[PATCH net-next v11 1/8] netlink: introduce type-checking attribute iteration for nlmsg

[Mark Bloch <mbloch@nvidia.com>]

From: Carolina Jubran <cjubran@nvidia.com>

Add the nlmsg_for_each_attr_type() macro to simplify iteration over
attributes of a specific type in a Netlink message.

Convert existing users in vxlan and nfsd to use the new macro.

Suggested-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Carolina Jubran <cjubran@nvidia.com>
Signed-off-by: Mark Bloch <mbloch@nvidia.com>
---
 drivers/net/vxlan/vxlan_vnifilter.c | 13 ++++-------
 fs/nfsd/nfsctl.c                    | 36 +++++++++++------------------
 include/net/netlink.h               | 14 +++++++++++
 3 files changed, 32 insertions(+), 31 deletions(-)

diff --git a/drivers/net/vxlan/vxlan_vnifilter.c b/drivers/net/vxlan/vxlan_vnifilter.c
index 4ff56d9f8f28..adc89e651e27 100644
--- a/drivers/net/vxlan/vxlan_vnifilter.c
+++ b/drivers/net/vxlan/vxlan_vnifilter.c
@@ -971,15 +971,10 @@ static int vxlan_vnifilter_process(struct sk_buff *skb, struct nlmsghdr *nlh,
 	if (!(vxlan->cfg.flags & VXLAN_F_VNIFILTER))
 		return -EOPNOTSUPP;
 
-	nlmsg_for_each_attr(attr, nlh, sizeof(*tmsg), rem) {
-		switch (nla_type(attr)) {
-		case VXLAN_VNIFILTER_ENTRY:
-			err = vxlan_process_vni_filter(vxlan, attr,
-						       nlh->nlmsg_type, extack);
-			break;
-		default:
-			continue;
-		}
+	nlmsg_for_each_attr_type(attr, VXLAN_VNIFILTER_ENTRY, nlh,
+				 sizeof(*tmsg), rem) {
+		err = vxlan_process_vni_filter(vxlan, attr, nlh->nlmsg_type,
+					       extack);
 		vnis++;
 		if (err)
 			break;
diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index 3f3e9f6c4250..786dbba0d7aa 100644
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -1621,10 +1621,9 @@ int nfsd_nl_threads_set_doit(struct sk_buff *skb, struct genl_info *info)
 		return -EINVAL;
 
 	/* count number of SERVER_THREADS values */
-	nlmsg_for_each_attr(attr, info->nlhdr, GENL_HDRLEN, rem) {
-		if (nla_type(attr) == NFSD_A_SERVER_THREADS)
-			count++;
-	}
+	nlmsg_for_each_attr_type(attr, NFSD_A_SERVER_THREADS, info->nlhdr,
+				 GENL_HDRLEN, rem)
+		count++;
 
 	mutex_lock(&nfsd_mutex);
 
@@ -1636,12 +1635,11 @@ int nfsd_nl_threads_set_doit(struct sk_buff *skb, struct genl_info *info)
 	}
 
 	i = 0;
-	nlmsg_for_each_attr(attr, info->nlhdr, GENL_HDRLEN, rem) {
-		if (nla_type(attr) == NFSD_A_SERVER_THREADS) {
-			nthreads[i++] = nla_get_u32(attr);
-			if (i >= nrpools)
-				break;
-		}
+	nlmsg_for_each_attr_type(attr, NFSD_A_SERVER_THREADS, info->nlhdr,
+				 GENL_HDRLEN, rem) {
+		nthreads[i++] = nla_get_u32(attr);
+		if (i >= nrpools)
+			break;
 	}
 
 	if (info->attrs[NFSD_A_SERVER_GRACETIME] ||
@@ -1782,14 +1780,12 @@ int nfsd_nl_version_set_doit(struct sk_buff *skb, struct genl_info *info)
 	for (i = 0; i <= NFSD_SUPPORTED_MINOR_VERSION; i++)
 		nfsd_minorversion(nn, i, NFSD_CLEAR);
 
-	nlmsg_for_each_attr(attr, info->nlhdr, GENL_HDRLEN, rem) {
+	nlmsg_for_each_attr_type(attr, NFSD_A_SERVER_PROTO_VERSION, info->nlhdr,
+				 GENL_HDRLEN, rem) {
 		struct nlattr *tb[NFSD_A_VERSION_MAX + 1];
 		u32 major, minor = 0;
 		bool enabled;
 
-		if (nla_type(attr) != NFSD_A_SERVER_PROTO_VERSION)
-			continue;
-
 		if (nla_parse_nested(tb, NFSD_A_VERSION_MAX, attr,
 				     nfsd_version_nl_policy, info->extack) < 0)
 			continue;
@@ -1940,14 +1936,12 @@ int nfsd_nl_listener_set_doit(struct sk_buff *skb, struct genl_info *info)
 	 * Walk the list of server_socks from userland and move any that match
 	 * back to sv_permsocks
 	 */
-	nlmsg_for_each_attr(attr, info->nlhdr, GENL_HDRLEN, rem) {
+	nlmsg_for_each_attr_type(attr, NFSD_A_SERVER_SOCK_ADDR, info->nlhdr,
+				 GENL_HDRLEN, rem) {
 		struct nlattr *tb[NFSD_A_SOCK_MAX + 1];
 		const char *xcl_name;
 		struct sockaddr *sa;
 
-		if (nla_type(attr) != NFSD_A_SERVER_SOCK_ADDR)
-			continue;
-
 		if (nla_parse_nested(tb, NFSD_A_SOCK_MAX, attr,
 				     nfsd_sock_nl_policy, info->extack) < 0)
 			continue;
@@ -2002,15 +1996,13 @@ int nfsd_nl_listener_set_doit(struct sk_buff *skb, struct genl_info *info)
 		svc_xprt_destroy_all(serv, net);
 
 	/* walk list of addrs again, open any that still don't exist */
-	nlmsg_for_each_attr(attr, info->nlhdr, GENL_HDRLEN, rem) {
+	nlmsg_for_each_attr_type(attr, NFSD_A_SERVER_SOCK_ADDR, info->nlhdr,
+				 GENL_HDRLEN, rem) {
 		struct nlattr *tb[NFSD_A_SOCK_MAX + 1];
 		const char *xcl_name;
 		struct sockaddr *sa;
 		int ret;
 
-		if (nla_type(attr) != NFSD_A_SERVER_SOCK_ADDR)
-			continue;
-
 		if (nla_parse_nested(tb, NFSD_A_SOCK_MAX, attr,
 				     nfsd_sock_nl_policy, info->extack) < 0)
 			continue;
diff --git a/include/net/netlink.h b/include/net/netlink.h
index 90a560dc167a..1a8356ca4b78 100644
--- a/include/net/netlink.h
+++ b/include/net/netlink.h
@@ -68,6 +68,8 @@
  *   nlmsg_for_each_msg()		loop over all messages
  *   nlmsg_validate()			validate netlink message incl. attrs
  *   nlmsg_for_each_attr()		loop over all attributes
+ *   nlmsg_for_each_attr_type()		loop over all attributes with the
+ *					given type
  *
  * Misc:
  *   nlmsg_report()			report back to application?
@@ -966,6 +968,18 @@ static inline u32 nlmsg_seq(const struct nlmsghdr *nlh)
 	nla_for_each_attr(pos, nlmsg_attrdata(nlh, hdrlen), \
 			  nlmsg_attrlen(nlh, hdrlen), rem)
 
+/**
+ * nlmsg_for_each_attr_type - iterate over a stream of attributes
+ * @pos: loop counter, set to the current attribute
+ * @type: required attribute type for @pos
+ * @nlh: netlink message header
+ * @hdrlen: length of the family specific header
+ * @rem: initialized to len, holds bytes currently remaining in stream
+ */
+#define nlmsg_for_each_attr_type(pos, type, nlh, hdrlen, rem) \
+	nlmsg_for_each_attr(pos, nlh, hdrlen, rem) \
+		if (nla_type(pos) == type)
+
 /**
  * nlmsg_put - Add a new netlink message to an skb
  * @skb: socket buffer to store message in
-- 
2.34.1