[PATCH bpf-next 1/2] libbpf: Skip BTF_KIND_FWD when counting duplicated type names

[Xu Kuohai <xukuohai@xxxxxxxxxx>]

If a FWD appears in the BTF before a STRUCT with the same name, the
STRUCT is dumped with a conflicted name:

    $ bpftool btf dump file vmlinux format raw | grep "'unix_sock'"
    [81287] FWD 'unix_sock' fwd_kind=struct
    [89336] STRUCT 'unix_sock' size=1024 vlen=14

    $ bpftool btf dump file vmlinux format c | grep "struct unix_sock"
    struct unix_sock;
    struct unix_sock___2 {	<--- conflict, the "___2" is unexpected
		    struct unix_sock___2 *unix_sk;

Fixes: 351131b51c7a ("libbpf: add btf_dump API for BTF-to-C conversion")
Signed-off-by: Xu Kuohai <xukuohai@xxxxxxxxxx>
---
 tools/lib/bpf/btf_dump.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/tools/lib/bpf/btf_dump.c b/tools/lib/bpf/btf_dump.c
index 07ebe70d3a30..55079efbd8f1 100644
--- a/tools/lib/bpf/btf_dump.c
+++ b/tools/lib/bpf/btf_dump.c
@@ -1505,13 +1505,15 @@ static const char *btf_dump_resolve_name(struct btf_dump *d, __u32 id,
 	if (s->name_resolved)
 		return *cached_name ? *cached_name : orig_name;
 
-	dup_cnt = btf_dump_name_dups(d, name_map, orig_name);
-	if (dup_cnt > 1) {
-		const size_t max_len = 256;
-		char new_name[max_len];
-
-		snprintf(new_name, max_len, "%s___%zu", orig_name, dup_cnt);
-		*cached_name = strdup(new_name);
+	if (!btf_is_fwd(t)) {
+		dup_cnt = btf_dump_name_dups(d, name_map, orig_name);
+		if (dup_cnt > 1) {
+			const size_t max_len = 256;
+			char new_name[max_len];
+
+			snprintf(new_name, max_len, "%s___%zu", orig_name, dup_cnt);
+			*cached_name = strdup(new_name);
+		}
 	}
 
 	s->name_resolved = 1;
-- 
2.30.2