int xdp_router_ipv4_prog()

in bpf/xdp_router_ipv4_kern.c [109:184]

• 69 lines of code
• 17 McCabe index (conditional complexity)

int xdp_router_ipv4_prog(struct xdp_md *ctx)
{
	void *data_end = (void *)(long)ctx->data_end;
	__be64 *dest_mac = NULL, *src_mac = NULL;
	void *data = (void *)(long)ctx->data;
	struct trie_value *prefix_value;
	int rc = XDP_DROP, forward_to;
	struct ethhdr *eth = data;
	union key_4 key4;
	long *value;
	u16 h_proto;
	u32 ipproto;
	u64 nh_off;

	nh_off = sizeof(*eth);
	if (data + nh_off > data_end)
		return rc;

	h_proto = eth->h_proto;

	if (h_proto == htons(ETH_P_8021Q) || h_proto == htons(ETH_P_8021AD)) {
		struct vlan_hdr *vhdr;

		vhdr = data + nh_off;
		nh_off += sizeof(struct vlan_hdr);
		if (data + nh_off > data_end)
			return rc;
		h_proto = vhdr->h_vlan_encapsulated_proto;
	}
	if (h_proto == htons(ETH_P_ARP)) {
		return XDP_PASS;
	} else if (h_proto == htons(ETH_P_IP)) {
		struct direct_map *direct_entry;
		__be32 src_ip = 0, dest_ip = 0;

		ipproto = parse_ipv4(data, nh_off, data_end, &src_ip, &dest_ip);
		direct_entry = bpf_map_lookup_elem(&exact_match, &dest_ip);
		/* Check for exact match, this would give a faster lookup*/
		if (direct_entry && direct_entry->mac && direct_entry->arp.mac) {
			src_mac = &direct_entry->mac;
			dest_mac = &direct_entry->arp.mac;
			forward_to = direct_entry->ifindex;
		} else {
			/* Look up in the trie for lpm*/
			key4.b32[0] = 32;
			key4.b8[4] = dest_ip & 0xff;
			key4.b8[5] = (dest_ip >> 8) & 0xff;
			key4.b8[6] = (dest_ip >> 16) & 0xff;
			key4.b8[7] = (dest_ip >> 24) & 0xff;
			prefix_value = bpf_map_lookup_elem(&lpm_map, &key4);
			if (!prefix_value)
				return XDP_DROP;
			src_mac = &prefix_value->value;
			if (!src_mac)
				return XDP_DROP;
			dest_mac = bpf_map_lookup_elem(&arp_table, &dest_ip);
			if (!dest_mac) {
				if (!prefix_value->gw)
					return XDP_DROP;
				dest_ip = prefix_value->gw;
				dest_mac = bpf_map_lookup_elem(&arp_table, &dest_ip);
			}
			forward_to = prefix_value->ifindex;
		}
	} else {
		ipproto = 0;
	}
	if (src_mac && dest_mac) {
		set_src_dst_mac(data, src_mac, dest_mac);
		value = bpf_map_lookup_elem(&rxcnt, &ipproto);
		if (value)
			*value += 1;
		return  bpf_redirect_map(&tx_port, forward_to, 0);
	}
	return rc;
}