/* include readable_v41 */#include	"icmpd.h"#include	<netinet/in_systm.h>#include	<netinet/ip.h>#include	<netinet/ip_icmp.h>#include	<netinet/udp.h>intreadable_v4(void){	int					i, hlen1, hlen2, icmplen, sport;	char				buf[MAXLINE];	char				srcstr[INET_ADDRSTRLEN], dststr[INET_ADDRSTRLEN];	ssize_t				n;	socklen_t			len;	struct ip			*ip, *hip;	struct icmp			*icmp;	struct udphdr		*udp;	struct sockaddr_in	from, dest;	struct icmpd_err	icmpd_err;	len = sizeof(from);	n = Recvfrom(fd4, buf, MAXLINE, 0, (SA *) &from, &len);	printf("%d bytes ICMPv4 from %s:",		   n, Sock_ntop_host((SA *) &from, len));	ip = (struct ip *) buf;		/* start of IP header */	hlen1 = ip->ip_hl << 2;		/* length of IP header */	icmp = (struct icmp *) (buf + hlen1);	/* start of ICMP header */	if ( (icmplen = n - hlen1) < 8)		err_quit("icmplen (%d) < 8", icmplen);	printf(" type = %d, code = %d\n", icmp->icmp_type, icmp->icmp_code);/* end readable_v41 *//* include readable_v42 */	if (icmp->icmp_type == ICMP_UNREACH ||		icmp->icmp_type == ICMP_TIMXCEED ||		icmp->icmp_type == ICMP_SOURCEQUENCH) {		if (icmplen < 8 + 20 + 8)			err_quit("icmplen (%d) < 8 + 20 + 8", icmplen);		hip = (struct ip *) (buf + hlen1 + 8);		hlen2 = hip->ip_hl << 2;		printf("\tsrcip = %s, dstip = %s, proto = %d\n",			   Inet_ntop(AF_INET, &hip->ip_src, srcstr, sizeof(srcstr)),			   Inet_ntop(AF_INET, &hip->ip_dst, dststr, sizeof(dststr)),			   hip->ip_p); 		if (hip->ip_p == IPPROTO_UDP) {			udp = (struct udphdr *) (buf + hlen1 + 8 + hlen2);			sport = udp->uh_sport;				/* 4find client's Unix domain socket, send headers */			for (i = 0; i <= maxi; i++) {				if (client[i].connfd >= 0 &&					client[i].family == AF_INET &&					client[i].lport == sport) {					bzero(&dest, sizeof(dest));					dest.sin_family = AF_INET;#ifdef	HAVE_SOCKADDR_SA_LEN					dest.sin_len = sizeof(dest);#endif					memcpy(&dest.sin_addr, &hip->ip_dst,						   sizeof(struct in_addr));					dest.sin_port = udp->uh_dport;					icmpd_err.icmpd_type = icmp->icmp_type;					icmpd_err.icmpd_code = icmp->icmp_code;					icmpd_err.icmpd_len = sizeof(struct sockaddr_in);					memcpy(&icmpd_err.icmpd_dest, &dest, sizeof(dest));						/* 4convert type & code to reasonable errno value */					icmpd_err.icmpd_errno = EHOSTUNREACH;	/* default */					if (icmp->icmp_type == ICMP_UNREACH) {						if (icmp->icmp_code == ICMP_UNREACH_PORT)							icmpd_err.icmpd_errno = ECONNREFUSED;						else if (icmp->icmp_code == ICMP_UNREACH_NEEDFRAG)							icmpd_err.icmpd_errno = EMSGSIZE;					}					Write(client[i].connfd, &icmpd_err, sizeof(icmpd_err));				}			}		}	}	return(--nready);}/* end readable_v42 */