[RFC bpf-next 09/23] xdp: Add VLAN tag hint

Larysa Zaremba
2023-08-24T19:34:16Z

Implement functionality that enables drivers to expose VLAN tag
to XDP code.

Signed-off-by: Larysa Zaremba <larysa.zaremba@intel.com>
---
Documentation/networking/xdp-rx-metadata.rst | 8 ++++-
include/net/xdp.h | 4 +++
kernel/bpf/offload.c | 2 ++
net/core/xdp.c | 34 ++++++++++++++++++++
4 files changed, 47 insertions(+), 1 deletion(-)

diff --git a/Documentation/networking/xdp-rx-metadata.rst b/Documentation/networking/xdp-rx-metadata.rst
index 25ce72af81c2..ea6dd79a21d3 100644
--- a/Documentation/networking/xdp-rx-metadata.rst
+++ b/Documentation/networking/xdp-rx-metadata.rst
@@ -18,7 +18,13 @@ Currently, the following kfuncs are supported. In the future, as more
metadata is supported, this set will grow:

.. kernel-doc:: net/core/xdp.c
- :identifiers: bpf_xdp_metadata_rx_timestamp bpf_xdp_metadata_rx_hash
+ :identifiers: bpf_xdp_metadata_rx_timestamp
+
+.. kernel-doc:: net/core/xdp.c
+ :identifiers: bpf_xdp_metadata_rx_hash
+
+.. kernel-doc:: net/core/xdp.c
+ :identifiers: bpf_xdp_metadata_rx_vlan_tag

An XDP program can use these kfuncs to read the metadata into stack
variables for its own consumption. Or, to pass the metadata on to other
diff --git a/include/net/xdp.h b/include/net/xdp.h
index 1e9870d5f025..8bb64fc76498 100644
--- a/include/net/xdp.h
+++ b/include/net/xdp.h
@@ -388,6 +388,8 @@ void xdp_attachment_setup(struct xdp_attachment_info *info,
bpf_xdp_metadata_rx_timestamp) \
XDP_METADATA_KFUNC(XDP_METADATA_KFUNC_RX_HASH, \
bpf_xdp_metadata_rx_hash) \
+ XDP_METADATA_KFUNC(XDP_METADATA_KFUNC_RX_VLAN_TAG, \
+ bpf_xdp_metadata_rx_vlan_tag) \

enum {
#define XDP_METADATA_KFUNC(name, _) name,
@@ -449,6 +451,8 @@ struct xdp_metadata_ops {
int (*xmo_rx_timestamp)(const struct xdp_md *ctx, u64 *timestamp);
int (*xmo_rx_hash)(const struct xdp_md *ctx, u32 *hash,
enum xdp_rss_hash_type *rss_type);
+ int (*xmo_rx_vlan_tag)(const struct xdp_md *ctx, u16 *vlan_tci,
+ __be16 *vlan_proto);
};

#ifdef CONFIG_NET
diff --git a/kernel/bpf/offload.c b/kernel/bpf/offload.c
index 3e4f2ec1af06..8be340cf06f9 100644
--- a/kernel/bpf/offload.c
+++ b/kernel/bpf/offload.c
@@ -849,6 +849,8 @@ void *bpf_dev_bound_resolve_kfunc(struct bpf_prog *prog, u32 func_id)
p = ops->xmo_rx_timestamp;
else if (func_id == bpf_xdp_metadata_kfunc_id(XDP_METADATA_KFUNC_RX_HASH))
p = ops->xmo_rx_hash;
+ else if (func_id == bpf_xdp_metadata_kfunc_id(XDP_METADATA_KFUNC_RX_VLAN_TAG))
+ p = ops->xmo_rx_vlan_tag;
out:
up_read(&bpf_devs_lock);

diff --git a/net/core/xdp.c b/net/core/xdp.c
index a70670fe9a2d..856e02bb4ce6 100644
--- a/net/core/xdp.c
+++ b/net/core/xdp.c
@@ -738,6 +738,40 @@ __bpf_kfunc int bpf_xdp_metadata_rx_hash(const struct xdp_md *ctx, u32 *hash,
return -EOPNOTSUPP;
}

+/**
+ * bpf_xdp_metadata_rx_vlan_tag - Get XDP packet outermost VLAN tag
+ * @ctx: XDP context pointer.
+ * @vlan_tci: Destination pointer for VLAN TCI (VID + DEI + PCP)
+ * @vlan_proto: Destination pointer for VLAN Tag protocol identifier (TPID).
+ *
+ * In case of success, ``vlan_proto`` contains *Tag protocol identifier (TPID)*,
+ * usually ``ETH_P_8021Q`` or ``ETH_P_8021AD``, but some networks can use
+ * custom TPIDs. ``vlan_proto`` is stored in **network byte order (BE)**
+ * and should be used as follows:
+ * ``if (vlan_proto == bpf_htons(ETH_P_8021Q)) do_something();``
+ *
+ * ``vlan_tci`` contains the remaining 16 bits of a VLAN tag.
+ * Driver is expected to provide those in **host byte order (usually LE)**,
+ * so the bpf program should not perform byte conversion.
+ * According to 802.1Q standard, *VLAN TCI (Tag control information)*
+ * is a bit field that contains:
+ * *VLAN identifier (VID)* that can be read with ``vlan_tci & 0xfff``,
+ * *Drop eligible indicator (DEI)* - 1 bit,
+ * *Priority code point (PCP)* - 3 bits.
+ * For detailed meaning of DEI and PCP, please refer to other sources.
+ *
+ * Return:
+ * * Returns 0 on success or ``-errno`` on error.
+ * * ``-EOPNOTSUPP`` : device driver doesn't implement kfunc
+ * * ``-ENODATA`` : VLAN tag was not stripped or is not available
+ */
+__bpf_kfunc int bpf_xdp_metadata_rx_vlan_tag(const struct xdp_md *ctx,
+ u16 *vlan_tci,
+ __be16 *vlan_proto)
+{
+ return -EOPNOTSUPP;
+}
+
__diag_pop();

BTF_SET8_START(xdp_metadata_kfunc_ids)
--
2.41.0