libc/netbsd/net/getnameinfo.c - platform/bionic - Git at Google

 /*	$NetBSD: getnameinfo.c,v 1.53 2012/09/26 23:13:00 christos Exp $	*/
 /*	$KAME: getnameinfo.c,v 1.45 2000/09/25 22:43:56 itojun Exp $	*/

 /*
  * Copyright (c) 2000 Ben Harris.
  * 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:
  * - Thread safe-ness must be checked
  * - 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.
  * - What is "local" in NI_FQDN?
  * - 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?
  *   XXX breaks backward compat for code that expects no scopeid.
  *   beware on merge.
  */

 #include <sys/cdefs.h>
 #if defined(LIBC_SCCS) && !defined(lint)
 __RCSID("$NetBSD: getnameinfo.c,v 1.53 2012/09/26 23:13:00 christos Exp $");
 #endif /* LIBC_SCCS and not lint */

 #include <sys/types.h>
 #include <sys/socket.h>
 #include <sys/un.h>
 #include <net/if.h>
 #include <net/if_ieee1394.h>
 #include <net/if_types.h>
 #include <netinet/in.h>
 #include <arpa/inet.h>
 #include <assert.h>
 #include <limits.h>
 #include <netdb.h>
 #ifdef ANDROID_CHANGES
 #include "arpa_nameser.h"
 #include "resolv_private.h"
 #include <sys/system_properties.h>
 #include <stdlib.h>
 #include <unistd.h>
 #include <errno.h>
 #define MIN(x,y) ((x) < (y) ? (x) : (y))
 #else
 #include <resolv.h>
 #endif
 #include <stddef.h>
 #include <string.h>

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

 struct sockinet {
 	u_char	si_len;
 	u_char	si_family;
 	u_short	si_port;
 };

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

 /*
  * Top-level getnameinfo() code.  Look at the address family, and pick an
  * appropriate function to call.
  */
 int getnameinfo(const struct sockaddr* sa, socklen_t salen, char* host, size_t hostlen, char* serv, size_t servlen, int flags)
 {
 	switch (sa->sa_family) {
 	case AF_INET:
 	case AF_INET6:
 		return getnameinfo_inet(sa, salen, host, hostlen,
 		    serv, servlen, flags);
 	case AF_LOCAL:
 		return getnameinfo_local(sa, salen, host, hostlen,
 		    serv, servlen, flags);
 	default:
 		return EAI_FAMILY;
 	}
 }

 /*
  * getnameinfo_local():
  * Format an local address into a printable format.
  */
 /* ARGSUSED */
 static int
 getnameinfo_local(const struct sockaddr *sa, socklen_t salen,
     char *host, socklen_t hostlen, char *serv, socklen_t servlen,
     int flags __attribute__((unused)))
 {
        const struct sockaddr_un *sun =
            (const struct sockaddr_un *)(const void *)sa;

        if (salen < (socklen_t) offsetof(struct sockaddr_un, sun_path)) {
            return EAI_FAMILY;
        }

        if (serv != NULL && servlen > 0)
                serv[0] = '\0';

        if (host && hostlen > 0)
                strlcpy(host, sun->sun_path,
                    MIN((socklen_t) sizeof(sun->sun_path) + 1, hostlen));

        return 0;
 }

 #ifdef ANDROID_CHANGES
 /* On success length of the host name is returned. A return
  * value of 0 means there's no host name associated with
  * the address. On failure -1 is returned in which case
  * normal execution flow shall continue. */
 static int
 android_gethostbyaddr_proxy(char* nameBuf, size_t nameBufLen, const void *addr, socklen_t addrLen, int addrFamily) {

 	int sock;
 	const int one = 1;
 	struct sockaddr_un proxy_addr;
 	const char* cache_mode = getenv("ANDROID_DNS_MODE");
 	FILE* proxy = NULL;
 	int result = -1;

 	if (cache_mode != NULL && strcmp(cache_mode, "local") == 0) {
 		// Don't use the proxy in local mode.  This is used by the
 		// proxy itself.
 		return -1;
 	}

 	// Temporary cautious hack to disable the DNS proxy for processes
 	// requesting special treatment.  Ideally the DNS proxy should
 	// accomodate these apps, though.
 	char propname[PROP_NAME_MAX];
 	char propvalue[PROP_VALUE_MAX];
 	snprintf(propname, sizeof(propname), "net.dns1.%d", getpid());
 	if (__system_property_get(propname, propvalue) > 0) {
 		return -1;
 	}
 	// create socket
 	sock = socket(AF_UNIX, SOCK_STREAM, 0);
 	if (sock < 0) {
 		return -1;
 	}

 	setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one));
 	memset(&proxy_addr, 0, sizeof(proxy_addr));
 	proxy_addr.sun_family = AF_UNIX;
 	strlcpy(proxy_addr.sun_path, "/dev/socket/dnsproxyd",
 			sizeof(proxy_addr.sun_path));
 	if (TEMP_FAILURE_RETRY(connect(sock, (const struct sockaddr*) (void*) &proxy_addr,
 							sizeof(proxy_addr))) != 0) {
 		close(sock);
 		return -1;
 	}

 	// send request to DnsProxyListener
 	proxy = fdopen(sock,"r+");
 	if (proxy == NULL) {
 		goto exit;
 	}

 	char buf[INET6_ADDRSTRLEN]; // big enough for IPv4 and IPv6
 	const char* addrStr = inet_ntop(addrFamily, addr, buf, sizeof(buf));
 	if (addrStr == NULL) {
 		goto exit;
 	}
 	if (fprintf(proxy, "gethostbyaddr %s %d %d", addrStr, addrLen, addrFamily) < 0) {
 		goto exit;
 	}

 	// literal NULL byte at end, required by FrameworkListener
 	if (fputc(0, proxy) == EOF || fflush(proxy) != 0) {
 		goto exit;
 	}

 	result = 0;
 	char msg_buf[4];
 	// read result code for gethostbyaddr
 	if (fread(msg_buf, 1, sizeof(msg_buf), proxy) != sizeof(msg_buf)) {
 		goto exit;
 	}

 	int result_code = (int)strtol(msg_buf, NULL, 10);
 	// verify the code itself
         // This should be synchronized to ResponseCode.h
         static const int DnsProxyQueryResult = 222;
 	if (result_code != DnsProxyQueryResult) {
 		goto exit;
 	}

 	uint32_t name_len;
 	if (fread(&name_len, sizeof(name_len), 1, proxy) != 1) {
 		goto exit;
 	}

 	name_len = ntohl(name_len);
 	if (name_len <= 0 || name_len >= nameBufLen) {
 		goto exit;
 	}

 	if (fread(nameBuf, name_len, 1, proxy) != 1) {
 		goto exit;
 	}

 	result = name_len;

  exit:
 	if (proxy != NULL) {
 		fclose(proxy);
 	}

 	return result;
 }
 #endif

 /*
  * getnameinfo_inet():
  * Format an IPv4 or IPv6 sockaddr into a printable string.
  */
 static int
 getnameinfo_inet(const struct sockaddr* sa, socklen_t salen,
        char *host, socklen_t hostlen,
        char *serv, socklen_t servlen,
        int flags)
 {
 	const struct afd *afd;
 	struct servent *sp;
 	struct hostent *hp;
 	u_short port;
 	int family, i;
 	const char *addr;
 	uint32_t v4a;
 	char numserv[512];
 	char numaddr[512];

 	/* sa is checked below */
 	/* host may be NULL */
 	/* serv may be NULL */

 	if (sa == NULL)
 		return EAI_FAIL;

 	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:
 	// http://b/1889275: callers should be allowed to provide too much
 	// space, but not too little.
 	if (salen < afd->a_socklen) {
 		return EAI_FAMILY;
 	}

 	/* network byte order */
 	port = ((const struct sockinet *)(const void *)sa)->si_port;
 	addr = (const char *)(const void *)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: rfc2553bis-03 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 > (size_t)servlen)
 				return EAI_MEMORY;
 			strlcpy(serv, sp->s_name, servlen);
 		} else {
 			snprintf(numserv, sizeof(numserv), "%u", ntohs(port));
 			if (strlen(numserv) + 1 > (size_t)servlen)
 				return EAI_MEMORY;
 			strlcpy(serv, numserv, servlen);
 		}
 	}

 	switch (sa->sa_family) {
 	case AF_INET:
 		v4a = (uint32_t)
 		    ntohl(((const struct sockaddr_in *)
 		    (const void *)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 *)(const void *)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: rfc2553bis-03 says that host == NULL or
 		 * hostlen == 0 means that the caller does not want the result.
 		 */
 	} else if (flags & NI_NUMERICHOST) {
 		size_t numaddrlen;

 		/* NUMERICHOST and NAMEREQD conflicts with each other */
 		if (flags & NI_NAMEREQD)
 			return EAI_NONAME;

 		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, numaddr, sizeof(numaddr))
 			    == NULL)
 				return EAI_SYSTEM;
 			numaddrlen = strlen(numaddr);
 			if (numaddrlen + 1 > (size_t)hostlen) /* don't forget terminator */
 				return EAI_MEMORY;
 			strlcpy(host, numaddr, hostlen);
 			break;
 		}
 	} else {
 #ifdef ANDROID_CHANGES
 		struct hostent android_proxy_hostent;
 		char android_proxy_buf[MAXDNAME];

 		int hostnamelen = android_gethostbyaddr_proxy(android_proxy_buf,
 				MAXDNAME, addr, afd->a_addrlen, afd->a_af);
 		if (hostnamelen > 0) {
 			hp = &android_proxy_hostent;
 			hp->h_name = android_proxy_buf;
 		} else if (!hostnamelen) {
 			hp = NULL;
 		} else {
 			hp = gethostbyaddr(addr, afd->a_addrlen, afd->a_af);
 		}
 #else
 		hp = gethostbyaddr(addr, afd->a_addrlen, afd->a_af);
 #endif

 		if (hp) {
 #if 0
 			/*
 			 * commented out, since "for local host" is not
 			 * implemented here - see RFC2553 p30
 			 */
 			if (flags & NI_NOFQDN) {
 				char *p;
 				p = strchr(hp->h_name, '.');
 				if (p)
 					*p = '\0';
 			}
 #endif
 			if (strlen(hp->h_name) + 1 > (size_t)hostlen) {
 				return EAI_MEMORY;
 			}
 			strlcpy(host, hp->h_name, hostlen);
 		} else {
 			if (flags & NI_NAMEREQD)
 				return EAI_NONAME;
 			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(const struct sockaddr *sa, const char *addr, char *host,
        socklen_t hostlen, int flags)
 {
 	size_t numaddrlen;
 	char numaddr[512];

 	assert(sa != NULL);
 	assert(addr != NULL);
 	assert(host != NULL);

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

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

 	if (((const struct sockaddr_in6 *)(const void *)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 ((size_t) zonelen + 1 + numaddrlen + 1 > (size_t)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(const struct sockaddr_in6 *sa6, char *buf, size_t bufsiz, int flags)
 {
 	unsigned int ifindex;
 	const struct in6_addr *a6;
 	int n;

 	assert(sa6 != NULL);
 	assert(buf != NULL);

 	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)) &&
 	    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 || (size_t) n >= bufsiz)
 		return -1;
 	else
 		return n;
 }
 #endif /* INET6 */
	/* $NetBSD: getnameinfo.c,v 1.53 2012/09/26 23:13:00 christos Exp $ */
	/* $KAME: getnameinfo.c,v 1.45 2000/09/25 22:43:56 itojun Exp $ */

	/*
	* Copyright (c) 2000 Ben Harris.
	* 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:
	* - Thread safe-ness must be checked
	* - 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.
	* - What is "local" in NI_FQDN?
	* - 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?
	* XXX breaks backward compat for code that expects no scopeid.
	* beware on merge.
	*/

	#include <sys/cdefs.h>
	#if defined(LIBC_SCCS) && !defined(lint)
	__RCSID("$NetBSD: getnameinfo.c,v 1.53 2012/09/26 23:13:00 christos Exp $");
	#endif /* LIBC_SCCS and not lint */

	#include <sys/types.h>
	#include <sys/socket.h>
	#include <sys/un.h>
	#include <net/if.h>
	#include <net/if_ieee1394.h>
	#include <net/if_types.h>
	#include <netinet/in.h>
	#include <arpa/inet.h>
	#include <assert.h>
	#include <limits.h>
	#include <netdb.h>
	#ifdef ANDROID_CHANGES
	#include "arpa_nameser.h"
	#include "resolv_private.h"
	#include <sys/system_properties.h>
	#include <stdlib.h>
	#include <unistd.h>
	#include <errno.h>
	#define MIN(x,y) ((x) < (y) ? (x) : (y))
	#else
	#include <resolv.h>
	#endif
	#include <stddef.h>
	#include <string.h>

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

	struct sockinet {
	u_char si_len;
	u_char si_family;
	u_short si_port;
	};

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

	/*
	* Top-level getnameinfo() code. Look at the address family, and pick an
	* appropriate function to call.
	*/
	int getnameinfo(const struct sockaddr* sa, socklen_t salen, char* host, size_t hostlen, char* serv, size_t servlen, int flags)
	{
	switch (sa->sa_family) {
	case AF_INET:
	case AF_INET6:
	return getnameinfo_inet(sa, salen, host, hostlen,
	serv, servlen, flags);
	case AF_LOCAL:
	return getnameinfo_local(sa, salen, host, hostlen,
	serv, servlen, flags);
	default:
	return EAI_FAMILY;
	}
	}

	/*
	* getnameinfo_local():
	* Format an local address into a printable format.
	*/
	/* ARGSUSED */
	static int
	getnameinfo_local(const struct sockaddr *sa, socklen_t salen,
	char host, socklen_t hostlen, char serv, socklen_t servlen,
	int flags __attribute__((unused)))
	{
	const struct sockaddr_un *sun =
	(const struct sockaddr_un )(const void )sa;

	if (salen < (socklen_t) offsetof(struct sockaddr_un, sun_path)) {
	return EAI_FAMILY;
	}

	if (serv != NULL && servlen > 0)
	serv[0] = '\0';

	if (host && hostlen > 0)
	strlcpy(host, sun->sun_path,
	MIN((socklen_t) sizeof(sun->sun_path) + 1, hostlen));

	return 0;
	}

	#ifdef ANDROID_CHANGES
	/* On success length of the host name is returned. A return
	* value of 0 means there's no host name associated with
	* the address. On failure -1 is returned in which case
	* normal execution flow shall continue. */
	static int
	android_gethostbyaddr_proxy(char* nameBuf, size_t nameBufLen, const void *addr, socklen_t addrLen, int addrFamily) {

	int sock;
	const int one = 1;
	struct sockaddr_un proxy_addr;
	const char* cache_mode = getenv("ANDROID_DNS_MODE");
	FILE* proxy = NULL;
	int result = -1;

	if (cache_mode != NULL && strcmp(cache_mode, "local") == 0) {
	// Don't use the proxy in local mode. This is used by the
	// proxy itself.
	return -1;
	}

	// Temporary cautious hack to disable the DNS proxy for processes
	// requesting special treatment. Ideally the DNS proxy should
	// accomodate these apps, though.
	char propname[PROP_NAME_MAX];
	char propvalue[PROP_VALUE_MAX];
	snprintf(propname, sizeof(propname), "net.dns1.%d", getpid());
	if (__system_property_get(propname, propvalue) > 0) {
	return -1;
	}
	// create socket
	sock = socket(AF_UNIX, SOCK_STREAM, 0);
	if (sock < 0) {
	return -1;
	}

	setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one));
	memset(&proxy_addr, 0, sizeof(proxy_addr));
	proxy_addr.sun_family = AF_UNIX;
	strlcpy(proxy_addr.sun_path, "/dev/socket/dnsproxyd",
	sizeof(proxy_addr.sun_path));
	if (TEMP_FAILURE_RETRY(connect(sock, (const struct sockaddr) (void) &proxy_addr,
	sizeof(proxy_addr))) != 0) {
	close(sock);
	return -1;
	}

	// send request to DnsProxyListener
	proxy = fdopen(sock,"r+");
	if (proxy == NULL) {
	goto exit;
	}

	char buf[INET6_ADDRSTRLEN]; // big enough for IPv4 and IPv6
	const char* addrStr = inet_ntop(addrFamily, addr, buf, sizeof(buf));
	if (addrStr == NULL) {
	goto exit;
	}
	if (fprintf(proxy, "gethostbyaddr %s %d %d", addrStr, addrLen, addrFamily) < 0) {
	goto exit;
	}

	// literal NULL byte at end, required by FrameworkListener
	if (fputc(0, proxy) == EOF \|\| fflush(proxy) != 0) {
	goto exit;
	}

	result = 0;
	char msg_buf[4];
	// read result code for gethostbyaddr
	if (fread(msg_buf, 1, sizeof(msg_buf), proxy) != sizeof(msg_buf)) {
	goto exit;
	}

	int result_code = (int)strtol(msg_buf, NULL, 10);
	// verify the code itself
	// This should be synchronized to ResponseCode.h
	static const int DnsProxyQueryResult = 222;
	if (result_code != DnsProxyQueryResult) {
	goto exit;
	}

	uint32_t name_len;
	if (fread(&name_len, sizeof(name_len), 1, proxy) != 1) {
	goto exit;
	}

	name_len = ntohl(name_len);
	if (name_len <= 0 \|\| name_len >= nameBufLen) {
	goto exit;
	}

	if (fread(nameBuf, name_len, 1, proxy) != 1) {
	goto exit;
	}

	result = name_len;

	exit:
	if (proxy != NULL) {
	fclose(proxy);
	}

	return result;
	}
	#endif

	/*
	* getnameinfo_inet():
	* Format an IPv4 or IPv6 sockaddr into a printable string.
	*/
	static int
	getnameinfo_inet(const struct sockaddr* sa, socklen_t salen,
	char *host, socklen_t hostlen,
	char *serv, socklen_t servlen,
	int flags)
	{
	const struct afd *afd;
	struct servent *sp;
	struct hostent *hp;
	u_short port;
	int family, i;
	const char *addr;
	uint32_t v4a;
	char numserv[512];
	char numaddr[512];

	/* sa is checked below */
	/* host may be NULL */
	/* serv may be NULL */

	if (sa == NULL)
	return EAI_FAIL;

	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:
	// http://b/1889275: callers should be allowed to provide too much
	// space, but not too little.
	if (salen < afd->a_socklen) {
	return EAI_FAMILY;
	}

	/* network byte order */
	port = ((const struct sockinet )(const void )sa)->si_port;
	addr = (const char )(const void )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: rfc2553bis-03 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 > (size_t)servlen)
	return EAI_MEMORY;
	strlcpy(serv, sp->s_name, servlen);
	} else {
	snprintf(numserv, sizeof(numserv), "%u", ntohs(port));
	if (strlen(numserv) + 1 > (size_t)servlen)
	return EAI_MEMORY;
	strlcpy(serv, numserv, servlen);
	}
	}

	switch (sa->sa_family) {
	case AF_INET:
	v4a = (uint32_t)
	ntohl(((const struct sockaddr_in *)
	(const void *)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 )(const void )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: rfc2553bis-03 says that host == NULL or
	* hostlen == 0 means that the caller does not want the result.
	*/
	} else if (flags & NI_NUMERICHOST) {
	size_t numaddrlen;

	/* NUMERICHOST and NAMEREQD conflicts with each other */
	if (flags & NI_NAMEREQD)
	return EAI_NONAME;

	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, numaddr, sizeof(numaddr))
	== NULL)
	return EAI_SYSTEM;
	numaddrlen = strlen(numaddr);
	if (numaddrlen + 1 > (size_t)hostlen) /* don't forget terminator */
	return EAI_MEMORY;
	strlcpy(host, numaddr, hostlen);
	break;
	}
	} else {
	#ifdef ANDROID_CHANGES
	struct hostent android_proxy_hostent;
	char android_proxy_buf[MAXDNAME];

	int hostnamelen = android_gethostbyaddr_proxy(android_proxy_buf,
	MAXDNAME, addr, afd->a_addrlen, afd->a_af);
	if (hostnamelen > 0) {
	hp = &android_proxy_hostent;
	hp->h_name = android_proxy_buf;
	} else if (!hostnamelen) {
	hp = NULL;
	} else {
	hp = gethostbyaddr(addr, afd->a_addrlen, afd->a_af);
	}
	#else
	hp = gethostbyaddr(addr, afd->a_addrlen, afd->a_af);
	#endif

	if (hp) {
	#if 0
	/*
	* commented out, since "for local host" is not
	* implemented here - see RFC2553 p30
	*/
	if (flags & NI_NOFQDN) {
	char *p;
	p = strchr(hp->h_name, '.');
	if (p)
	*p = '\0';
	}
	#endif
	if (strlen(hp->h_name) + 1 > (size_t)hostlen) {
	return EAI_MEMORY;
	}
	strlcpy(host, hp->h_name, hostlen);
	} else {
	if (flags & NI_NAMEREQD)
	return EAI_NONAME;
	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(const struct sockaddr sa, const char addr, char *host,
	socklen_t hostlen, int flags)
	{
	size_t numaddrlen;
	char numaddr[512];

	assert(sa != NULL);
	assert(addr != NULL);
	assert(host != NULL);

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

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

	if (((const struct sockaddr_in6 )(const void )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 ((size_t) zonelen + 1 + numaddrlen + 1 > (size_t)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(const struct sockaddr_in6 sa6, char buf, size_t bufsiz, int flags)
	{
	unsigned int ifindex;
	const struct in6_addr *a6;
	int n;

	assert(sa6 != NULL);
	assert(buf != NULL);

	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)) &&
	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 \|\| (size_t) n >= bufsiz)
	return -1;
	else
	return n;
	}
	#endif /* INET6 */