getnameinfo.c   [plain text]

/*	$KAME: getnameinfo.c,v 1.72 2005/01/13 04:12:03 itojun Exp $	*/

/*
 * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the project nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * Issues to be discussed:
 * - RFC2553 says that we should raise error on short buffer.  X/Open says
 *   we need to truncate the result.  We obey RFC2553 (and X/Open should be
 *   modified).  ipngwg rough consensus seems to follow RFC2553.  RFC3493 says
 *   nothing about it, but defines a new error code EAI_OVERFLOW which seems
 *   to be intended the code for this case.
 * - What is "local" in NI_NOFQDN?  (see comments in the code)
 * - NI_NAMEREQD and NI_NUMERICHOST conflict with each other.
 * - (KAME extension) always attach textual scopeid (fe80::1%lo0), if
 *   sin6_scope_id is filled - standardization status?
 * - what should we do if we should do getservbyport("sctp")?
 */

/*
 * Considerations about thread-safeness
 *   The code in this file is thread-safe, and so the thread-safeness of
 *   getnameinfo() depends on the property of backend functions.
 *     - getservbyport() is not thread safe for most systems we are targeting.
 *     - getipnodebyaddr() is thread safe.  However, many resolver libraries
 *       used in the function are not thread safe.
 *     - gethostbyaddr() is usually not thread safe.
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#ifndef HAVE_GETNAMEINFO

#include <sys/types.h>
#include <sys/socket.h>
#include <net/if.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <arpa/nameser.h>
#include <netdb.h>
#include <resolv.h>
#include <string.h>
#include <stddef.h>
#include <errno.h>

#include <inttypes.h>
#include "fetchmail.h"
#include "getaddrinfo.h"

static const struct afd {
	int a_af;
	int a_addrlen;
	int a_socklen;
	int a_off;
	int a_portoff;
} afdl [] = {
#ifdef INET6
	{PF_INET6, sizeof(struct in6_addr), sizeof(struct sockaddr_in6),
	 offsetof(struct sockaddr_in6, sin6_addr),
	 offsetof(struct sockaddr_in6, sin6_port)},
#endif
	{PF_INET, sizeof(struct in_addr), sizeof(struct sockaddr_in),
	 offsetof(struct sockaddr_in, sin_addr),
	 offsetof(struct sockaddr_in, sin_port)},
	{0, 0, 0, 0, 0},
};

#ifdef INET6
static int ip6_parsenumeric __P((const struct sockaddr *, const char *, char *,
				 size_t, int));
static int ip6_sa2str __P((const struct sockaddr_in6 *, char *, size_t, int));
#endif

int
getnameinfo(sa, salen, host, hostlen, serv, servlen, flags)
	const struct sockaddr *sa;
#ifdef HAVE_SOCKLEN_T
	socklen_t salen;
#else
	unsigned int salen;
#endif
	char *host;
	size_t hostlen;
	char *serv;
	size_t servlen;
	int flags;
{
	const struct afd *afd;
	struct servent *sp;
	struct hostent *hp;
	u_short port;
	int family, i;
	const char *addr;
	u_int32_t v4a;
	int h_error;
	char numserv[512];
	char numaddr[512];

	if (sa == NULL)
		return EAI_FAIL;

#ifdef HAVE_SA_LEN	/*XXX*/
	if (sa->sa_len != salen)
		return EAI_FAIL;
#endif

	family = sa->sa_family;
	for (i = 0; afdl[i].a_af; i++)
		if (afdl[i].a_af == family) {
			afd = &afdl[i];
			goto found;
		}
	return EAI_FAMILY;

 found:
	if (salen != afd->a_socklen)
		return EAI_FAIL;

	/* network byte order */
	memcpy(&port, (const char *)sa + afd->a_portoff, sizeof(port));
	addr = (const char *)sa + afd->a_off;

	if (serv == NULL || servlen == 0) {
		/*
		 * do nothing in this case.
		 * in case you are wondering if "&&" is more correct than
		 * "||" here: RFC3493 says that serv == NULL OR servlen == 0
		 * means that the caller does not want the result.
		 */
	} else {
		if (flags & NI_NUMERICSERV)
			sp = NULL;
		else {
			sp = getservbyport(port,
				(flags & NI_DGRAM) ? "udp" : "tcp");
		}
		if (sp) {
			if (strlen(sp->s_name) + 1 > servlen)
				return EAI_OVERFLOW;
			strlcpy(serv, sp->s_name, servlen);
		} else {
			snprintf(numserv, sizeof(numserv), "%u", ntohs(port));
			if (strlen(numserv) + 1 > servlen)
				return EAI_OVERFLOW;
			strlcpy(serv, numserv, servlen);
		}
	}

	switch (sa->sa_family) {
	case AF_INET:
		v4a = (u_int32_t)
		    ntohl(((const struct sockaddr_in *)sa)->sin_addr.s_addr);
		if (IN_MULTICAST(v4a) || IN_EXPERIMENTAL(v4a))
			flags |= NI_NUMERICHOST;
		v4a >>= IN_CLASSA_NSHIFT;
		if (v4a == 0)
			flags |= NI_NUMERICHOST;
		break;
#ifdef INET6
	case AF_INET6:
	    {
		const struct sockaddr_in6 *sin6;
		sin6 = (const struct sockaddr_in6 *)sa;
		switch (sin6->sin6_addr.s6_addr[0]) {
		case 0x00:
			if (IN6_IS_ADDR_V4MAPPED(&sin6->sin6_addr))
				;
			else if (IN6_IS_ADDR_LOOPBACK(&sin6->sin6_addr))
				;
			else
				flags |= NI_NUMERICHOST;
			break;
		default:
			if (IN6_IS_ADDR_LINKLOCAL(&sin6->sin6_addr))
				flags |= NI_NUMERICHOST;
			else if (IN6_IS_ADDR_MULTICAST(&sin6->sin6_addr))
				flags |= NI_NUMERICHOST;
			break;
		}
	    }
		break;
#endif
	}
	if (host == NULL || hostlen == 0) {
		/*
		 * do nothing in this case.
		 * in case you are wondering if "&&" is more correct than
		 * "||" here: RFC3493 says that host == NULL or hostlen == 0
		 * means that the caller does not want the result.
		 */
	} else if (flags & NI_NUMERICHOST) {
		/* NUMERICHOST and NAMEREQD conflicts with each other */
		if (flags & NI_NAMEREQD)
			return EAI_NONAME;

		goto numeric;
	} else {
#ifdef USE_GETIPNODEBY
		hp = getipnodebyaddr(addr, afd->a_addrlen, afd->a_af, &h_error);
#else
		hp = gethostbyaddr(addr, afd->a_addrlen, afd->a_af);
#ifdef HAVE_H_ERRNO
		h_error = h_errno;
#else
		h_error = EINVAL;
#endif
#endif

		if (hp) {
#if 0
			if (flags & NI_NOFQDN) {
				/*
				 * According to RFC3493 section 6.2, NI_NOFQDN
				 * means "node name portion of the FQDN shall
				 * be returned for local hosts."  The following
				 * code tries to implement it by returning the
				 * first label (the part before the first
				 * period) of the FQDN.  However, it is not
				 * clear if this always makes sense, since the
				 * given address may be outside of "local
				 * hosts."  Due to the unclear description, we
				 * disable the code in this implementation.
				 */
				char *p;
				p = strchr(hp->h_name, '.');
				if (p)
					*p = '\0';
			}
#endif
			if (strlen(hp->h_name) + 1 > hostlen) {
#ifdef USE_GETIPNODEBY
				freehostent(hp);
#endif
				return EAI_OVERFLOW;
			}
			strlcpy(host, hp->h_name, hostlen);
#ifdef USE_GETIPNODEBY
			freehostent(hp);
#endif
		} else {
			if (flags & NI_NAMEREQD)
				return EAI_NONAME;

		  numeric:
			switch(afd->a_af) {
#ifdef INET6
			case AF_INET6:
			{
				int error;

				if ((error = ip6_parsenumeric(sa, addr, host,
							      hostlen,
							      flags)) != 0)
					return(error);
				break;
			}
#endif
			default:
				if (inet_ntop(afd->a_af, addr, host,
				    hostlen) == NULL)
					return EAI_SYSTEM;
				break;
			}
		}
	}
	return(0);
}

#ifdef INET6
static int
ip6_parsenumeric(sa, addr, host, hostlen, flags)
	const struct sockaddr *sa;
	const char *addr;
	char *host;
	size_t hostlen;
	int flags;
{
	int numaddrlen;
	char numaddr[512];

	if (inet_ntop(AF_INET6, addr, numaddr, sizeof(numaddr)) == NULL)
		return EAI_SYSTEM;

	numaddrlen = strlen(numaddr);
	if (numaddrlen + 1 > hostlen) /* don't forget terminator */
		return EAI_OVERFLOW;
	strlcpy(host, numaddr, hostlen);

	if (((const struct sockaddr_in6 *)sa)->sin6_scope_id) {
		char zonebuf[MAXHOSTNAMELEN];
		int zonelen;

		zonelen = ip6_sa2str(
		    (const struct sockaddr_in6 *)(const void *)sa,
		    zonebuf, sizeof(zonebuf), flags);
		if (zonelen < 0)
			return EAI_OVERFLOW;
		if (zonelen + 1 + numaddrlen + 1 > hostlen)
			return EAI_OVERFLOW;

		/* construct <numeric-addr><delim><zoneid> */
		memcpy(host + numaddrlen + 1, zonebuf,
		    (size_t)zonelen);
		host[numaddrlen] = SCOPE_DELIMITER;
		host[numaddrlen + 1 + zonelen] = '\0';
	}

	return 0;
}

/* ARGSUSED */
static int
ip6_sa2str(sa6, buf, bufsiz, flags)
	const struct sockaddr_in6 *sa6;
	char *buf;
	size_t bufsiz;
	int flags;
{
	unsigned int ifindex;
	const struct in6_addr *a6;
	int n;

	ifindex = (unsigned int)sa6->sin6_scope_id;
	a6 = &sa6->sin6_addr;

#ifdef NI_NUMERICSCOPE
	if ((flags & NI_NUMERICSCOPE) != 0) {
		n = snprintf(buf, bufsiz, "%u", sa6->sin6_scope_id);
		if (n < 0 || n >= bufsiz)
			return -1;
		else
			return n;
	}
#endif

	/* if_indextoname() does not take buffer size.  not a good api... */
	if ((IN6_IS_ADDR_LINKLOCAL(a6) || IN6_IS_ADDR_MC_LINKLOCAL(a6) ||
	     IN6_IS_ADDR_MC_NODELOCAL(a6)) && bufsiz >= IF_NAMESIZE) {
		char *p = if_indextoname(ifindex, buf);
		if (p)
			return (strlen(p));
	}

	/* last resort */
	n = snprintf(buf, bufsiz, "%u", sa6->sin6_scope_id);
	if (n < 0 || n >= bufsiz)
		return -1;
	else
		return n;
}
#endif /* INET6 */
#endif