#include	"unp.h"intmcast_set_ttl(int sockfd, int val){	switch (sockfd_to_family(sockfd)) {	case AF_INET: {		u_char		ttl;		ttl = val;		return(setsockopt(sockfd, IPPROTO_IP, IP_MULTICAST_TTL,						  &ttl, sizeof(ttl)));	}#ifdef	IPV6	case AF_INET6: {		int		hop;		hop = val;		return(setsockopt(sockfd, IPPROTO_IPV6, IPV6_MULTICAST_HOPS,						  &hop, sizeof(hop)));	}#endif	default:		errno = EPROTONOSUPPORT;		return(-1);	}}voidMcast_set_ttl(int sockfd, int val){	if (mcast_set_ttl(sockfd, val) < 0)		err_sys("mcast_set_ttl error");}