libbpf: Introduce libbpf_bpf_link_type_str

This change introduces a new function, libbpf_bpf_link_type_str, to the
public libbpf API. The function allows users to get a string
representation for a bpf_link_type enum variant.
Signed-off-by: Daniel Müller <deso@posteo.net>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Quentin Monnet <quentin@isovalent.com>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20220523230428.3077108-11-deso@posteo.net

tools/lib/bpf/libbpf.c

@@ -118,6 +118,19 @@ static const char * const attach_type_name[] = {
 	[BPF_TRACE_KPROBE_MULTI]	= "trace_kprobe_multi",
 };
 
+static const char * const link_type_name[] = {
+	[BPF_LINK_TYPE_UNSPEC]			= "unspec",
+	[BPF_LINK_TYPE_RAW_TRACEPOINT]		= "raw_tracepoint",
+	[BPF_LINK_TYPE_TRACING]			= "tracing",
+	[BPF_LINK_TYPE_CGROUP]			= "cgroup",
+	[BPF_LINK_TYPE_ITER]			= "iter",
+	[BPF_LINK_TYPE_NETNS]			= "netns",
+	[BPF_LINK_TYPE_XDP]			= "xdp",
+	[BPF_LINK_TYPE_PERF_EVENT]		= "perf_event",
+	[BPF_LINK_TYPE_KPROBE_MULTI]		= "kprobe_multi",
+	[BPF_LINK_TYPE_STRUCT_OPS]		= "struct_ops",
+};
+
 static const char * const map_type_name[] = {
 	[BPF_MAP_TYPE_UNSPEC]			= "unspec",
 	[BPF_MAP_TYPE_HASH]			= "hash",
@@ -9423,6 +9436,14 @@ const char *libbpf_bpf_attach_type_str(enum bpf_attach_type t)
 	return attach_type_name[t];
 }
 
+const char *libbpf_bpf_link_type_str(enum bpf_link_type t)
+{
+	if (t < 0 || t >= ARRAY_SIZE(link_type_name))
+		return NULL;
+
+	return link_type_name[t];
+}
+
 const char *libbpf_bpf_map_type_str(enum bpf_map_type t)
 {
 	if (t < 0 || t >= ARRAY_SIZE(map_type_name))

tools/lib/bpf/libbpf.h

@@ -60,6 +60,15 @@ LIBBPF_API int libbpf_strerror(int err, char *buf, size_t size);
  */
 LIBBPF_API const char *libbpf_bpf_attach_type_str(enum bpf_attach_type t);
 
+/**
+ * @brief **libbpf_bpf_link_type_str()** converts the provided link type value
+ * into a textual representation.
+ * @param t The link type.
+ * @return Pointer to a static string identifying the link type. NULL is
+ * returned for unknown **bpf_link_type** values.
+ */
+LIBBPF_API const char *libbpf_bpf_link_type_str(enum bpf_link_type t);
+
 /**
  * @brief **libbpf_bpf_map_type_str()** converts the provided map type value
  * into a textual representation.

tools/lib/bpf/libbpf.map

@@ -463,6 +463,7 @@ LIBBPF_0.8.0 {
 LIBBPF_1.0.0 {
 	global:
 		libbpf_bpf_attach_type_str;
+		libbpf_bpf_link_type_str;
 		libbpf_bpf_map_type_str;
 		libbpf_bpf_prog_type_str;