getaddrinfo.c

用于嵌入式Linux系统的标准C的库函数

		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 *)(void *)
			    ai->ai_addr)->sin_port = port;
			break;
#ifdef INET6
		case AF_INET6:
			((struct sockaddr_in6 *)(void *)
			    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;
}

/*
 * post-2553: AI_ADDRCONFIG check.  if we use getipnodeby* as backend, backend
 * will take care of it.
 * the semantics of AI_ADDRCONFIG is not defined well.  we are not sure
 * if the code is right or not.
 *
 * XXX PF_UNSPEC -> PF_INET6 + PF_INET mapping needs to be in sync with
 * _dns_getaddrinfo.
 */
static int
addrconfig(pai)
	struct addrinfo *pai;
{
	int s, af;

	/*
	 * TODO:
	 * Note that implementation dependent test for address
	 * configuration should be done everytime called
	 * (or apropriate interval),
	 * because addresses will be dynamically assigned or deleted.
	 */
	af = pai->ai_family;
	if (af == AF_UNSPEC) {
		if ((s = socket(AF_INET6, SOCK_DGRAM, 0)) < 0)
			af = AF_INET;
		else {
			close(s);
			if ((s = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
				af = AF_INET6;
			else
				close(s);
		}
	}
	if (af != AF_UNSPEC) {
		if ((s = socket(af, SOCK_DGRAM, 0)) < 0)
			return 0;
		close(s);
	}
	pai->ai_family = af;
	return 1;
}

#ifdef INET6
/* convert a string to a scope identifier. XXX: IPv6 specific */
static int
ip6_str2scopeid(scope, sin6)
	char *scope;
	struct sockaddr_in6 *sin6;
{
	int scopeid;
	struct in6_addr *a6 = &sin6->sin6_addr;
	char *ep;

	/* empty scopeid portion is invalid */
	if (*scope == '\0')
		return -1;

	if (IN6_IS_ADDR_LINKLOCAL(a6) || IN6_IS_ADDR_MC_LINKLOCAL(a6)) {
		/*
		 * We currently assume a one-to-one mapping between links
		 * and interfaces, so we simply use interface indices for
		 * like-local scopes.
		 */
		scopeid = if_nametoindex(scope);
		if (scopeid == 0)
			goto trynumeric;
		return(scopeid);
	}

	/* still unclear about literal, allow numeric only - placeholder */
	if (IN6_IS_ADDR_SITELOCAL(a6) || IN6_IS_ADDR_MC_SITELOCAL(a6))
		goto trynumeric;
	if (IN6_IS_ADDR_MC_ORGLOCAL(a6))
		goto trynumeric;
	else
		goto trynumeric;	/* global */

	/* try to convert to a numeric id as a last resort */
  trynumeric:
	scopeid = (int)strtoul(scope, &ep, 10);
	if (*ep == '\0')
		return scopeid;
	else
		return -1;
}
#endif

#ifdef DEBUG
static const char AskedForGot[] =
	"gethostby*.getanswer: asked for \"%s\", got \"%s\"";
#endif
static FILE *hostf = NULL;

static struct addrinfo *
getanswer(answer, anslen, qname, qtype, pai)
	const querybuf *answer;
	int anslen;
	const char *qname;
	int qtype;
	const struct addrinfo *pai;
{
	struct addrinfo sentinel, *cur;
	struct addrinfo ai;
	const struct afd *afd;
	char *canonname;
	const HEADER *hp;
	const u_char *cp;
	int n;
	const u_char *eom;
	char *bp;
	int type, class, buflen, ancount, qdcount;
	int haveanswer, had_error;
	char tbuf[MAXDNAME];
	int (*name_ok)(const char *);
	char hostbuf[8*1024];

	memset(&sentinel, 0, sizeof(sentinel));
	cur = &sentinel;

	canonname = NULL;
	eom = answer->buf + anslen;
	switch (qtype) {
	case T_A:
	case T_AAAA:
	case T_ANY:	/*use T_ANY only for T_A/T_AAAA lookup*/
		name_ok = res_hnok;
		break;
	default:
		return (NULL);	/* XXX should be abort(); */
	}
	/*
	 * find first satisfactory answer
	 */
	hp = &answer->hdr;
	ancount = ntohs(hp->ancount);
	qdcount = ntohs(hp->qdcount);
	bp = hostbuf;
	buflen = sizeof hostbuf;
	cp = answer->buf + HFIXEDSZ;
	if (qdcount != 1) {
		h_errno = NO_RECOVERY;
		return (NULL);
	}
	n = dn_expand(answer->buf, eom, cp, bp, buflen);
	if ((n < 0) || !(*name_ok)(bp)) {
		h_errno = NO_RECOVERY;
		return (NULL);
	}
	cp += n + QFIXEDSZ;
	if (qtype == T_A || qtype == T_AAAA || qtype == T_ANY) {
		/* res_send() has already verified that the query name is the
		 * same as the one we sent; this just gets the expanded name
		 * (i.e., with the succeeding search-domain tacked on).
		 */
		n = strlen(bp) + 1;		/* for the \0 */
		if (n >= MAXHOSTNAMELEN) {
			h_errno = NO_RECOVERY;
			return (NULL);
		}
		canonname = bp;
		bp += n;
		buflen -= n;
		/* The qname can be abbreviated, but h_name is now absolute. */
		qname = canonname;
	}
	haveanswer = 0;
	had_error = 0;
	while (ancount-- > 0 && cp < eom && !had_error) {
		n = dn_expand(answer->buf, eom, cp, bp, buflen);
		if ((n < 0) || !(*name_ok)(bp)) {
			had_error++;
			continue;
		}
		cp += n;			/* name */
		type = _getshort(cp);
 		cp += INT16SZ;			/* type */
		class = _getshort(cp);
 		cp += INT16SZ + INT32SZ;	/* class, TTL */
		n = _getshort(cp);
		cp += INT16SZ;			/* len */
		if (class != C_IN) {
			/* XXX - debug? syslog? */
			cp += n;
			continue;		/* XXX - had_error++ ? */
		}
		if ((qtype == T_A || qtype == T_AAAA || qtype == T_ANY) &&
		    type == T_CNAME) {
			n = dn_expand(answer->buf, eom, cp, tbuf, sizeof tbuf);
			if ((n < 0) || !(*name_ok)(tbuf)) {
				had_error++;
				continue;
			}
			cp += n;
			/* Get canonical name. */
			n = strlen(tbuf) + 1;	/* for the \0 */
			if (n > buflen || n >= MAXHOSTNAMELEN) {
				had_error++;
				continue;
			}
			strcpy(bp, tbuf);
			canonname = bp;
			bp += n;
			buflen -= n;
			continue;
		}
		if (qtype == T_ANY) {
			if (!(type == T_A || type == T_AAAA)) {
				cp += n;
				continue;
			}
		} else if (type != qtype) {
#ifdef DEBUG
			if (type != T_KEY && type != T_SIG)
				syslog(LOG_NOTICE|LOG_AUTH,
	       "gethostby*.getanswer: asked for \"%s %s %s\", got type \"%s\"",
				       qname, p_class(C_IN), p_type(qtype),
				       p_type(type));
#endif
			cp += n;
			continue;		/* XXX - had_error++ ? */
		}
		switch (type) {
		case T_A:
		case T_AAAA:
			if (strcasecmp(canonname, bp) != 0) {
#ifdef DEBUG
				syslog(LOG_NOTICE|LOG_AUTH,
				       AskedForGot, canonname, bp);
#endif
				cp += n;
				continue;	/* XXX - had_error++ ? */
			}
			if (type == T_A && n != INADDRSZ) {
				cp += n;
				continue;
			}
			if (type == T_AAAA && n != IN6ADDRSZ) {
				cp += n;
				continue;
			}
#ifdef FILTER_V4MAPPED
			if (type == T_AAAA) {
				struct in6_addr in6;
				memcpy(&in6, cp, sizeof(in6));
				if (IN6_IS_ADDR_V4MAPPED(&in6)) {
					cp += n;
					continue;
				}
			}
#endif
			if (!haveanswer) {
				int nn;

				canonname = bp;
				nn = strlen(bp) + 1;	/* for the \0 */
				bp += nn;
				buflen -= nn;
			}

			/* don't overwrite pai */
			ai = *pai;
			ai.ai_family = (type == T_A) ? AF_INET : AF_INET6;
			afd = find_afd(ai.ai_family);
			if (afd == NULL) {
				cp += n;
				continue;
			}
			cur->ai_next = get_ai(&ai, afd, (const char *)cp);
			if (cur->ai_next == NULL)
				had_error++;
			while (cur && cur->ai_next)
				cur = cur->ai_next;
			cp += n;
			break;
		default:
			abort();
		}
		if (!had_error)
			haveanswer++;
	}
	if (haveanswer) {
		if (!canonname)
			(void)get_canonname(pai, sentinel.ai_next, qname);
		else
			(void)get_canonname(pai, sentinel.ai_next, canonname);
		h_errno = NETDB_SUCCESS;
		return sentinel.ai_next;
	}

	h_errno = NO_RECOVERY;
	return NULL;
}

/*ARGSUSED*/
static int
_dns_getaddrinfo(rv, cb_data, ap)
	void	*rv;
	void	*cb_data;
	va_list	 ap;
{
	struct addrinfo *ai;
	querybuf buf, buf2;
	const char *name;
	const struct addrinfo *pai;
	struct addrinfo sentinel, *cur;
	struct res_target q, q2;

	name = va_arg(ap, char *);
	pai = va_arg(ap, const struct addrinfo *);

	memset(&q, 0, sizeof(q2));
	memset(&q2, 0, sizeof(q2));
	memset(&sentinel, 0, sizeof(sentinel));
	cur = &sentinel;

	switch (pai->ai_family) {
	case AF_UNSPEC:
		/* prefer IPv6 */
		q.qclass = C_IN;
		q.qtype = T_AAAA;
		q.answer = buf.buf;
		q.anslen = sizeof(buf);
		q.next = &q2;
		q2.qclass = C_IN;
		q2.qtype = T_A;
		q2.answer = buf2.buf;
		q2.anslen = sizeof(buf2);
		break;
	case AF_INET:
		q.qclass = C_IN;
		q.qtype = T_A;
		q.answer = buf.buf;
		q.anslen = sizeof(buf);
		break;
	case AF_INET6:
		q.qclass = C_IN;
		q.qtype = T_AAAA;
		q.answer = buf.buf;
		q.anslen = sizeof(buf);
		break;
	default:
		return NS_UNAVAIL;
	}
	if (res_searchN(name, &q) < 0)
		return NS_NOTFOUND;
	ai = getanswer(&buf, q.n, q.name, q.qtype, pai);
	if (ai) {
		cur->ai_next = ai;
		while (cur && cur->ai_next)
			cur = cur->ai_next;
	}
	if (q.next) {
		ai = getanswer(&buf2, q2.n, q2.name, q2.qtype, pai);
		if (ai)
			cur->ai_next = ai;
	}
	if (sentinel.ai_next == NULL)
		switch (h_errno) {
		case HOST_NOT_FOUND:
			return NS_NOTFOUND;
		case TRY_AGAIN:
			return NS_TRYAGAIN;
		default:
			return NS_UNAVAIL;
		}
	*((struct addrinfo **)rv) = sentinel.ai_next;
	return NS_SUCCESS;
}

static void
_sethtent()
{
	if (!hostf)
		hostf = fopen(_PATH_HOSTS, "r" );
	else
		rewind(hostf);
}

static void
_endhtent()
{
	if (hostf) {
		(void) fclose(hostf);
		hostf = NULL;
	}
}

static struct addrinfo *
_gethtent(name, pai)
	const char *name;
	const struct addrinfo *pai;
{
	char *p;
	char *cp, *tname, *cname;
	struct addrinfo hints, *res0, *res;
	int error;
	const char *addr;
	char hostbuf[8*1024];

	if (!hostf && !(hostf = fopen(_PATH_HOSTS, "r" )))
		return (NULL);
 again:
	if (!(p = fgets(hostbuf, sizeof hostbuf, hostf)))
		return (NULL);
	if (*p == '#')
		goto again;
	if (!(cp = strpbrk(p, "#\n")))
		goto again;
	*cp = '\0';
	if (!(cp = strpbrk(p, " \t")))
		goto again;
	*cp++ = '\0';
	addr = p;
	cname = NULL;
	/* if this is not something we're looking for, skip it. */
	while (cp && *cp) {
		if (*cp == ' ' || *cp == '\t') {
			cp++;
			continue;
		}
		tname = cp;
		if (cname == NULL)
			cname = cp;
		if ((cp = strpbrk(cp, " \t")) != NULL)
			*cp++ = '\0';
		if (strcasecmp(name, tname) == 0)
			goto found;
	}
	goto again;

found:
	hints = *pai;
	hints.ai_flags = AI_NUMERICHOST;
	error = getaddrinfo(addr, NULL, &hints, &res0);
	if (error)
		goto again;
#ifdef FILTER_V4MAPPED
	/* XXX should check all items in the chain */
	if (res0->ai_family == AF_INET6 &&
	    IN6_IS_ADDR_V4MAPPED(&((struct sockaddr_in6 *)res0->ai_addr)->sin6_addr)) {
		freeaddrinfo(res0);
		goto again;
	}
#endif
	for (res = res0; res; res = res->ai_next) {
		/* cover it up */
		res->ai_flags = pai->ai_flags;