[PATCH bpf-next v2 3/5] libbpf: Add bpf_prog_stream_open()

[Kumar Kartikeya Dwivedi <memxor@gmail.com>]

Expose the BPF_PROG_STREAM_OPEN command through a low-level libbpf wrapper.
The options structure carries stream open flags, including non-blocking
mode, while leaving room for future extensions.

Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 tools/lib/bpf/bpf.c      | 19 +++++++++++++++++++
 tools/lib/bpf/bpf.h      | 24 ++++++++++++++++++++++++
 tools/lib/bpf/libbpf.map |  1 +
 3 files changed, 44 insertions(+)

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index a9de7f107cf7..b49822d212ae 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -1466,6 +1466,25 @@ int bpf_prog_stream_read(int prog_fd, __u32 stream_id, void *buf, __u32 buf_len,
 	return libbpf_err_errno(err);
 }
 
+int bpf_prog_stream_open(int prog_fd, __u32 stream_id,
+			 const struct bpf_prog_stream_open_opts *opts)
+{
+	const size_t attr_sz = offsetofend(union bpf_attr, prog_stream_open);
+	union bpf_attr attr;
+	int fd;
+
+	if (!OPTS_VALID(opts, bpf_prog_stream_open_opts))
+		return libbpf_err(-EINVAL);
+
+	memset(&attr, 0, attr_sz);
+	attr.prog_stream_open.prog_fd = prog_fd;
+	attr.prog_stream_open.stream_id = stream_id;
+	attr.prog_stream_open.flags = OPTS_GET(opts, flags, 0);
+
+	fd = sys_bpf_fd(BPF_PROG_STREAM_OPEN, &attr, attr_sz);
+	return libbpf_err_errno(fd);
+}
+
 int bpf_prog_assoc_struct_ops(int prog_fd, int map_fd,
 			      struct bpf_prog_assoc_struct_ops_opts *opts)
 {
diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
index 490e8cb4ba53..826d9cc9ab65 100644
--- a/tools/lib/bpf/bpf.h
+++ b/tools/lib/bpf/bpf.h
@@ -759,10 +759,34 @@ struct bpf_prog_stream_read_opts {
  *
  * @return The number of bytes read, on success; negative error code, otherwise
  * (errno is also set to the error code)
+ *
+ * For blocking reads and polling, prefer **bpf_prog_stream_open**.
  */
 LIBBPF_API int bpf_prog_stream_read(int prog_fd, __u32 stream_id, void *buf, __u32 buf_len,
 				    struct bpf_prog_stream_read_opts *opts);
 
+struct bpf_prog_stream_open_opts {
+	size_t sz;
+	__u32 flags;
+	size_t :0;
+};
+#define bpf_prog_stream_open_opts__last_field flags
+
+/**
+ * @brief **bpf_prog_stream_open** opens a file descriptor for a BPF stream of
+ * a given BPF program.
+ *
+ * @param prog_fd FD for the BPF program whose BPF stream is to be opened.
+ * @param stream_id ID of the BPF stream to be opened.
+ * @param opts optional options, can be NULL. BPF_F_STREAM_NONBLOCK requests a
+ * non-blocking descriptor.
+ *
+ * @return A new stream FD, on success; negative error code, otherwise (errno
+ * is also set to the error code)
+ */
+LIBBPF_API int bpf_prog_stream_open(int prog_fd, __u32 stream_id,
+				    const struct bpf_prog_stream_open_opts *opts);
+
 struct bpf_prog_assoc_struct_ops_opts {
 	size_t sz;
 	__u32 flags;
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 18d27d20102e..53b7b591325f 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -459,6 +459,7 @@ LIBBPF_1.7.0 {
 LIBBPF_1.8.0 {
 	global:
 		bpf_map__attach_cgroup_opts;
+		bpf_prog_stream_open;
 		bpf_program__add_flags;
 		bpf_program__attach_tracing_multi;
 		bpf_program__clear_flags;
-- 
2.53.0