libbpf: Add ring__consume

Add ring__consume to consume a single ringbuffer, analogous to
ring_buffer__consume.

Signed-off-by: Martin Kelly <martin.kelly@crowdstrike.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20230925215045.2375758-14-martin.kelly@crowdstrike.com

src/libbpf.h

@@ -1312,6 +1312,16 @@ LIBBPF_API size_t ring__size(const struct ring *r);
  */
 LIBBPF_API int ring__map_fd(const struct ring *r);
 
+/**
+ * @brief **ring__consume()** consumes available ringbuffer data without event
+ * polling.
+ *
+ * @param r A ringbuffer object.
+ * @return The number of records consumed (or INT_MAX, whichever is less), or
+ * a negative number if any of the callbacks return an error.
+ */
+LIBBPF_API int ring__consume(struct ring *r);
+
 struct user_ring_buffer_opts {
 	size_t sz; /* size of this struct, for forward/backward compatibility */
 };

src/libbpf.map

@@ -401,6 +401,7 @@ LIBBPF_1.3.0 {
 		bpf_program__attach_tcx;
 		bpf_program__attach_uprobe_multi;
 		ring__avail_data_size;
+		ring__consume;
 		ring__consumer_pos;
 		ring__map_fd;
 		ring__producer_pos;

src/ringbuf.c

@@ -371,6 +371,17 @@ int ring__map_fd(const struct ring *r)
 	return r->map_fd;
 }
 
+int ring__consume(struct ring *r)
+{
+	int64_t res;
+
+	res = ringbuf_process_ring(r);
+	if (res < 0)
+		return libbpf_err(res);
+
+	return res > INT_MAX ? INT_MAX : res;
+}
+
 static void user_ringbuf_unmap_ring(struct user_ring_buffer *rb)
 {
 	if (rb->consumer_pos) {