/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright 2015 Gary Mills
 * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*      Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
/*        All Rights Reserved   */

/*
 * University Copyright- Copyright (c) 1982, 1986, 1988
 * The Regents of the University of California
 * All Rights Reserved
 *
 * University Acknowledgment- Portions of this document are derived from
 * software developed by the University of California, Berkeley, and its
 * contributors.
 */

#include <sys/types.h>
#include <sys/sockio.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <stropts.h>
#include <arpa/nameser.h>
#include <resolv.h>

#include <netinet/in.h>
#include <net/if.h>
#include <netinet/if_ether.h>
#include <arpa/inet.h>

/*
 * Undocumented external function in libnsl
 */
extern int
getdomainname(char *, int);

#define MAXIFS  256

/*
 * Resolver state default settings
 */

struct state _res = {
        RES_TIMEOUT,            /* retransmition time interval */
        4,                              /* number of times to retransmit */
        RES_DEFAULT,            /* options flags */
        1,                              /* number of name servers */
};

/*
 * Set up default settings.  If the configuration file exist, the values
 * there will have precedence.  Otherwise, the server address is set to
 * INADDR_LOOPBACK and the default domain name comes from the gethostname().
 * BUT if the NIS/RPC domain name is set, that is used if all else fails.
 *
 * The configuration file should only be used if you want to redefine your
 * domain or run without a server on your machine.
 *
 * Note the user can always override then domain name with the environment
 * variable LOCALDOMAIN which has absolute priority.
 *
 *
 * Return 0 if completes successfully, -1 on error
 */
int
res_init(void)
{
        register FILE *fp;
        register char *cp, **pp;
        register int n;
        char buf[BUFSIZ];
        int nserv = 0;    /* number of nameserver records read from file */
        int haveenv = 0;
        int havesearch = 0;

        _res.nsaddr.sin_addr.s_addr =  htonl(INADDR_LOOPBACK); /* INADDR_ANY */
        _res.nsaddr.sin_family = AF_INET;
        _res.nsaddr.sin_port = htons(NAMESERVER_PORT);
        _res.nscount = 1;

#ifdef SIOCGIFNUM
        {       int numifs, s, n, int_up;
                struct ifconf ifc;
                register struct ifreq *ifrp;
                struct ifreq ifr;
                unsigned bufsize;
                unsigned int flags;
                char *buf;

                if ((s = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
                        perror("socket");
                        return (-1);
                }
                if (ioctl(s, SIOCGIFNUM, (char *)&numifs) < 0) {
                        numifs = MAXIFS;
                }
                bufsize = numifs * sizeof (struct ifreq);
                buf = (char *)malloc(bufsize);
                if (buf == NULL) {
                        perror("out of memory");
                        (void) close(s);
                        return (-1);
                }
                ifc.ifc_len = bufsize;
                ifc.ifc_buf = buf;
                if (ioctl(s, SIOCGIFCONF, (char *)&ifc) < 0) {
                        perror("ifconfig: SIOCGIFCONF");
                        (void) close(s);
                        free(buf);
                        return (-1);
                }

                int_up = 0;
                ifrp = ifc.ifc_req;
                for (n = ifc.ifc_len / sizeof (struct ifreq); n > 0;
                                                                n--, ifrp++) {
                        (void) memset((void *) &ifr, 0, sizeof (ifr));
                        strncpy(ifr.ifr_name, ifrp->ifr_name,
                                                        sizeof (ifr.ifr_name));
                        if (ioctl(s, SIOCGIFFLAGS, (char *)&ifr) < 0) {
                                perror("SIOCGIFFLAGS");
                                (void) close(s);
                                free(buf);
                                return (-1);
                        }
                        flags = ifr.ifr_flags;
                        /* we are looking for a non-loopback interface */
                        if ((flags & IFF_UP) && ((flags & IFF_LOOPBACK) == 0))
                                int_up = 1;
                }
                (void) close(s);
                free(buf);
                if (int_up == 0) /* all the non-LOOPBACK interfaces are DOWN */
                        return (-1);
        }
#endif /* SIOCGIFNUM */


        /*
         * for the benefit of hidden NIS domains, we use the same procedure
         * as sendmail: convert leading + to dot, then drop to first dot
         */
        (void) getdomainname(buf, BUFSIZ);
        if (buf[0] == '+')
                buf[0] = '.';
#ifdef SYSV
        cp = strchr(buf, (int)'.');
#else
        cp = index(buf, '.');
#endif
        if (cp == NULL)
                strcpy(_res.defdname, buf);
        else
                strcpy(_res.defdname, cp+1);

        /* Allow user to override the local domain definition */
        if ((cp = getenv("LOCALDOMAIN")) != NULL) {
        (void) strncpy(_res.defdname, cp, sizeof (_res.defdname));
        haveenv++;
        }

        if ((fp = fopen(_PATH_RESCONF, "r")) != NULL) {
        /* read the config file */
        while (fgets(buf, sizeof (buf), fp) != NULL) {
            /* read default domain name */
            if (!strncmp(buf, "domain", sizeof ("domain") - 1)) {
                if (haveenv)    /* skip if have from environ */
                            continue;
                cp = buf + sizeof ("domain") - 1;
                while (*cp == ' ' || *cp == '\t')
                    cp++;
                if ((*cp == '\0') || (*cp == '\n'))
                    continue;
                (void) strncpy(_res.defdname, cp, sizeof (_res.defdname) - 1);
#ifdef SYSV
                if ((cp = strchr(_res.defdname, (int)'\n')) != NULL)
#else
                if ((cp = index(_res.defdname, '\n')) != NULL)
#endif
                    *cp = '\0';
                havesearch = 0;
                continue;
            }
            /* set search list */
            if (!strncmp(buf, "search", sizeof ("search") - 1)) {
                if (haveenv)    /* skip if have from environ */
                    continue;
                cp = buf + sizeof ("search") - 1;
                while (*cp == ' ' || *cp == '\t')
                    cp++;
                if ((*cp == '\0') || (*cp == '\n'))
                    continue;
                (void) strncpy(_res.defdname, cp, sizeof (_res.defdname) - 1);
#ifdef SYSV
                if ((cp = strchr(_res.defdname, (int)'\n')) != NULL)
#else
                if ((cp = index(_res.defdname, '\n')) != NULL)
#endif
                    *cp = '\0';
                /*
                 * Set search list to be blank-separated strings
                 * on rest of line.
                 */
                cp = _res.defdname;
                pp = _res.dnsrch;
                *pp++ = cp;
                for (n = 0; *cp && pp < _res.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 (!strncmp(buf, "nameserver", sizeof ("nameserver") - 1) &&
                (nserv < MAXNS)) {
                cp = buf + sizeof ("nameserver") - 1;
                while (*cp == ' ' || *cp == '\t')
                    cp++;
                if ((*cp == '\0') || (*cp == '\n'))
                    continue;
                if ((_res.nsaddr_list[nserv].sin_addr.s_addr =
                                inet_addr(cp)) == (unsigned) -1) {
                    _res.nsaddr_list[n].sin_addr.s_addr = INADDR_ANY;
                    continue;
                }
                _res.nsaddr_list[nserv].sin_family = AF_INET;
                _res.nsaddr_list[nserv].sin_port = htons(NAMESERVER_PORT);
                nserv++;
                continue;
            }
        }
        if (nserv > 1)
            _res.nscount = nserv;
        (void) fclose(fp);
        }
        if (_res.defdname[0] == 0) {
        if (gethostname(buf, sizeof (_res.defdname)) == 0 &&
#ifdef SYSV
            (cp = strchr(buf, (int)'.')))
#else
            (cp = index(buf, '.')))
#endif
                (void) strcpy(_res.defdname, cp + 1);
        }

        /* find components of local domain that might be searched */
        if (havesearch == 0) {
        pp = _res.dnsrch;
        *pp++ = _res.defdname;
        for (cp = _res.defdname, n = 0; *cp; cp++)
            if (*cp == '.')
                n++;
        cp = _res.defdname;
        for (; n >= LOCALDOMAINPARTS && pp < _res.dnsrch + MAXDFLSRCH; n--) {
#ifdef SYSV
            cp = strchr(cp, (int)'.');
#else
            cp = index(cp, '.');
#endif
            *pp++ = ++cp;
        }
        *pp++ = 0;
        }
        _res.options |= RES_INIT;
        return (0);
}