/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2012-2013 The FreeBSD Foundation
 *
 * This software was developed by Pawel Jakub Dawidek under sponsorship from
 * the FreeBSD Foundation.
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS 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 AUTHORS 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.
 */

#include <sys/cdefs.h>
#include <sys/dnv.h>
#include <sys/nv.h>
#include <netinet/in.h>

#include <assert.h>
#include <errno.h>
#include <netdb.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <libcasper.h>
#include <libcasper_service.h>

#include "cap_dns.h"

static struct hostent hent;

static void
hostent_free(struct hostent *hp)
{
        unsigned int ii;

        free(hp->h_name);
        hp->h_name = NULL;
        if (hp->h_aliases != NULL) {
                for (ii = 0; hp->h_aliases[ii] != NULL; ii++)
                        free(hp->h_aliases[ii]);
                free(hp->h_aliases);
                hp->h_aliases = NULL;
        }
        if (hp->h_addr_list != NULL) {
                for (ii = 0; hp->h_addr_list[ii] != NULL; ii++)
                        free(hp->h_addr_list[ii]);
                free(hp->h_addr_list);
                hp->h_addr_list = NULL;
        }
}

static struct hostent *
hostent_unpack(const nvlist_t *nvl, struct hostent *hp)
{
        unsigned int ii, nitems;
        char nvlname[64];
        int n;

        hostent_free(hp);

        hp->h_name = strdup(nvlist_get_string(nvl, "name"));
        if (hp->h_name == NULL)
                goto fail;
        hp->h_addrtype = (int)nvlist_get_number(nvl, "addrtype");
        hp->h_length = (int)nvlist_get_number(nvl, "length");

        nitems = (unsigned int)nvlist_get_number(nvl, "naliases");
        hp->h_aliases = calloc(nitems + 1, sizeof(hp->h_aliases[0]));
        if (hp->h_aliases == NULL)
                goto fail;
        for (ii = 0; ii < nitems; ii++) {
                n = snprintf(nvlname, sizeof(nvlname), "alias%u", ii);
                assert(n > 0 && n < (int)sizeof(nvlname));
                hp->h_aliases[ii] =
                    strdup(nvlist_get_string(nvl, nvlname));
                if (hp->h_aliases[ii] == NULL)
                        goto fail;
        }
        hp->h_aliases[ii] = NULL;

        nitems = (unsigned int)nvlist_get_number(nvl, "naddrs");
        hp->h_addr_list = calloc(nitems + 1, sizeof(hp->h_addr_list[0]));
        if (hp->h_addr_list == NULL)
                goto fail;
        for (ii = 0; ii < nitems; ii++) {
                hp->h_addr_list[ii] = malloc(hp->h_length);
                if (hp->h_addr_list[ii] == NULL)
                        goto fail;
                n = snprintf(nvlname, sizeof(nvlname), "addr%u", ii);
                assert(n > 0 && n < (int)sizeof(nvlname));
                bcopy(nvlist_get_binary(nvl, nvlname, NULL),
                    hp->h_addr_list[ii], hp->h_length);
        }
        hp->h_addr_list[ii] = NULL;

        return (hp);
fail:
        hostent_free(hp);
        h_errno = NO_RECOVERY;
        return (NULL);
}

struct hostent *
cap_gethostbyname(cap_channel_t *chan, const char *name)
{

        return (cap_gethostbyname2(chan, name, AF_INET));
}

struct hostent *
cap_gethostbyname2(cap_channel_t *chan, const char *name, int type)
{
        struct hostent *hp;
        nvlist_t *nvl;

        nvl = nvlist_create(0);
        nvlist_add_string(nvl, "cmd", "gethostbyname");
        nvlist_add_number(nvl, "family", (uint64_t)type);
        nvlist_add_string(nvl, "name", name);
        nvl = cap_xfer_nvlist(chan, nvl);
        if (nvl == NULL) {
                h_errno = NO_RECOVERY;
                return (NULL);
        }
        if (nvlist_get_number(nvl, "error") != 0) {
                h_errno = (int)nvlist_get_number(nvl, "error");
                nvlist_destroy(nvl);
                return (NULL);
        }

        hp = hostent_unpack(nvl, &hent);
        nvlist_destroy(nvl);
        return (hp);
}

struct hostent *
cap_gethostbyaddr(cap_channel_t *chan, const void *addr, socklen_t len,
    int type)
{
        struct hostent *hp;
        nvlist_t *nvl;

        nvl = nvlist_create(0);
        nvlist_add_string(nvl, "cmd", "gethostbyaddr");
        nvlist_add_binary(nvl, "addr", addr, (size_t)len);
        nvlist_add_number(nvl, "family", (uint64_t)type);
        nvl = cap_xfer_nvlist(chan, nvl);
        if (nvl == NULL) {
                h_errno = NO_RECOVERY;
                return (NULL);
        }
        if (nvlist_get_number(nvl, "error") != 0) {
                h_errno = (int)nvlist_get_number(nvl, "error");
                nvlist_destroy(nvl);
                return (NULL);
        }
        hp = hostent_unpack(nvl, &hent);
        nvlist_destroy(nvl);
        return (hp);
}

static struct addrinfo *
addrinfo_unpack(const nvlist_t *nvl)
{
        struct addrinfo *ai;
        const void *addr;
        size_t addrlen;
        const char *canonname;

        addr = nvlist_get_binary(nvl, "ai_addr", &addrlen);
        ai = malloc(sizeof(*ai) + addrlen);
        if (ai == NULL)
                return (NULL);
        ai->ai_flags = (int)nvlist_get_number(nvl, "ai_flags");
        ai->ai_family = (int)nvlist_get_number(nvl, "ai_family");
        ai->ai_socktype = (int)nvlist_get_number(nvl, "ai_socktype");
        ai->ai_protocol = (int)nvlist_get_number(nvl, "ai_protocol");
        ai->ai_addrlen = (socklen_t)addrlen;
        canonname = dnvlist_get_string(nvl, "ai_canonname", NULL);
        if (canonname != NULL) {
                ai->ai_canonname = strdup(canonname);
                if (ai->ai_canonname == NULL) {
                        free(ai);
                        return (NULL);
                }
        } else {
                ai->ai_canonname = NULL;
        }
        ai->ai_addr = (void *)(ai + 1);
        bcopy(addr, ai->ai_addr, addrlen);
        ai->ai_next = NULL;

        return (ai);
}

int
cap_getaddrinfo(cap_channel_t *chan, const char *hostname, const char *servname,
    const struct addrinfo *hints, struct addrinfo **res)
{
        struct addrinfo *firstai, *prevai, *curai;
        unsigned int ii;
        const nvlist_t *nvlai;
        char nvlname[64];
        nvlist_t *nvl;
        int error, n;

        nvl = nvlist_create(0);
        nvlist_add_string(nvl, "cmd", "getaddrinfo");
        if (hostname != NULL)
                nvlist_add_string(nvl, "hostname", hostname);
        if (servname != NULL)
                nvlist_add_string(nvl, "servname", servname);
        if (hints != NULL) {
                nvlist_add_number(nvl, "hints.ai_flags",
                    (uint64_t)hints->ai_flags);
                nvlist_add_number(nvl, "hints.ai_family",
                    (uint64_t)hints->ai_family);
                nvlist_add_number(nvl, "hints.ai_socktype",
                    (uint64_t)hints->ai_socktype);
                nvlist_add_number(nvl, "hints.ai_protocol",
                    (uint64_t)hints->ai_protocol);
        }
        nvl = cap_xfer_nvlist(chan, nvl);
        if (nvl == NULL)
                return (EAI_MEMORY);
        if (nvlist_get_number(nvl, "error") != 0) {
                error = (int)nvlist_get_number(nvl, "error");
                nvlist_destroy(nvl);
                return (error);
        }

        nvlai = NULL;
        firstai = prevai = curai = NULL;
        for (ii = 0; ; ii++) {
                n = snprintf(nvlname, sizeof(nvlname), "res%u", ii);
                assert(n > 0 && n < (int)sizeof(nvlname));
                if (!nvlist_exists_nvlist(nvl, nvlname))
                        break;
                nvlai = nvlist_get_nvlist(nvl, nvlname);
                curai = addrinfo_unpack(nvlai);
                if (curai == NULL)
                        break;
                if (prevai != NULL)
                        prevai->ai_next = curai;
                else if (firstai == NULL)
                        firstai = curai;
                prevai = curai;
        }
        nvlist_destroy(nvl);
        if (curai == NULL && nvlai != NULL) {
                if (firstai != NULL)
                        freeaddrinfo(firstai);
                return (EAI_MEMORY);
        }

        *res = firstai;
        return (0);
}

int
cap_getnameinfo(cap_channel_t *chan, const struct sockaddr *sa, socklen_t salen,
    char *host, size_t hostlen, char *serv, size_t servlen, int flags)
{
        nvlist_t *nvl;
        int error;

        nvl = nvlist_create(0);
        nvlist_add_string(nvl, "cmd", "getnameinfo");
        nvlist_add_number(nvl, "hostlen", (uint64_t)hostlen);
        nvlist_add_number(nvl, "servlen", (uint64_t)servlen);
        nvlist_add_binary(nvl, "sa", sa, (size_t)salen);
        nvlist_add_number(nvl, "flags", (uint64_t)flags);
        nvl = cap_xfer_nvlist(chan, nvl);
        if (nvl == NULL)
                return (EAI_MEMORY);
        if (nvlist_get_number(nvl, "error") != 0) {
                error = (int)nvlist_get_number(nvl, "error");
                nvlist_destroy(nvl);
                return (error);
        }

        if (host != NULL && nvlist_exists_string(nvl, "host"))
                strlcpy(host, nvlist_get_string(nvl, "host"), hostlen);
        if (serv != NULL && nvlist_exists_string(nvl, "serv"))
                strlcpy(serv, nvlist_get_string(nvl, "serv"), servlen);
        nvlist_destroy(nvl);
        return (0);
}

static void
limit_remove(nvlist_t *limits, const char *prefix)
{
        const char *name;
        size_t prefixlen;
        void *cookie;

        prefixlen = strlen(prefix);
again:
        cookie = NULL;
        while ((name = nvlist_next(limits, NULL, &cookie)) != NULL) {
                if (strncmp(name, prefix, prefixlen) == 0) {
                        nvlist_free(limits, name);
                        goto again;
                }
        }
}

int
cap_dns_type_limit(cap_channel_t *chan, const char * const *types,
    size_t ntypes)
{
        nvlist_t *limits;
        unsigned int i;
        char nvlname[64];
        int n;

        if (cap_limit_get(chan, &limits) < 0)
                return (-1);
        if (limits == NULL)
                limits = nvlist_create(0);
        else
                limit_remove(limits, "type");
        for (i = 0; i < ntypes; i++) {
                n = snprintf(nvlname, sizeof(nvlname), "type%u", i);
                assert(n > 0 && n < (int)sizeof(nvlname));
                nvlist_add_string(limits, nvlname, types[i]);
        }
        return (cap_limit_set(chan, limits));
}

int
cap_dns_family_limit(cap_channel_t *chan, const int *families,
    size_t nfamilies)
{
        nvlist_t *limits;
        unsigned int i;
        char nvlname[64];
        int n;

        if (cap_limit_get(chan, &limits) < 0)
                return (-1);
        if (limits == NULL)
                limits = nvlist_create(0);
        else
                limit_remove(limits, "family");
        for (i = 0; i < nfamilies; i++) {
                n = snprintf(nvlname, sizeof(nvlname), "family%u", i);
                assert(n > 0 && n < (int)sizeof(nvlname));
                nvlist_add_number(limits, nvlname, (uint64_t)families[i]);
        }
        return (cap_limit_set(chan, limits));
}

/*
 * Service functions.
 */
static bool
dns_allowed_type(const nvlist_t *limits, const char *type)
{
        const char *name;
        bool notypes;
        void *cookie;

        if (limits == NULL)
                return (true);

        notypes = true;
        cookie = NULL;
        while ((name = nvlist_next(limits, NULL, &cookie)) != NULL) {
                if (strncmp(name, "type", sizeof("type") - 1) != 0)
                        continue;
                notypes = false;
                if (strcmp(nvlist_get_string(limits, name), type) == 0)
                        return (true);
        }

        /* If there are no types at all, allow any type. */
        if (notypes)
                return (true);

        return (false);
}

static bool
dns_allowed_family(const nvlist_t *limits, int family)
{
        const char *name;
        bool nofamilies;
        void *cookie;

        if (limits == NULL)
                return (true);

        nofamilies = true;
        cookie = NULL;
        while ((name = nvlist_next(limits, NULL, &cookie)) != NULL) {
                if (strncmp(name, "family", sizeof("family") - 1) != 0)
                        continue;
                nofamilies = false;
                if (family == AF_UNSPEC)
                        continue;
                if (nvlist_get_number(limits, name) == (uint64_t)family)
                        return (true);
        }

        /* If there are no families at all, allow any family. */
        if (nofamilies)
                return (true);

        return (false);
}

static void
hostent_pack(const struct hostent *hp, nvlist_t *nvl)
{
        unsigned int ii;
        char nvlname[64];
        int n;

        nvlist_add_string(nvl, "name", hp->h_name);
        nvlist_add_number(nvl, "addrtype", (uint64_t)hp->h_addrtype);
        nvlist_add_number(nvl, "length", (uint64_t)hp->h_length);

        if (hp->h_aliases == NULL) {
                nvlist_add_number(nvl, "naliases", 0);
        } else {
                for (ii = 0; hp->h_aliases[ii] != NULL; ii++) {
                        n = snprintf(nvlname, sizeof(nvlname), "alias%u", ii);
                        assert(n > 0 && n < (int)sizeof(nvlname));
                        nvlist_add_string(nvl, nvlname, hp->h_aliases[ii]);
                }
                nvlist_add_number(nvl, "naliases", (uint64_t)ii);
        }

        if (hp->h_addr_list == NULL) {
                nvlist_add_number(nvl, "naddrs", 0);
        } else {
                for (ii = 0; hp->h_addr_list[ii] != NULL; ii++) {
                        n = snprintf(nvlname, sizeof(nvlname), "addr%u", ii);
                        assert(n > 0 && n < (int)sizeof(nvlname));
                        nvlist_add_binary(nvl, nvlname, hp->h_addr_list[ii],
                            (size_t)hp->h_length);
                }
                nvlist_add_number(nvl, "naddrs", (uint64_t)ii);
        }
}

static int
dns_gethostbyname(const nvlist_t *limits, const nvlist_t *nvlin,
    nvlist_t *nvlout)
{
        struct hostent *hp;
        int family;

        if (!dns_allowed_type(limits, "NAME2ADDR") &&
            !dns_allowed_type(limits, "NAME"))
                return (NO_RECOVERY);

        family = (int)nvlist_get_number(nvlin, "family");

        if (!dns_allowed_family(limits, family))
                return (NO_RECOVERY);

        hp = gethostbyname2(nvlist_get_string(nvlin, "name"), family);
        if (hp == NULL)
                return (h_errno);
        hostent_pack(hp, nvlout);
        return (0);
}

static int
dns_gethostbyaddr(const nvlist_t *limits, const nvlist_t *nvlin,
    nvlist_t *nvlout)
{
        struct hostent *hp;
        const void *addr;
        size_t addrsize;
        int family;

        if (!dns_allowed_type(limits, "ADDR2NAME") &&
            !dns_allowed_type(limits, "ADDR"))
                return (NO_RECOVERY);

        family = (int)nvlist_get_number(nvlin, "family");

        if (!dns_allowed_family(limits, family))
                return (NO_RECOVERY);

        addr = nvlist_get_binary(nvlin, "addr", &addrsize);
        hp = gethostbyaddr(addr, (socklen_t)addrsize, family);
        if (hp == NULL)
                return (h_errno);
        hostent_pack(hp, nvlout);
        return (0);
}

static int
dns_getnameinfo(const nvlist_t *limits, const nvlist_t *nvlin, nvlist_t *nvlout)
{
        struct sockaddr_storage sast;
        const void *sabin;
        char *host, *serv;
        size_t sabinsize, hostlen, servlen;
        socklen_t salen;
        int error, flags;

        if (!dns_allowed_type(limits, "ADDR2NAME") &&
            !dns_allowed_type(limits, "ADDR"))
                return (NO_RECOVERY);

        error = 0;
        host = serv = NULL;
        memset(&sast, 0, sizeof(sast));

        hostlen = (size_t)nvlist_get_number(nvlin, "hostlen");
        servlen = (size_t)nvlist_get_number(nvlin, "servlen");

        if (hostlen > 0) {
                host = calloc(1, hostlen);
                if (host == NULL) {
                        error = EAI_MEMORY;
                        goto out;
                }
        }
        if (servlen > 0) {
                serv = calloc(1, servlen);
                if (serv == NULL) {
                        error = EAI_MEMORY;
                        goto out;
                }
        }

        sabin = nvlist_get_binary(nvlin, "sa", &sabinsize);
        if (sabinsize > sizeof(sast)) {
                error = EAI_FAIL;
                goto out;
        }

        memcpy(&sast, sabin, sabinsize);
        salen = (socklen_t)sabinsize;

        if ((sast.ss_family != AF_INET ||
             salen != sizeof(struct sockaddr_in)) &&
            (sast.ss_family != AF_INET6 ||
             salen != sizeof(struct sockaddr_in6))) {
                error = EAI_FAIL;
                goto out;
        }

        if (!dns_allowed_family(limits, (int)sast.ss_family)) {
                error = NO_RECOVERY;
                goto out;
        }

        flags = (int)nvlist_get_number(nvlin, "flags");

        error = getnameinfo((struct sockaddr *)&sast, salen, host, hostlen,
            serv, servlen, flags);
        if (error != 0)
                goto out;

        if (host != NULL)
                nvlist_move_string(nvlout, "host", host);
        if (serv != NULL)
                nvlist_move_string(nvlout, "serv", serv);
out:
        if (error != 0) {
                free(host);
                free(serv);
        }
        return (error);
}

static nvlist_t *
addrinfo_pack(const struct addrinfo *ai)
{
        nvlist_t *nvl;

        nvl = nvlist_create(0);
        nvlist_add_number(nvl, "ai_flags", (uint64_t)ai->ai_flags);
        nvlist_add_number(nvl, "ai_family", (uint64_t)ai->ai_family);
        nvlist_add_number(nvl, "ai_socktype", (uint64_t)ai->ai_socktype);
        nvlist_add_number(nvl, "ai_protocol", (uint64_t)ai->ai_protocol);
        nvlist_add_binary(nvl, "ai_addr", ai->ai_addr, (size_t)ai->ai_addrlen);
        if (ai->ai_canonname != NULL)
                nvlist_add_string(nvl, "ai_canonname", ai->ai_canonname);

        return (nvl);
}

static int
dns_getaddrinfo(const nvlist_t *limits, const nvlist_t *nvlin, nvlist_t *nvlout)
{
        struct addrinfo hints, *hintsp, *res, *cur;
        const char *hostname, *servname;
        char nvlname[64];
        nvlist_t *elem;
        unsigned int ii;
        int error, family, n;

        if (!dns_allowed_type(limits, "NAME2ADDR") &&
            !dns_allowed_type(limits, "NAME"))
                return (NO_RECOVERY);

        hostname = dnvlist_get_string(nvlin, "hostname", NULL);
        servname = dnvlist_get_string(nvlin, "servname", NULL);
        if (nvlist_exists_number(nvlin, "hints.ai_flags")) {
                hints.ai_flags = (int)nvlist_get_number(nvlin,
                    "hints.ai_flags");
                hints.ai_family = (int)nvlist_get_number(nvlin,
                    "hints.ai_family");
                hints.ai_socktype = (int)nvlist_get_number(nvlin,
                    "hints.ai_socktype");
                hints.ai_protocol = (int)nvlist_get_number(nvlin,
                    "hints.ai_protocol");
                hints.ai_addrlen = 0;
                hints.ai_addr = NULL;
                hints.ai_canonname = NULL;
                hints.ai_next = NULL;
                hintsp = &hints;
                family = hints.ai_family;
        } else {
                hintsp = NULL;
                family = AF_UNSPEC;
        }

        if (!dns_allowed_family(limits, family))
                return (NO_RECOVERY);

        error = getaddrinfo(hostname, servname, hintsp, &res);
        if (error != 0)
                goto out;

        for (cur = res, ii = 0; cur != NULL; cur = cur->ai_next, ii++) {
                elem = addrinfo_pack(cur);
                n = snprintf(nvlname, sizeof(nvlname), "res%u", ii);
                assert(n > 0 && n < (int)sizeof(nvlname));
                nvlist_move_nvlist(nvlout, nvlname, elem);
        }

        freeaddrinfo(res);
        error = 0;
out:
        return (error);
}

static bool
limit_has_entry(const nvlist_t *limits, const char *prefix)
{
        const char *name;
        size_t prefixlen;
        void *cookie;

        if (limits == NULL)
                return (false);

        prefixlen = strlen(prefix);

        cookie = NULL;
        while ((name = nvlist_next(limits, NULL, &cookie)) != NULL) {
                if (strncmp(name, prefix, prefixlen) == 0)
                        return (true);
        }

        return (false);
}

static int
dns_limit(const nvlist_t *oldlimits, const nvlist_t *newlimits)
{
        const char *name;
        void *cookie;
        int nvtype;
        bool hastype, hasfamily;

        hastype = false;
        hasfamily = false;

        cookie = NULL;
        while ((name = nvlist_next(newlimits, &nvtype, &cookie)) != NULL) {
                if (nvtype == NV_TYPE_STRING) {
                        const char *type;

                        if (strncmp(name, "type", sizeof("type") - 1) != 0)
                                return (EINVAL);
                        type = nvlist_get_string(newlimits, name);
                        if (strcmp(type, "ADDR2NAME") != 0 &&
                            strcmp(type, "NAME2ADDR") != 0 &&
                            strcmp(type, "ADDR") != 0 &&
                            strcmp(type, "NAME") != 0) {
                                return (EINVAL);
                        }
                        if (!dns_allowed_type(oldlimits, type))
                                return (ENOTCAPABLE);
                        hastype = true;
                } else if (nvtype == NV_TYPE_NUMBER) {
                        int family;

                        if (strncmp(name, "family", sizeof("family") - 1) != 0)
                                return (EINVAL);
                        family = (int)nvlist_get_number(newlimits, name);
                        if (!dns_allowed_family(oldlimits, family))
                                return (ENOTCAPABLE);
                        hasfamily = true;
                } else {
                        return (EINVAL);
                }
        }

        /*
         * If the new limit doesn't mention type or family we have to
         * check if the current limit does have those. Missing type or
         * family in the limit means that all types or families are
         * allowed.
         */
        if (!hastype) {
                if (limit_has_entry(oldlimits, "type"))
                        return (ENOTCAPABLE);
        }
        if (!hasfamily) {
                if (limit_has_entry(oldlimits, "family"))
                        return (ENOTCAPABLE);
        }

        return (0);
}

static int
dns_command(const char *cmd, const nvlist_t *limits, nvlist_t *nvlin,
    nvlist_t *nvlout)
{
        int error;

        if (strcmp(cmd, "gethostbyname") == 0)
                error = dns_gethostbyname(limits, nvlin, nvlout);
        else if (strcmp(cmd, "gethostbyaddr") == 0)
                error = dns_gethostbyaddr(limits, nvlin, nvlout);
        else if (strcmp(cmd, "getnameinfo") == 0)
                error = dns_getnameinfo(limits, nvlin, nvlout);
        else if (strcmp(cmd, "getaddrinfo") == 0)
                error = dns_getaddrinfo(limits, nvlin, nvlout);
        else
                error = NO_RECOVERY;

        return (error);
}

CREATE_SERVICE("system.dns", dns_limit, dns_command, 0);