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#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_HASH);
__uint(max_entries, MAX_MAP_ENTRIES);
__type(key, __u64); // blocked mac address
// i just like her for the o(1) key lookup
// we don't care about the value
__type(value, __u16);
} mac_blacklist_map SEC(".maps");
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 mac_src_parse(struct xdp_md *ctx, __u64 *mac)
{
__u64 len, *usage;
void *data_end = (void *)(long)ctx->data_end;
struct ethhdr *eth = (void *)(long)ctx->data;
if ((void *) (eth + 1) > data_end)
return -1;
if (eth->h_proto != bpf_htons(ETH_P_IP) &&
eth->h_proto != bpf_htons(ETH_P_IPV6)) {
return -1;
}
*mac = nchar6_to_u64(eth->h_source);
return 0;
}
SEC("xdp")
int mac_filter(struct xdp_md *ctx)
{
__u64 mac;
int ret, *blocked;
ret = mac_src_parse(ctx, &mac);
if (ret < 0)
return XDP_PASS;
blocked = bpf_map_lookup_elem(&mac_blacklist_map, &mac);
if (blocked)
return XDP_DROP;
return XDP_PASS;
}
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