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>

2 files changed, 16 insertions, 22 deletions

diff --git a/net/core/bpf_sk_storage.c b/net/core/bpf_sk_storage.c
index 6c4d90b24d46..bc01b3aa6b0f 100644
--- a/net/core/bpf_sk_storage.c
+++ b/net/core/bpf_sk_storage.c
@@ -496,27 +496,22 @@ bpf_sk_storage_diag_alloc(const struct nlattr *nla_stgs)
 	if (!bpf_capable())
 		return ERR_PTR(-EPERM);
 
-	nla_for_each_nested(nla, nla_stgs, rem) {
-		if (nla_type(nla) == SK_DIAG_BPF_STORAGE_REQ_MAP_FD) {
-			if (nla_len(nla) != sizeof(u32))
-				return ERR_PTR(-EINVAL);
-			nr_maps++;
-		}
+	nla_for_each_nested_type(nla, SK_DIAG_BPF_STORAGE_REQ_MAP_FD,
+				 nla_stgs, rem) {
+		if (nla_len(nla) != sizeof(u32))
+			return ERR_PTR(-EINVAL);
+		nr_maps++;
 	}
 
 	diag = kzalloc(struct_size(diag, maps, nr_maps), GFP_KERNEL);
 	if (!diag)
 		return ERR_PTR(-ENOMEM);
 
-	nla_for_each_nested(nla, nla_stgs, rem) {
-		struct bpf_map *map;
-		int map_fd;
-
-		if (nla_type(nla) != SK_DIAG_BPF_STORAGE_REQ_MAP_FD)
-			continue;
+	nla_for_each_nested_type(nla, SK_DIAG_BPF_STORAGE_REQ_MAP_FD,
+				 nla_stgs, rem) {
+		int map_fd = nla_get_u32(nla);
+		struct bpf_map *map = bpf_map_get(map_fd);
 
-		map_fd = nla_get_u32(nla);
-		map = bpf_map_get(map_fd);
 		if (IS_ERR(map)) {
 			err = PTR_ERR(map);
 			goto err_free;
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index a3d7847ce69d..283e42f48af6 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -5245,15 +5245,14 @@ static int rtnl_bridge_dellink(struct sk_buff *skb, struct nlmsghdr *nlh,
 
 	br_spec = nlmsg_find_attr(nlh, sizeof(struct ifinfomsg), IFLA_AF_SPEC);
 	if (br_spec) {
-		nla_for_each_nested(attr, br_spec, rem) {
-			if (nla_type(attr) == IFLA_BRIDGE_FLAGS) {
-				if (nla_len(attr) < sizeof(flags))
-					return -EINVAL;
+		nla_for_each_nested_type(attr, IFLA_BRIDGE_FLAGS, br_spec,
+					 rem) {
+			if (nla_len(attr) < sizeof(flags))
+				return -EINVAL;
 
-				have_flags = true;
-				flags = nla_get_u16(attr);
-				break;
-			}
+			have_flags = true;
+			flags = nla_get_u16(attr);
+			break;
 		}
 	}