getaddrinfo.c

libcap是一个在linux下的抓包工具

		return 0;
	hp = gethostbyname(hostname);
#ifdef HAVE_H_ERRNO
	h_error = h_errno;
#else
	h_error = EINVAL;
#endif
#endif /*HAVE_GETHOSTBYNAME2*/
#endif /*USE_GETIPNODEBY*/

	if (hp == NULL) {
		switch (h_error) {
		case HOST_NOT_FOUND:
		case NO_DATA:
			error = EAI_NODATA;
			break;
		case TRY_AGAIN:
			error = EAI_AGAIN;
			break;
		case NO_RECOVERY:
		case NETDB_INTERNAL:
		default:
			error = EAI_FAIL;
			break;
		}
	} else if ((hp->h_name == NULL) || (hp->h_name[0] == 0)
			|| (hp->h_addr_list[0] == NULL)) {
#ifdef USE_GETIPNODEBY
		freehostent(hp);
#endif
		hp = NULL;
		error = EAI_FAIL;
	}

	if (hp == NULL)
		goto free;

#ifdef USE_GETIPNODEBY
	aplist = hp->h_addr_list;
#else
	/*
	 * hp will be overwritten if we use gethostbyname2().
	 * always deep copy for simplification.
	 */
	for (naddrs = 0; hp->h_addr_list[naddrs] != NULL; naddrs++)
		;
	naddrs++;
	aplist = (char **)malloc(sizeof(aplist[0]) * naddrs);
	apbuf = (char *)malloc(hp->h_length * naddrs);
	if (aplist == NULL || apbuf == NULL) {
		error = EAI_MEMORY;
		goto free;
	}
	memset(aplist, 0, sizeof(aplist[0]) * naddrs);
	for (i = 0; i < naddrs; i++) {
		if (hp->h_addr_list[i] == NULL) {
			aplist[i] = NULL;
			continue;
		}
		memcpy(&apbuf[i * hp->h_length], hp->h_addr_list[i],
			hp->h_length);
		aplist[i] = &apbuf[i * hp->h_length];
	}
#endif

	for (i = 0; aplist[i] != NULL; i++) {
		af = hp->h_addrtype;
		ap = aplist[i];
#ifdef AF_INET6
		if (af == AF_INET6
		 && IN6_IS_ADDR_V4MAPPED((struct in6_addr *)ap)) {
			af = AF_INET;
			ap = ap + sizeof(struct in6_addr)
				- sizeof(struct in_addr);
		}
#endif

		if (af != pai->ai_family)
			continue;

		if ((pai->ai_flags & AI_CANONNAME) == 0) {
			GET_AI(cur->ai_next, afd, ap);
			GET_PORT(cur->ai_next, servname);
		} else {
			/*
			 * if AI_CANONNAME and if reverse lookup
			 * fail, return ai anyway to pacify
			 * calling application.
			 *
			 * XXX getaddrinfo() is a name->address
			 * translation function, and it looks
			 * strange that we do addr->name
			 * translation here.
			 */
			get_name(ap, afd, &cur->ai_next,
				ap, pai, servname);
		}

		while (cur && cur->ai_next)
			cur = cur->ai_next;
	}

	*res = sentinel.ai_next;
	return 0;

free:
#ifdef USE_GETIPNODEBY
	if (hp)
		freehostent(hp);
#endif
	if (aplist)
		free(aplist);
	if (apbuf)
		free(apbuf);
	if (sentinel.ai_next)
		freeaddrinfo(sentinel.ai_next);
	return error;
}

/*
 * hostname == NULL.
 * passive socket -> anyaddr (0.0.0.0 or ::)
 * non-passive socket -> localhost (127.0.0.1 or ::1)
 */
static int
explore_null(pai, hostname, servname, res)
	const struct addrinfo *pai;
	const char *hostname;
	const char *servname;
	struct addrinfo **res;
{
	int s;
	const struct afd *afd;
	struct addrinfo *cur;
	struct addrinfo sentinel;
	int error;

	*res = NULL;
	sentinel.ai_next = NULL;
	cur = &sentinel;

	/*
	 * filter out AFs that are not supported by the kernel
	 * XXX errno?
	 */
	s = socket(pai->ai_family, SOCK_DGRAM, 0);
	if (s < 0) {
		if (errno != EMFILE)
			return 0;
	} else
		close(s);

	/*
	 * if the servname does not match socktype/protocol, ignore it.
	 */
	if (get_portmatch(pai, servname) != 0)
		return 0;

	afd = find_afd(pai->ai_family);

	if (pai->ai_flags & AI_PASSIVE) {
		GET_AI(cur->ai_next, afd, afd->a_addrany);
		/* xxx meaningless?
		 * GET_CANONNAME(cur->ai_next, "anyaddr");
		 */
		GET_PORT(cur->ai_next, servname);
	} else {
		GET_AI(cur->ai_next, afd, afd->a_loopback);
		/* xxx meaningless?
		 * GET_CANONNAME(cur->ai_next, "localhost");
		 */
		GET_PORT(cur->ai_next, servname);
	}
	cur = cur->ai_next;

	*res = sentinel.ai_next;
	return 0;

free:
	if (sentinel.ai_next)
		freeaddrinfo(sentinel.ai_next);
	return error;
}

/*
 * numeric hostname
 */
static int
explore_numeric(pai, hostname, servname, res)
	const struct addrinfo *pai;
	const char *hostname;
	const char *servname;
	struct addrinfo **res;
{
	const struct afd *afd;
	struct addrinfo *cur;
	struct addrinfo sentinel;
	int error;
	char pton[PTON_MAX];
	int flags;

	*res = NULL;
	sentinel.ai_next = NULL;
	cur = &sentinel;

	/*
	 * if the servname does not match socktype/protocol, ignore it.
	 */
	if (get_portmatch(pai, servname) != 0)
		return 0;

	afd = find_afd(pai->ai_family);
	flags = pai->ai_flags;

	if (inet_pton(afd->a_af, hostname, pton) == 1) {
		u_int32_t v4a;
#ifdef INET6
		u_char pfx;
#endif

		switch (afd->a_af) {
		case AF_INET:
			v4a = (u_int32_t)ntohl(((struct in_addr *)pton)->s_addr);
			if (IN_MULTICAST(v4a) || IN_EXPERIMENTAL(v4a))
				flags &= ~AI_CANONNAME;
			v4a >>= IN_CLASSA_NSHIFT;
			if (v4a == 0 || v4a == IN_LOOPBACKNET)
				flags &= ~AI_CANONNAME;
			break;
#ifdef INET6
		case AF_INET6:
			pfx = ((struct in6_addr *)pton)->s6_addr[0];
			if (pfx == 0 || pfx == 0xfe || pfx == 0xff)
				flags &= ~AI_CANONNAME;
			break;
#endif
		}

		if (pai->ai_family == afd->a_af ||
		    pai->ai_family == PF_UNSPEC /*?*/) {
			if ((flags & AI_CANONNAME) == 0) {
				GET_AI(cur->ai_next, afd, pton);
				GET_PORT(cur->ai_next, servname);
			} else {
				/*
				 * if AI_CANONNAME and if reverse lookup
				 * fail, return ai anyway to pacify
				 * calling application.
				 *
				 * XXX getaddrinfo() is a name->address
				 * translation function, and it looks
				 * strange that we do addr->name
				 * translation here.
				 */
				get_name(pton, afd, &cur->ai_next,
					pton, pai, servname);
			}
			while (cur && cur->ai_next)
				cur = cur->ai_next;
		} else 
			ERR(EAI_FAMILY);	/*xxx*/
	}

	*res = sentinel.ai_next;
	return 0;

free:
bad:
	if (sentinel.ai_next)
		freeaddrinfo(sentinel.ai_next);
	return error;
}

/*
 * numeric hostname with scope
 */
static int
explore_numeric_scope(pai, hostname, servname, res)
	const struct addrinfo *pai;
	const char *hostname;
	const char *servname;
	struct addrinfo **res;
{
#ifndef SCOPE_DELIMITER
	return explore_numeric(pai, hostname, servname, res);
#else
	const struct afd *afd;
	struct addrinfo *cur;
	int error;
	char *cp, *hostname2 = NULL;
	int scope;
	struct sockaddr_in6 *sin6;

	/*
	 * if the servname does not match socktype/protocol, ignore it.
	 */
	if (get_portmatch(pai, servname) != 0)
		return 0;

	afd = find_afd(pai->ai_family);
	if (!afd->a_scoped)
		return explore_numeric(pai, hostname, servname, res);

	cp = strchr(hostname, SCOPE_DELIMITER);
	if (cp == NULL)
		return explore_numeric(pai, hostname, servname, res);

	/*
	 * Handle special case of <scoped_address><delimiter><scope id>
	 */
	hostname2 = strdup(hostname);
	if (hostname2 == NULL)
		return EAI_MEMORY;
	/* terminate at the delimiter */
	hostname2[cp - hostname] = '\0';

	cp++;
	switch (pai->ai_family) {
#ifdef INET6
	case AF_INET6:
		scope = if_nametoindex(cp);
		if (scope == 0) {
			free(hostname2);
			return (EAI_NONAME);
		}
		break;
#endif
	}

	error = explore_numeric(pai, hostname2, servname, res);
	if (error == 0) {
		for (cur = *res; cur; cur = cur->ai_next) {
			if (cur->ai_family != AF_INET6)
				continue;
			sin6 = (struct sockaddr_in6 *)cur->ai_addr;
			if (IN6_IS_ADDR_LINKLOCAL(&sin6->sin6_addr) ||
			    IN6_IS_ADDR_MC_LINKLOCAL(&sin6->sin6_addr))
				sin6->sin6_scope_id = scope;
		}
	}

	free(hostname2);

	return error;
#endif
}

static int
get_name(addr, afd, res, numaddr, pai, servname)
	const char *addr;
	const struct afd *afd;
	struct addrinfo **res;
	char *numaddr;
	const struct addrinfo *pai;
	const char *servname;
{
	struct hostent *hp = NULL;
	struct addrinfo *cur = NULL;
	int error = 0;
	char *ap = NULL, *cn = NULL;
#ifdef USE_GETIPNODEBY
	int h_error;

	hp = getipnodebyaddr(addr, afd->a_addrlen, afd->a_af, &h_error);
#else
	hp = gethostbyaddr(addr, afd->a_addrlen, afd->a_af);
#endif
	if (hp && hp->h_name && hp->h_name[0] && hp->h_addr_list[0]) {
#ifdef USE_GETIPNODEBY
		GET_AI(cur, afd, hp->h_addr_list[0]);
		GET_PORT(cur, servname);
		GET_CANONNAME(cur, hp->h_name);
#else
		/* hp will be damaged if we use gethostbyaddr() */
		if ((ap = (char *)malloc(hp->h_length)) == NULL) {
			error = EAI_MEMORY;
			goto free;
		}
		memcpy(ap, hp->h_addr_list[0], hp->h_length);
		if ((cn = strdup(hp->h_name)) == NULL) {
			error = EAI_MEMORY;
			goto free;
		}

		GET_AI(cur, afd, ap);
		GET_PORT(cur, servname);
		GET_CANONNAME(cur, cn);
		free(ap); ap = NULL;
		free(cn); cn = NULL;
#endif
	} else {
		GET_AI(cur, afd, numaddr);
		GET_PORT(cur, servname);
	}
	
#ifdef USE_GETIPNODEBY
	if (hp)
		freehostent(hp);
#endif
	*res = cur;
	return SUCCESS;
 free:
	if (cur)
		freeaddrinfo(cur);
	if (ap)
		free(ap);
	if (cn)
		free(cn);
#ifdef USE_GETIPNODEBY
	if (hp)
		freehostent(hp);
#endif
	*res = NULL;
	return error;
}

static int
get_canonname(pai, ai, str)
	const struct addrinfo *pai;
	struct addrinfo *ai;
	const char *str;
{
	if ((pai->ai_flags & AI_CANONNAME) != 0) {
		ai->ai_canonname = (char *)malloc(strlen(str) + 1);
		if (ai->ai_canonname == NULL)
			return EAI_MEMORY;
		strcpy(ai->ai_canonname, str);
	}
	return 0;
}

static struct addrinfo *
get_ai(pai, afd, addr)
	const struct addrinfo *pai;
	const struct afd *afd;
	const char *addr;
{
	char *p;
	struct addrinfo *ai;

	ai = (struct addrinfo *)malloc(sizeof(struct addrinfo)
		+ (afd->a_socklen));
	if (ai == NULL)
		return NULL;

	memcpy(ai, pai, sizeof(struct addrinfo));
	ai->ai_addr = (struct sockaddr *)(ai + 1);
	memset(ai->ai_addr, 0, afd->a_socklen);
#ifdef HAVE_SOCKADDR_SA_LEN
	ai->ai_addr->sa_len = afd->a_socklen;
#endif
	ai->ai_addrlen = afd->a_socklen;
	ai->ai_addr->sa_family = ai->ai_family = afd->a_af;
	p = (char *)(ai->ai_addr);
	memcpy(p + afd->a_off, addr, afd->a_addrlen);
	return ai;
}

static int
get_portmatch(ai, servname)
	const struct addrinfo *ai;
	const char *servname;
{

	/* get_port does not touch first argument. when matchonly == 1. */
	return get_port((struct addrinfo *)ai, servname, 1);
}

static int
get_port(ai, servname, matchonly)
	struct addrinfo *ai;
	const char *servname;
	int matchonly;
{
	const char *proto;
	struct servent *sp;
	int port;
	int allownumeric;

	if (servname == NULL)
		return 0;
	switch (ai->ai_family) {
	case AF_INET:
#ifdef AF_INET6
	case AF_INET6:
#endif
		break;
	default:
		return 0;
	}

	switch (ai->ai_socktype) {
	case SOCK_RAW:
		return EAI_SERVICE;
	case SOCK_DGRAM:
	case SOCK_STREAM:
		allownumeric = 1;
		break;
	case ANY:
		allownumeric = 0;
		break;
	default:
		return EAI_SOCKTYPE;
	}

	if (str_isnumber(servname)) {
		if (!allownumeric)
			return EAI_SERVICE;
		port = htons(atoi(servname));
		if (port < 0 || port > 65535)
			return EAI_SERVICE;
	} else {
		switch (ai->ai_socktype) {
		case SOCK_DGRAM:
			proto = "udp";
			break;
		case SOCK_STREAM:
			proto = "tcp";
			break;
		default:
			proto = NULL;
			break;
		}

		if ((sp = getservbyname(servname, proto)) == NULL)
			return EAI_SERVICE;
		port = sp->s_port;
	}

	if (!matchonly) {
		switch (ai->ai_family) {
		case AF_INET:
			((struct sockaddr_in *)ai->ai_addr)->sin_port = port;
			break;
#ifdef INET6
		case AF_INET6:
			((struct sockaddr_in6 *)ai->ai_addr)->sin6_port = port;
			break;
#endif
		}
	}

	return 0;
}

static const struct afd *
find_afd(af)
	int af;
{
	const struct afd *afd;

	if (af == PF_UNSPEC)
		return NULL;
	for (afd = afdl; afd->a_af; afd++) {
		if (afd->a_af == af)
			return afd;
	}
	return NULL;
}