netlink: introduce type-checking attribute iteration

There are, especially with multi-attr arrays, many cases
of needing to iterate all attributes of a specific type
in a netlink message or a nested attribute. Add specific
macros to support that case.

Also convert many instances using this spatch:

    @@
    iterator nla_for_each_attr;
    iterator name nla_for_each_attr_type;
    identifier nla;
    expression head, len, rem;
    expression ATTR;
    type T;
    identifier x;
    @@
    -nla_for_each_attr(nla, head, len, rem)
    +nla_for_each_attr_type(nla, ATTR, head, len, rem)
     {
    <... T x; ...>
    -if (nla_type(nla) == ATTR) {
     ...
    -}
     }

    @@
    identifier nla;
    iterator nla_for_each_nested;
    iterator name nla_for_each_nested_type;
    expression attr, rem;
    expression ATTR;
    type T;
    identifier x;
    @@
    -nla_for_each_nested(nla, attr, rem)
    +nla_for_each_nested_type(nla, ATTR, attr, rem)
     {
    <... T x; ...>
    -if (nla_type(nla) == ATTR) {
     ...
    -}
     }

    @@
    iterator nla_for_each_attr;
    iterator name nla_for_each_attr_type;
    identifier nla;
    expression head, len, rem;
    expression ATTR;
    type T;
    identifier x;
    @@
    -nla_for_each_attr(nla, head, len, rem)
    +nla_for_each_attr_type(nla, ATTR, head, len, rem)
     {
    <... T x; ...>
    -if (nla_type(nla) != ATTR) continue;
     ...
     }

    @@
    identifier nla;
    iterator nla_for_each_nested;
    iterator name nla_for_each_nested_type;
    expression attr, rem;
    expression ATTR;
    type T;
    identifier x;
    @@
    -nla_for_each_nested(nla, attr, rem)
    +nla_for_each_nested_type(nla, ATTR, attr, rem)
     {
    <... T x; ...>
    -if (nla_type(nla) != ATTR) continue;
     ...
     }

Although I had to undo one bad change this made, and
I also adjusted some other code for whitespace and to
use direct variable initialization now.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Link: https://lore.kernel.org/r/20240328203144.b5a6c895fb80.I1869b44767379f204998ff44dd239803f39c23e0@changeid
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 27 insertions, 0 deletions

diff --git a/include/net/netlink.h b/include/net/netlink.h
index c19ff921b661..1d2bbcc50212 100644
--- a/include/net/netlink.h
+++ b/include/net/netlink.h
@@ -157,7 +157,11 @@
  *   nla_parse()			parse and validate stream of attrs
  *   nla_parse_nested()			parse nested attributes
  *   nla_for_each_attr()		loop over all attributes
+ *   nla_for_each_attr_type()		loop over all attributes with the
+ *					given type
  *   nla_for_each_nested()		loop over the nested attributes
+ *   nla_for_each_nested_type()		loop over the nested attributes with
+ *					the given type
  *=========================================================================
  */
 
@@ -2071,6 +2075,18 @@ static inline int nla_total_size_64bit(int payload)
 	     pos = nla_next(pos, &(rem)))
 
 /**
+ * nla_for_each_attr_type - iterate over a stream of attributes
+ * @pos: loop counter, set to current attribute
+ * @type: required attribute type for @pos
+ * @head: head of attribute stream
+ * @len: length of attribute stream
+ * @rem: initialized to len, holds bytes currently remaining in stream
+ */
+#define nla_for_each_attr_type(pos, type, head, len, rem) \
+	nla_for_each_attr(pos, head, len, rem) \
+		if (nla_type(pos) == type)
+
+/**
  * nla_for_each_nested - iterate over nested attributes
  * @pos: loop counter, set to current attribute
  * @nla: attribute containing the nested attributes
@@ -2080,6 +2096,17 @@ static inline int nla_total_size_64bit(int payload)
 	nla_for_each_attr(pos, nla_data(nla), nla_len(nla), rem)
 
 /**
+ * nla_for_each_nested_type - iterate over nested attributes
+ * @pos: loop counter, set to current attribute
+ * @type: required attribute type for @pos
+ * @nla: attribute containing the nested attributes
+ * @rem: initialized to len, holds bytes currently remaining in stream
+ */
+#define nla_for_each_nested_type(pos, type, nla, rem) \
+	nla_for_each_nested(pos, nla, rem) \
+		if (nla_type(pos) == type)
+
+/**
  * nla_is_last - Test if attribute is last in stream
  * @nla: attribute to test
  * @rem: bytes remaining in stream