libbpf: Add ring__producer_pos, ring__consumer_pos

Add APIs to get the producer and consumer position for a given
ringbuffer.

Signed-off-by: Martin Kelly <martin.kelly@crowdstrike.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20230925215045.2375758-6-martin.kelly@crowdstrike.com

src/libbpf.h

@@ -1264,6 +1264,24 @@ LIBBPF_API int ring_buffer__epoll_fd(const struct ring_buffer *rb);
 LIBBPF_API struct ring *ring_buffer__ring(struct ring_buffer *rb,
 					  unsigned int idx);
 
+/**
+ * @brief **ring__consumer_pos()** returns the current consumer position in the
+ * given ringbuffer.
+ *
+ * @param r A ringbuffer object.
+ * @return The current consumer position.
+ */
+LIBBPF_API unsigned long ring__consumer_pos(const struct ring *r);
+
+/**
+ * @brief **ring__producer_pos()** returns the current producer position in the
+ * given ringbuffer.
+ *
+ * @param r A ringbuffer object.
+ * @return The current producer position.
+ */
+LIBBPF_API unsigned long ring__producer_pos(const struct ring *r);
+
 struct user_ring_buffer_opts {
 	size_t sz; /* size of this struct, for forward/backward compatibility */
 };