/*      $Id: dnsproc.c,v 1.12 2021/12/13 13:30:39 jca Exp $ */
/*
 * Copyright (c) 2016 Kristaps Dzonsons <kristaps@bsd.lv>
 *
 * 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 THE AUTHORS DISCLAIM ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHORS 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/socket.h>
#include <arpa/inet.h>

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

#include "extern.h"

struct  addr {
        int      family; /* 4 for PF_INET, 6 for PF_INET6 */
        char     ip[INET6_ADDRSTRLEN];
};

/*
 * This is a modified version of host_dns in config.c of OpenBSD's ntpd.
 */
/*
 * Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
 *
 * 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 THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR 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.
 */
static ssize_t
host_dns(const char *s, struct addr *vec)
{
        struct addrinfo          hints, *res0, *res;
        int                      error;
        ssize_t                  vecsz;
        struct sockaddr         *sa;

        memset(&hints, 0, sizeof(hints));
        hints.ai_family = PF_UNSPEC;
        hints.ai_socktype = SOCK_DGRAM; /* DUMMY */
        hints.ai_flags = AI_ADDRCONFIG;

        error = getaddrinfo(s, NULL, &hints, &res0);

        if (error == EAI_AGAIN ||
                /* FIXME */
#ifndef __FreeBSD__
            error == EAI_NODATA ||
#endif
            error == EAI_NONAME)
                return 0;

        if (error) {
                warnx("%s: parse error: %s",
                    s, gai_strerror(error));
                return -1;
        }

        for (vecsz = 0, res = res0;
            res != NULL && vecsz < MAX_SERVERS_DNS;
            res = res->ai_next) {
                if (res->ai_family != AF_INET &&
                    res->ai_family != AF_INET6)
                        continue;

                sa = res->ai_addr;

                if (res->ai_family == AF_INET) {
                        vec[vecsz].family = 4;
                        inet_ntop(AF_INET,
                            &(((struct sockaddr_in *)sa)->sin_addr),
                                vec[vecsz].ip, INET6_ADDRSTRLEN);
                } else {
                        vec[vecsz].family = 6;
                        inet_ntop(AF_INET6,
                            &(((struct sockaddr_in6 *)sa)->sin6_addr),
                            vec[vecsz].ip, INET6_ADDRSTRLEN);
                }

                dodbg("%s: DNS: %s", s, vec[vecsz].ip);
                vecsz++;
        }

        freeaddrinfo(res0);
        return vecsz;
}

int
dnsproc(int nfd)
{
        char            *look = NULL, *last = NULL;
        struct addr      v[MAX_SERVERS_DNS];
        int              rc = 0, cc;
        long             lval;
        ssize_t          vsz = 0;
        size_t           i;
        enum dnsop       op;

        if (pledge("stdio dns", NULL) == -1) {
                warn("pledge");
                goto out;
        }

        /*
         * This is simple: just loop on a request operation, and each
         * time we write back zero or more entries.
         * Also do a simple trick and cache the last lookup.
         */

        for (;;) {
                op = DNS__MAX;
                if ((lval = readop(nfd, COMM_DNS)) == 0)
                        op = DNS_STOP;
                else if (lval == DNS_LOOKUP)
                        op = lval;

                if (op == DNS__MAX) {
                        warnx("unknown operation from netproc");
                        goto out;
                } else if (op == DNS_STOP)
                        break;

                if ((look = readstr(nfd, COMM_DNSQ)) == NULL)
                        goto out;

                /*
                 * Check if we're asked to repeat the lookup.
                 * If not, request it from host_dns().
                 */

                if (last == NULL || strcmp(look, last)) {
                        if ((vsz = host_dns(look, v)) < 0)
                                goto out;

                        free(last);
                        last = look;
                        look = NULL;
                } else {
                        free(look);
                        look = NULL;
                }

                if ((cc = writeop(nfd, COMM_DNSLEN, vsz)) == 0)
                        break;
                else if (cc < 0)
                        goto out;
                for (i = 0; i < (size_t)vsz; i++) {
                        if (writeop(nfd, COMM_DNSF, v[i].family) <= 0)
                                goto out;
                        if (writestr(nfd, COMM_DNSA, v[i].ip) <= 0)
                                goto out;
                }
        }

        rc = 1;
out:
        close(nfd);
        free(look);
        free(last);
        return rc;
}