/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/

/***
  This file is part of nss-myhostname.

  Copyright 2008-2011 Lennart Poettering

  nss-myhostname is free software; you can redistribute it and/or
  modify it under the terms of the GNU Lesser General Public License
  as published by the Free Software Foundation; either version 2.1 of
  the License, or (at your option) any later version.

  nss-myhostname is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public
  License along with nss-myhostname; If not, see
  <http://www.gnu.org/licenses/>.
***/

#include <limits.h>
#include <nss.h>
#include <sys/types.h>
#include <netdb.h>
#include <errno.h>
#include <string.h>
#include <assert.h>
#include <unistd.h>
#include <net/if.h>
#include <stdlib.h>
#include <arpa/inet.h>

#include "ifconf.h"

/* We use 127.0.0.2 as IPv4 address. This has the advantage over
 * 127.0.0.1 that it can be translated back to the local hostname. For
 * IPv6 we use ::1 which unfortunately will not translate back to the
 * hostname but instead something like "localhost6" or so. */

#define LOCALADDRESS_IPV4 (htonl(0x7F000002))
#define LOCALADDRESS_IPV6 &in6addr_loopback
#define LOOPBACK_INTERFACE "lo"

#define ALIGN(a) (((a+sizeof(void*)-1)/sizeof(void*))*sizeof(void*))

enum nss_status _nss_myhostname_gethostbyname4_r(
                const char *name,
                struct gaih_addrtuple **pat,
                char *buffer, size_t buflen,
                int *errnop, int *h_errnop,
                int32_t *ttlp) _public_;

enum nss_status _nss_myhostname_gethostbyname3_r(
                const char *name,
                int af,
                struct hostent *host,
                char *buffer, size_t buflen,
                int *errnop, int *h_errnop,
                int32_t *ttlp,
                char **canonp) _public_;

enum nss_status _nss_myhostname_gethostbyname2_r(
                const char *name,
                int af,
                struct hostent *host,
                char *buffer, size_t buflen,
                int *errnop, int *h_errnop) _public_;

enum nss_status _nss_myhostname_gethostbyname_r(
                const char *name,
                struct hostent *host,
                char *buffer, size_t buflen,
                int *errnop, int *h_errnop) _public_;

enum nss_status _nss_myhostname_gethostbyaddr2_r(
                const void* addr, socklen_t len,
                int af,
                struct hostent *host,
                char *buffer, size_t buflen,
                int *errnop, int *h_errnop,
                int32_t *ttlp) _public_;

enum nss_status _nss_myhostname_gethostbyaddr_r(
                const void* addr, socklen_t len,
                int af,
                struct hostent *host,
                char *buffer, size_t buflen,
                int *errnop, int *h_errnop) _public_;

enum nss_status _nss_myhostname_gethostbyname4_r(
                const char *name,
                struct gaih_addrtuple **pat,
                char *buffer, size_t buflen,
                int *errnop, int *h_errnop,
                int32_t *ttlp) {

        unsigned lo_ifi;
        char hn[HOST_NAME_MAX+1];
        size_t l, idx, ms;
        char *r_name;
        struct gaih_addrtuple *r_tuple, *r_tuple_prev = NULL;
        struct address *addresses = NULL, *a;
        unsigned n_addresses = 0, n;

        memset(hn, 0, sizeof(hn));
        if (gethostname(hn, sizeof(hn)-1) < 0) {
                *errnop = errno;
                *h_errnop = NO_RECOVERY;
                return NSS_STATUS_UNAVAIL;
        }

        if (strcasecmp(name, hn) != 0) {
                *errnop = ENOENT;
                *h_errnop = HOST_NOT_FOUND;
                return NSS_STATUS_NOTFOUND;
        }

        /* If this fails, n_addresses is 0. Which is fine */
        ifconf_acquire_addresses(&addresses, &n_addresses);

        /* If this call fails we fill in 0 as scope. Which is fine */
        lo_ifi = if_nametoindex(LOOPBACK_INTERFACE);

        l = strlen(hn);
        ms = ALIGN(l+1)+ALIGN(sizeof(struct gaih_addrtuple))*(n_addresses > 0 ? n_addresses : 2);
        if (buflen < ms) {
                *errnop = ENOMEM;
                *h_errnop = NO_RECOVERY;
                free(addresses);
                return NSS_STATUS_TRYAGAIN;
        }

        /* First, fill in hostname */
        r_name = buffer;
        memcpy(r_name, hn, l+1);
        idx = ALIGN(l+1);

        if (n_addresses <= 0) {
                /* Second, fill in IPv6 tuple */
                r_tuple = (struct gaih_addrtuple*) (buffer + idx);
                r_tuple->next = r_tuple_prev;
                r_tuple->name = r_name;
                r_tuple->family = AF_INET6;
                memcpy(r_tuple->addr, LOCALADDRESS_IPV6, 16);
                r_tuple->scopeid = (uint32_t) lo_ifi;

                idx += ALIGN(sizeof(struct gaih_addrtuple));
                r_tuple_prev = r_tuple;

                /* Third, fill in IPv4 tuple */
                r_tuple = (struct gaih_addrtuple*) (buffer + idx);
                r_tuple->next = r_tuple_prev;
                r_tuple->name = r_name;
                r_tuple->family = AF_INET;
                *(uint32_t*) r_tuple->addr = LOCALADDRESS_IPV4;
                r_tuple->scopeid = (uint32_t) lo_ifi;

                idx += ALIGN(sizeof(struct gaih_addrtuple));
                r_tuple_prev = r_tuple;
        }

        /* Fourth, fill actual addresses in, but in backwards order */
        for (a = addresses + n_addresses - 1, n = 0; n < n_addresses; n++, a--) {
                r_tuple = (struct gaih_addrtuple*) (buffer + idx);
                r_tuple->next = r_tuple_prev;
                r_tuple->name = r_name;
                r_tuple->family = a->family;
                r_tuple->scopeid = a->ifindex;
                memcpy(r_tuple->addr, a->address, 16);

                idx += ALIGN(sizeof(struct gaih_addrtuple));
                r_tuple_prev = r_tuple;
        }

        /* Verify the size matches */
        assert(idx == ms);

        *pat = r_tuple_prev;

        if (ttlp)
                *ttlp = 0;

        free(addresses);

        return NSS_STATUS_SUCCESS;
}

static enum nss_status fill_in_hostent(
                const char *hn,
                int af,
                struct hostent *result,
                char *buffer, size_t buflen,
                int *errnop, int *h_errnop,
                int32_t *ttlp,
                char **canonp) {

        size_t l, idx, ms;
        char *r_addr, *r_name, *r_aliases, *r_addr_list;
        size_t alen;
        struct address *addresses = NULL, *a;
        unsigned n_addresses = 0, n, c;

        alen = PROTO_ADDRESS_SIZE(af);

        ifconf_acquire_addresses(&addresses, &n_addresses);

        for (a = addresses, n = 0, c = 0; n < n_addresses; a++, n++)
                if (af == a->family)
                        c++;

        l = strlen(hn);
        ms = ALIGN(l+1)+
                sizeof(char*)+
                (c > 0 ? c : 1)*ALIGN(alen)+
                (c > 0 ? c+1 : 2)*sizeof(char*);

        if (buflen < ms) {
                *errnop = ENOMEM;
                *h_errnop = NO_RECOVERY;
                free(addresses);
                return NSS_STATUS_TRYAGAIN;
        }

        /* First, fill in hostname */
        r_name = buffer;
        memcpy(r_name, hn, l+1);
        idx = ALIGN(l+1);

        /* Second, create (empty) aliases array */
        r_aliases = buffer + idx;
        *(char**) r_aliases = NULL;
        idx += sizeof(char*);

        /* Third, add addresses */
        r_addr = buffer + idx;
        if (c > 0) {
                unsigned i = 0;

                for (a = addresses, n = 0; n < n_addresses; a++, n++) {
                        if (af != a->family)
                                continue;

                        memcpy(r_addr + i*ALIGN(alen), a->address, alen);
                        i++;
                }

                assert(i == c);
                idx += c*ALIGN(alen);
        } else {
                if (af == AF_INET)
                        *(uint32_t*) r_addr = LOCALADDRESS_IPV4;
                else
                        memcpy(r_addr, LOCALADDRESS_IPV6, 16);

                idx += ALIGN(alen);
        }

        /* Fourth, add address pointer array */
        r_addr_list = buffer + idx;
        if (c > 0) {
                unsigned i = 0;

                for (a = addresses, n = 0; n < n_addresses; a++, n++) {
                        if (af != a->family)
                                continue;

                        ((char**) r_addr_list)[i] = (r_addr + i*ALIGN(alen));
                        i++;
                }

                assert(i == c);
                ((char**) r_addr_list)[c] = NULL;
                idx += (c+1)*sizeof(char*);

        } else {
                ((char**) r_addr_list)[0] = r_addr;
                ((char**) r_addr_list)[1] = NULL;
                idx += 2*sizeof(char*);
        }

        /* Verify the size matches */
        assert(idx == ms);

        result->h_name = r_name;
        result->h_aliases = (char**) r_aliases;
        result->h_addrtype = af;
        result->h_length = alen;
        result->h_addr_list = (char**) r_addr_list;

        if (ttlp)
                *ttlp = 0;

        if (canonp)
                *canonp = r_name;

        free(addresses);

        return NSS_STATUS_SUCCESS;
}

enum nss_status _nss_myhostname_gethostbyname3_r(
                const char *name,
                int af,
                struct hostent *host,
                char *buffer, size_t buflen,
                int *errnop, int *h_errnop,
                int32_t *ttlp,
                char **canonp) {

        char hn[HOST_NAME_MAX+1];

        if (af == AF_UNSPEC)
                af = AF_INET;

        if (af != AF_INET && af != AF_INET6) {
                *errnop = EAFNOSUPPORT;
                *h_errnop = NO_DATA;
                return NSS_STATUS_UNAVAIL;
        }

        memset(hn, 0, sizeof(hn));
        if (gethostname(hn, sizeof(hn)-1) < 0) {
                *errnop = errno;
                *h_errnop = NO_RECOVERY;
                return NSS_STATUS_UNAVAIL;
        }

        if (strcasecmp(name, hn) != 0) {
                *errnop = ENOENT;
                *h_errnop = HOST_NOT_FOUND;
                return NSS_STATUS_NOTFOUND;
        }

        return fill_in_hostent(hn, af, host, buffer, buflen, errnop, h_errnop, ttlp, canonp);
}

enum nss_status _nss_myhostname_gethostbyname2_r(
                const char *name,
                int af,
                struct hostent *host,
                char *buffer, size_t buflen,
                int *errnop, int *h_errnop) {

        return _nss_myhostname_gethostbyname3_r(
                        name,
                        af,
                        host,
                        buffer, buflen,
                        errnop, h_errnop,
                        NULL,
                        NULL);
}

enum nss_status _nss_myhostname_gethostbyname_r(
                const char *name,
                struct hostent *host,
                char *buffer, size_t buflen,
                int *errnop, int *h_errnop) {

        return _nss_myhostname_gethostbyname3_r(
                        name,
                        AF_UNSPEC,
                        host,
                        buffer, buflen,
                        errnop, h_errnop,
                        NULL,
                        NULL);
}

enum nss_status _nss_myhostname_gethostbyaddr2_r(
                const void* addr, socklen_t len,
                int af,
                struct hostent *host,
                char *buffer, size_t buflen,
                int *errnop, int *h_errnop,
                int32_t *ttlp) {

        char hn[HOST_NAME_MAX+1];
        struct address *addresses = NULL, *a;
        unsigned n_addresses = 0, n;

        if (len != PROTO_ADDRESS_SIZE(af)) {
                *errnop = EINVAL;
                *h_errnop = NO_RECOVERY;
                return NSS_STATUS_UNAVAIL;
        }

        if (af == AF_INET) {

                if ((*(uint32_t*) addr) == LOCALADDRESS_IPV4)
                        goto found;

        } else if (af == AF_INET6) {

                if (memcmp(addr, LOCALADDRESS_IPV6, 16) == 0)
                        goto found;

        } else {
                *errnop = EAFNOSUPPORT;
                *h_errnop = NO_DATA;
                return NSS_STATUS_UNAVAIL;
        }

        ifconf_acquire_addresses(&addresses, &n_addresses);

        for (a = addresses, n = 0; n < n_addresses; n++, a++) {
                if (af != a->family)
                        continue;

                if (memcmp(addr, a->address, PROTO_ADDRESS_SIZE(af)) == 0)
                        goto found;
        }

        *errnop = ENOENT;
        *h_errnop = HOST_NOT_FOUND;

        free(addresses);
        return NSS_STATUS_NOTFOUND;

found:
        free(addresses);

        memset(hn, 0, sizeof(hn));
        if (gethostname(hn, sizeof(hn)-1) < 0) {
                *errnop = errno;
                *h_errnop = NO_RECOVERY;

                return NSS_STATUS_UNAVAIL;
        }

        return fill_in_hostent(hn, af, host, buffer, buflen, errnop, h_errnop, ttlp, NULL);

}

enum nss_status _nss_myhostname_gethostbyaddr_r(
                const void* addr, socklen_t len,
                int af,
                struct hostent *host,
                char *buffer, size_t buflen,
                int *errnop, int *h_errnop) {

        return _nss_myhostname_gethostbyaddr2_r(
                        addr, len,
                        af,
                        host,
                        buffer, buflen,
                        errnop, h_errnop,
                        NULL);
}