* [PATCH net-next v2] netlink: policy: report the big endian attributes
@ 2026-09-12 20:24 Jakub Kicinski
0 siblings, 0 replies; only message in thread
From: Jakub Kicinski @ 2026-09-12 20:24 UTC (permalink / raw)
To: davem
Cc: netdev, edumazet, pabeni, andrew+netdev, horms, Jakub Kicinski,
donald.hunter, johannes, fw, pablo
Paolo pointed out an issue flagged at low priority by Sashiko -
we're currently not handling BE{16,32} attributes in policy dumps.
Commit 3f4285d741b4 ("netlink: specs: fou: local-v4 and peer-v4 are big
endian") flipped two fou attributes from NLA_U32 to NLA_BE32.
This made them vanish from the policy dump.
Follow the YAML spec format and treat byte order as a property of
a u16 / u32 rather than a type of its own. I don't have a strong
preference either way. The YNL format "feels cleaner" but the
kernel's separate type is easier when handling decoding.
I don't think that the policy type is actually usable for decoding
(since it only contains input types) so I went with YNL and added
the separate attr.
A missing byte order means host order, again like in the YAML specs.
Link: https://lore.kernel.org/ab90f970-0ebb-4c07-b7b1-db3f91395116@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
v2:
- add netlink.h to Makefile.deps of nlctrl (fix tools build)
v1: https://lore.kernel.org/20260908235500.1642031-1-kuba@kernel.org
CC: donald.hunter@gmail.com
CC: johannes@sipsolutions.net
CC: fw@strlen.de
CC: pablo@netfilter.org
---
Documentation/netlink/specs/nlctrl.yaml | 15 +++++++++++++++
tools/net/ynl/Makefile.deps | 3 ++-
include/uapi/linux/netlink.h | 14 ++++++++++++++
net/netlink/policy.c | 16 ++++++++++++++--
tools/net/ynl/pyynl/lib/ynl.py | 8 +++++++-
5 files changed, 52 insertions(+), 4 deletions(-)
diff --git a/Documentation/netlink/specs/nlctrl.yaml b/Documentation/netlink/specs/nlctrl.yaml
index 8b4472a6aa36..7e7c158e3e73 100644
--- a/Documentation/netlink/specs/nlctrl.yaml
+++ b/Documentation/netlink/specs/nlctrl.yaml
@@ -42,6 +42,16 @@ doc: |
- bitfield32
- sint
- uint
+ -
+ name: policy-byte-order
+ doc: |
+ Byte order of an integer attribute. Zero is left unused so that it
+ can be taken to mean host byte order.
+ enum-name: netlink-policy-byte-order
+ type: enum
+ value-start: 1
+ entries:
+ - big-endian
attribute-sets:
-
@@ -152,6 +162,11 @@ doc: |
-
name: pad
type: pad
+ -
+ name: byte-order
+ doc: Byte order of the attribute, absent means host byte order.
+ type: u32
+ enum: policy-byte-order
-
name: op-policy-attrs
name-prefix: ctrl-attr-policy-
diff --git a/tools/net/ynl/Makefile.deps b/tools/net/ynl/Makefile.deps
index 2771375339d9..1e746e25e2bc 100644
--- a/tools/net/ynl/Makefile.deps
+++ b/tools/net/ynl/Makefile.deps
@@ -30,7 +30,8 @@ CFLAGS_mptcp_pm:=$(call get_hdr_inc,_LINUX_MPTCP_PM_H,mptcp_pm.h)
CFLAGS_net_shaper:=$(call get_hdr_inc,_LINUX_NET_SHAPER_H,net_shaper.h)
CFLAGS_netdev:=$(call get_hdr_inc,_LINUX_NETDEV_H,netdev.h)
CFLAGS_nl80211:=$(call get_hdr_inc,__LINUX_NL802121_H,nl80211.h)
-CFLAGS_nlctrl:=$(call get_hdr_inc,__LINUX_GENERIC_NETLINK_H,genetlink.h)
+CFLAGS_nlctrl:=$(call get_hdr_inc,__LINUX_GENERIC_NETLINK_H,genetlink.h) \
+ $(call get_hdr_inc,__LINUX_NETLINK_H,netlink.h)
CFLAGS_nfsd:=$(call get_hdr_inc,_LINUX_NFSD_NETLINK_H,nfsd_netlink.h)
CFLAGS_ovpn:=$(call get_hdr_inc,_LINUX_OVPN_H,ovpn.h)
CFLAGS_ovs_datapath:=$(call get_hdr_inc,__LINUX_OPENVSWITCH_H,openvswitch.h)
diff --git a/include/uapi/linux/netlink.h b/include/uapi/linux/netlink.h
index f87aaf28a649..82c41aeb4357 100644
--- a/include/uapi/linux/netlink.h
+++ b/include/uapi/linux/netlink.h
@@ -329,6 +329,17 @@ enum netlink_attribute_type {
NL_ATTR_TYPE_UINT,
};
+/**
+ * enum netlink_policy_byte_order - byte order of an integer attribute
+ * @NL_POLICY_BYTE_ORDER_BIG_ENDIAN: big endian (network byte order)
+ *
+ * Zero is left unassigned so that it keeps meaning host byte order,
+ * which is also what a missing byte order means.
+ */
+enum netlink_policy_byte_order {
+ NL_POLICY_BYTE_ORDER_BIG_ENDIAN = 1,
+};
+
/**
* enum netlink_policy_type_attr - policy type attributes
* @NL_POLICY_TYPE_ATTR_UNSPEC: unused
@@ -356,6 +367,8 @@ enum netlink_attribute_type {
* bitfield32 type (U32)
* @NL_POLICY_TYPE_ATTR_MASK: mask of valid bits for unsigned integers (U64)
* @NL_POLICY_TYPE_ATTR_PAD: pad attribute for 64-bit alignment
+ * @NL_POLICY_TYPE_ATTR_BYTE_ORDER: byte order of an integer attribute,
+ * &enum netlink_policy_byte_order, absent if host byte order (U32)
*
* @__NL_POLICY_TYPE_ATTR_MAX: number of attributes
* @NL_POLICY_TYPE_ATTR_MAX: highest attribute number
@@ -374,6 +387,7 @@ enum netlink_policy_type_attr {
NL_POLICY_TYPE_ATTR_BITFIELD32_MASK,
NL_POLICY_TYPE_ATTR_PAD,
NL_POLICY_TYPE_ATTR_MASK,
+ NL_POLICY_TYPE_ATTR_BYTE_ORDER,
/* keep last */
__NL_POLICY_TYPE_ATTR_MAX,
diff --git a/net/netlink/policy.c b/net/netlink/policy.c
index 08b006c48f06..574d44b7d518 100644
--- a/net/netlink/policy.c
+++ b/net/netlink/policy.c
@@ -234,6 +234,11 @@ int netlink_policy_dump_attr_size_estimate(const struct nla_policy *pt)
/* maximum is common, u64 min/max with padding */
return common +
2 * (nla_attr_size(0) + nla_attr_size(sizeof(u64)));
+ case NLA_BE16:
+ case NLA_BE32:
+ /* same as the unsigned types, plus the byte order */
+ return common + nla_attr_size(sizeof(u32)) +
+ 2 * (nla_attr_size(0) + nla_attr_size(sizeof(u64)));
case NLA_BITFIELD32:
return common + nla_attr_size(sizeof(u32));
case NLA_STRING:
@@ -289,21 +294,28 @@ __netlink_policy_dump_write_attr(struct netlink_policy_dump_state *state,
case NLA_U16:
case NLA_U32:
case NLA_U64:
+ case NLA_BE16:
+ case NLA_BE32:
case NLA_UINT:
case NLA_MSECS: {
struct netlink_range_validation range;
if (pt->type == NLA_U8)
type = NL_ATTR_TYPE_U8;
- else if (pt->type == NLA_U16)
+ else if (pt->type == NLA_U16 || pt->type == NLA_BE16)
type = NL_ATTR_TYPE_U16;
- else if (pt->type == NLA_U32)
+ else if (pt->type == NLA_U32 || pt->type == NLA_BE32)
type = NL_ATTR_TYPE_U32;
else if (pt->type == NLA_U64)
type = NL_ATTR_TYPE_U64;
else
type = NL_ATTR_TYPE_UINT;
+ if ((pt->type == NLA_BE16 || pt->type == NLA_BE32) &&
+ nla_put_u32(skb, NL_POLICY_TYPE_ATTR_BYTE_ORDER,
+ NL_POLICY_BYTE_ORDER_BIG_ENDIAN))
+ goto nla_put_failure;
+
if (pt->validation_type == NLA_VALIDATE_MASK) {
if (nla_put_u64_64bit(skb, NL_POLICY_TYPE_ATTR_MASK,
pt->mask,
diff --git a/tools/net/ynl/pyynl/lib/ynl.py b/tools/net/ynl/pyynl/lib/ynl.py
index 8682bf588e1f..fb5acb8acded 100644
--- a/tools/net/ynl/pyynl/lib/ynl.py
+++ b/tools/net/ynl/pyynl/lib/ynl.py
@@ -115,6 +115,7 @@ from .nlspec import SpecFamily
NL_POLICY_TYPE_ATTR_BITFIELD32_MASK = 10
NL_POLICY_TYPE_ATTR_PAD = 11
NL_POLICY_TYPE_ATTR_MASK = 12
+ NL_POLICY_TYPE_ATTR_BYTE_ORDER = 13
AttrType = Enum('AttrType', ['flag', 'u8', 'u16', 'u32', 'u64',
's8', 's16', 's32', 's64',
@@ -122,6 +123,8 @@ from .nlspec import SpecFamily
'nested', 'nested-array',
'bitfield32', 'sint', 'uint'])
+ ByteOrder = Enum('ByteOrder', ['big-endian'], start=1)
+
class NlError(Exception):
def __init__(self, nl_msg):
self.nl_msg = nl_msg
@@ -158,7 +161,7 @@ from .nlspec import SpecFamily
Each policy entry always has a 'type' attribute (e.g. u32, string,
nested). Optional attributes depending on the 'type': min-value,
- max-value, min-length, max-length, mask.
+ max-value, min-length, max-length, mask, byte-order.
Policies can form infinite nesting loops. These loops are trimmed
when policy is converted to a dict with pol.to_dict().
@@ -454,6 +457,9 @@ from .nlspec import SpecFamily
policy['bitfield32-mask'] = attr.as_scalar('u32')
elif attr.type == Netlink.NL_POLICY_TYPE_ATTR_MASK:
policy['mask'] = attr.as_scalar('u64')
+ elif attr.type == Netlink.NL_POLICY_TYPE_ATTR_BYTE_ORDER:
+ byte_order = attr.as_scalar('u32')
+ policy['byte-order'] = Netlink.ByteOrder(byte_order).name
return policy
--
2.55.0
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