1 files changed, 53 insertions, 0 deletions
diff --git a/examples/bpf/bpf_shared.c b/examples/bpf/bpf_shared.c
new file mode 100644
index 0000000..99a332f
--- /dev/null
+++ b/examples/bpf/bpf_shared.c
@@ -0,0 +1,53 @@
+#include "../../include/bpf_api.h"
+
+/* Minimal, stand-alone toy map pinning example:
+ *
+ * clang -target bpf -O2 [...] -o bpf_shared.o -c bpf_shared.c
+ * tc filter add dev foo parent 1: bpf obj bpf_shared.o sec egress
+ * tc filter add dev foo parent ffff: bpf obj bpf_shared.o sec ingress
+ *
+ * Both classifier will share the very same map instance in this example,
+ * so map content can be accessed from ingress *and* egress side!
+ *
+ * This example has a pinning of PIN_OBJECT_NS, so it's private and
+ * thus shared among various program sections within the object.
+ *
+ * A setting of PIN_GLOBAL_NS would place it into a global namespace,
+ * so that it can be shared among different object files. A setting
+ * of PIN_NONE (= 0) means no sharing, so each tc invocation a new map
+ * instance is being created.
+ */
+
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__uint(key_size, sizeof(uint32_t));
+	__uint(value_size, sizeof(uint32_t));
+	__uint(max_entries, 1);
+	__uint(pinning, LIBBPF_PIN_BY_NAME);	/* or LIBBPF_PIN_NONE */
+} map_sh __section(".maps");
+
+__section("egress")
+int emain(struct __sk_buff *skb)
+{
+	int key = 0, *val;
+
+	val = map_lookup_elem(&map_sh, &key);
+	if (val)
+		lock_xadd(val, 1);
+
+	return BPF_H_DEFAULT;
+}
+
+__section("ingress")
+int imain(struct __sk_buff *skb)
+{
+	int key = 0, *val;
+
+	val = map_lookup_elem(&map_sh, &key);
+	if (val)
+		printt("map val: %d\n", *val);
+
+	return BPF_H_DEFAULT;
+}
+
+BPF_LICENSE("GPL");