-static size_t ether_size = sizeof(struct ether_header);
-static size_t arp_size = sizeof(struct ether_arp);
-static size_t ip_size = sizeof(struct ip);
-static size_t icmp_size = sizeof(struct icmp) - sizeof(struct ip);
-static size_t ip6_size = sizeof(struct ip6_hdr);
-static size_t icmp6_size = sizeof(struct icmp6_hdr);
-static size_t ns_size = sizeof(struct nd_neighbor_solicit);
-static size_t opt_size = sizeof(struct nd_opt_hdr);
+static const size_t ether_size = sizeof(struct ether_header);
+static const size_t arp_size = sizeof(struct ether_arp);
+static const size_t ip_size = sizeof(struct ip);
+static const size_t icmp_size = sizeof(struct icmp) - sizeof(struct ip);
+static const size_t ip6_size = sizeof(struct ip6_hdr);
+static const size_t icmp6_size = sizeof(struct icmp6_hdr);
+static const size_t ns_size = sizeof(struct nd_neighbor_solicit);
+static const size_t opt_size = sizeof(struct nd_opt_hdr);