common: generalize xdp_stats_map from packet04

Create two header files in common/ that makes it easy
to create xdp_stats for XDP/BPF programs.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>

Author: netoptimizer

common/xdp_stats_kern.h

@@ -0,0 +1,50 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/* Used *ONLY* by BPF-prog running kernel side. */
+#ifndef __XDP_STATS_KERN_H
+#define __XDP_STATS_KERN_H
+
+/* Data record type 'struct datarec' is defined in common/xdp_stats_kern_user.h,
+ * programs using this header must first include that file.
+ */
+#ifndef __XDP_STATS_KERN_USER_H
+#warning "You forgot to #include <../common/xdp_stats_kern_user.h>"
+#include <../common/xdp_stats_kern_user.h>
+#endif
+
+/* Keeps stats per (enum) xdp_action */
+struct bpf_map_def SEC("maps") xdp_stats_map = {
+	.type        = BPF_MAP_TYPE_PERCPU_ARRAY,
+	.key_size    = sizeof(__u32),
+	.value_size  = sizeof(struct datarec),
+	.max_entries = XDP_ACTION_MAX,
+};
+
+static __always_inline
+__u32 xdp_stats_record_action(struct xdp_md *ctx, __u32 action)
+{
+	void *data_end = (void *)(long)ctx->data_end;
+	void *data     = (void *)(long)ctx->data;
+
+	if (action >= XDP_ACTION_MAX)
+		return XDP_ABORTED;
+
+	/* Lookup in kernel BPF-side return pointer to actual data record */
+	struct datarec *rec = bpf_map_lookup_elem(&xdp_stats_map, &action);
+	if (!rec)
+		return XDP_ABORTED;
+
+	/* Calculate packet length */
+	__u64 bytes = data_end - data;
+
+	/* BPF_MAP_TYPE_PERCPU_ARRAY returns a data record specific to current
+	 * CPU and XDP hooks runs under Softirq, which makes it safe to update
+	 * without atomic operations.
+	 */
+	rec->rx_packets++;
+	rec->rx_bytes += bytes;
+
+	return action;
+}
+
+#endif /* __XDP_STATS_KERN_H */

common/xdp_stats_kern_user.h

@@ -0,0 +1,19 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/* Used by BPF-prog kernel side BPF-progs and userspace programs,
+ * for sharing xdp_stats common struct and DEFINEs.
+ */
+#ifndef __XDP_STATS_KERN_USER_H
+#define __XDP_STATS_KERN_USER_H
+
+/* This is the data record stored in the map */
+struct datarec {
+	__u64 rx_packets;
+	__u64 rx_bytes;
+};
+
+#ifndef XDP_ACTION_MAX
+#define XDP_ACTION_MAX (XDP_REDIRECT + 1)
+#endif
+
+#endif /* __XDP_STATS_KERN_USER_H */