1 files changed, 102 insertions, 0 deletions
diff --git a/usage/bpf.c b/usage/bpf.c
new file mode 100644
index 0000000..8b2343a
--- /dev/null
+++ b/usage/bpf.c
@@ -0,0 +1,102 @@
+#include <linux/bpf.h>
+#include <linux/if_ether.h>
+#include <linux/ip.h>
+
+#include <bpf/bpf_endian.h>
+#include <bpf/bpf_helpers.h>
+
+#define MAX_MAP_ENTRIES 4096
+
+char __license[] SEC("license") = "GPL";
+
+struct {
+	__uint(type, BPF_MAP_TYPE_LRU_HASH);
+	__uint(max_entries, MAX_MAP_ENTRIES);
+	__type(key, __u64);   // source mac address
+	__type(value, __u64); // no of bytes
+} ingress_ip4_usage_map SEC(".maps");
+
+struct {
+	__uint(type, BPF_MAP_TYPE_LRU_HASH);
+	__uint(max_entries, MAX_MAP_ENTRIES);
+	__type(key, __u64);   // destination mac address
+	__type(value, __u64); // no of bytes
+} egress_ip4_usage_map SEC(".maps");
+
+typedef enum {
+	UPDATE_USAGE_INGRESS,
+	UPDATE_USAGE_EGRESS,
+} update_usage_t;
+
+static __always_inline __u64 nchar6_to_u64(unsigned char bytes[6])
+{
+	union {
+		char bytes[6];
+		__u64 i;
+	} ret;
+
+	ret.i = 0;
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+	ret.bytes[0] = bytes[5];
+	ret.bytes[1] = bytes[4];
+	ret.bytes[2] = bytes[3];
+	ret.bytes[3] = bytes[2];
+	ret.bytes[4] = bytes[1];
+	ret.bytes[5] = bytes[0];
+#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+	ret.bytes[0] = bytes[0];
+	ret.bytes[1] = bytes[1];
+	ret.bytes[2] = bytes[2];
+	ret.bytes[3] = bytes[3];
+	ret.bytes[4] = bytes[4];
+	ret.bytes[5] = bytes[5];
+#endif
+
+	return ret.i;
+}
+
+static __always_inline int update_usage(void *map, struct __sk_buff *skb,
+					update_usage_t traffic)
+{
+	__u64 mac, len, *usage;
+
+	void *data_end = (void *)(long)skb->data_end;
+	struct ethhdr *eth = (void *)(long)skb->data;
+
+	if ((void *) (eth + 1) > data_end)
+		return TCX_PASS;
+
+	if (skb->protocol != bpf_htons(ETH_P_IP) &&
+	    skb->protocol != bpf_htons(ETH_P_IPV6)) {
+		return TCX_PASS;
+	}
+
+	len = skb->len - sizeof(struct ethhdr);
+	if (traffic == UPDATE_USAGE_INGRESS) {
+		mac = nchar6_to_u64(eth->h_source);
+	} else {
+		mac = nchar6_to_u64(eth->h_dest);
+	}
+
+	usage = bpf_map_lookup_elem(map, &mac);
+	if (!usage) {
+		/* no entry in the map for this IP address yet. */
+		bpf_map_update_elem(map, &mac, &len, BPF_ANY);
+	} else {
+		__sync_fetch_and_add(usage, len);
+	}
+
+	return TCX_PASS;
+}
+
+SEC("tc")
+int ingress_func(struct __sk_buff *skb)
+{
+	return update_usage(&ingress_ip4_usage_map, skb, UPDATE_USAGE_INGRESS);
+}
+
+SEC("tc")
+int egress__func(struct __sk_buff *skb)
+{
+	return update_usage(&egress_ip4_usage_map, skb, UPDATE_USAGE_EGRESS);
+}