--- ./tcpkill.c.orig	2001-03-17 09:10:43.000000000 +0100
+++ ./tcpkill.c	2014-07-22 13:20:14.000000000 +0200
@@ -39,17 +39,18 @@
 static void
 tcp_kill_cb(u_char *user, const struct pcap_pkthdr *pcap, const u_char *pkt)
 {
-	struct libnet_ip_hdr *ip;
+	struct libnet_ipv4_hdr *ip;
 	struct libnet_tcp_hdr *tcp;
-	u_char ctext[64], buf[IP_H + TCP_H];
+	u_char ctext[64];
 	u_int32_t seq, win;
-	int i, *sock, len;
+	int i, len;
+	libnet_t *l;
 
-	sock = (int *)user;
+	l = (libnet_t *)user;
 	pkt += pcap_off;
 	len = pcap->caplen - pcap_off;
 
-	ip = (struct libnet_ip_hdr *)pkt;
+	ip = (struct libnet_ipv4_hdr *)pkt;
 	if (ip->ip_p != IPPROTO_TCP)
 		return;
 	
@@ -57,34 +58,31 @@
 	if (tcp->th_flags & (TH_SYN|TH_FIN|TH_RST))
 		return;
 
-	libnet_build_ip(TCP_H, 0, 0, 0, 64, IPPROTO_TCP,
-			ip->ip_dst.s_addr, ip->ip_src.s_addr,
-			NULL, 0, buf);
-
-	libnet_build_tcp(ntohs(tcp->th_dport), ntohs(tcp->th_sport),
-			 0, 0, TH_RST, 0, 0, NULL, 0, buf + IP_H);
-	
 	seq = ntohl(tcp->th_ack);
 	win = ntohs(tcp->th_win);
 	
 	snprintf(ctext, sizeof(ctext), "%s:%d > %s:%d:",
-		 libnet_host_lookup(ip->ip_src.s_addr, 0),
+		 libnet_addr2name4(ip->ip_src.s_addr, LIBNET_DONT_RESOLVE),
 		 ntohs(tcp->th_sport),
-		 libnet_host_lookup(ip->ip_dst.s_addr, 0),
+		 libnet_addr2name4(ip->ip_dst.s_addr, LIBNET_DONT_RESOLVE),
 		 ntohs(tcp->th_dport));
 	
-	ip = (struct libnet_ip_hdr *)buf;
-	tcp = (struct libnet_tcp_hdr *)(ip + 1);
-	
 	for (i = 0; i < Opt_severity; i++) {
-		ip->ip_id = libnet_get_prand(PRu16);
 		seq += (i * win);
-		tcp->th_seq = htonl(seq);
 		
-		libnet_do_checksum(buf, IPPROTO_TCP, TCP_H);
+		libnet_clear_packet(l);
 		
-		if (libnet_write_ip(*sock, buf, sizeof(buf)) < 0)
-			warn("write_ip");
+		libnet_build_tcp(ntohs(tcp->th_dport), ntohs(tcp->th_sport),
+				 seq, 0, TH_RST, 0, 0, 0, LIBNET_TCP_H, 
+				 NULL, 0, l, 0);
+		
+		libnet_build_ipv4(LIBNET_IPV4_H + LIBNET_TCP_H, 0,
+				  libnet_get_prand(LIBNET_PRu16), 0, 64,
+				  IPPROTO_TCP, 0, ip->ip_dst.s_addr,
+				  ip->ip_src.s_addr, NULL, 0, l, 0);
+		
+		if (libnet_write(l) < 0)
+			warn("write");
 		
 		fprintf(stderr, "%s R %lu:%lu(0) win 0\n", ctext, seq, seq);
 	}
@@ -95,8 +93,10 @@
 {
 	extern char *optarg;
 	extern int optind;
-	int c, sock;
+	int c;
 	char *p, *intf, *filter, ebuf[PCAP_ERRBUF_SIZE];
+	char libnet_ebuf[LIBNET_ERRBUF_SIZE];
+	libnet_t *l;
 	pcap_t *pd;
 	
 	intf = NULL;
@@ -136,14 +136,14 @@
 	if ((pcap_off = pcap_dloff(pd)) < 0)
 		errx(1, "couldn't determine link layer offset");
 	
-	if ((sock = libnet_open_raw_sock(IPPROTO_RAW)) == -1)
+	if ((l = libnet_init(LIBNET_RAW4, intf, libnet_ebuf)) == NULL)
 		errx(1, "couldn't initialize sending");
 	
-	libnet_seed_prand();
+	libnet_seed_prand(l);
 	
 	warnx("listening on %s [%s]", intf, filter);
 	
-	pcap_loop(pd, -1, tcp_kill_cb, (u_char *)&sock);
+	pcap_loop(pd, -1, tcp_kill_cb, (u_char *)l);
   
 	/* NOTREACHED */