[PATCH net-next v2 0/6] netlink: support reporting missing attributes

[PATCH net-next v2 0/6] netlink: support reporting missing attributes

[Jakub Kicinski]

This series adds support for reporting missing attributes
in a structured way. We can't point at things which don't
exist so we point at the containing nest or preceding
fixed header and report which attr type we expected to see.

Example of (YAML-based) user space reporting ethtool header
missing:

 Kernel error: missing attribute: .header

I was tempted to integrate the check with the policy
but it seems tricky without doing a full scan, and there
may be a ton of attrs in the policy. So leaving that
for later.

v2:
 - add patch 1
 - remove the nest attr if the attr is missing in the root

Jakub Kicinski (6):
  netlink: factor out extack composition
  netlink: add support for ext_ack missing attributes
  netlink: add helpers for extack attr presence checking
  devlink: use missing attribute ext_ack
  ethtool: strset: report missing ETHTOOL_A_STRINGSET_ID via ext_ack
  ethtool: report missing header via ext_ack in the default handler

 Documentation/userspace-api/netlink/intro.rst |  7 +-
 include/linux/netlink.h                       | 24 +++++
 include/net/genetlink.h                       |  7 ++
 include/uapi/linux/netlink.h                  |  6 ++
 net/core/devlink.c                            | 41 ++++----
 net/ethtool/netlink.c                         |  3 +
 net/ethtool/strset.c                          |  2 +-
 net/netlink/af_netlink.c                      | 97 +++++++++++++------
 8 files changed, 133 insertions(+), 54 deletions(-)

-- 
2.37.2

[PATCH net-next v2 1/6] netlink: factor out extack composition

[Jakub Kicinski]

The ext_ack writing code looks very "organically grown".
Move the calculation of the size and writing out to helpers.
This is more idiomatic and gives us the ability to return early
avoiding the long (and randomly ordered) "if" conditions.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
--
v2: new patch
---
CC: fw@strlen.de
---
 net/netlink/af_netlink.c | 85 ++++++++++++++++++++++++++--------------
 1 file changed, 55 insertions(+), 30 deletions(-)

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 0cd91f813a3b..9bcbe491c798 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -2400,6 +2400,57 @@ int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
 }
 EXPORT_SYMBOL(__netlink_dump_start);
 
+static size_t
+netlink_ack_tlv_len(struct netlink_sock *nlk, int err,
+		    const struct netlink_ext_ack *extack)
+{
+	size_t tlvlen;
+
+	if (!extack || !(nlk->flags & NETLINK_F_EXT_ACK))
+		return 0;
+
+	tlvlen = 0;
+	if (extack->_msg)
+		tlvlen += nla_total_size(strlen(extack->_msg) + 1);
+	if (extack->cookie_len)
+		tlvlen += nla_total_size(extack->cookie_len);
+
+	/* Following attributes are only reported as error (not warning) */
+	if (!err)
+		return tlvlen;
+
+	if (extack->bad_attr)
+		tlvlen += nla_total_size(sizeof(u32));
+	if (extack->policy)
+		tlvlen += netlink_policy_dump_attr_size_estimate(extack->policy);
+
+	return tlvlen;
+}
+
+static void
+netlink_ack_tlv_fill(struct sk_buff *in_skb, struct sk_buff *skb,
+		     struct nlmsghdr *nlh,  int err,
+		     const struct netlink_ext_ack *extack)
+{
+	if (extack->_msg)
+		WARN_ON(nla_put_string(skb, NLMSGERR_ATTR_MSG, extack->_msg));
+	if (extack->cookie_len)
+		WARN_ON(nla_put(skb, NLMSGERR_ATTR_COOKIE,
+				extack->cookie_len, extack->cookie));
+
+	if (!err)
+		return;
+
+	if (extack->bad_attr &&
+	    !WARN_ON((u8 *)extack->bad_attr < in_skb->data ||
+		     (u8 *)extack->bad_attr >= in_skb->data + in_skb->len))
+		WARN_ON(nla_put_u32(skb, NLMSGERR_ATTR_OFFS,
+				    (u8 *)extack->bad_attr - (u8 *)nlh));
+	if (extack->policy)
+		netlink_policy_dump_write_attr(skb, extack->policy,
+					       NLMSGERR_ATTR_POLICY);
+}
+
 void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err,
 		 const struct netlink_ext_ack *extack)
 {
@@ -2407,29 +2458,20 @@ void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err,
 	struct nlmsghdr *rep;
 	struct nlmsgerr *errmsg;
 	size_t payload = sizeof(*errmsg);
-	size_t tlvlen = 0;
 	struct netlink_sock *nlk = nlk_sk(NETLINK_CB(in_skb).sk);
 	unsigned int flags = 0;
-	bool nlk_has_extack = nlk->flags & NETLINK_F_EXT_ACK;
+	size_t tlvlen;
 
 	/* Error messages get the original request appened, unless the user
 	 * requests to cap the error message, and get extra error data if
 	 * requested.
 	 */
-	if (nlk_has_extack && extack && extack->_msg)
-		tlvlen += nla_total_size(strlen(extack->_msg) + 1);
-
 	if (err && !(nlk->flags & NETLINK_F_CAP_ACK))
 		payload += nlmsg_len(nlh);
 	else
 		flags |= NLM_F_CAPPED;
-	if (err && nlk_has_extack && extack && extack->bad_attr)
-		tlvlen += nla_total_size(sizeof(u32));
-	if (nlk_has_extack && extack && extack->cookie_len)
-		tlvlen += nla_total_size(extack->cookie_len);
-	if (err && nlk_has_extack && extack && extack->policy)
-		tlvlen += netlink_policy_dump_attr_size_estimate(extack->policy);
 
+	tlvlen = netlink_ack_tlv_len(nlk, err, extack);
 	if (tlvlen)
 		flags |= NLM_F_ACK_TLVS;
 
@@ -2446,25 +2488,8 @@ void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err,
 	errmsg->error = err;
 	memcpy(&errmsg->msg, nlh, payload > sizeof(*errmsg) ? nlh->nlmsg_len : sizeof(*nlh));
 
-	if (nlk_has_extack && extack) {
-		if (extack->_msg) {
-			WARN_ON(nla_put_string(skb, NLMSGERR_ATTR_MSG,
-					       extack->_msg));
-		}
-		if (err && extack->bad_attr &&
-		    !WARN_ON((u8 *)extack->bad_attr < in_skb->data ||
-			     (u8 *)extack->bad_attr >= in_skb->data +
-						       in_skb->len))
-			WARN_ON(nla_put_u32(skb, NLMSGERR_ATTR_OFFS,
-					    (u8 *)extack->bad_attr -
-					    (u8 *)nlh));
-		if (extack->cookie_len)
-			WARN_ON(nla_put(skb, NLMSGERR_ATTR_COOKIE,
-					extack->cookie_len, extack->cookie));
-		if (extack->policy)
-			netlink_policy_dump_write_attr(skb, extack->policy,
-						       NLMSGERR_ATTR_POLICY);
-	}
+	if (tlvlen)
+		netlink_ack_tlv_fill(in_skb, skb, nlh, err, extack);
 
 	nlmsg_end(skb, rep);
 
-- 
2.37.2

[PATCH net-next v2 2/6] netlink: add support for ext_ack missing attributes

[Jakub Kicinski]

There is currently no way to report via extack in a structured way
that an attribute is missing. This leads to families resorting to
string messages.

Add a pair of attributes - @offset and @type for machine-readable
way of reporting missing attributes. The @offset points to the
nest which should have contained the attribute, @type is the
expected nla_type. The offset will be skipped if the attribute
is missing at the message level rather than inside a nest.

User space should be able to figure out which attribute enum
(AKA attribute space AKA attribute set) the nest pointed to by
@offset is using.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
--
v2: use missing nest as indication of root attrs (Johannes)
---
CC: corbet@lwn.net
CC: jacob.e.keller@intel.com
CC: fw@strlen.de
CC: razor@blackwall.org
CC: linux-doc@vger.kernel.org
---
 Documentation/userspace-api/netlink/intro.rst |  7 +++++--
 include/linux/netlink.h                       | 13 +++++++++++++
 include/uapi/linux/netlink.h                  |  6 ++++++
 net/netlink/af_netlink.c                      | 12 ++++++++++++
 4 files changed, 36 insertions(+), 2 deletions(-)

diff --git a/Documentation/userspace-api/netlink/intro.rst b/Documentation/userspace-api/netlink/intro.rst
index 94337f79e077..8f1220756412 100644
--- a/Documentation/userspace-api/netlink/intro.rst
+++ b/Documentation/userspace-api/netlink/intro.rst
@@ -359,8 +359,8 @@ compatibility this feature has to be explicitly enabled by setting
 the ``NETLINK_EXT_ACK`` setsockopt() to ``1``.
 
 Types of extended ack attributes are defined in enum nlmsgerr_attrs.
-The two most commonly used attributes are ``NLMSGERR_ATTR_MSG``
-and ``NLMSGERR_ATTR_OFFS``.
+The most commonly used attributes are ``NLMSGERR_ATTR_MSG``,
+``NLMSGERR_ATTR_OFFS`` and ``NLMSGERR_ATTR_MISS_*``.
 
 ``NLMSGERR_ATTR_MSG`` carries a message in English describing
 the encountered problem. These messages are far more detailed
@@ -368,6 +368,9 @@ than what can be expressed thru standard UNIX error codes.
 
 ``NLMSGERR_ATTR_OFFS`` points to the attribute which caused the problem.
 
+``NLMSGERR_ATTR_MISS_TYPE`` and ``NLMSGERR_ATTR_MISS_NEST``
+inform about a missing attribute.
+
 Extended ACKs can be reported on errors as well as in case of success.
 The latter should be treated as a warning.
 
diff --git a/include/linux/netlink.h b/include/linux/netlink.h
index bda1c385cffb..2e647157f383 100644
--- a/include/linux/netlink.h
+++ b/include/linux/netlink.h
@@ -71,6 +71,8 @@ netlink_kernel_create(struct net *net, int unit, struct netlink_kernel_cfg *cfg)
  *	%NL_SET_ERR_MSG
  * @bad_attr: attribute with error
  * @policy: policy for a bad attribute
+ * @miss_type: attribute type which was missing
+ * @miss_nest: nest missing an attribute (NULL if missing top level attr)
  * @cookie: cookie data to return to userspace (for success)
  * @cookie_len: actual cookie data length
  */
@@ -78,6 +80,8 @@ struct netlink_ext_ack {
 	const char *_msg;
 	const struct nlattr *bad_attr;
 	const struct nla_policy *policy;
+	const void *miss_nest;
+	u16 miss_type;
 	u8 cookie[NETLINK_MAX_COOKIE_LEN];
 	u8 cookie_len;
 };
@@ -126,6 +130,15 @@ struct netlink_ext_ack {
 #define NL_SET_ERR_MSG_ATTR(extack, attr, msg)		\
 	NL_SET_ERR_MSG_ATTR_POL(extack, attr, NULL, msg)
 
+#define NL_SET_ERR_ATTR_MISS(extack, nest, type)  do {	\
+	struct netlink_ext_ack *__extack = (extack);	\
+							\
+	if (__extack) {					\
+		__extack->miss_nest = (nest);		\
+		__extack->miss_type = (type);		\
+	}						\
+} while (0)
+
 static inline void nl_set_extack_cookie_u64(struct netlink_ext_ack *extack,
 					    u64 cookie)
 {
diff --git a/include/uapi/linux/netlink.h b/include/uapi/linux/netlink.h
index e0ab261ceca2..e0689dbd2cde 100644
--- a/include/uapi/linux/netlink.h
+++ b/include/uapi/linux/netlink.h
@@ -140,6 +140,10 @@ struct nlmsgerr {
  *	be used - in the success case - to identify a created
  *	object or operation or similar (binary)
  * @NLMSGERR_ATTR_POLICY: policy for a rejected attribute
+ * @NLMSGERR_ATTR_MISS_TYPE: type of a missing required attribute,
+ *	%NLMSGERR_ATTR_MISS_NEST will not be present if the attribute was
+ *	missing at the message level
+ * @NLMSGERR_ATTR_MISS_NEST: offset of the nest where attribute was missing
  * @__NLMSGERR_ATTR_MAX: number of attributes
  * @NLMSGERR_ATTR_MAX: highest attribute number
  */
@@ -149,6 +153,8 @@ enum nlmsgerr_attrs {
 	NLMSGERR_ATTR_OFFS,
 	NLMSGERR_ATTR_COOKIE,
 	NLMSGERR_ATTR_POLICY,
+	NLMSGERR_ATTR_MISS_TYPE,
+	NLMSGERR_ATTR_MISS_NEST,
 
 	__NLMSGERR_ATTR_MAX,
 	NLMSGERR_ATTR_MAX = __NLMSGERR_ATTR_MAX - 1
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 9bcbe491c798..8b9a372b09b3 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -2423,6 +2423,10 @@ netlink_ack_tlv_len(struct netlink_sock *nlk, int err,
 		tlvlen += nla_total_size(sizeof(u32));
 	if (extack->policy)
 		tlvlen += netlink_policy_dump_attr_size_estimate(extack->policy);
+	if (extack->miss_type)
+		tlvlen += nla_total_size(sizeof(u32));
+	if (extack->miss_nest)
+		tlvlen += nla_total_size(sizeof(u32));
 
 	return tlvlen;
 }
@@ -2449,6 +2453,14 @@ netlink_ack_tlv_fill(struct sk_buff *in_skb, struct sk_buff *skb,
 	if (extack->policy)
 		netlink_policy_dump_write_attr(skb, extack->policy,
 					       NLMSGERR_ATTR_POLICY);
+	if (extack->miss_type)
+		WARN_ON(nla_put_u32(skb, NLMSGERR_ATTR_MISS_TYPE,
+				    extack->miss_type));
+	if (extack->miss_nest &&
+	    !WARN_ON((u8 *)extack->miss_nest < in_skb->data ||
+		     (u8 *)extack->miss_nest > in_skb->data + in_skb->len))
+		WARN_ON(nla_put_u32(skb, NLMSGERR_ATTR_MISS_NEST,
+				    (u8 *)extack->miss_nest - (u8 *)nlh));
 }
 
 void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err,
-- 
2.37.2

[PATCH net-next v2 3/6] netlink: add helpers for extack attr presence checking

[Jakub Kicinski]

Being able to check attribute presence and set extack
if not on one line is handy, add helpers.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
--
v2: squash old genetlink and netlink patches now that
    we don't need special handling of fixed headers (Johannes)
---
CC: fw@strlen.de
---
 include/linux/netlink.h | 11 +++++++++++
 include/net/genetlink.h |  7 +++++++
 2 files changed, 18 insertions(+)

diff --git a/include/linux/netlink.h b/include/linux/netlink.h
index 2e647157f383..f30b66996058 100644
--- a/include/linux/netlink.h
+++ b/include/linux/netlink.h
@@ -139,6 +139,17 @@ struct netlink_ext_ack {
 	}						\
 } while (0)
 
+#define NL_REQ_ATTR_CHECK(extack, nest, tb, type) ({		\
+	struct nlattr **__tb = (tb);				\
+	u32 __attr = (type);					\
+	int __retval;						\
+								\
+	__retval = !__tb[__attr];				\
+	if (__retval)						\
+		NL_SET_ERR_ATTR_MISS((extack), (nest), __attr);	\
+	__retval;						\
+})
+
 static inline void nl_set_extack_cookie_u64(struct netlink_ext_ack *extack,
 					    u64 cookie)
 {
diff --git a/include/net/genetlink.h b/include/net/genetlink.h
index 56a50e1c51b9..c41b20783ad0 100644
--- a/include/net/genetlink.h
+++ b/include/net/genetlink.h
@@ -107,6 +107,13 @@ static inline void genl_info_net_set(struct genl_info *info, struct net *net)
 
 #define GENL_SET_ERR_MSG(info, msg) NL_SET_ERR_MSG((info)->extack, msg)
 
+/* Report that a root attribute is missing */
+#define GENL_REQ_ATTR_CHECK(info, attr) ({				\
+	struct genl_info *__info = (info);				\
+									\
+	NL_REQ_ATTR_CHECK(__info->extack, NULL, __info->attrs, (attr)); \
+})
+
 enum genl_validate_flags {
 	GENL_DONT_VALIDATE_STRICT		= BIT(0),
 	GENL_DONT_VALIDATE_DUMP			= BIT(1),
-- 
2.37.2

[PATCH net-next v2 4/6] devlink: use missing attribute ext_ack

[Jakub Kicinski]

Devlink with its global attr policy has a lot of attribute
presence check, use the new ext ack reporting when they are
missing.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
CC: jiri@nvidia.com
---
 net/core/devlink.c | 41 ++++++++++++++++++++---------------------
 1 file changed, 20 insertions(+), 21 deletions(-)

diff --git a/net/core/devlink.c b/net/core/devlink.c
index b50bcc18b8d9..e0073981e92d 100644
--- a/net/core/devlink.c
+++ b/net/core/devlink.c
@@ -1710,7 +1710,7 @@ static int devlink_nl_cmd_port_split_doit(struct sk_buff *skb,
 	struct devlink *devlink = info->user_ptr[0];
 	u32 count;
 
-	if (!info->attrs[DEVLINK_ATTR_PORT_SPLIT_COUNT])
+	if (GENL_REQ_ATTR_CHECK(info, DEVLINK_ATTR_PORT_SPLIT_COUNT))
 		return -EINVAL;
 	if (!devlink->ops->port_split)
 		return -EOPNOTSUPP;
@@ -1838,7 +1838,7 @@ static int devlink_nl_cmd_port_del_doit(struct sk_buff *skb,
 	if (!devlink->ops->port_del)
 		return -EOPNOTSUPP;
 
-	if (!info->attrs[DEVLINK_ATTR_PORT_INDEX]) {
+	if (GENL_REQ_ATTR_CHECK(info, DEVLINK_ATTR_PORT_INDEX)) {
 		NL_SET_ERR_MSG_MOD(extack, "Port index is not specified");
 		return -EINVAL;
 	}
@@ -2690,7 +2690,7 @@ static int devlink_nl_cmd_sb_pool_set_doit(struct sk_buff *skb,
 	if (err)
 		return err;
 
-	if (!info->attrs[DEVLINK_ATTR_SB_POOL_SIZE])
+	if (GENL_REQ_ATTR_CHECK(info, DEVLINK_ATTR_SB_POOL_SIZE))
 		return -EINVAL;
 
 	size = nla_get_u32(info->attrs[DEVLINK_ATTR_SB_POOL_SIZE]);
@@ -2900,7 +2900,7 @@ static int devlink_nl_cmd_sb_port_pool_set_doit(struct sk_buff *skb,
 	if (err)
 		return err;
 
-	if (!info->attrs[DEVLINK_ATTR_SB_THRESHOLD])
+	if (GENL_REQ_ATTR_CHECK(info, DEVLINK_ATTR_SB_THRESHOLD))
 		return -EINVAL;
 
 	threshold = nla_get_u32(info->attrs[DEVLINK_ATTR_SB_THRESHOLD]);
@@ -3156,7 +3156,7 @@ static int devlink_nl_cmd_sb_tc_pool_bind_set_doit(struct sk_buff *skb,
 	if (err)
 		return err;
 
-	if (!info->attrs[DEVLINK_ATTR_SB_THRESHOLD])
+	if (GENL_REQ_ATTR_CHECK(info, DEVLINK_ATTR_SB_THRESHOLD))
 		return -EINVAL;
 
 	threshold = nla_get_u32(info->attrs[DEVLINK_ATTR_SB_THRESHOLD]);
@@ -3845,7 +3845,7 @@ static int devlink_nl_cmd_dpipe_entries_get(struct sk_buff *skb,
 	struct devlink_dpipe_table *table;
 	const char *table_name;
 
-	if (!info->attrs[DEVLINK_ATTR_DPIPE_TABLE_NAME])
+	if (GENL_REQ_ATTR_CHECK(info, DEVLINK_ATTR_DPIPE_TABLE_NAME))
 		return -EINVAL;
 
 	table_name = nla_data(info->attrs[DEVLINK_ATTR_DPIPE_TABLE_NAME]);
@@ -4029,8 +4029,9 @@ static int devlink_nl_cmd_dpipe_table_counters_set(struct sk_buff *skb,
 	const char *table_name;
 	bool counters_enable;
 
-	if (!info->attrs[DEVLINK_ATTR_DPIPE_TABLE_NAME] ||
-	    !info->attrs[DEVLINK_ATTR_DPIPE_TABLE_COUNTERS_ENABLED])
+	if (GENL_REQ_ATTR_CHECK(info, DEVLINK_ATTR_DPIPE_TABLE_NAME) ||
+	    GENL_REQ_ATTR_CHECK(info,
+				DEVLINK_ATTR_DPIPE_TABLE_COUNTERS_ENABLED))
 		return -EINVAL;
 
 	table_name = nla_data(info->attrs[DEVLINK_ATTR_DPIPE_TABLE_NAME]);
@@ -4119,8 +4120,8 @@ static int devlink_nl_cmd_resource_set(struct sk_buff *skb,
 	u64 size;
 	int err;
 
-	if (!info->attrs[DEVLINK_ATTR_RESOURCE_ID] ||
-	    !info->attrs[DEVLINK_ATTR_RESOURCE_SIZE])
+	if (GENL_REQ_ATTR_CHECK(info, DEVLINK_ATTR_RESOURCE_ID) ||
+	    GENL_REQ_ATTR_CHECK(info, DEVLINK_ATTR_RESOURCE_SIZE))
 		return -EINVAL;
 	resource_id = nla_get_u64(info->attrs[DEVLINK_ATTR_RESOURCE_ID]);
 
@@ -4755,7 +4756,7 @@ static int devlink_nl_cmd_flash_update(struct sk_buff *skb,
 	if (!devlink->ops->flash_update)
 		return -EOPNOTSUPP;
 
-	if (!info->attrs[DEVLINK_ATTR_FLASH_UPDATE_FILE_NAME])
+	if (GENL_REQ_ATTR_CHECK(info, DEVLINK_ATTR_FLASH_UPDATE_FILE_NAME))
 		return -EINVAL;
 
 	supported_params = devlink->ops->supported_flash_update_params;
@@ -4936,10 +4937,8 @@ static int devlink_nl_cmd_selftests_run(struct sk_buff *skb,
 	if (!devlink->ops->selftest_run || !devlink->ops->selftest_check)
 		return -EOPNOTSUPP;
 
-	if (!info->attrs[DEVLINK_ATTR_SELFTESTS]) {
-		NL_SET_ERR_MSG_MOD(info->extack, "selftest required");
+	if (GENL_REQ_ATTR_CHECK(info, DEVLINK_ATTR_SELFTESTS))
 		return -EINVAL;
-	}
 
 	attrs = info->attrs[DEVLINK_ATTR_SELFTESTS];
 
@@ -5393,7 +5392,7 @@ static int
 devlink_param_type_get_from_info(struct genl_info *info,
 				 enum devlink_param_type *param_type)
 {
-	if (!info->attrs[DEVLINK_ATTR_PARAM_TYPE])
+	if (GENL_REQ_ATTR_CHECK(info, DEVLINK_ATTR_PARAM_TYPE))
 		return -EINVAL;
 
 	switch (nla_get_u8(info->attrs[DEVLINK_ATTR_PARAM_TYPE])) {
@@ -5470,7 +5469,7 @@ devlink_param_get_from_info(struct list_head *param_list,
 {
 	char *param_name;
 
-	if (!info->attrs[DEVLINK_ATTR_PARAM_NAME])
+	if (GENL_REQ_ATTR_CHECK(info, DEVLINK_ATTR_PARAM_NAME))
 		return NULL;
 
 	param_name = nla_data(info->attrs[DEVLINK_ATTR_PARAM_NAME]);
@@ -5536,7 +5535,7 @@ static int __devlink_nl_cmd_param_set_doit(struct devlink *devlink,
 			return err;
 	}
 
-	if (!info->attrs[DEVLINK_ATTR_PARAM_VALUE_CMODE])
+	if (GENL_REQ_ATTR_CHECK(info, DEVLINK_ATTR_PARAM_VALUE_CMODE))
 		return -EINVAL;
 	cmode = nla_get_u8(info->attrs[DEVLINK_ATTR_PARAM_VALUE_CMODE]);
 	if (!devlink_param_cmode_is_supported(param, cmode))
@@ -6056,7 +6055,7 @@ static int devlink_nl_cmd_region_get_doit(struct sk_buff *skb,
 	unsigned int index;
 	int err;
 
-	if (!info->attrs[DEVLINK_ATTR_REGION_NAME])
+	if (GENL_REQ_ATTR_CHECK(info, DEVLINK_ATTR_REGION_NAME))
 		return -EINVAL;
 
 	if (info->attrs[DEVLINK_ATTR_PORT_INDEX]) {
@@ -6189,8 +6188,8 @@ static int devlink_nl_cmd_region_del(struct sk_buff *skb,
 	unsigned int index;
 	u32 snapshot_id;
 
-	if (!info->attrs[DEVLINK_ATTR_REGION_NAME] ||
-	    !info->attrs[DEVLINK_ATTR_REGION_SNAPSHOT_ID])
+	if (GENL_REQ_ATTR_CHECK(info, DEVLINK_ATTR_REGION_NAME) ||
+	    GENL_REQ_ATTR_CHECK(info, DEVLINK_ATTR_REGION_SNAPSHOT_ID))
 		return -EINVAL;
 
 	region_name = nla_data(info->attrs[DEVLINK_ATTR_REGION_NAME]);
@@ -6238,7 +6237,7 @@ devlink_nl_cmd_region_new(struct sk_buff *skb, struct genl_info *info)
 	u8 *data;
 	int err;
 
-	if (!info->attrs[DEVLINK_ATTR_REGION_NAME]) {
+	if (GENL_REQ_ATTR_CHECK(info, DEVLINK_ATTR_REGION_NAME)) {
 		NL_SET_ERR_MSG_MOD(info->extack, "No region name provided");
 		return -EINVAL;
 	}
-- 
2.37.2

[PATCH net-next v2 5/6] ethtool: strset: report missing ETHTOOL_A_STRINGSET_ID via ext_ack

[Jakub Kicinski]

Strset needs ETHTOOL_A_STRINGSET_ID, use it as an example of
reporting attrs missing in nests.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
---
 net/ethtool/strset.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ethtool/strset.c b/net/ethtool/strset.c
index 2d51b7ab4dc5..3f7de54d85fb 100644
--- a/net/ethtool/strset.c
+++ b/net/ethtool/strset.c
@@ -167,7 +167,7 @@ static int strset_get_id(const struct nlattr *nest, u32 *val,
 			       get_stringset_policy, extack);
 	if (ret < 0)
 		return ret;
-	if (!tb[ETHTOOL_A_STRINGSET_ID])
+	if (NL_REQ_ATTR_CHECK(extack, nest, tb, ETHTOOL_A_STRINGSET_ID))
 		return -EINVAL;
 
 	*val = nla_get_u32(tb[ETHTOOL_A_STRINGSET_ID]);
-- 
2.37.2

[PATCH net-next v2 6/6] ethtool: report missing header via ext_ack in the default handler

[Jakub Kicinski]

The actual presence check for the header is in
ethnl_parse_header_dev_get() but it's a few layers in,
and already has a ton of arguments so let's just pick
the low handing fruit and check for missing header in
the default request handler.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
CC: idosch@nvidia.com
---
 net/ethtool/netlink.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/ethtool/netlink.c b/net/ethtool/netlink.c
index e26079e11835..0ccb177aaf04 100644
--- a/net/ethtool/netlink.c
+++ b/net/ethtool/netlink.c
@@ -361,6 +361,9 @@ static int ethnl_default_doit(struct sk_buff *skb, struct genl_info *info)
 	ops = ethnl_default_requests[cmd];
 	if (WARN_ONCE(!ops, "cmd %u has no ethnl_request_ops\n", cmd))
 		return -EOPNOTSUPP;
+	if (GENL_REQ_ATTR_CHECK(info, ops->hdr_attr))
+		return -EINVAL;
+
 	req_info = kzalloc(ops->req_info_size, GFP_KERNEL);
 	if (!req_info)
 		return -ENOMEM;
-- 
2.37.2

Re: [PATCH net-next v2 1/6] netlink: factor out extack composition

[Johannes Berg]

On Wed, 2022-08-24 at 19:41 -0700, Jakub Kicinski wrote:
> 
> +static void
> +netlink_ack_tlv_fill(struct sk_buff *in_skb, struct sk_buff *skb,
> +		     struct nlmsghdr *nlh,  int err,

nit: two spaces

johannes

Re: [PATCH net-next v2 2/6] netlink: add support for ext_ack missing attributes

[Johannes Berg]

On Wed, 2022-08-24 at 19:41 -0700, Jakub Kicinski wrote:
> 
> + * @miss_type: attribute type which was missing
> + * @miss_nest: nest missing an attribute (NULL if missing top level attr)

nit: maybe use %NULL for appropriate formatting in generated
documentation

>  	const char *_msg;
>  	const struct nlattr *bad_attr;
>  	const struct nla_policy *policy;
> +	const void *miss_nest;

Can be 'const struct nlattr *' now, no? No longer points to a random
header.

johannes

Re: [PATCH net-next v2 0/6] netlink: support reporting missing attributes

[Johannes Berg]

On Wed, 2022-08-24 at 19:41 -0700, Jakub Kicinski wrote:
> This series adds support for reporting missing attributes
> in a structured way. We can't point at things which don't
> exist so we point at the containing nest or preceding
> fixed header
> 

If you were planning to use the cover letter for anything, then that "or
preceding fixed header" should now be removed :)

Apart from the couple of nits I just sent,

Reviewed-by: Johannes Berg <johannes@sipsolutions.net>

(for the whole set)

Thanks for doing this!

johannes

Re: [PATCH net-next v2 6/6] ethtool: report missing header via ext_ack in the default handler

[Ido Schimmel]

On Wed, Aug 24, 2022 at 07:41:22PM -0700, Jakub Kicinski wrote:
> The actual presence check for the header is in
> ethnl_parse_header_dev_get() but it's a few layers in,
> and already has a ton of arguments so let's just pick
> the low handing fruit and check for missing header in

s/handing/hanging/

> the default request handler.
> 
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
> ---
> CC: idosch@nvidia.com

Reviewed-by: Ido Schimmel <idosch@nvidia.com>

Nice idea. Wanted to ask why you kept the error messages for some of the
devlink attributes, but then I figured that user space first needs to
learn to interpret 'NLMSGERR_ATTR_MISS_TYPE' and
'NLMSGERR_ATTR_MISS_NEST'. Do you plan to patch iproute2/ethtool after
the kernel patches are accepted?

Re: [PATCH net-next v2 6/6] ethtool: report missing header via ext_ack in the default handler

[Jakub Kicinski]

On Thu, 25 Aug 2022 15:19:02 +0300 Ido Schimmel wrote:
> Nice idea. Wanted to ask why you kept the error messages for some of the
> devlink attributes, but then I figured that user space first needs to
> learn to interpret 'NLMSGERR_ATTR_MISS_TYPE' and
> 'NLMSGERR_ATTR_MISS_NEST'.

Nod.

> Do you plan to patch iproute2/ethtool after the kernel patches are accepted?

I think ethtool may be doable, I don't remember iproute2 having good
support for NLMSGERR_ATTR_OFFS (i.e. resolving offsets), but no, I'm
not planning to patch either :( Too few hours in a day :(