static void read_arp()

in bpf/xdp_router_ipv4_user.c [381:464]

• 79 lines of code
• 14 McCabe index (conditional complexity)

static void read_arp(struct nlmsghdr *nh, int nll)
{
	struct rtattr *rt_attr;
	char dsts[24], mac[24];
	struct ndmsg *rt_msg;
	int rtl, ndm_family;

	struct arp_table {
		__be64 mac;
		__be32 dst;
	} arp_entry;
	struct direct_map {
		struct arp_table arp;
		int ifindex;
		__be64 mac;
	} direct_entry;

	if (nh->nlmsg_type == RTM_GETNEIGH)
		printf("READING arp entry\n");
	printf("Address         HwAddress\n");
	for (; NLMSG_OK(nh, nll); nh = NLMSG_NEXT(nh, nll)) {
		struct in_addr dst_addr;
		char mac_str[18];
		int len = 0, i;

		rt_msg = (struct ndmsg *)NLMSG_DATA(nh);
		rt_attr = (struct rtattr *)RTM_RTA(rt_msg);
		ndm_family = rt_msg->ndm_family;
		rtl = RTM_PAYLOAD(nh);
		for (; RTA_OK(rt_attr, rtl); rt_attr = RTA_NEXT(rt_attr, rtl)) {
			switch (rt_attr->rta_type) {
			case NDA_DST:
				sprintf(dsts, "%u",
					*((__be32 *)RTA_DATA(rt_attr)));
				break;
			case NDA_LLADDR:
				sprintf(mac, "%lld",
					*((__be64 *)RTA_DATA(rt_attr)));
				break;
			default:
				break;
			}
		}
		arp_entry.dst = atoi(dsts);
		arp_entry.mac = atol(mac);

		dst_addr.s_addr = arp_entry.dst;
		for (i = 0; i < 6; i++)
			len += snprintf(mac_str + len, 18 - len, "%02llx%s",
					((arp_entry.mac >> i * 8) & 0xff),
					i < 5 ? ":" : "");
		printf("%-16s%s\n", inet_ntoa(dst_addr), mac_str);

		if (ndm_family == AF_INET) {
			if (bpf_map_lookup_elem(exact_match_map_fd,
						&arp_entry.dst,
						&direct_entry) == 0) {
				if (nh->nlmsg_type == RTM_DELNEIGH) {
					direct_entry.arp.dst = 0;
					direct_entry.arp.mac = 0;
				} else if (nh->nlmsg_type == RTM_NEWNEIGH) {
					direct_entry.arp.dst = arp_entry.dst;
					direct_entry.arp.mac = arp_entry.mac;
				}
				assert(bpf_map_update_elem(exact_match_map_fd,
							   &arp_entry.dst,
							   &direct_entry, 0
							   ) == 0);
				memset(&direct_entry, 0, sizeof(direct_entry));
			}
			if (nh->nlmsg_type == RTM_DELNEIGH) {
				assert(bpf_map_delete_elem(arp_table_map_fd,
							   &arp_entry.dst) == 0);
			} else if (nh->nlmsg_type == RTM_NEWNEIGH) {
				assert(bpf_map_update_elem(arp_table_map_fd,
							   &arp_entry.dst,
							   &arp_entry.mac, 0
							   ) == 0);
			}
		}
		memset(&arp_entry, 0, sizeof(arp_entry));
		memset(dsts, 0, sizeof(dsts));
	}
}