libbpf: Add extended attach/detach opts

Extend libbpf attach opts and add a new detach opts API so this can be used
to add/remove fd-based tc BPF programs. For concrete usage examples, see the
extensive selftests that have been developed as part of this series.

Co-developed-by: Nikolay Aleksandrov <razor@blackwall.org>
Signed-off-by: Nikolay Aleksandrov <razor@blackwall.org>
Co-developed-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

tools/lib/bpf/bpf.c

@@ -661,6 +661,26 @@ int bpf_prog_detach2(int prog_fd, int target_fd, enum bpf_attach_type type)
 	return libbpf_err_errno(ret);
 }
 
+int bpf_prog_detach_opts(int prog_fd, int target_fd,
+			 enum bpf_attach_type type,
+			 const struct bpf_prog_detach_opts *opts)
+{
+	union bpf_attr attr;
+	int ret;
+
+	if (!OPTS_VALID(opts, bpf_prog_detach_opts))
+		return libbpf_err(-EINVAL);
+
+	memset(&attr, 0, sizeof(attr));
+	attr.target_fd	   = target_fd;
+	attr.attach_bpf_fd = prog_fd;
+	attr.attach_type   = type;
+	attr.attach_priority = OPTS_GET(opts, attach_priority, 0);
+
+	ret = sys_bpf(BPF_PROG_DETACH, &attr, sizeof(attr));
+	return libbpf_err_errno(ret);
+}
+
 int bpf_link_create(int prog_fd, int target_fd,
 		    enum bpf_attach_type attach_type,
 		    const struct bpf_link_create_opts *opts)

tools/lib/bpf/bpf.h

@@ -286,8 +286,11 @@ LIBBPF_API int bpf_obj_get_opts(const char *pathname,
 
 struct bpf_prog_attach_opts {
 	size_t sz; /* size of this struct for forward/backward compatibility */
-	unsigned int flags;
-	int replace_prog_fd;
+	__u32 flags;
+	union {
+		int replace_prog_fd;
+		__u32 attach_priority;
+	};
 };
 #define bpf_prog_attach_opts__last_field replace_prog_fd
 
@@ -296,9 +299,19 @@ LIBBPF_API int bpf_prog_attach(int prog_fd, int attachable_fd,
 LIBBPF_API int bpf_prog_attach_opts(int prog_fd, int attachable_fd,
 				     enum bpf_attach_type type,
 				     const struct bpf_prog_attach_opts *opts);
+
+struct bpf_prog_detach_opts {
+	size_t sz; /* size of this struct for forward/backward compatibility */
+	__u32 attach_priority;
+};
+#define bpf_prog_detach_opts__last_field attach_priority
+
 LIBBPF_API int bpf_prog_detach(int attachable_fd, enum bpf_attach_type type);
 LIBBPF_API int bpf_prog_detach2(int prog_fd, int attachable_fd,
 				enum bpf_attach_type type);
+LIBBPF_API int bpf_prog_detach_opts(int prog_fd, int target_fd,
+				    enum bpf_attach_type type,
+				    const struct bpf_prog_detach_opts *opts);
 
 union bpf_iter_link_info; /* defined in up-to-date linux/bpf.h */
 struct bpf_link_create_opts {

tools/lib/bpf/libbpf.map

@@ -357,6 +357,7 @@ LIBBPF_1.0.0 {
 	global:
 		bpf_obj_get_opts;
 		bpf_prog_query_opts;
+		bpf_prog_detach_opts;
 		bpf_program__attach_ksyscall;
 		btf__add_enum64;
 		btf__add_enum64_value;