resolv/res_init.c

/*	$NetBSD: res_init.c,v 1.8 2006/03/19 03:10:08 christos Exp $	*/

/*
 * Copyright (c) 1985, 1989, 1993
 *    The Regents of the University of California.  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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 * 	This product includes software developed by the University of
 * 	California, Berkeley and its contributors.
 * 4. Neither the name of the University 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 REGENTS 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 REGENTS 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.
 */

/*
 * Portions Copyright (c) 1993 by Digital Equipment Corporation.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies, and that
 * the name of Digital Equipment Corporation not be used in advertising or
 * publicity pertaining to distribution of the document or software without
 * specific, written prior permission.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
 * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS.   IN NO EVENT SHALL DIGITAL EQUIPMENT
 * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
 * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
 * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
 * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
 * SOFTWARE.
 */

/*
 * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
 * Portions Copyright (c) 1996-1999 by Internet Software Consortium.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
 * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <sys/param.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <sys/types.h>

#include <arpa/inet.h>
#include <arpa/nameser.h>
#include <netinet/in.h>

#include <ctype.h>
#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#ifdef ANDROID_CHANGES
#include <errno.h>
#include <fcntl.h>
#endif /* ANDROID_CHANGES */

/* ensure that sockaddr_in6 and IN6ADDR_ANY_INIT are declared / defined */
#ifdef ANDROID_CHANGES
#include "resolv_netid.h"
#include "resolv_private.h"
#else
#include <resolv.h>
#endif

#include "res_private.h"

/* Options.  Should all be left alone. */
#ifndef DEBUG
#define DEBUG
#endif

static void res_setoptions __P((res_state, const char*, const char*) );

#ifdef RESOLVSORT
static const char sort_mask[] = "/&";
#define ISSORTMASK(ch) (strchr(sort_mask, ch) != NULL)
static uint32_t net_mask(struct in_addr);
#endif

#if !defined(isascii) /* XXX - could be a function */
#define isascii(c) (!(c & 0200))
#endif

/*
 * Resolver state default settings.
 */

/*
 * Set up default settings.  If the configuration file exist, the values
 * there will have precedence.  Otherwise, the server address is set to
 * INADDR_ANY and the default domain name comes from the gethostname().
 *
 * An interrim version of this code (BIND 4.9, pre-4.4BSD) used 127.0.0.1
 * rather than INADDR_ANY ("0.0.0.0") as the default name server address
 * since it was noted that INADDR_ANY actually meant ``the first interface
 * you "ifconfig"'d at boot time'' and if this was a SLIP or PPP interface,
 * it had to be "up" in order for you to reach your own name server.  It
 * was later decided that since the recommended practice is to always
 * install local static routes through 127.0.0.1 for all your network
 * interfaces, that we could solve this problem without a code change.
 *
 * The configuration file should always be used, since it is the only way
 * to specify a default domain.  If you are running a server on your local
 * machine, you should say "nameserver 0.0.0.0" or "nameserver 127.0.0.1"
 * in the configuration file.
 *
 * Return 0 if completes successfully, -1 on error
 */
int res_ninit(res_state statp) {
    extern int __res_vinit(res_state, int);

    return (__res_vinit(statp, 0));
}

/* This function has to be reachable by res_data.c but not publicly. */
int __res_vinit(res_state statp, int preinit) {
#if !defined(__BIONIC__)
    register FILE* fp;
#endif
    register char *cp, **pp;
#if !defined(__BIONIC__)
    register int n;
#endif
    char buf[BUFSIZ];
    int nserv = 0; /* number of nameserver records read from file */
#if !defined(__BIONIC__)
    int haveenv = 0;
#endif
    int havesearch = 0;
#ifdef RESOLVSORT
    int nsort = 0;
#endif
#if !defined(__BIONIC__)
    char* net;
#endif
    int dots;
    union res_sockaddr_union u[2];

    if ((statp->options & RES_INIT) != 0U) res_ndestroy(statp);

    if (!preinit) {
        statp->netid = NETID_UNSET;
        statp->retrans = RES_TIMEOUT;
        statp->retry = RES_DFLRETRY;
        statp->options = RES_DEFAULT;
        statp->id = res_randomid();
        statp->_mark = MARK_UNSET;
    }

    memset(u, 0, sizeof(u));
#ifdef USELOOPBACK
    u[nserv].sin.sin_addr = inet_makeaddr(IN_LOOPBACKNET, 1);
#else
    u[nserv].sin.sin_addr.s_addr = INADDR_ANY;
#endif
    u[nserv].sin.sin_family = AF_INET;
    u[nserv].sin.sin_port = htons(NAMESERVER_PORT);
#ifdef HAVE_SA_LEN
    u[nserv].sin.sin_len = sizeof(struct sockaddr_in);
#endif
    nserv++;
#ifdef HAS_INET6_STRUCTS
#ifdef USELOOPBACK
    u[nserv].sin6.sin6_addr = in6addr_loopback;
#else
    u[nserv].sin6.sin6_addr = in6addr_any;
#endif
    u[nserv].sin6.sin6_family = AF_INET6;
    u[nserv].sin6.sin6_port = htons(NAMESERVER_PORT);
#ifdef HAVE_SA_LEN
    u[nserv].sin6.sin6_len = sizeof(struct sockaddr_in6);
#endif
    nserv++;
#endif
    statp->nscount = 0;
    statp->ndots = 1;
    statp->pfcode = 0;
    statp->_vcsock = -1;
    statp->_flags = 0;
    statp->qhook = NULL;
    statp->rhook = NULL;
    statp->_u._ext.nscount = 0;
    statp->_u._ext.ext = malloc(sizeof(*statp->_u._ext.ext));
    if (statp->_u._ext.ext != NULL) {
        memset(statp->_u._ext.ext, 0, sizeof(*statp->_u._ext.ext));
        statp->_u._ext.ext->nsaddrs[0].sin = statp->nsaddr;
        strcpy(statp->_u._ext.ext->nsuffix, "ip6.arpa");
        strcpy(statp->_u._ext.ext->nsuffix2, "ip6.int");
    }
    statp->nsort = 0;
    res_setservers(statp, u, nserv);

#if defined(__BIONIC__)
    /* Ignore the environment. */
#else
    /* Allow user to override the local domain definition */
    if ((cp = getenv("LOCALDOMAIN")) != NULL) {
        (void) strncpy(statp->defdname, cp, sizeof(statp->defdname) - 1);
        statp->defdname[sizeof(statp->defdname) - 1] = '\0';
        haveenv++;

        /*
         * Set search list to be blank-separated strings
         * from rest of env value.  Permits users of LOCALDOMAIN
         * to still have a search list, and anyone to set the
         * one that they want to use as an individual (even more
         * important now that the rfc1535 stuff restricts searches)
         */
        cp = statp->defdname;
        pp = statp->dnsrch;
        *pp++ = cp;
        for (n = 0; *cp && pp < statp->dnsrch + MAXDNSRCH; cp++) {
            if (*cp == '\n') /* silly backwards compat */
                break;
            else if (*cp == ' ' || *cp == '\t') {
                *cp = 0;
                n = 1;
            } else if (n) {
                *pp++ = cp;
                n = 0;
                havesearch = 1;
            }
        }
        /* null terminate last domain if there are excess */
        while (*cp != '\0' && *cp != ' ' && *cp != '\t' && *cp != '\n') cp++;
        *cp = '\0';
        *pp++ = 0;
    }
    if (nserv > 0) statp->nscount = nserv;
#endif

#ifndef ANDROID_CHANGES /* !ANDROID_CHANGES - IGNORE resolv.conf in Android */
#define MATCH(line, name)                      \
    (!strncmp(line, name, sizeof(name) - 1) && \
     (line[sizeof(name) - 1] == ' ' || line[sizeof(name) - 1] == '\t'))

    nserv = 0;
    if ((fp = fopen(_PATH_RESCONF, "re")) != NULL) {
        /* read the config file */
        while (fgets(buf, sizeof(buf), fp) != NULL) {
            /* skip comments */
            if (*buf == ';' || *buf == '#') continue;
            /* read default domain name */
            if (MATCH(buf, "domain")) {
                if (haveenv) /* skip if have from environ */
                    continue;
                cp = buf + sizeof("domain") - 1;
                while (*cp == ' ' || *cp == '\t') cp++;
                if ((*cp == '\0') || (*cp == '\n')) continue;
                strncpy(statp->defdname, cp, sizeof(statp->defdname) - 1);
                statp->defdname[sizeof(statp->defdname) - 1] = '\0';
                if ((cp = strpbrk(statp->defdname, " \t\n")) != NULL) *cp = '\0';
                havesearch = 0;
                continue;
            }
            /* set search list */
            if (MATCH(buf, "search")) {
                if (haveenv) /* skip if have from environ */
                    continue;
                cp = buf + sizeof("search") - 1;
                while (*cp == ' ' || *cp == '\t') cp++;
                if ((*cp == '\0') || (*cp == '\n')) continue;
                strncpy(statp->defdname, cp, sizeof(statp->defdname) - 1);
                statp->defdname[sizeof(statp->defdname) - 1] = '\0';
                if ((cp = strchr(statp->defdname, '\n')) != NULL) *cp = '\0';
                /*
                 * Set search list to be blank-separated strings
                 * on rest of line.
                 */
                cp = statp->defdname;
                pp = statp->dnsrch;
                *pp++ = cp;
                for (n = 0; *cp && pp < statp->dnsrch + MAXDNSRCH; cp++) {
                    if (*cp == ' ' || *cp == '\t') {
                        *cp = 0;
                        n = 1;
                    } else if (n) {
                        *pp++ = cp;
                        n = 0;
                    }
                }
                /* null terminate last domain if there are excess */
                while (*cp != '\0' && *cp != ' ' && *cp != '\t') cp++;
                *cp = '\0';
                *pp++ = 0;
                havesearch = 1;
                continue;
            }
            /* read nameservers to query */
            if (MATCH(buf, "nameserver") && nserv < MAXNS) {
                struct addrinfo hints, *ai;
                char sbuf[NI_MAXSERV];
                const size_t minsiz = sizeof(statp->_u._ext.ext->nsaddrs[0]);

                cp = buf + sizeof("nameserver") - 1;
                while (*cp == ' ' || *cp == '\t') cp++;
                cp[strcspn(cp, ";# \t\n")] = '\0';
                if ((*cp != '\0') && (*cp != '\n')) {
                    memset(&hints, 0, sizeof(hints));
                    hints.ai_family = PF_UNSPEC;
                    hints.ai_socktype = SOCK_DGRAM; /*dummy*/
                    hints.ai_flags = AI_NUMERICHOST;
                    sprintf(sbuf, "%u", NAMESERVER_PORT);
                    if (getaddrinfo(cp, sbuf, &hints, &ai) == 0 && ai->ai_addrlen <= minsiz) {
                        if (statp->_u._ext.ext != NULL) {
                            memcpy(&statp->_u._ext.ext->nsaddrs[nserv], ai->ai_addr,
                                   ai->ai_addrlen);
                        }
                        if (ai->ai_addrlen <= sizeof(statp->nsaddr_list[nserv])) {
                            memcpy(&statp->nsaddr_list[nserv], ai->ai_addr, ai->ai_addrlen);
                        } else
                            statp->nsaddr_list[nserv].sin_family = 0;
                        freeaddrinfo(ai);
                        nserv++;
                    }
                }
                continue;
            }
            if (MATCH(buf, "sortlist")) {
                struct in_addr a;

                cp = buf + sizeof("sortlist") - 1;
                while (nsort < MAXRESOLVSORT) {
                    while (*cp == ' ' || *cp == '\t') cp++;
                    if (*cp == '\0' || *cp == '\n' || *cp == ';') break;
                    net = cp;
                    while (*cp && !ISSORTMASK(*cp) && *cp != ';' && isascii(*cp) &&
                           !isspace((unsigned char) *cp))
                        cp++;
                    n = *cp;
                    *cp = 0;
                    if (inet_aton(net, &a)) {
                        statp->sort_list[nsort].addr = a;
                        if (ISSORTMASK(n)) {
                            *cp++ = n;
                            net = cp;
                            while (*cp && *cp != ';' && isascii(*cp) &&
                                   !isspace((unsigned char) *cp))
                                cp++;
                            n = *cp;
                            *cp = 0;
                            if (inet_aton(net, &a)) {
                                statp->sort_list[nsort].mask = a.s_addr;
                            } else {
                                statp->sort_list[nsort].mask =
                                        net_mask(statp->sort_list[nsort].addr);
                            }
                        } else {
                            statp->sort_list[nsort].mask = net_mask(statp->sort_list[nsort].addr);
                        }
                        nsort++;
                    }
                    *cp = n;
                }
                continue;
            }
            if (MATCH(buf, "options")) {
                res_setoptions(statp, buf + sizeof("options") - 1, "conf");
                continue;
            }
        }
        if (nserv > 0) statp->nscount = nserv;
        statp->nsort = nsort;
        (void) fclose(fp);
    }
#endif /* !ANDROID_CHANGES */
/*
 * Last chance to get a nameserver.  This should not normally
 * be necessary
 */
#ifdef NO_RESOLV_CONF
    if (nserv == 0) nserv = get_nameservers(statp);
#endif

    if (statp->defdname[0] == 0 && gethostname(buf, sizeof(statp->defdname) - 1) == 0 &&
        (cp = strchr(buf, '.')) != NULL)
        strcpy(statp->defdname, cp + 1);

    /* find components of local domain that might be searched */
    if (havesearch == 0) {
        pp = statp->dnsrch;
        *pp++ = statp->defdname;
        *pp = NULL;

        dots = 0;
        for (cp = statp->defdname; *cp; cp++) dots += (*cp == '.');

        cp = statp->defdname;
        while (pp < statp->dnsrch + MAXDFLSRCH) {
            if (dots < LOCALDOMAINPARTS) break;
            cp = strchr(cp, '.') + 1; /* we know there is one */
            *pp++ = cp;
            dots--;
        }
        *pp = NULL;
#ifdef DEBUG
        if (statp->options & RES_DEBUG) {
            printf(";; res_init()... default dnsrch list:\n");
            for (pp = statp->dnsrch; *pp; pp++) printf(";;\t%s\n", *pp);
            printf(";;\t..END..\n");
        }
#endif
    }

    if ((cp = getenv("RES_OPTIONS")) != NULL) res_setoptions(statp, cp, "env");
    if (nserv > 0) {
        statp->nscount = nserv;
        statp->options |= RES_INIT;
    }
    return (0);
}

static void res_setoptions(res_state statp, const char* options, const char* source) {
    const char* cp = options;
    int i;
    struct __res_state_ext* ext = statp->_u._ext.ext;

#ifdef DEBUG
    if (statp->options & RES_DEBUG)
        printf(";; res_setoptions(\"%s\", \"%s\")...\n", options, source);
#endif
    while (*cp) {
        /* skip leading and inner runs of spaces */
        while (*cp == ' ' || *cp == '\t') cp++;
        /* search for and process individual options */
        if (!strncmp(cp, "ndots:", sizeof("ndots:") - 1)) {
            i = atoi(cp + sizeof("ndots:") - 1);
            if (i <= RES_MAXNDOTS)
                statp->ndots = i;
            else
                statp->ndots = RES_MAXNDOTS;
#ifdef DEBUG
            if (statp->options & RES_DEBUG) printf(";;\tndots=%d\n", statp->ndots);
#endif
        } else if (!strncmp(cp, "timeout:", sizeof("timeout:") - 1)) {
            i = atoi(cp + sizeof("timeout:") - 1);
            if (i <= RES_MAXRETRANS)
                statp->retrans = i;
            else
                statp->retrans = RES_MAXRETRANS;
#ifdef DEBUG
            if (statp->options & RES_DEBUG) printf(";;\ttimeout=%d\n", statp->retrans);
#endif
        } else if (!strncmp(cp, "attempts:", sizeof("attempts:") - 1)) {
            i = atoi(cp + sizeof("attempts:") - 1);
            if (i <= RES_MAXRETRY)
                statp->retry = i;
            else
                statp->retry = RES_MAXRETRY;
#ifdef DEBUG
            if (statp->options & RES_DEBUG) printf(";;\tattempts=%d\n", statp->retry);
#endif
        } else if (!strncmp(cp, "debug", sizeof("debug") - 1)) {
#ifdef DEBUG
            if (!(statp->options & RES_DEBUG)) {
                printf(";; res_setoptions(\"%s\", \"%s\")..\n", options, source);
                statp->options |= RES_DEBUG;
            }
            printf(";;\tdebug\n");
#endif
        } else if (!strncmp(cp, "no_tld_query", sizeof("no_tld_query") - 1) ||
                   !strncmp(cp, "no-tld-query", sizeof("no-tld-query") - 1)) {
            statp->options |= RES_NOTLDQUERY;
        } else if (!strncmp(cp, "inet6", sizeof("inet6") - 1)) {
            statp->options |= RES_USE_INET6;
        } else if (!strncmp(cp, "rotate", sizeof("rotate") - 1)) {
            statp->options |= RES_ROTATE;
        } else if (!strncmp(cp, "no-check-names", sizeof("no-check-names") - 1)) {
            statp->options |= RES_NOCHECKNAME;
        }
#ifdef RES_USE_EDNS0
        else if (!strncmp(cp, "edns0", sizeof("edns0") - 1)) {
            statp->options |= RES_USE_EDNS0;
        }
#endif
        else if (!strncmp(cp, "dname", sizeof("dname") - 1)) {
            statp->options |= RES_USE_DNAME;
        } else if (!strncmp(cp, "nibble:", sizeof("nibble:") - 1)) {
            if (ext == NULL) goto skip;
            cp += sizeof("nibble:") - 1;
            i = MIN(strcspn(cp, " \t"), sizeof(ext->nsuffix) - 1);
            strncpy(ext->nsuffix, cp, (size_t) i);
            ext->nsuffix[i] = '\0';
        } else if (!strncmp(cp, "nibble2:", sizeof("nibble2:") - 1)) {
            if (ext == NULL) goto skip;
            cp += sizeof("nibble2:") - 1;
            i = MIN(strcspn(cp, " \t"), sizeof(ext->nsuffix2) - 1);
            strncpy(ext->nsuffix2, cp, (size_t) i);
            ext->nsuffix2[i] = '\0';
        } else if (!strncmp(cp, "v6revmode:", sizeof("v6revmode:") - 1)) {
            cp += sizeof("v6revmode:") - 1;
            /* "nibble" and "bitstring" used to be valid */
            if (!strncmp(cp, "single", sizeof("single") - 1)) {
                statp->options |= RES_NO_NIBBLE2;
            } else if (!strncmp(cp, "both", sizeof("both") - 1)) {
                statp->options &= ~RES_NO_NIBBLE2;
            }
        } else {
            /* XXX - print a warning here? */
        }
    skip:
        /* skip to next run of spaces */
        while (*cp && *cp != ' ' && *cp != '\t') cp++;
    }
}

#ifdef RESOLVSORT
/* XXX - should really support CIDR which means explicit masks always. */
static uint32_t net_mask(struct in_addr in) /*!< XXX - should really use system's version of this */
{
    register uint32_t i = ntohl(in.s_addr);

    if (IN_CLASSA(i))
        return (htonl(IN_CLASSA_NET));
    else if (IN_CLASSB(i))
        return (htonl(IN_CLASSB_NET));
    return (htonl(IN_CLASSC_NET));
}
#endif

/*%
 * This routine is for closing the socket if a virtual circuit is used and
 * the program wants to close it.  This provides support for endhostent()
 * which expects to close the socket.
 *
 * This routine is not expected to be user visible.
 */
void res_nclose(res_state statp) {
    int ns;

    if (statp->_vcsock >= 0) {
        (void) close(statp->_vcsock);
        statp->_vcsock = -1;
        statp->_flags &= ~(RES_F_VC | RES_F_CONN);
    }
    for (ns = 0; ns < statp->_u._ext.nscount; ns++) {
        if (statp->_u._ext.nssocks[ns] != -1) {
            (void) close(statp->_u._ext.nssocks[ns]);
            statp->_u._ext.nssocks[ns] = -1;
        }
    }
}

void res_ndestroy(res_state statp) {
    res_nclose(statp);
    if (statp->_u._ext.ext != NULL) free(statp->_u._ext.ext);
    statp->options &= ~RES_INIT;
    statp->_u._ext.ext = NULL;
}

const char* res_get_nibblesuffix(res_state statp) {
    if (statp->_u._ext.ext) return (statp->_u._ext.ext->nsuffix);
    return ("ip6.arpa");
}

const char* res_get_nibblesuffix2(res_state statp) {
    if (statp->_u._ext.ext) return (statp->_u._ext.ext->nsuffix2);
    return ("ip6.int");
}

void res_setservers(res_state statp, const union res_sockaddr_union* set, int cnt) {
    int i, nserv;
    size_t size;

    /* close open servers */
    res_nclose(statp);

    /* cause rtt times to be forgotten */
    statp->_u._ext.nscount = 0;

    nserv = 0;
    for (i = 0; i < cnt && nserv < MAXNS; i++) {
        switch (set->sin.sin_family) {
            case AF_INET:
                size = sizeof(set->sin);
                if (statp->_u._ext.ext)
                    memcpy(&statp->_u._ext.ext->nsaddrs[nserv], &set->sin, size);
                if (size <= sizeof(statp->nsaddr_list[nserv]))
                    memcpy(&statp->nsaddr_list[nserv], &set->sin, size);
                else
                    statp->nsaddr_list[nserv].sin_family = 0;
                nserv++;
                break;

#ifdef HAS_INET6_STRUCTS
            case AF_INET6:
                size = sizeof(set->sin6);
                if (statp->_u._ext.ext)
                    memcpy(&statp->_u._ext.ext->nsaddrs[nserv], &set->sin6, size);
                if (size <= sizeof(statp->nsaddr_list[nserv]))
                    memcpy(&statp->nsaddr_list[nserv], &set->sin6, size);
                else
                    statp->nsaddr_list[nserv].sin_family = 0;
                nserv++;
                break;
#endif

            default:
                break;
        }
        set++;
    }
    statp->nscount = nserv;
}

int res_getservers(res_state statp, union res_sockaddr_union* set, int cnt) {
    int i;
    size_t size;
    uint16_t family;

    for (i = 0; i < statp->nscount && i < cnt; i++) {
        if (statp->_u._ext.ext)
            family = statp->_u._ext.ext->nsaddrs[i].sin.sin_family;
        else
            family = statp->nsaddr_list[i].sin_family;

        switch (family) {
            case AF_INET:
                size = sizeof(set->sin);
                if (statp->_u._ext.ext)
                    memcpy(&set->sin, &statp->_u._ext.ext->nsaddrs[i], size);
                else
                    memcpy(&set->sin, &statp->nsaddr_list[i], size);
                break;

#ifdef HAS_INET6_STRUCTS
            case AF_INET6:
                size = sizeof(set->sin6);
                if (statp->_u._ext.ext)
                    memcpy(&set->sin6, &statp->_u._ext.ext->nsaddrs[i], size);
                else
                    memcpy(&set->sin6, &statp->nsaddr_list[i], size);
                break;
#endif

            default:
                set->sin.sin_family = 0;
                break;
        }
        set++;
    }
    return (statp->nscount);
}

#ifdef ANDROID_CHANGES
void res_setnetcontext(res_state statp, const struct android_net_context* netcontext) {
    if (statp != NULL) {
        statp->netid = netcontext->dns_netid;
        statp->_mark = netcontext->dns_mark;
        statp->qhook = netcontext->qhook;
        if (netcontext->flags & NET_CONTEXT_FLAG_USE_EDNS) {
            statp->options |= RES_USE_EDNS0 | RES_USE_DNSSEC;
        }
    }
}

#endif /* ANDROID_CHANGES */