readable_v4.c

unix网络编程第一卷socket编程书上的全部源代码

/* include readable_v41 */
#include	"icmpd.h"
#include	<netinet/in_systm.h>
#include	<netinet/ip.h>
#include	<netinet/ip_icmp.h>
#include	<netinet/udp.h>

int
readable_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 */