/*
 * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
 * 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.
 */

/* Imports. */

#include "port_before.h"

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

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

#include <ctype.h>
#include <errno.h>
#include <netdb.h>
#include <resolv.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <isc/memcluster.h>
#include <irs.h>

#include "port_after.h"

#include "irs_p.h"
#include "dns_p.h"

#ifdef SPRINTF_CHAR
# define SPRINTF(x) strlen(sprintf/**/x)
#else
# define SPRINTF(x) sprintf x
#endif

/* Definitions. */

#define MAXALIASES      35

#define MAXPACKET       (64*1024)

struct pvt {
        struct nwent    net;
        char *          ali[MAXALIASES];
        char            buf[BUFSIZ+1];
        struct __res_state * res;
        void            (*free_res)(void *);
};

typedef union {
        long    al;
        char    ac;
} align;

enum by_what { by_addr, by_name };

/* Forwards. */

static void             nw_close(struct irs_nw *);
static struct nwent *   nw_byname(struct irs_nw *, const char *, int);
static struct nwent *   nw_byaddr(struct irs_nw *, void *, int, int);
static struct nwent *   nw_next(struct irs_nw *);
static void             nw_rewind(struct irs_nw *);
static void             nw_minimize(struct irs_nw *);
static struct __res_state * nw_res_get(struct irs_nw *this);
static void             nw_res_set(struct irs_nw *this,
                                   struct __res_state *res,
                                   void (*free_res)(void *));

static struct nwent *   get1101byaddr(struct irs_nw *, u_char *, int);
static struct nwent *   get1101byname(struct irs_nw *, const char *);
static struct nwent *   get1101answer(struct irs_nw *,
                                      u_char *ansbuf, int anslen,
                                      enum by_what by_what,
                                      int af, const char *name,
                                      const u_char *addr, int addrlen);
static struct nwent *   get1101mask(struct irs_nw *this, struct nwent *);
static int              make1101inaddr(const u_char *, int, char *, int);
static void             normalize_name(char *name);
static int              init(struct irs_nw *this);

/* Exports. */

struct irs_nw *
irs_dns_nw(struct irs_acc *this) {
        struct irs_nw *nw;
        struct pvt *pvt;

        UNUSED(this);

        if (!(pvt = memget(sizeof *pvt))) {
                errno = ENOMEM;
                return (NULL);
        }
        memset(pvt, 0, sizeof *pvt);
        if (!(nw = memget(sizeof *nw))) {
                memput(pvt, sizeof *pvt);
                errno = ENOMEM;
                return (NULL);
        }
        memset(nw, 0x5e, sizeof *nw);
        nw->private = pvt;
        nw->close = nw_close;
        nw->byname = nw_byname;
        nw->byaddr = nw_byaddr;
        nw->next = nw_next;
        nw->rewind = nw_rewind;
        nw->minimize = nw_minimize;
        nw->res_get = nw_res_get;
        nw->res_set = nw_res_set;
        return (nw);
}

/* Methods. */

static void
nw_close(struct irs_nw *this) {
        struct pvt *pvt = (struct pvt *)this->private;

        nw_minimize(this);

        if (pvt->res && pvt->free_res)
                (*pvt->free_res)(pvt->res);

        memput(pvt, sizeof *pvt);
        memput(this, sizeof *this);
}

static struct nwent *
nw_byname(struct irs_nw *this, const char *name, int af) {
        struct pvt *pvt = (struct pvt *)this->private;

        if (init(this) == -1)
                return (NULL);

        switch (af) {
        case AF_INET:
                return (get1101byname(this, name));
        default:
                (void)NULL;
        }
        RES_SET_H_ERRNO(pvt->res, NETDB_INTERNAL);
        errno = EAFNOSUPPORT;
        return (NULL);
}

static struct nwent *
nw_byaddr(struct irs_nw *this, void *net, int len, int af) {
        struct pvt *pvt = (struct pvt *)this->private;

        if (init(this) == -1)
                return (NULL);

        switch (af) {
        case AF_INET:
                return (get1101byaddr(this, net, len));
        default:
                (void)NULL;
        }
        RES_SET_H_ERRNO(pvt->res, NETDB_INTERNAL);
        errno = EAFNOSUPPORT;
        return (NULL);
}

static struct nwent *
nw_next(struct irs_nw *this) {

        UNUSED(this);

        return (NULL);
}

static void
nw_rewind(struct irs_nw *this) {
        UNUSED(this);
        /* NOOP */
}

static void
nw_minimize(struct irs_nw *this) {
        struct pvt *pvt = (struct pvt *)this->private;

        if (pvt->res)
                res_nclose(pvt->res);
}

static struct __res_state *
nw_res_get(struct irs_nw *this) {
        struct pvt *pvt = (struct pvt *)this->private;

        if (!pvt->res) {
                struct __res_state *res;
                res = (struct __res_state *)malloc(sizeof *res);
                if (!res) {
                        errno = ENOMEM;
                        return (NULL);
                }
                memset(res, 0, sizeof *res);
                nw_res_set(this, res, free);
        }

        return (pvt->res);
}

static void
nw_res_set(struct irs_nw *this, struct __res_state *res,
                void (*free_res)(void *)) {
        struct pvt *pvt = (struct pvt *)this->private;

        if (pvt->res && pvt->free_res) {
                res_nclose(pvt->res);
                (*pvt->free_res)(pvt->res);
        }

        pvt->res = res;
        pvt->free_res = free_res;
}

/* Private. */

static struct nwent *
get1101byname(struct irs_nw *this, const char *name) {
        struct pvt *pvt = (struct pvt *)this->private;
        u_char *ansbuf;
        int anslen;
        struct nwent *result;

        ansbuf = memget(MAXPACKET);
        if (ansbuf == NULL) {
                errno = ENOMEM;
                RES_SET_H_ERRNO(pvt->res, NETDB_INTERNAL);
                return (NULL);
        }
        anslen = res_nsearch(pvt->res, name, C_IN, T_PTR, ansbuf, MAXPACKET);
        if (anslen < 0) {
                memput(ansbuf, MAXPACKET);
                return (NULL);
        }
        result = get1101mask(this, get1101answer(this, ansbuf, anslen, by_name,
                                                 AF_INET, name, NULL, 0));
        memput(ansbuf, MAXPACKET);
        return (result);
}

static struct nwent *
get1101byaddr(struct irs_nw *this, u_char *net, int len) {
        struct pvt *pvt = (struct pvt *)this->private;
        char qbuf[sizeof "255.255.255.255.in-addr.arpa"];
        struct nwent *result;
        u_char *ansbuf;
        int anslen;

        if (len < 1 || len > 32) {
                errno = EINVAL;
                RES_SET_H_ERRNO(pvt->res, NETDB_INTERNAL);
                return (NULL);
        }
        if (make1101inaddr(net, len, qbuf, sizeof qbuf) < 0)
                return (NULL);
        ansbuf = memget(MAXPACKET);
        if (ansbuf == NULL) {
                errno = ENOMEM;
                RES_SET_H_ERRNO(pvt->res, NETDB_INTERNAL);
                return (NULL);
        }
        anslen = res_nquery(pvt->res, qbuf, C_IN, T_PTR, ansbuf, MAXPACKET);
        if (anslen < 0) {
                memput(ansbuf, MAXPACKET);
                return (NULL);
        }
        result = get1101mask(this, get1101answer(this, ansbuf, anslen, by_addr,
                                                 AF_INET, NULL, net, len));
        memput(ansbuf, MAXPACKET);
        return (result);
}

static struct nwent *
get1101answer(struct irs_nw *this,
              u_char *ansbuf, int anslen, enum by_what by_what,
              int af, const char *name, const u_char *addr, int addrlen)
{
        struct pvt *pvt = (struct pvt *)this->private;
        int type, class, ancount, qdcount, haveanswer;
        char *bp, *ep, **ap;
        u_char *cp, *eom;
        HEADER *hp;

        /* Initialize, and parse header. */
        eom = ansbuf + anslen;
        if (ansbuf + HFIXEDSZ > eom) {
                RES_SET_H_ERRNO(pvt->res, NO_RECOVERY);
                return (NULL);
        }
        hp = (HEADER *)ansbuf;
        cp = ansbuf + HFIXEDSZ;
        qdcount = ntohs(hp->qdcount);
        while (qdcount-- > 0) {
                int n = dn_skipname(cp, eom);
                cp += n + QFIXEDSZ;
                if (n < 0 || cp > eom) {
                        RES_SET_H_ERRNO(pvt->res, NO_RECOVERY);
                        return (NULL);
                }
        }
        ancount = ntohs(hp->ancount);
        if (!ancount) {
                if (hp->aa)
                        RES_SET_H_ERRNO(pvt->res, HOST_NOT_FOUND);
                else
                        RES_SET_H_ERRNO(pvt->res, TRY_AGAIN);
                return (NULL);
        }

        /* Prepare a return structure. */
        bp = pvt->buf;
        ep = pvt->buf + sizeof(pvt->buf);
        pvt->net.n_name = NULL;
        pvt->net.n_aliases = pvt->ali;
        pvt->net.n_addrtype = af;
        pvt->net.n_addr = NULL;
        pvt->net.n_length = addrlen;

        /* Save input key if given. */
        switch (by_what) {
        case by_name:
                if (name != NULL) {
                        int n = strlen(name) + 1;

                        if (n > (ep - bp)) {
                                RES_SET_H_ERRNO(pvt->res, NO_RECOVERY);
                                return (NULL);
                        }
                        pvt->net.n_name = strcpy(bp, name);     /* (checked) */
                        bp += n;
                }
                break;
        case by_addr:
                if (addr != NULL && addrlen != 0) {
                        int n = addrlen / 8 + ((addrlen % 8) != 0);

                        if (INADDRSZ > (ep - bp)) {
                                RES_SET_H_ERRNO(pvt->res, NO_RECOVERY);
                                return (NULL);
                        }
                        memset(bp, 0, INADDRSZ);
                        memcpy(bp, addr, n);
                        pvt->net.n_addr = bp;
                        bp += INADDRSZ;
                }
                break;
        default:
                abort();
        }

        /* Parse the answer, collect aliases. */
        ap = pvt->ali;
        haveanswer = 0;
        while (--ancount >= 0 && cp < eom) {
                int n = dn_expand(ansbuf, eom, cp, bp, ep - bp);

                cp += n;                /*%< Owner */
                if (n < 0 || !maybe_dnok(pvt->res, bp) ||
                    cp + 3 * INT16SZ + INT32SZ > eom) {
                        RES_SET_H_ERRNO(pvt->res, NO_RECOVERY);
                        return (NULL);
                }
                GETSHORT(type, cp);     /*%< Type */
                GETSHORT(class, cp);    /*%< Class */
                cp += INT32SZ;          /*%< TTL */
                GETSHORT(n, cp);        /*%< RDLENGTH */
                if (class == C_IN && type == T_PTR) {
                        int nn;

                        nn = dn_expand(ansbuf, eom, cp, bp, ep - bp);
                        if (nn < 0 || !maybe_hnok(pvt->res, bp) || nn != n) {
                                RES_SET_H_ERRNO(pvt->res, NO_RECOVERY);
                                return (NULL);
                        }
                        normalize_name(bp);
                        switch (by_what) {
                        case by_addr: {
                                if (pvt->net.n_name == NULL)
                                        pvt->net.n_name = bp;
                                else if (ns_samename(pvt->net.n_name, bp) == 1)
                                        break;
                                else
                                        *ap++ = bp;
                                nn = strlen(bp) + 1;
                                bp += nn;
                                haveanswer++;
                                break;
                            }
                        case by_name: {
                                u_int b1, b2, b3, b4;

                                if (pvt->net.n_addr != NULL ||
                                    sscanf(bp, "%u.%u.%u.%u.in-addr.arpa",
                                           &b1, &b2, &b3, &b4) != 4)
                                        break;
                                if ((ep - bp) < INADDRSZ) {
                                        RES_SET_H_ERRNO(pvt->res, NO_RECOVERY);
                                        return (NULL);
                                }
                                pvt->net.n_addr = bp;
                                *bp++ = b4;
                                *bp++ = b3;
                                *bp++ = b2;
                                *bp++ = b1;
                                pvt->net.n_length = INADDRSZ * 8;
                                haveanswer++;
                            }
                        }
                }
                cp += n;                /*%< RDATA */
        }
        if (!haveanswer) {
                RES_SET_H_ERRNO(pvt->res, TRY_AGAIN);
                return (NULL);
        }
        *ap = NULL;

        return (&pvt->net);
}

static struct nwent *
get1101mask(struct irs_nw *this, struct nwent *nwent) {
        struct pvt *pvt = (struct pvt *)this->private;
        char qbuf[sizeof "255.255.255.255.in-addr.arpa"], owner[MAXDNAME];
        int anslen, type, class, ancount, qdcount;
        u_char *ansbuf, *cp, *eom;
        HEADER *hp;

        if (!nwent)
                return (NULL);
        if (make1101inaddr(nwent->n_addr, nwent->n_length, qbuf, sizeof qbuf)
            < 0) {
                /* "First, do no harm." */
                return (nwent);
        }

        ansbuf = memget(MAXPACKET);
        if (ansbuf == NULL) {
                errno = ENOMEM;
                RES_SET_H_ERRNO(pvt->res, NETDB_INTERNAL);
                return (NULL);
        }
        /* Query for the A RR that would hold this network's mask. */
        anslen = res_nquery(pvt->res, qbuf, C_IN, T_A, ansbuf, MAXPACKET);
        if (anslen < HFIXEDSZ) {
                memput(ansbuf, MAXPACKET);
                return (nwent);
        }

        /* Initialize, and parse header. */
        hp = (HEADER *)ansbuf;
        cp = ansbuf + HFIXEDSZ;
        eom = ansbuf + anslen;
        qdcount = ntohs(hp->qdcount);
        while (qdcount-- > 0) {
                int n = dn_skipname(cp, eom);
                cp += n + QFIXEDSZ;
                if (n < 0 || cp > eom) {
                        memput(ansbuf, MAXPACKET);
                        return (nwent);
                }
        }
        ancount = ntohs(hp->ancount);

        /* Parse the answer, collect aliases. */
        while (--ancount >= 0 && cp < eom) {
                int n = dn_expand(ansbuf, eom, cp, owner, sizeof owner);

                if (n < 0 || !maybe_dnok(pvt->res, owner))
                        break;
                cp += n;                /*%< Owner */
                if (cp + 3 * INT16SZ + INT32SZ > eom)
                        break;
                GETSHORT(type, cp);     /*%< Type */
                GETSHORT(class, cp);    /*%< Class */
                cp += INT32SZ;          /*%< TTL */
                GETSHORT(n, cp);        /*%< RDLENGTH */
                if (cp + n > eom)
                        break;
                if (n == INADDRSZ && class == C_IN && type == T_A &&
                    ns_samename(qbuf, owner) == 1) {
                        /* This A RR indicates the actual netmask. */
                        int nn, mm;

                        nwent->n_length = 0;
                        for (nn = 0; nn < INADDRSZ; nn++)
                                for (mm = 7; mm >= 0; mm--)
                                        if (cp[nn] & (1 << mm))
                                                nwent->n_length++;
                                        else
                                                break;
                }
                cp += n;                /*%< RDATA */
        }
        memput(ansbuf, MAXPACKET);
        return (nwent);
}

static int
make1101inaddr(const u_char *net, int bits, char *name, int size) {
        int n, m;
        char *ep;

        ep = name + size;

        /* Zero fill any whole bytes left out of the prefix. */
        for (n = (32 - bits) / 8; n > 0; n--) {
                if (ep - name < (int)(sizeof "0."))
                        goto emsgsize;
                m = SPRINTF((name, "0."));
                name += m;
        }

        /* Format the partial byte, if any, within the prefix. */
        if ((n = bits % 8) != 0) {
                if (ep - name < (int)(sizeof "255."))
                        goto emsgsize;
                m = SPRINTF((name, "%u.",
                             net[bits / 8] & ~((1 << (8 - n)) - 1)));
                name += m;
        }

        /* Format the whole bytes within the prefix. */
        for (n = bits / 8; n > 0; n--) {
                if (ep - name < (int)(sizeof "255."))
                        goto emsgsize;
                m = SPRINTF((name, "%u.", net[n - 1]));
                name += m;
        }

        /* Add the static text. */
        if (ep - name < (int)(sizeof "in-addr.arpa"))
                goto emsgsize;
        (void) SPRINTF((name, "in-addr.arpa"));
        return (0);

 emsgsize:
        errno = EMSGSIZE;
        return (-1);
}

static void
normalize_name(char *name) {
        char *t;

        /* Make lower case. */
        for (t = name; *t; t++)
                if (isascii((unsigned char)*t) && isupper((unsigned char)*t))
                        *t = tolower((*t)&0xff);

        /* Remove trailing dots. */
        while (t > name && t[-1] == '.')
                *--t = '\0';
}

static int
init(struct irs_nw *this) {
        struct pvt *pvt = (struct pvt *)this->private;

        if (!pvt->res && !nw_res_get(this))
                return (-1);
        if (((pvt->res->options & RES_INIT) == 0U) &&
            res_ninit(pvt->res) == -1)
                return (-1);
        return (0);
}

/*! \file */