(struct net_device *dev,
 
 	return 0;
 }
+
+static struct net_device *bpf_fib_vlan_input_dev(struct net_device *dev,
+						 const struct bpf_fib_lookup *params)
+{
+	__be16 proto = params->h_vlan_proto;
+	struct net_device *vlan_dev;
+	u16 vid;
+
+	if (proto != htons(ETH_P_8021Q) && proto != htons(ETH_P_8021AD))
+		return ERR_PTR(-EINVAL);
+
+	vid = ntohs(params->h_vlan_TCI) & VLAN_VID_MASK;
+	vlan_dev = __vlan_find_dev_deep_rcu(dev, proto, vid);
+	if (!vlan_dev || !(vlan_dev->flags & IFF_UP) ||
+	    !net_eq(dev_net(vlan_dev), dev_net(dev)))
+		return NULL;
+
+	return vlan_dev;
+}
 #endif
 
 #if IS_ENABLED(CONFIG_INET)
@@ -6246,6 +6265,14 @@ static int bpf_ipv4_fib_lookup(struct net *net, struct bpf_fib_lookup *params,
 	if (unlikely(!dev))
 		return -ENODEV;
 
+	if (flags & BPF_FIB_LOOKUP_VLAN_INPUT) {
+		dev = bpf_fib_vlan_input_dev(dev, params);
+		if (IS_ERR(dev))
+			return PTR_ERR(dev);
+		if (!dev)
+			return BPF_FIB_LKUP_RET_NOT_FWDED;
+	}
+
 	/* verify forwarding is enabled on this interface */
 	in_dev = __in_dev_get_rcu(dev);
 	if (unlikely(!in_dev || !IN_DEV_FORWARD(in_dev)))
@@ -6255,7 +6282,11 @@ static int bpf_ipv4_fib_lookup(struct net *net, struct bpf_fib_lookup *params,
 		fl4.flowi4_iif = 1;
 		fl4.flowi4_oif = params->ifindex;
 	} else {
-		fl4.flowi4_iif = params->ifindex;
+		/*
+		 * dev->ifindex, not params->ifindex: VLAN_INPUT may have
+		 * resolved dev to a subinterface above.
+		 */
+		fl4.flowi4_iif = dev->ifindex;
 		fl4.flowi4_oif = 0;
 	}
 	fl4.flowi4_dscp = inet_dsfield_to_dscp(params->tos);
@@ -6394,6 +6425,14 @@ static int bpf_ipv6_fib_lookup(struct net *net, struct bpf_fib_lookup *params,
 	if (unlikely(!dev))
 		return -ENODEV;
 
+	if (flags & BPF_FIB_LOOKUP_VLAN_INPUT) {
+		dev = bpf_fib_vlan_input_dev(dev, params);
+		if (IS_ERR(dev))
+			return PTR_ERR(dev);
+		if (!dev)
+			return BPF_FIB_LKUP_RET_NOT_FWDED;
+	}
+
 	idev = __in6_dev_get_safely(dev);
 	if (unlikely(!idev || !READ_ONCE(idev->cnf.forwarding)))
 		return BPF_FIB_LKUP_RET_FWD_DISABLED;
@@ -6402,7 +6441,12 @@ static int bpf_ipv6_fib_lookup(struct net *net, struct bpf_fib_lookup *params,
 		fl6.flowi6_iif = 1;
 		oif = fl6.flowi6_oif = params->ifindex;
 	} else {
-		oif = fl6.flowi6_iif = params->ifindex;
+		/*
+		 * dev->ifindex, not params->ifindex: VLAN_INPUT may have
+		 * resolved dev to a subinterface above.
+		 */
+		oif = dev->ifindex;
+		fl6.flowi6_iif = oif;
 		fl6.flowi6_oif = 0;
 		strict = RT6_LOOKUP_F_HAS_SADDR;
 	}
@@ -6515,7 +6559,19 @@ static int bpf_ipv6_fib_lookup(struct net *net, struct bpf_fib_lookup *params,
 #define BPF_FIB_LOOKUP_MASK (BPF_FIB_LOOKUP_DIRECT | BPF_FIB_LOOKUP_OUTPUT | \
 			     BPF_FIB_LOOKUP_SKIP_NEIGH | BPF_FIB_LOOKUP_TBID | \
 			     BPF_FIB_LOOKUP_SRC | BPF_FIB_LOOKUP_MARK | \
-			     BPF_FIB_LOOKUP_VLAN)
+			     BPF_FIB_LOOKUP_VLAN | BPF_FIB_LOOKUP_VLAN_INPUT)
+
+static bool bpf_fib_lookup_flags_ok(u32 flags)
+{
+	if (flags & ~BPF_FIB_LOOKUP_MASK)
+		return false;
+
+	if ((flags & BPF_FIB_LOOKUP_VLAN_INPUT) &&
+	    (flags & (BPF_FIB_LOOKUP_TBID | BPF_FIB_LOOKUP_OUTPUT)))
+		return false;
+
+	return true;
+}
 
 BPF_CALL_4(bpf_xdp_fib_lookup, struct xdp_buff *, ctx,
 	   struct bpf_fib_lookup *, params, int, plen, u32, flags)
@@ -6523,7 +6579,7 @@ BPF_CALL_4(bpf_xdp_fib_lookup, struct xdp_buff *, ctx,
 	if (plen < sizeof(*params))
 		return -EINVAL;
 
-	if (flags & ~BPF_FIB_LOOKUP_MASK)
+	if (!bpf_fib_lookup_flags_ok(flags))
 		return -EINVAL;
 
 	switch (params->family) {
@@ -6562,7 +6618,7 @@ BPF_CALL_4(bpf_skb_fib_lookup, struct sk_buff *, skb,
 	if (plen < sizeof(*params))
 		return -EINVAL;
 
-	if (flags & ~BPF_FIB_LOOKUP_MASK)
+	if (!bpf_fib_lookup_flags_ok(flags))
 		return -EINVAL;
 
 	if (params->tot_len)
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index f1ac9266a2ab..23bc3109619d 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -3547,6 +3547,22 @@ union bpf_attr {
  *			are written only on success; other output fields keep
  *			the helper's existing behaviour, so a frag-needed result
  *			still reports the route mtu in *params*->mtu_result.
+ *		**BPF_FIB_LOOKUP_VLAN_INPUT**
+ *			Treat *params*->h_vlan_proto and *params*->h_vlan_TCI
+ *			as an input VLAN tag and run the lookup as if ingress
+ *			had happened on the VLAN subinterface carrying that tag
+ *			on *params*->ifindex. The VID is the low 12 bits of
+ *			*params*->h_vlan_TCI; *params*->h_vlan_proto must be
+ *			ETH_P_8021Q or ETH_P_8021AD in network byte order, else
+ *			**-EINVAL**. If *params*->ifindex is itself a VLAN
+ *			device, its inner (QinQ) subinterface is matched; for a
+ *			bond or team, pass the master's ifindex. An unmatched
+ *			tag, a down device, or one in another namespace returns
+ *			**BPF_FIB_LKUP_RET_NOT_FWDED**, mirroring real ingress.
+ *			A VID of 0 is looked up literally, so do not set this
+ *			flag for priority-tagged frames. Cannot be combined with
+ *			**BPF_FIB_LOOKUP_TBID** or **BPF_FIB_LOOKUP_OUTPUT**
+ *			(returns **-EINVAL**).
  *
  *		*ctx* is either **struct xdp_md** for XDP programs or
  *		**struct sk_buff** tc cls_act programs.
@@ -7343,6 +7359,7 @@ enum {
 	BPF_FIB_LOOKUP_SRC     = (1U << 4),
 	BPF_FIB_LOOKUP_MARK    = (1U << 5),
 	BPF_FIB_LOOKUP_VLAN    = (1U << 6),
+	BPF_FIB_LOOKUP_VLAN_INPUT = (1U << 7),
 };
 
 enum {
@@ -7412,7 +7429,9 @@ struct bpf_fib_lookup {
 			/*
 			 * output with BPF_FIB_LOOKUP_VLAN: set from the
 			 * resolved egress VLAN device (see the flag); zeroed
-			 * on other successful lookups.
+			 * on other successful lookups. input with
+			 * BPF_FIB_LOOKUP_VLAN_INPUT: the VLAN tag to scope
+			 * the lookup by.
 			 */
 			__be16	h_vlan_proto;
 			__be16	h_vlan_TCI;
-- 
2.54.0

[PATCH bpf-next v3 3/3] selftests/bpf: Add bpf_fib_lookup() VLAN flag tests

[Avinash Duduskar]

Cover both directions of the new VLAN flags in the fib_lookup test,
36 table cases plus a dedicated cross-netns subtest.

For BPF_FIB_LOOKUP_VLAN the egress cases assert: without the flag the
lookup returns the VLAN netdev's ifindex and zeroed vlan fields, with
the flag it returns the parent's ifindex plus the tag (including via
a neighbour resolved on the VLAN device, in OUTPUT mode, over a bond,
and through a DIRECT|TBID table), with the flag on a non-VLAN egress
it changes nothing, for a stacked VLAN it leaves ifindex untouched
with the vlan fields zero, and a frag-needed return reports the route
mtu in mtu_result while leaving the swap unwritten.

For BPF_FIB_LOOKUP_VLAN_INPUT, an iif rule on the subinterface routes
the same destination to a different gateway, so the asserted gateway
shows which device the lookup used as ingress: without the flag the
main table answers, with a matching tag the subinterface's table
does, with or without SKIP_NEIGH, and BPF_FIB_LOOKUP_SRC selects the
subinterface's address. A VRF-enslaved subinterface selects the VRF
table through the l3mdev rule and, with DIRECT, through
l3mdev_fib_table_rcu(). One case sets BPF_FIB_LOOKUP_VLAN as well and
asserts both directions work in a single lookup. Resolution semantics
are pinned: an 802.1ad tag resolves its device, PCP and DEI bits in
h_vlan_TCI are ignored, a VLAN ifindex resolves the inner QinQ
device, a tag on a bond master resolves while the same tag on the
bond port does not.

The error cases assert -EINVAL for an invalid h_vlan_proto on both
address families, for the TBID and OUTPUT flag combinations and for
an unknown flag bit, and BPF_FIB_LKUP_RET_NOT_FWDED for a VID with no
configured device on both families, for a VID-0 priority tag and for
a device that exists but is down. The failure cases also assert that
params is left untouched.

A separate subtest moves a VLAN device into a second netns while it
stays registered on its parent, and checks both directions refuse to
cross the boundary: the input flag fails closed with the tag and
ifindex untouched, and the egress flag does not publish the foreign
parent's ifindex.

The tbid read-back check is skipped for DIRECT cases that set
BPF_FIB_LOOKUP_VLAN, since a successful swap packs the vlan fields
into the union the check reads.

Re-run the cases through bpf_xdp_fib_lookup() as well: the egress flag
exists because VLAN devices have no XDP xmit, so XDP is the primary
consumer. bpf_prog_test_run uses the netns' loopback for the xdp context's
device, so the lookup runs against the test netns' FIB, and the
path-independent results (return code, swapped ifindex, vlan tag, gateway)
are asserted to match the skb path.

Signed-off-by: Avinash Duduskar <avinash.duduskar@gmail.com>
---
 .../selftests/bpf/prog_tests/fib_lookup.c     | 554 +++++++++++++++++-
 .../testing/selftests/bpf/progs/fib_lookup.c  |   9 +
 2 files changed, 559 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/fib_lookup.c b/tools/testing/selftests/bpf/prog_tests/fib_lookup.c
index bd7658958004..987a691fe078 100644
--- a/tools/testing/selftests/bpf/prog_tests/fib_lookup.c
+++ b/tools/testing/selftests/bpf/prog_tests/fib_lookup.c
@@ -2,6 +2,7 @@
 /* Copyright (c) 2023 Meta Platforms, Inc. and affiliates. */
 
 #include <linux/rtnetlink.h>
+#include <linux/if_ether.h>
 #include <sys/types.h>
 #include <net/if.h>
 
@@ -37,6 +38,41 @@
 #define IPV6_LOCAL		"fd01::3"
 #define IPV6_GW1		"fd01::1"
 #define IPV6_GW2		"fd01::2"
+#define VLAN_ID			100
+#define VLAN_IFACE		"veth1.100"
+#define VLAN_ID_DOWN		102
+#define VLAN_IFACE_DOWN		"veth1.102"
+#define QINQ_OUTER_IFACE	"veth1.200"
+#define QINQ_INNER_IFACE	"veth1.200.300"
+#define VLAN_TABLE		"300"
+#define IPV4_VLAN_IFACE_ADDR	"10.5.0.254"
+#define IPV4_VLAN_EGRESS_DST	"10.5.0.2"
+#define IPV4_QINQ_DST		"10.7.0.2"
+#define IPV4_VLAN_DST		"10.6.0.2"
+#define IPV4_VLAN_GW		"10.5.0.1"
+#define IPV6_VLAN_IFACE_ADDR	"fd02::254"
+#define IPV6_VLAN_EGRESS_DST	"fd02::2"
+#define IPV6_VLAN_DST		"fd03::2"
+#define IPV6_VLAN_GW		"fd02::1"
+#define VLAN_VID_UNUSED		999
+#define VRF_IFACE		"vrf-blue"
+#define VRF_TABLE		"1000"
+#define VRF_VLAN_ID		101
+#define VRF_VLAN_IFACE		"veth1.101"
+#define IPV4_VRF_IFACE_ADDR	"10.8.0.254"
+#define IPV4_VRF_GW		"10.8.0.1"
+#define IPV4_VRF_DST		"10.9.0.2"
+#define TBID_VLAN_ID		50
+#define TBID_VLAN_IFACE		"veth2.50"
+#define IPV4_TBID_VLAN_DST	"172.2.0.2"
+#define IPV4_BOND_VLAN_DST	"10.11.0.2"
+#define IPV4_VLAN_MTU_DST	"10.5.9.2"
+#define QINQ_AD_VLAN_ID		200
+#define QINQ_INNER_VLAN_ID	300
+#define BOND_IFACE		"bond99"
+#define BOND_PORT		"veth3"
+#define BOND_PORT_PEER		"veth4"
+#define BOND_VLAN_ID		500
 #define DMAC			"11:11:11:11:11:11"
 #define DMAC_INIT { 0x11, 0x11, 0x11, 0x11, 0x11, 0x11, }
 #define DMAC2			"01:01:01:01:01:01"
@@ -52,6 +88,17 @@ struct fib_lookup_test {
 	__u32 tbid;
 	__u8 dmac[6];
 	__u32 mark;
+	/*
+	 * input tag with BPF_FIB_LOOKUP_VLAN_INPUT; expected output tag
+	 * with BPF_FIB_LOOKUP_VLAN (checked when check_vlan is set)
+	 */
+	__u16 vlan_proto;
+	__u16 vlan_id;
+	bool check_vlan;
+	const char *expected_dev; /* expected params->ifindex after lookup */
+	const char *iif;	  /* override the default veth1 input device */
+	__u16 tot_len;		  /* triggers the in-lookup mtu check when set */
+	__u16 expected_mtu;	  /* expected mtu_result (union with tot_len) */
 };
 
 static const struct fib_lookup_test tests[] = {
@@ -142,6 +189,209 @@ static const struct fib_lookup_test tests[] = {
 	  .expected_dst = IPV6_GW1,
 	  .lookup_flags = BPF_FIB_LOOKUP_SKIP_NEIGH,
 	  .mark = MARK, },
+	/* vlan egress resolution */
+	{ .desc = "IPv4 VLAN egress, no flag",
+	  .daddr = IPV4_VLAN_EGRESS_DST, .expected_ret = BPF_FIB_LKUP_RET_SUCCESS,
+	  .lookup_flags = BPF_FIB_LOOKUP_SKIP_NEIGH,
+	  .expected_dev = VLAN_IFACE, .check_vlan = true, },
+	{ .desc = "IPv4 VLAN egress, single VLAN",
+	  .daddr = IPV4_VLAN_EGRESS_DST, .expected_ret = BPF_FIB_LKUP_RET_SUCCESS,
+	  .lookup_flags = BPF_FIB_LOOKUP_VLAN | BPF_FIB_LOOKUP_SKIP_NEIGH,
+	  .expected_dev = "veth1", .check_vlan = true,
+	  .vlan_proto = ETH_P_8021Q, .vlan_id = VLAN_ID, },
+	/*
+	 * skb path without tot_len: mtu_result is the FIB result (VLAN)
+	 * device's mtu (1400) with or without the swap, not the parent's (1500)
+	 */
+	{ .desc = "IPv4 VLAN egress, skb-path mtu is the VLAN device's without the flag",
+	  .daddr = IPV4_VLAN_EGRESS_DST, .expected_ret = BPF_FIB_LKUP_RET_SUCCESS,
+	  .lookup_flags = BPF_FIB_LOOKUP_SKIP_NEIGH,
+	  .expected_dev = VLAN_IFACE, .check_vlan = true, .expected_mtu = 1400, },
+	{ .desc = "IPv4 VLAN egress, skb-path mtu stays the VLAN device's after the swap",
+	  .daddr = IPV4_VLAN_EGRESS_DST, .expected_ret = BPF_FIB_LKUP_RET_SUCCESS,
+	  .lookup_flags = BPF_FIB_LOOKUP_VLAN | BPF_FIB_LOOKUP_SKIP_NEIGH,
+	  .expected_dev = "veth1", .check_vlan = true,
+	  .vlan_proto = ETH_P_8021Q, .vlan_id = VLAN_ID, .expected_mtu = 1400, },
+	{ .desc = "IPv4 VLAN egress, flag set but egress is not a VLAN",
+	  .daddr = IPV4_NUD_FAILED_ADDR, .expected_ret = BPF_FIB_LKUP_RET_SUCCESS,
+	  .lookup_flags = BPF_FIB_LOOKUP_VLAN | BPF_FIB_LOOKUP_SKIP_NEIGH,
+	  .expected_dev = "veth1", .check_vlan = true, },
+	{ .desc = "IPv4 VLAN egress, stacked VLAN untouched",
+	  .daddr = IPV4_QINQ_DST, .expected_ret = BPF_FIB_LKUP_RET_SUCCESS,
+	  .lookup_flags = BPF_FIB_LOOKUP_VLAN | BPF_FIB_LOOKUP_SKIP_NEIGH,
+	  .expected_dev = QINQ_INNER_IFACE, .check_vlan = true, },
+	{ .desc = "IPv6 VLAN egress, single VLAN",
+	  .daddr = IPV6_VLAN_EGRESS_DST, .expected_ret = BPF_FIB_LKUP_RET_SUCCESS,
+	  .lookup_flags = BPF_FIB_LOOKUP_VLAN | BPF_FIB_LOOKUP_SKIP_NEIGH,
+	  .expected_dev = "veth1", .check_vlan = true,
+	  .vlan_proto = ETH_P_8021Q, .vlan_id = VLAN_ID, },
+	{ .desc = "IPv4 VLAN egress, neighbour on the VLAN device",
+	  .daddr = IPV4_VLAN_EGRESS_DST, .expected_ret = BPF_FIB_LKUP_RET_SUCCESS,
+	  .lookup_flags = BPF_FIB_LOOKUP_VLAN,
+	  .expected_dev = "veth1", .check_vlan = true,
+	  .vlan_proto = ETH_P_8021Q, .vlan_id = VLAN_ID, .dmac = DMAC_INIT, },
+	{ .desc = "IPv4 VLAN egress in OUTPUT mode",
+	  .daddr = IPV4_VLAN_EGRESS_DST, .expected_ret = BPF_FIB_LKUP_RET_SUCCESS,
+	  .iif = VLAN_IFACE,
+	  .lookup_flags = BPF_FIB_LOOKUP_OUTPUT | BPF_FIB_LOOKUP_VLAN |
+			  BPF_FIB_LOOKUP_SKIP_NEIGH,
+	  .expected_dev = "veth1", .check_vlan = true,
+	  .vlan_proto = ETH_P_8021Q, .vlan_id = VLAN_ID, },
+	{ .desc = "IPv4 VLAN egress over a bond",
+	  .daddr = IPV4_BOND_VLAN_DST, .expected_ret = BPF_FIB_LKUP_RET_SUCCESS,
+	  .lookup_flags = BPF_FIB_LOOKUP_VLAN | BPF_FIB_LOOKUP_SKIP_NEIGH,
+	  .expected_dev = BOND_IFACE, .check_vlan = true,
+	  .vlan_proto = ETH_P_8021Q, .vlan_id = BOND_VLAN_ID, },
+	{ .desc = "IPv4 VLAN egress via TBID table",
+	  .daddr = IPV4_TBID_VLAN_DST, .expected_ret = BPF_FIB_LKUP_RET_SUCCESS,
+	  .lookup_flags = BPF_FIB_LOOKUP_DIRECT | BPF_FIB_LOOKUP_TBID |
+			  BPF_FIB_LOOKUP_VLAN | BPF_FIB_LOOKUP_SKIP_NEIGH,
+	  .tbid = 100,
+	  .expected_dev = "veth2", .check_vlan = true,
+	  .vlan_proto = ETH_P_8021Q, .vlan_id = TBID_VLAN_ID, },
+	{ .desc = "IPv4 VLAN egress, success writes mtu_result with the swap",
+	  .daddr = IPV4_VLAN_MTU_DST, .expected_ret = BPF_FIB_LKUP_RET_SUCCESS,
+	  .tot_len = 500, .expected_mtu = 1000,
+	  .lookup_flags = BPF_FIB_LOOKUP_VLAN | BPF_FIB_LOOKUP_SKIP_NEIGH,
+	  .expected_dev = "veth1", .check_vlan = true,
+	  .vlan_proto = ETH_P_8021Q, .vlan_id = VLAN_ID, },
+	{ .desc = "IPv4 VLAN egress, FRAG_NEEDED reports mtu, swap unwritten",
+	  .daddr = IPV4_VLAN_MTU_DST, .expected_ret = BPF_FIB_LKUP_RET_FRAG_NEEDED,
+	  .tot_len = 1400, .expected_mtu = 1000,
+	  .lookup_flags = BPF_FIB_LOOKUP_VLAN | BPF_FIB_LOOKUP_SKIP_NEIGH,
+	  .expected_dev = "veth1", .check_vlan = true, },
+	/* vlan tag as lookup input */
+	{ .desc = "IPv4 VLAN input, no flag",
+	  .daddr = IPV4_VLAN_DST, .expected_ret = BPF_FIB_LKUP_RET_SUCCESS,
+	  .expected_dst = IPV4_GW1,
+	  .lookup_flags = BPF_FIB_LOOKUP_SKIP_NEIGH, },
+	{ .desc = "IPv4 VLAN input, tag selects subinterface route",
+	  .daddr = IPV4_VLAN_DST, .expected_ret = BPF_FIB_LKUP_RET_SUCCESS,
+	  .expected_dst = IPV4_VLAN_GW, .expected_dev = VLAN_IFACE,
+	  .lookup_flags = BPF_FIB_LOOKUP_VLAN_INPUT | BPF_FIB_LOOKUP_SKIP_NEIGH,
+	  .vlan_proto = ETH_P_8021Q, .vlan_id = VLAN_ID, },
+	{ .desc = "IPv6 VLAN input, tag selects subinterface route",
+	  .daddr = IPV6_VLAN_DST, .expected_ret = BPF_FIB_LKUP_RET_SUCCESS,
+	  .expected_dst = IPV6_VLAN_GW, .expected_dev = VLAN_IFACE,
+	  .lookup_flags = BPF_FIB_LOOKUP_VLAN_INPUT | BPF_FIB_LOOKUP_SKIP_NEIGH,
+	  .vlan_proto = ETH_P_8021Q, .vlan_id = VLAN_ID, },
+	{ .desc = "IPv4 VLAN input and egress combined",
+	  .daddr = IPV4_VLAN_DST, .expected_ret = BPF_FIB_LKUP_RET_SUCCESS,
+	  .expected_dst = IPV4_VLAN_GW, .expected_dev = "veth1",
+	  .check_vlan = true,
+	  .lookup_flags = BPF_FIB_LOOKUP_VLAN_INPUT | BPF_FIB_LOOKUP_VLAN |
+			  BPF_FIB_LOOKUP_SKIP_NEIGH,
+	  .vlan_proto = ETH_P_8021Q, .vlan_id = VLAN_ID, },
+	{ .desc = "IPv4 VLAN input, neighbour resolved on the route",
+	  .daddr = IPV4_VLAN_DST, .expected_ret = BPF_FIB_LKUP_RET_SUCCESS,
+	  .expected_dst = IPV4_VLAN_GW, .expected_dev = VLAN_IFACE,
+	  .lookup_flags = BPF_FIB_LOOKUP_VLAN_INPUT,
+	  .vlan_proto = ETH_P_8021Q, .vlan_id = VLAN_ID, .dmac = DMAC_INIT2, },
+	{ .desc = "IPv4 VLAN input, source address from the subinterface",
+	  .daddr = IPV4_VLAN_DST, .expected_ret = BPF_FIB_LKUP_RET_SUCCESS,
+	  .expected_src = IPV4_VLAN_IFACE_ADDR,
+	  .lookup_flags = BPF_FIB_LOOKUP_VLAN_INPUT | BPF_FIB_LOOKUP_SRC |
+			  BPF_FIB_LOOKUP_SKIP_NEIGH,
+	  .vlan_proto = ETH_P_8021Q, .vlan_id = VLAN_ID, },
+	/*
+	 * VRF: the resolved subinterface is enslaved, so the l3mdev rule
+	 * (full lookup) and l3mdev_fib_table_rcu() (DIRECT) must select
+	 * the VRF table from the resolved ingress
+	 */
+	{ .desc = "IPv4 VLAN input, VRF subinterface, no flag",
+	  .daddr = IPV4_VRF_DST, .expected_ret = BPF_FIB_LKUP_RET_SUCCESS,
+	  .expected_dst = IPV4_GW1,
+	  .lookup_flags = BPF_FIB_LOOKUP_SKIP_NEIGH, },
+	{ .desc = "IPv4 VLAN input, tag selects VRF table",
+	  .daddr = IPV4_VRF_DST, .expected_ret = BPF_FIB_LKUP_RET_SUCCESS,
+	  .expected_dst = IPV4_VRF_GW, .expected_dev = VRF_VLAN_IFACE,
+	  .lookup_flags = BPF_FIB_LOOKUP_VLAN_INPUT | BPF_FIB_LOOKUP_SKIP_NEIGH,
+	  .vlan_proto = ETH_P_8021Q, .vlan_id = VRF_VLAN_ID, },
+	{ .desc = "IPv4 VLAN input, DIRECT uses VRF table from resolved ingress",
+	  .daddr = IPV4_VRF_DST, .expected_ret = BPF_FIB_LKUP_RET_SUCCESS,
+	  .expected_dst = IPV4_VRF_GW, .expected_dev = VRF_VLAN_IFACE,
+	  .lookup_flags = BPF_FIB_LOOKUP_VLAN_INPUT | BPF_FIB_LOOKUP_DIRECT |
+			  BPF_FIB_LOOKUP_SKIP_NEIGH,
+	  .vlan_proto = ETH_P_8021Q, .vlan_id = VRF_VLAN_ID, },
+	/*
+	 * failure arms also assert params is left untouched: ifindex still
+	 * names the physical device and the input tag bytes survive
+	 */
+	{ .desc = "IPv4 VLAN input, invalid proto",
+	  .daddr = IPV4_VLAN_DST, .expected_ret = -EINVAL,
+	  .expected_dev = "veth1", .check_vlan = true,
+	  .lookup_flags = BPF_FIB_LOOKUP_VLAN_INPUT | BPF_FIB_LOOKUP_SKIP_NEIGH,
+	  .vlan_proto = 0x1234, .vlan_id = VLAN_ID, },
+	{ .desc = "IPv4 VLAN input, unmatched VID",
+	  .daddr = IPV4_VLAN_DST, .expected_ret = BPF_FIB_LKUP_RET_NOT_FWDED,
+	  .expected_dev = "veth1", .check_vlan = true,
+	  .lookup_flags = BPF_FIB_LOOKUP_VLAN_INPUT | BPF_FIB_LOOKUP_SKIP_NEIGH,
+	  .vlan_proto = ETH_P_8021Q, .vlan_id = VLAN_VID_UNUSED, },
+	{ .desc = "IPv4 VLAN input, subinterface down",
+	  .daddr = IPV4_VLAN_DST, .expected_ret = BPF_FIB_LKUP_RET_NOT_FWDED,
+	  .expected_dev = "veth1", .check_vlan = true,
+	  .lookup_flags = BPF_FIB_LOOKUP_VLAN_INPUT | BPF_FIB_LOOKUP_SKIP_NEIGH,
+	  .vlan_proto = ETH_P_8021Q, .vlan_id = VLAN_ID_DOWN, },
+	/*
+	 * the resolver runs before the forwarding check, so on devices
+	 * with forwarding off FWD_DISABLED (not NOT_FWDED) proves the tag
+	 * resolved to that device and the lookup used it as ingress
+	 */
+	{ .desc = "IPv4 VLAN input, 802.1ad tag",
+	  .daddr = IPV4_VLAN_DST, .expected_ret = BPF_FIB_LKUP_RET_FWD_DISABLED,
+	  .lookup_flags = BPF_FIB_LOOKUP_VLAN_INPUT | BPF_FIB_LOOKUP_SKIP_NEIGH,
+	  .vlan_proto = ETH_P_8021AD, .vlan_id = QINQ_AD_VLAN_ID, },
+	{ .desc = "IPv4 VLAN input, PCP and DEI bits ignored in TCI",
+	  .daddr = IPV4_VLAN_DST, .expected_ret = BPF_FIB_LKUP_RET_SUCCESS,
+	  .expected_dst = IPV4_VLAN_GW,
+	  .lookup_flags = BPF_FIB_LOOKUP_VLAN_INPUT | BPF_FIB_LOOKUP_SKIP_NEIGH,
+	  .vlan_proto = ETH_P_8021Q, .vlan_id = 0xe000 | VLAN_ID, },
+	{ .desc = "IPv4 VLAN input, inner QinQ device from VLAN ifindex",
+	  .daddr = IPV4_VLAN_DST, .expected_ret = BPF_FIB_LKUP_RET_FWD_DISABLED,
+	  .iif = QINQ_OUTER_IFACE,
+	  .lookup_flags = BPF_FIB_LOOKUP_VLAN_INPUT | BPF_FIB_LOOKUP_SKIP_NEIGH,
+	  .vlan_proto = ETH_P_8021Q, .vlan_id = QINQ_INNER_VLAN_ID, },
+	/*
+	 * bonding: the VLANs live on the master, as on receive, where the
+	 * frame is steered to the master before VLAN processing; a port
+	 * ifindex does not match (ports carry vid state but no VLAN devs)
+	 */
+	{ .desc = "IPv4 VLAN input, tag on bond master resolves",
+	  .daddr = IPV4_VLAN_DST, .expected_ret = BPF_FIB_LKUP_RET_FWD_DISABLED,
+	  .iif = BOND_IFACE,
+	  .lookup_flags = BPF_FIB_LOOKUP_VLAN_INPUT | BPF_FIB_LOOKUP_SKIP_NEIGH,
+	  .vlan_proto = ETH_P_8021Q, .vlan_id = BOND_VLAN_ID, },
+	{ .desc = "IPv4 VLAN input, tag on bond port does not match",
+	  .daddr = IPV4_VLAN_DST, .expected_ret = BPF_FIB_LKUP_RET_NOT_FWDED,
+	  .iif = BOND_PORT, .expected_dev = BOND_PORT, .check_vlan = true,
+	  .lookup_flags = BPF_FIB_LOOKUP_VLAN_INPUT | BPF_FIB_LOOKUP_SKIP_NEIGH,
+	  .vlan_proto = ETH_P_8021Q, .vlan_id = BOND_VLAN_ID, },
+	{ .desc = "IPv6 VLAN input, invalid proto",
+	  .daddr = IPV6_VLAN_DST, .expected_ret = -EINVAL,
+	  .expected_dev = "veth1", .check_vlan = true,
+	  .lookup_flags = BPF_FIB_LOOKUP_VLAN_INPUT | BPF_FIB_LOOKUP_SKIP_NEIGH,
+	  .vlan_proto = 0x1234, .vlan_id = VLAN_ID, },
+	{ .desc = "IPv4 VLAN input, VID 0 priority tag fails closed",
+	  .daddr = IPV4_VLAN_DST, .expected_ret = BPF_FIB_LKUP_RET_NOT_FWDED,
+	  .expected_dev = "veth1", .check_vlan = true,
+	  .lookup_flags = BPF_FIB_LOOKUP_VLAN_INPUT | BPF_FIB_LOOKUP_SKIP_NEIGH,
+	  .vlan_proto = ETH_P_8021Q, .vlan_id = 0, },
+	{ .desc = "IPv6 VLAN input, unmatched VID",
+	  .daddr = IPV6_VLAN_DST, .expected_ret = BPF_FIB_LKUP_RET_NOT_FWDED,
+	  .expected_dev = "veth1", .check_vlan = true,
+	  .lookup_flags = BPF_FIB_LOOKUP_VLAN_INPUT | BPF_FIB_LOOKUP_SKIP_NEIGH,
+	  .vlan_proto = ETH_P_8021Q, .vlan_id = VLAN_VID_UNUSED, },
+	{ .desc = "unknown flag bit rejected",
+	  .daddr = IPV4_VLAN_DST, .expected_ret = -EINVAL,
+	  .lookup_flags = (1 << 14) | BPF_FIB_LOOKUP_SKIP_NEIGH, },
+	{ .desc = "IPv4 VLAN input rejected with TBID",
+	  .daddr = IPV4_VLAN_DST, .expected_ret = -EINVAL,
+	  .lookup_flags = BPF_FIB_LOOKUP_VLAN_INPUT | BPF_FIB_LOOKUP_TBID,
+	  .vlan_proto = ETH_P_8021Q, .vlan_id = VLAN_ID, },
+	{ .desc = "IPv4 VLAN input rejected with OUTPUT",
+	  .daddr = IPV4_VLAN_DST, .expected_ret = -EINVAL,
+	  .lookup_flags = BPF_FIB_LOOKUP_VLAN_INPUT | BPF_FIB_LOOKUP_OUTPUT,
+	  .vlan_proto = ETH_P_8021Q, .vlan_id = VLAN_ID, },
 };
 
 static int setup_netns(void)
@@ -204,6 +454,110 @@ static int setup_netns(void)
 	SYS(fail, "ip rule add prio 2 fwmark %d lookup %s", MARK, MARK_TABLE);
 	SYS(fail, "ip -6 rule add prio 2 fwmark %d lookup %s", MARK, MARK_TABLE);
 
+	/*
+	 * Setup for vlan tests: a subinterface for egress resolution and
+	 * tag-as-input, a QinQ stack, and an iif rule so the input tests
+	 * observe which device the lookup used as ingress.
+	 */
+	SYS(fail, "ip link add link veth1 name %s type vlan id %d",
+	    VLAN_IFACE, VLAN_ID);
+	SYS(fail, "ip link set dev %s up", VLAN_IFACE);
+	/*
+	 * lower than the veth1 parent (1500): the skb-path mtu check uses the
+	 * FIB result (VLAN) device, so mtu_result is this value with or
+	 * without the egress swap, which two arms below pin
+	 */
+	SYS(fail, "ip link set dev %s mtu 1400", VLAN_IFACE);
+	SYS(fail, "ip addr add %s/24 dev %s", IPV4_VLAN_IFACE_ADDR, VLAN_IFACE);
+	SYS(fail, "ip addr add %s/64 dev %s nodad", IPV6_VLAN_IFACE_ADDR, VLAN_IFACE);
+
+	/*
+	 * stays down: the input flag must treat its tag the way real
+	 * ingress treats a frame arriving on a down VLAN device (drop)
+	 */
+	SYS(fail, "ip link add link veth1 name %s type vlan id %d",
+	    VLAN_IFACE_DOWN, VLAN_ID_DOWN);
+
+	err = write_sysctl("/proc/sys/net/ipv4/conf/" VLAN_IFACE "/forwarding", "1");
+	if (!ASSERT_OK(err, "write_sysctl(net.ipv4.conf." VLAN_IFACE ".forwarding)"))
+		goto fail;
+
+	err = write_sysctl("/proc/sys/net/ipv6/conf/" VLAN_IFACE "/forwarding", "1");
+	if (!ASSERT_OK(err, "write_sysctl(net.ipv6.conf." VLAN_IFACE ".forwarding)"))
+		goto fail;
+
+	SYS(fail, "ip link add link veth1 name %s type vlan proto 802.1ad id 200",
+	    QINQ_OUTER_IFACE);
+	SYS(fail, "ip link add link %s name %s type vlan id 300",
+	    QINQ_OUTER_IFACE, QINQ_INNER_IFACE);
+	SYS(fail, "ip link set dev %s up", QINQ_OUTER_IFACE);
+	SYS(fail, "ip link set dev %s up", QINQ_INNER_IFACE);
+	SYS(fail, "ip route add %s/32 dev %s", IPV4_QINQ_DST, QINQ_INNER_IFACE);
+
+	SYS(fail, "ip route add %s/32 via %s", IPV4_VLAN_DST, IPV4_GW1);
+	SYS(fail, "ip route add table %s %s/32 via %s",
+	    VLAN_TABLE, IPV4_VLAN_DST, IPV4_VLAN_GW);
+	SYS(fail, "ip rule add prio 3 iif %s lookup %s", VLAN_IFACE, VLAN_TABLE);
+	SYS(fail, "ip -6 route add %s/128 via %s", IPV6_VLAN_DST, IPV6_GW1);
+	SYS(fail, "ip -6 route add table %s %s/128 via %s",
+	    VLAN_TABLE, IPV6_VLAN_DST, IPV6_VLAN_GW);
+	SYS(fail, "ip -6 rule add prio 3 iif %s lookup %s", VLAN_IFACE, VLAN_TABLE);
+
+	/*
+	 * a bond with one port and a VLAN on the bond: VLANs on a bond
+	 * live on the master, so resolution succeeds for the master's
+	 * ifindex and fails closed for a port's, matching receive, which
+	 * steers the frame to the master before VLAN processing
+	 */
+	SYS(fail, "ip link add %s type bond", BOND_IFACE);
+	SYS(fail, "ip link add %s type veth peer name %s", BOND_PORT, BOND_PORT_PEER);
+	SYS(fail, "ip link set %s master %s", BOND_PORT, BOND_IFACE);
+	SYS(fail, "ip link set dev %s up", BOND_IFACE);
+	SYS(fail, "ip link set dev %s up", BOND_PORT);
+	SYS(fail, "ip link add link %s name %s.%d type vlan id %d",
+	    BOND_IFACE, BOND_IFACE, BOND_VLAN_ID, BOND_VLAN_ID);
+	SYS(fail, "ip link set dev %s.%d up", BOND_IFACE, BOND_VLAN_ID);
+	SYS(fail, "ip route add %s/32 dev %s.%d",
+	    IPV4_BOND_VLAN_DST, BOND_IFACE, BOND_VLAN_ID);
+
+	/*
+	 * a VRF with its own dedicated subinterface (the iif rules above
+	 * must not see it), for the table-selection-by-ingress cases
+	 */
+	SYS(fail, "ip link add %s type vrf table %s", VRF_IFACE, VRF_TABLE);
+	SYS(fail, "ip link set dev %s up", VRF_IFACE);
+	SYS(fail, "ip link add link veth1 name %s type vlan id %d",
+	    VRF_VLAN_IFACE, VRF_VLAN_ID);
+	SYS(fail, "ip link set %s master %s", VRF_VLAN_IFACE, VRF_IFACE);
+	SYS(fail, "ip link set dev %s up", VRF_VLAN_IFACE);
+	SYS(fail, "ip addr add %s/24 dev %s", IPV4_VRF_IFACE_ADDR, VRF_VLAN_IFACE);
+	err = write_sysctl("/proc/sys/net/ipv4/conf/" VRF_VLAN_IFACE "/forwarding", "1");
+	if (!ASSERT_OK(err, "write_sysctl(net.ipv4.conf." VRF_VLAN_IFACE ".forwarding)"))
+		goto fail;
+	SYS(fail, "ip route add %s/32 via %s", IPV4_VRF_DST, IPV4_GW1);
+	SYS(fail, "ip route add table %s %s/32 via %s",
+	    VRF_TABLE, IPV4_VRF_DST, IPV4_VRF_GW);
+
+	/* neighbours on the VLAN subinterface for the non-SKIP_NEIGH cases */
+	err = write_sysctl("/proc/sys/net/ipv4/neigh/" VLAN_IFACE "/gc_stale_time", "900");
+	if (!ASSERT_OK(err, "write_sysctl(net.ipv4.neigh." VLAN_IFACE ".gc_stale_time)"))
+		goto fail;
+	SYS(fail, "ip neigh add %s dev %s lladdr %s nud stale",
+	    IPV4_VLAN_EGRESS_DST, VLAN_IFACE, DMAC);
+	SYS(fail, "ip neigh add %s dev %s lladdr %s nud stale",
+	    IPV4_VLAN_GW, VLAN_IFACE, DMAC2);
+
+	/* a VLAN on veth2 with a route in the tbid test table */
+	SYS(fail, "ip link add link veth2 name %s type vlan id %d",
+	    TBID_VLAN_IFACE, TBID_VLAN_ID);
+	SYS(fail, "ip link set dev %s up", TBID_VLAN_IFACE);
+	SYS(fail, "ip route add table 100 %s/32 dev %s",
+	    IPV4_TBID_VLAN_DST, TBID_VLAN_IFACE);
+
+	/* a locked-mtu route via the subinterface for the FRAG_NEEDED case */
+	SYS(fail, "ip route add %s/32 dev %s mtu lock 1000",
+	    IPV4_VLAN_MTU_DST, VLAN_IFACE);
+
 	return 0;
 fail:
 	return -1;
@@ -218,9 +572,16 @@ static int set_lookup_params(struct bpf_fib_lookup *params,
 	memset(params, 0, sizeof(*params));
 
 	params->l4_protocol = IPPROTO_TCP;
-	params->ifindex = ifindex;
+	params->ifindex = test->iif ? if_nametoindex(test->iif) : ifindex;
 	params->tbid = test->tbid;
 	params->mark = test->mark;
+	params->tot_len = test->tot_len;
+
+	/* h_vlan_proto/h_vlan_TCI union with tbid */
+	if (test->lookup_flags & BPF_FIB_LOOKUP_VLAN_INPUT) {
+		params->h_vlan_proto = htons(test->vlan_proto);
+		params->h_vlan_TCI = htons(test->vlan_id);
+	}
 
 	if (inet_pton(AF_INET6, test->daddr, params->ipv6_dst) == 1) {
 		params->family = AF_INET6;
@@ -298,7 +659,7 @@ void test_fib_lookup(void)
 	struct nstoken *nstoken = NULL;
 	struct __sk_buff skb = { };
 	struct fib_lookup *skel;
-	int prog_fd, err, ret, i;
+	int prog_fd, xdp_fd, err, ret, i;
 
 	/* The test does not use the skb->data, so
 	 * use pkt_v6 for both v6 and v4 test.
@@ -309,11 +670,16 @@ void test_fib_lookup(void)
 		    .ctx_in = &skb,
 		    .ctx_size_in = sizeof(skb),
 	);
+	LIBBPF_OPTS(bpf_test_run_opts, xdp_opts,
+		    .data_in = &pkt_v6,
+		    .data_size_in = sizeof(pkt_v6),
+	);
 
 	skel = fib_lookup__open_and_load();
 	if (!ASSERT_OK_PTR(skel, "skel open_and_load"))
 		return;
 	prog_fd = bpf_program__fd(skel->progs.fib_lookup);
+	xdp_fd = bpf_program__fd(skel->progs.fib_lookup_xdp);
 
 	SYS(fail, "ip netns add %s", NS_TEST);
 
@@ -352,6 +718,21 @@ void test_fib_lookup(void)
 		if (tests[i].expected_dst)
 			assert_dst_ip(fib_params, tests[i].expected_dst);
 
+		if (tests[i].expected_dev)
+			ASSERT_EQ(fib_params->ifindex,
+				  if_nametoindex(tests[i].expected_dev), "ifindex");
+
+		if (tests[i].expected_mtu)
+			ASSERT_EQ(fib_params->mtu_result, tests[i].expected_mtu,
+				  "mtu_result");
+
+		if (tests[i].check_vlan) {
+			ASSERT_EQ(fib_params->h_vlan_proto,
+				  htons(tests[i].vlan_proto), "h_vlan_proto");
+			ASSERT_EQ(fib_params->h_vlan_TCI,
+				  htons(tests[i].vlan_id), "h_vlan_TCI");
+		}
+
 		ret = memcmp(tests[i].dmac, fib_params->dmac, sizeof(tests[i].dmac));
 		if (!ASSERT_EQ(ret, 0, "dmac not match")) {
 			char expected[18], actual[18];
@@ -361,17 +742,182 @@ void test_fib_lookup(void)
 			printf("dmac expected %s actual %s ", expected, actual);
 		}
 
-		// ensure tbid is zero'd out after fib lookup.
-		if (tests[i].lookup_flags & BPF_FIB_LOOKUP_DIRECT) {
+		/*
+		 * ensure tbid is zero'd out after fib lookup. With
+		 * BPF_FIB_LOOKUP_VLAN the union holds the packed vlan
+		 * fields instead, so skip the check for those.
+		 */
+		if ((tests[i].lookup_flags & BPF_FIB_LOOKUP_DIRECT) &&
+		    !(tests[i].lookup_flags & BPF_FIB_LOOKUP_VLAN)) {
 			if (!ASSERT_EQ(skel->bss->fib_params.tbid, 0,
 					"expected fib_params.tbid to be zero"))
 				goto fail;
 		}
 	}
 
+	/*
+	 * Re-run the cases through bpf_xdp_fib_lookup(). test_run uses the
+	 * current netns' loopback for ctx->rxq->dev, so dev_net() is NS_TEST
+	 * and the lookup runs against its FIB. The path-independent results
+	 * (return code, swapped ifindex, vlan tag, gateway) must match the skb
+	 * path; the no-tot_len mtu_result is skb-specific and not rechecked.
+	 */
+	for (i = 0; i < ARRAY_SIZE(tests); i++) {
+		if (set_lookup_params(fib_params, &tests[i], skb.ifindex))
+			continue;
+
+		skel->bss->fib_lookup_ret = -1;
+		skel->bss->lookup_flags = tests[i].lookup_flags;
+
+		err = bpf_prog_test_run_opts(xdp_fd, &xdp_opts);
+		if (!ASSERT_OK(err, "xdp test_run"))
+			continue;
+
+		if (!ASSERT_EQ(skel->bss->fib_lookup_ret, tests[i].expected_ret,
+			       "xdp fib_lookup_ret"))
+			printf("(xdp) %s\n", tests[i].desc);
+
+		if (tests[i].expected_dev)
+			ASSERT_EQ(fib_params->ifindex,
+				  if_nametoindex(tests[i].expected_dev),
+				  "xdp ifindex");
+
+		if (tests[i].expected_dst)
+			assert_dst_ip(fib_params, tests[i].expected_dst);
+
+		if (tests[i].check_vlan) {
+			ASSERT_EQ(fib_params->h_vlan_proto,
+				  htons(tests[i].vlan_proto), "xdp h_vlan_proto");
+			ASSERT_EQ(fib_params->h_vlan_TCI,
+				  htons(tests[i].vlan_id), "xdp h_vlan_TCI");
+		}
+	}
+
 fail:
 	if (nstoken)
 		close_netns(nstoken);
 	SYS_NOFAIL("ip netns del " NS_TEST);
 	fib_lookup__destroy(skel);
 }
+
+#define NS_VLAN_A	"fib_lookup_vlan_ns_a"
+#define NS_VLAN_B	"fib_lookup_vlan_ns_b"
+
+/*
+ * A VLAN device can be moved to another netns while staying registered
+ * on its parent. Neither direction may then cross the boundary: the
+ * egress flag must not publish the foreign parent's ifindex, and the
+ * input flag must fail closed rather than use a foreign ingress.
+ */
+void test_fib_lookup_vlan_netns(void)
+{
+	struct bpf_fib_lookup *fib_params;
+	struct nstoken *nstoken = NULL;
+	struct __sk_buff skb = { };
+	struct fib_lookup *skel = NULL;
+	int prog_fd, err, parent_idx, vlan_idx;
+
+	LIBBPF_OPTS(bpf_test_run_opts, run_opts,
+		    .data_in = &pkt_v6,
+		    .data_size_in = sizeof(pkt_v6),
+		    .ctx_in = &skb,
+		    .ctx_size_in = sizeof(skb),
+	);
+
+	skel = fib_lookup__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel open_and_load"))
+		return;
+	prog_fd = bpf_program__fd(skel->progs.fib_lookup);
+	fib_params = &skel->bss->fib_params;
+
+	SYS(fail, "ip netns add %s", NS_VLAN_A);
+	SYS(fail, "ip netns add %s", NS_VLAN_B);
+
+	nstoken = open_netns(NS_VLAN_A);
+	if (!ASSERT_OK_PTR(nstoken, "open_netns(a)"))
+		goto fail;
+
+	SYS(fail, "ip link add veth7 type veth peer name veth8");
+	SYS(fail, "ip link set dev veth7 up");
+	SYS(fail, "ip link add link veth7 name veth7.66 type vlan id 66");
+	SYS(fail, "ip link set veth7.66 netns %s", NS_VLAN_B);
+
+	parent_idx = if_nametoindex("veth7");
+	if (!ASSERT_NEQ(parent_idx, 0, "if_nametoindex(veth7)"))
+		goto fail;
+
+	/*
+	 * input: the moved device is still in veth7's VLAN group, but it
+	 * lives in another netns, so the lookup must fail closed
+	 */
+	skb.ifindex = parent_idx;
+	memset(fib_params, 0, sizeof(*fib_params));
+	fib_params->family = AF_INET;
+	fib_params->l4_protocol = IPPROTO_TCP;
+	fib_params->ifindex = parent_idx;
+	fib_params->h_vlan_proto = htons(ETH_P_8021Q);
+	fib_params->h_vlan_TCI = htons(66);
+	if (!ASSERT_EQ(inet_pton(AF_INET, "10.66.0.2", &fib_params->ipv4_dst),
+		       1, "inet_pton(dst)"))
+		goto fail;
+
+	skel->bss->fib_lookup_ret = -1;
+	skel->bss->lookup_flags = BPF_FIB_LOOKUP_VLAN_INPUT |
+				  BPF_FIB_LOOKUP_SKIP_NEIGH;
+	err = bpf_prog_test_run_opts(prog_fd, &run_opts);
+	if (!ASSERT_OK(err, "test_run(input)"))
+		goto fail;
+	ASSERT_EQ(skel->bss->fib_lookup_ret, BPF_FIB_LKUP_RET_NOT_FWDED,
+		  "input across netns fails closed");
+	ASSERT_EQ(fib_params->ifindex, parent_idx, "ifindex untouched");
+	ASSERT_EQ(fib_params->h_vlan_TCI, htons(66), "tag untouched");
+
+	close_netns(nstoken);
+	nstoken = open_netns(NS_VLAN_B);
+	if (!ASSERT_OK_PTR(nstoken, "open_netns(b)"))
+		goto fail;
+
+	/*
+	 * egress: the fib result is the VLAN device here, but its parent
+	 * is in the other netns, so the swap must not happen
+	 */
+	SYS(fail, "ip link set dev veth7.66 up");
+	SYS(fail, "ip addr add 10.66.0.1/24 dev veth7.66");
+	err = write_sysctl("/proc/sys/net/ipv4/conf/veth7.66/forwarding", "1");
+	if (!ASSERT_OK(err, "write_sysctl(forwarding)"))
+		goto fail;
+
+	vlan_idx = if_nametoindex("veth7.66");
+	if (!ASSERT_NEQ(vlan_idx, 0, "if_nametoindex(veth7.66)"))
+		goto fail;
+
+	skb.ifindex = vlan_idx;
+	memset(fib_params, 0, sizeof(*fib_params));
+	fib_params->family = AF_INET;
+	fib_params->l4_protocol = IPPROTO_TCP;
+	fib_params->ifindex = vlan_idx;
+	if (!ASSERT_EQ(inet_pton(AF_INET, "10.66.0.2", &fib_params->ipv4_dst),
+		       1, "inet_pton(dst)") ||
+	    !ASSERT_EQ(inet_pton(AF_INET, "10.66.0.1", &fib_params->ipv4_src),
+		       1, "inet_pton(src)"))
+		goto fail;
+
+	skel->bss->fib_lookup_ret = -1;
+	skel->bss->lookup_flags = BPF_FIB_LOOKUP_VLAN |
+				  BPF_FIB_LOOKUP_SKIP_NEIGH;
+	err = bpf_prog_test_run_opts(prog_fd, &run_opts);
+	if (!ASSERT_OK(err, "test_run(egress)"))
+		goto fail;
+	ASSERT_EQ(skel->bss->fib_lookup_ret, BPF_FIB_LKUP_RET_SUCCESS,
+		  "egress lookup succeeds");
+	ASSERT_EQ(fib_params->ifindex, vlan_idx,
+		  "foreign parent not published");
+	ASSERT_EQ(fib_params->h_vlan_TCI, 0, "vlan fields zero");
+
+fail:
+	if (nstoken)
+		close_netns(nstoken);
+	SYS_NOFAIL("ip netns del " NS_VLAN_A);
+	SYS_NOFAIL("ip netns del " NS_VLAN_B);
+	fib_lookup__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/progs/fib_lookup.c b/tools/testing/selftests/bpf/progs/fib_lookup.c
index 7b5dd2214ff4..f43e22d33814 100644
--- a/tools/testing/selftests/bpf/progs/fib_lookup.c
+++ b/tools/testing/selftests/bpf/progs/fib_lookup.c
@@ -19,4 +19,13 @@ int fib_lookup(struct __sk_buff *skb)
 	return TC_ACT_SHOT;
 }
 
+SEC("xdp")
+int fib_lookup_xdp(struct xdp_md *ctx)
+{
+	fib_lookup_ret = bpf_fib_lookup(ctx, &fib_params, sizeof(fib_params),
+					lookup_flags);
+
+	return XDP_DROP;
+}
+
 char _license[] SEC("license") = "GPL";
-- 
2.54.0

Re: [PATCH bpf-next v3 0/3] bpf: bidirectional VLAN support for bpf_fib_lookup()

[Toke Høiland-Jørgensen]

Avinash Duduskar <avinash.duduskar@gmail.com> writes:

> This series adds VLAN awareness to bpf_fib_lookup() in both directions.
> BPF_FIB_LOOKUP_VLAN resolves a VLAN egress to its underlying real device
> plus the VLAN tag (XDP programs need this because VLAN devices have no XDP
> xmit), and BPF_FIB_LOOKUP_VLAN_INPUT runs the lookup as if a tagged frame
> had arrived on the matching VLAN subinterface, for iif policy routing and
> VRF table selection.
>
> The l3mdev/VRF flow-init fix that was patch 1 in v1 and v2 has been split
> out and sent to bpf on its own, since it is an independent Fixes:-tagged
> fix that routes to stable on its own schedule. This series is otherwise
> independent of it: on the default CONFIG_INIT_STACK_ALL_ZERO the VRF
> selftests pass with or without the fix. Only the one full-lookup VRF arm
> ("IPv4 VLAN input, tag selects VRF table") depends on it, and only on
> INIT_STACK_ALL_PATTERN or NONE builds, where the uninitialized
> flowi_l3mdev otherwise misses the l3mdev rule and the lookup falls
> through to the main table. Applying the l3mdev fix first closes that
> window.
>
> Changes v2 -> v3 (all from Toke's review unless noted):
>
> - Split the l3mdev/VRF flow-init fix out to a standalone bpf submission
>   (it was patch 1 in v2).
>
> - Patch 2 (VLAN_INPUT): bpf_fib_vlan_input_dev() returns a
>   struct net_device * with ERR_PTR() for the -EINVAL case and NULL for
>   NOT_FWDED, instead of an int return and a **dev out-parameter.
>
> - Trim the BPF_FIB_LOOKUP_VLAN and BPF_FIB_LOOKUP_VLAN_INPUT UAPI doc
>   blocks, and drop the in-function comments that restated the commit
>   message or the flag doc.
>
> - Patch 1 (VLAN egress): on the skb path without tot_len, the deferred mtu
>   check now runs against the resolved egress (VLAN) device, not the parent
>   params->ifindex was swapped to, so a VLAN device with a smaller mtu than
>   its parent is no longer checked against, or reported as, the parent's
>   larger mtu. Found by the bpf ci bot; this was an open question in v2.
>
> - Patch 3 (selftests): re-run every case through bpf_xdp_fib_lookup() as
>   well, since the feature targets XDP; and flip the no-tot_len mtu arm to
>   expect the VLAN device's mtu after the fix above.
>
> Open questions (defaults chosen, noted here in case a maintainer
> prefers otherwise):
>
> 1. An unmatched, down, or foreign-netns tag returns
>    BPF_FIB_LKUP_RET_NOT_FWDED, matching the DIRECT path when
>    fib_get_table() finds no table, rather than a new return code.
>
> 2. BPF_FIB_LOOKUP_OUTPUT | BPF_FIB_LOOKUP_VLAN_INPUT is rejected with
>    -EINVAL; restricting now keeps relaxing later backward-compatible.
>
> 3. The name BPF_FIB_LOOKUP_VLAN_INPUT reads oddly next to
>    BPF_FIB_LOOKUP_OUTPUT. A pair like _VLAN_EGRESS/_VLAN_INGRESS is an
>    option while nothing is merged.

These three are fine as-is, I think.

> 4. The egress flag leaves a VLAN it cannot reduce to a physical parent
>    plus one tag (QinQ, or a parent in another namespace) as SUCCESS with
>    the VLAN device's ifindex and the vlan fields zero, like a plain
>    lookup. The input side instead fails closed (NOT_FWDED) on the
>    cross-namespace case. An XDP caller cannot xmit on a VLAN device, and
>    a zero h_vlan_proto does not distinguish this result from a physical
>    egress, so returning NOT_FWDED would be safer for XDP. But the two
>    cases differ: a foreign-netns parent is clearly fail-worthy, while a
>    QinQ egress is still a forwardable route (tc xmits on the inner VLAN
>    device), so failing it closed would reject a usable route. Should
>    egress signal NOT_FWDED, for both or only foreign-netns? I left it
>    best-effort, but will change it if you prefer.

This one is a bit more ambiguous. Specifically, the inability for an XDP
program to distinguish between a route that actually targets a physical
device, and one that targets a VLAN device that couldn't be resolved for
whatever reason.

Since this is a new feature that's opt-in, I think I would lean towards
failing lookups with a new error code (BPF_FIB_LKUP_RET_VLAN_FAILURE,
say) if the lookup finds a VLAN device but can't actually resolve the
parent. That way the XDP program can repeat the lookup without the
BPF_FIB_LOOKUP_VLAN flag if it really wants the ifindex of that VLAN
device, but that will be explicit and not hidden.

-Toke