gistfile1.txt

static __always_inline void *xdp_data(const struct xdp_md *xdp)
{
	return (void *)(unsigned long)xdp->data;
}

static __always_inline void *xdp_data_end(const struct xdp_md *xdp)
{
	return (void *)(unsigned long)xdp->data_end;
}

static __always_inline bool xdp_no_room(const void *needed, const void *limit)
{
	return needed > limit;
}

struct lpm_v4_key {
	struct bpf_lpm_trie_key lpm;
	__u8 addr[4];
};

struct lpm_val {
	__u32 ref_count;
};

[...]

static __always_inline int check_v4(struct xdp_md *xdp)
{
	void *data_end = xdp_data_end(xdp);
	void *data = xdp_data(xdp);
	struct iphdr *ipv4_hdr = data + sizeof(struct ethhdr);
	struct lpm_v4_key pfx;
	__u16 dest_port;

	if (xdp_no_room(ipv4_hdr + 1, data_end)) {
		return XDP_DROP;
	}

	__builtin_memcpy(pfx.lpm.data, &ipv4_hdr->saddr, sizeof(pfx.addr));
	pfx.lpm.prefixlen = 32;

	if (map_lookup_elem(&calico_prefilter_v4, &pfx)) {

[...]
}

static __always_inline int check_prefilter(struct xdp_md *xdp)
{
	void *data_end = xdp_data_end(xdp);
	void *data = xdp_data(xdp);
	struct ethhdr *eth = data;
	__u16 proto;

	if (xdp_no_room(eth + 1, data_end)) {
		return XDP_DROP;
	}

	proto = eth->h_proto;
	if (proto == bpf_htons(ETH_P_IP)) {
		return check_v4(xdp);
	} else {
		/* other traffic can continue */
		return XDP_PASS;
	}
}

__section("pre-filter")
int xdp_enter(struct xdp_md *xdp)
{
	return check_prefilter(xdp);
}

char ____license[] __section("license")  = "Apache-2.0";