[PATCH bpf-next] libbpf: try to add a name for bpftool self-created maps

[Hangbin Liu <liuhangbin@gmail.com>]

As discussed before[1], the bpftool self-created maps can appear in final
map show output due to deferred removal in kernel. These maps don't have
a name, which would make users confused about where it comes from.

Adding names for these maps could make users know what these maps used for.
It also could make some tests (like test_offload.py, which skip base maps
without names as a workaround) filter them out.

As Quentin suggested, add a small wrapper to fall back with no name
if kernel is not supported.

[1] https://lore.kernel.org/bpf/CAEf4BzY66WPKQbDe74AKZ6nFtZjq5e+G3Ji2egcVytB9R6_sGQ@mail.gmail.com/

Suggested-by: Quentin Monnet <quentin@isovalent.com>
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
---
 tools/lib/bpf/libbpf.c | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 77e3797cf75a..db4f1a02b9e0 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -4423,6 +4423,22 @@ static int probe_kern_prog_name(void)
 	return probe_fd(ret);
 }
 
+static int probe_kern_map_name(enum bpf_map_type map_type,
+			       const char *map_name, __u32 key_size,
+			       __u32 value_size, __u32 max_entries,
+			       const struct bpf_map_create_opts *opts)
+{
+	int map;
+
+	map = bpf_map_create(map_type, map_name, key_size, value_size, max_entries, opts);
+	if (map < 0 && errno == EINVAL) {
+		/* Retry without name */
+		map = bpf_map_create(map_type, NULL, key_size, value_size, max_entries, opts);
+	}
+
+	return map;
+}
+
 static int probe_kern_global_data(void)
 {
 	char *cp, errmsg[STRERR_BUFSIZE];
@@ -4434,7 +4450,7 @@ static int probe_kern_global_data(void)
 	};
 	int ret, map, insn_cnt = ARRAY_SIZE(insns);
 
-	map = bpf_map_create(BPF_MAP_TYPE_ARRAY, NULL, sizeof(int), 32, 1, NULL);
+	map = probe_kern_map_name(BPF_MAP_TYPE_ARRAY, "global_data", sizeof(int), 32, 1, NULL);
 	if (map < 0) {
 		ret = -errno;
 		cp = libbpf_strerror_r(ret, errmsg, sizeof(errmsg));
@@ -4567,7 +4583,7 @@ static int probe_kern_array_mmap(void)
 	LIBBPF_OPTS(bpf_map_create_opts, opts, .map_flags = BPF_F_MMAPABLE);
 	int fd;
 
-	fd = bpf_map_create(BPF_MAP_TYPE_ARRAY, NULL, sizeof(int), sizeof(int), 1, &opts);
+	fd = probe_kern_map_name(BPF_MAP_TYPE_ARRAY, "array_mmap", sizeof(int), sizeof(int), 1, &opts);
 	return probe_fd(fd);
 }
 
@@ -4614,7 +4630,7 @@ static int probe_prog_bind_map(void)
 	};
 	int ret, map, prog, insn_cnt = ARRAY_SIZE(insns);
 
-	map = bpf_map_create(BPF_MAP_TYPE_ARRAY, NULL, sizeof(int), 32, 1, NULL);
+	map = probe_kern_map_name(BPF_MAP_TYPE_ARRAY, "bind_map_detect", sizeof(int), 32, 1, NULL);
 	if (map < 0) {
 		ret = -errno;
 		cp = libbpf_strerror_r(ret, errmsg, sizeof(errmsg));
-- 
2.35.3