return sizeof(*ip6h);
 }
 
-static void setup_sockaddr(int domain, const char *str_addr, void *sockaddr)
+
+static void setup_sockaddr(int domain, const char *str_addr,
+                          struct sockaddr_storage *sockaddr)
 {
        struct sockaddr_in6 *addr6 = (void *) sockaddr;
        struct sockaddr_in *addr4 = (void *) sockaddr;
 
        switch (domain) {
        case PF_INET:
+               memset(addr4, 0, sizeof(*addr4));
                addr4->sin_family = AF_INET;
                addr4->sin_port = htons(cfg_port);
-               if (inet_pton(AF_INET, str_addr, &(addr4->sin_addr)) != 1)
+               if (str_addr &&
+                   inet_pton(AF_INET, str_addr, &(addr4->sin_addr)) != 1)
                        error(1, 0, "ipv4 parse error: %s", str_addr);
                break;
        case PF_INET6:
+               memset(addr6, 0, sizeof(*addr6));
                addr6->sin6_family = AF_INET6;
                addr6->sin6_port = htons(cfg_port);
-               if (inet_pton(AF_INET6, str_addr, &(addr6->sin6_addr)) != 1)
+               if (str_addr &&
+                   inet_pton(AF_INET6, str_addr, &(addr6->sin6_addr)) != 1)
                        error(1, 0, "ipv6 parse error: %s", str_addr);
                break;
        default:
                                    sizeof(struct tcphdr) -
                                    40 /* max tcp options */;
        int c;
+       char *daddr = NULL, *saddr = NULL;
 
        cfg_payload_len = max_payload_len;
 
                        cfg_cpu = strtol(optarg, NULL, 0);
                        break;
                case 'D':
-                       setup_sockaddr(cfg_family, optarg, &cfg_dst_addr);
+                       daddr = optarg;
                        break;
                case 'i':
                        cfg_ifindex = if_nametoindex(optarg);
                        cfg_cork_mixed = true;
                        break;
                case 'p':
-                       cfg_port = htons(strtoul(optarg, NULL, 0));
+                       cfg_port = strtoul(optarg, NULL, 0);
                        break;
                case 'r':
                        cfg_rx = true;
                        cfg_payload_len = strtoul(optarg, NULL, 0);
                        break;
                case 'S':
-                       setup_sockaddr(cfg_family, optarg, &cfg_src_addr);
+                       saddr = optarg;
                        break;
                case 't':
                        cfg_runtime_ms = 200 + strtoul(optarg, NULL, 10) * 1000;
                        break;
                }
        }
+       setup_sockaddr(cfg_family, daddr, &cfg_dst_addr);
+       setup_sockaddr(cfg_family, saddr, &cfg_src_addr);
 
        if (cfg_payload_len > max_payload_len)
                error(1, 0, "-s: payload exceeds max (%d)", max_payload_len);