path: root/nsprpub/pr/src/misc/prnetdb.c

/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "primpl.h"

#include <string.h>

#if defined(LINUX)
#include <sys/un.h>
#endif

/*
 * On Unix, the error code for gethostbyname() and gethostbyaddr()
 * is returned in the global variable h_errno, instead of the usual
 * errno.
 */
#if defined(XP_UNIX)
#if defined(_PR_NEED_H_ERRNO)
extern int h_errno;
#endif
#define _MD_GETHOST_ERRNO() h_errno
#else
#define _MD_GETHOST_ERRNO() _MD_ERRNO()
#endif

/*
 * The meaning of the macros related to gethostbyname, gethostbyaddr,
 * and gethostbyname2 is defined below.
 * - _PR_HAVE_THREADSAFE_GETHOST: the gethostbyXXX functions return
 *   the result in thread specific storage.  For example, AIX, HP-UX.
 * -  _PR_HAVE_GETHOST_R: have the gethostbyXXX_r functions. See next
 *   two macros.
 * - _PR_HAVE_GETHOST_R_INT: the gethostbyXXX_r functions return an
 *   int.  For example, Linux glibc.
 * - _PR_HAVE_GETHOST_R_POINTER: the gethostbyXXX_r functions return
 *   a struct hostent* pointer.  For example, Solaris.
 */
#if defined(_PR_NO_PREEMPT) || defined(_PR_HAVE_GETHOST_R) \
    || defined(_PR_HAVE_THREADSAFE_GETHOST)
#define _PR_NO_DNS_LOCK
#endif

#if defined(_PR_NO_DNS_LOCK)
#define LOCK_DNS()
#define UNLOCK_DNS()
#else
PRLock *_pr_dnsLock = NULL;
#define LOCK_DNS() PR_Lock(_pr_dnsLock)
#define UNLOCK_DNS() PR_Unlock(_pr_dnsLock)
#endif  /* defined(_PR_NO_DNS_LOCK) */

/*
 * Some platforms have the reentrant getprotobyname_r() and
 * getprotobynumber_r().  However, they come in three flavors.
 * Some return a pointer to struct protoent, others return
 * an int, and glibc's flavor takes five arguments.
 */

#if defined(SOLARIS) || (defined(BSDI) && defined(_REENTRANT)) \
    || (defined(LINUX) && defined(_REENTRANT) \
        && defined(__GLIBC__) && __GLIBC__ < 2)
#define _PR_HAVE_GETPROTO_R
#define _PR_HAVE_GETPROTO_R_POINTER
#endif

#if defined(AIX4_3_PLUS) || (defined(AIX) && defined(_THREAD_SAFE)) \
    || (defined(HPUX10_10) && defined(_REENTRANT)) \
        || (defined(HPUX10_20) && defined(_REENTRANT)) \
        || defined(OPENBSD)
#define _PR_HAVE_GETPROTO_R
#define _PR_HAVE_GETPROTO_R_INT
#endif

#if __FreeBSD_version >= 602000
#define _PR_HAVE_GETPROTO_R
#define _PR_HAVE_5_ARG_GETPROTO_R
#endif

/* BeOS has glibc but not the glibc-style getprotobyxxx_r functions. */
#if (defined(__GLIBC__) && __GLIBC__ >= 2)
#define _PR_HAVE_GETPROTO_R
#define _PR_HAVE_5_ARG_GETPROTO_R
#endif

#if !defined(_PR_HAVE_GETPROTO_R)
PRLock* _getproto_lock = NULL;
#endif

#if defined(_PR_INET6_PROBE)
extern PRBool _pr_ipv6_is_present(void);
#endif

#define _PR_IN6_IS_ADDR_UNSPECIFIED(a)              \
                (((a)->pr_s6_addr32[0] == 0) && \
                ((a)->pr_s6_addr32[1] == 0) &&      \
                ((a)->pr_s6_addr32[2] == 0) &&      \
                ((a)->pr_s6_addr32[3] == 0))

#define _PR_IN6_IS_ADDR_LOOPBACK(a)                 \
               (((a)->pr_s6_addr32[0] == 0) &&  \
               ((a)->pr_s6_addr32[1] == 0)      &&  \
               ((a)->pr_s6_addr32[2] == 0)      &&  \
               ((a)->pr_s6_addr[12] == 0)       &&  \
               ((a)->pr_s6_addr[13] == 0)       &&  \
               ((a)->pr_s6_addr[14] == 0)       &&  \
               ((a)->pr_s6_addr[15] == 0x1U))

const PRIPv6Addr _pr_in6addr_any =  {{{
            0, 0, 0, 0,
            0, 0, 0, 0,
            0, 0, 0, 0,
            0, 0, 0, 0
        }
    }
};

const PRIPv6Addr _pr_in6addr_loopback = {{{
            0, 0, 0, 0,
            0, 0, 0, 0,
            0, 0, 0, 0,
            0, 0, 0, 0x1U
        }
    }
};
/*
 * The values at bytes 10 and 11 are compared using pointers to
 * 8-bit fields, and not 32-bit fields, to make the comparison work on
 * both big-endian and little-endian systems
 */

#define _PR_IN6_IS_ADDR_V4MAPPED(a)         \
        (((a)->pr_s6_addr32[0] == 0)    &&  \
        ((a)->pr_s6_addr32[1] == 0) &&  \
        ((a)->pr_s6_addr[8] == 0)       &&  \
        ((a)->pr_s6_addr[9] == 0)       &&  \
        ((a)->pr_s6_addr[10] == 0xff)   &&  \
        ((a)->pr_s6_addr[11] == 0xff))

#define _PR_IN6_IS_ADDR_V4COMPAT(a)         \
        (((a)->pr_s6_addr32[0] == 0) && \
        ((a)->pr_s6_addr32[1] == 0) &&      \
        ((a)->pr_s6_addr32[2] == 0))

#define _PR_IN6_V4MAPPED_TO_IPADDR(a) ((a)->pr_s6_addr32[3])

#if defined(_PR_INET6) && defined(_PR_HAVE_GETHOSTBYNAME2)

/*
 * The _pr_QueryNetIfs() function finds out if the system has
 * IPv4 or IPv6 source addresses configured and sets _pr_have_inet_if
 * and _pr_have_inet6_if accordingly.
 *
 * We have an implementation using SIOCGIFCONF ioctl and a
 * default implementation that simply sets _pr_have_inet_if
 * and _pr_have_inet6_if to true.  A better implementation
 * would be to use the routing sockets (see Chapter 17 of
 * W. Richard Stevens' Unix Network Programming, Vol. 1, 2nd. Ed.)
 */

static PRLock *_pr_query_ifs_lock = NULL;
static PRBool _pr_have_inet_if = PR_FALSE;
static PRBool _pr_have_inet6_if = PR_FALSE;

#undef DEBUG_QUERY_IFS

#if defined(AIX) \
    || (defined(DARWIN) && !defined(HAVE_GETIFADDRS))

/*
 * Use SIOCGIFCONF ioctl on platforms that don't have routing
 * sockets.  Warning: whether SIOCGIFCONF ioctl returns AF_INET6
 * network interfaces is not portable.
 *
 * The _pr_QueryNetIfs() function is derived from the code in
 * src/lib/libc/net/getifaddrs.c in BSD Unix and the code in
 * Section 16.6 of W. Richard Stevens' Unix Network Programming,
 * Vol. 1, 2nd. Ed.
 */

#include <sys/ioctl.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <net/if.h>

#ifdef DEBUG_QUERY_IFS
static void
_pr_PrintIfreq(struct ifreq *ifr)
{
    PRNetAddr addr;
    struct sockaddr *sa;
    const char* family;
    char addrstr[64];

    sa = &ifr->ifr_addr;
    if (sa->sa_family == AF_INET) {
        struct sockaddr_in *sin = (struct sockaddr_in *)sa;
        family = "inet";
        memcpy(&addr.inet.ip, &sin->sin_addr, sizeof(sin->sin_addr));
    } else if (sa->sa_family == AF_INET6) {
        struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)sa;
        family = "inet6";
        memcpy(&addr.ipv6.ip, &sin6->sin6_addr, sizeof(sin6->sin6_addr));
    } else {
        return;  /* skip if not AF_INET or AF_INET6 */
    }
    addr.raw.family = sa->sa_family;
    PR_NetAddrToString(&addr, addrstr, sizeof(addrstr));
    printf("%s: %s %s\n", ifr->ifr_name, family, addrstr);
}
#endif

static void
_pr_QueryNetIfs(void)
{
    int sock;
    int rv;
    struct ifconf ifc;
    struct ifreq *ifr;
    struct ifreq *lifr;
    PRUint32 len, lastlen;
    char *buf;

    if ((sock = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
        return;
    }

    /* Issue SIOCGIFCONF request in a loop. */
    lastlen = 0;
    len = 100 * sizeof(struct ifreq);  /* initial buffer size guess */
    for (;;) {
        buf = (char *)PR_Malloc(len);
        if (NULL == buf) {
            close(sock);
            return;
        }
        ifc.ifc_buf = buf;
        ifc.ifc_len = len;
        rv = ioctl(sock, SIOCGIFCONF, &ifc);
        if (rv < 0) {
            if (errno != EINVAL || lastlen != 0) {
                close(sock);
                PR_Free(buf);
                return;
            }
        } else {
            if (ifc.ifc_len == lastlen) {
                break;    /* success, len has not changed */
            }
            lastlen = ifc.ifc_len;
        }
        len += 10 * sizeof(struct ifreq);  /* increment */
        PR_Free(buf);
    }
    close(sock);

    ifr = ifc.ifc_req;
    lifr = (struct ifreq *)&ifc.ifc_buf[ifc.ifc_len];

    while (ifr < lifr) {
        struct sockaddr *sa;
        int sa_len;

#ifdef DEBUG_QUERY_IFS
        _pr_PrintIfreq(ifr);
#endif
        sa = &ifr->ifr_addr;
        if (sa->sa_family == AF_INET) {
            struct sockaddr_in *sin = (struct sockaddr_in *) sa;
            if (sin->sin_addr.s_addr != htonl(INADDR_LOOPBACK)) {
                _pr_have_inet_if = PR_TRUE;
            }
        } else if (sa->sa_family == AF_INET6) {
            struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *) sa;
            if (!IN6_IS_ADDR_LOOPBACK(&sin6->sin6_addr)
                && !IN6_IS_ADDR_LINKLOCAL(&sin6->sin6_addr)) {
                _pr_have_inet6_if = PR_TRUE;
            }
        }

#ifdef _PR_HAVE_SOCKADDR_LEN
        sa_len = PR_MAX(sa->sa_len, sizeof(struct sockaddr));
#else
        switch (sa->sa_family) {
#ifdef AF_LINK
            case AF_LINK:
                sa_len = sizeof(struct sockaddr_dl);
                break;
#endif
            case AF_INET6:
                sa_len = sizeof(struct sockaddr_in6);
                break;
            default:
                sa_len = sizeof(struct sockaddr);
                break;
        }
#endif
        ifr = (struct ifreq *)(((char *)sa) + sa_len);
    }
    PR_Free(buf);
}

#elif (defined(DARWIN) && defined(HAVE_GETIFADDRS)) || defined(FREEBSD) \
    || defined(NETBSD) || defined(OPENBSD)

/*
 * Use the BSD getifaddrs function.
 */

#include <sys/types.h>
#include <sys/socket.h>
#include <ifaddrs.h>
#include <netinet/in.h>

#ifdef DEBUG_QUERY_IFS
static void
_pr_PrintIfaddrs(struct ifaddrs *ifa)
{
    struct sockaddr *sa;
    const char* family;
    void *addrp;
    char addrstr[64];

    sa = ifa->ifa_addr;
    if (sa->sa_family == AF_INET) {
        struct sockaddr_in *sin = (struct sockaddr_in *)sa;
        family = "inet";
        addrp = &sin->sin_addr;
    } else if (sa->sa_family == AF_INET6) {
        struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)sa;
        family = "inet6";
        addrp = &sin6->sin6_addr;
    } else {
        return;  /* skip if not AF_INET or AF_INET6 */
    }
    inet_ntop(sa->sa_family, addrp, addrstr, sizeof(addrstr));
    printf("%s: %s %s\n", ifa->ifa_name, family, addrstr);
}
#endif

static void
_pr_QueryNetIfs(void)
{
    struct ifaddrs *ifp;
    struct ifaddrs *ifa;

    if (getifaddrs(&ifp) == -1) {
        return;
    }
    for (ifa = ifp; ifa; ifa = ifa->ifa_next) {
        struct sockaddr *sa;

#ifdef DEBUG_QUERY_IFS
        _pr_PrintIfaddrs(ifa);
#endif
        sa = ifa->ifa_addr;
        if (sa->sa_family == AF_INET) {
            struct sockaddr_in *sin = (struct sockaddr_in *) sa;
            if (sin->sin_addr.s_addr != htonl(INADDR_LOOPBACK)) {
                _pr_have_inet_if = 1;
            }
        } else if (sa->sa_family == AF_INET6) {
            struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *) sa;
            if (!IN6_IS_ADDR_LOOPBACK(&sin6->sin6_addr)
                && !IN6_IS_ADDR_LINKLOCAL(&sin6->sin6_addr)) {
                _pr_have_inet6_if = 1;
            }
        }
    }
    freeifaddrs(ifp);
}

#else  /* default */

/*
 * Emulate the code in NSPR 4.2 or older.  PR_GetIPNodeByName behaves
 * as if the system had both IPv4 and IPv6 source addresses configured.
 */
static void
_pr_QueryNetIfs(void)
{
    _pr_have_inet_if = PR_TRUE;
    _pr_have_inet6_if = PR_TRUE;
}

#endif

#endif  /* _PR_INET6 && _PR_HAVE_GETHOSTBYNAME2 */

void _PR_InitNet(void)
{
#if defined(XP_UNIX)
#ifdef HAVE_NETCONFIG
    /*
     * This one-liner prevents the endless re-open's and re-read's of
     * /etc/netconfig on EACH and EVERY call to accept(), connect(), etc.
     */
    (void)setnetconfig();
#endif
#endif
#if !defined(_PR_NO_DNS_LOCK)
    _pr_dnsLock = PR_NewLock();
#endif
#if !defined(_PR_HAVE_GETPROTO_R)
    _getproto_lock = PR_NewLock();
#endif
#if defined(_PR_INET6) && defined(_PR_HAVE_GETHOSTBYNAME2)
    _pr_query_ifs_lock = PR_NewLock();
#endif
}

void _PR_CleanupNet(void)
{
#if !defined(_PR_NO_DNS_LOCK)
    if (_pr_dnsLock) {
        PR_DestroyLock(_pr_dnsLock);
        _pr_dnsLock = NULL;
    }
#endif
#if !defined(_PR_HAVE_GETPROTO_R)
    if (_getproto_lock) {
        PR_DestroyLock(_getproto_lock);
        _getproto_lock = NULL;
    }
#endif
#if defined(_PR_INET6) && defined(_PR_HAVE_GETHOSTBYNAME2)
    if (_pr_query_ifs_lock) {
        PR_DestroyLock(_pr_query_ifs_lock);
        _pr_query_ifs_lock = NULL;
    }
#endif
}

/*
** Allocate space from the buffer, aligning it to "align" before doing
** the allocation. "align" must be a power of 2.
*/
static char *Alloc(PRIntn amount, char **bufp, PRIntn *buflenp, PRIntn align)
{
    char *buf = *bufp;
    PRIntn buflen = *buflenp;

    if (align && ((long)buf & (align - 1))) {
        PRIntn skip = align - ((ptrdiff_t)buf & (align - 1));
        if (buflen < skip) {
            return 0;
        }
        buf += skip;
        buflen -= skip;
    }
    if (buflen < amount) {
        return 0;
    }
    *bufp = buf + amount;
    *buflenp = buflen - amount;
    return buf;
}

typedef enum _PRIPAddrConversion {
    _PRIPAddrNoConversion,
    _PRIPAddrIPv4Mapped,
    _PRIPAddrIPv4Compat
} _PRIPAddrConversion;

/*
** Convert an IPv4 address (v4) to an IPv4-mapped IPv6 address (v6).
*/
static void MakeIPv4MappedAddr(const char *v4, char *v6)
{
    memset(v6, 0, 10);
    memset(v6 + 10, 0xff, 2);
    memcpy(v6 + 12, v4, 4);
}

/*
** Convert an IPv4 address (v4) to an IPv4-compatible IPv6 address (v6).
*/
static void MakeIPv4CompatAddr(const char *v4, char *v6)
{
    memset(v6, 0, 12);
    memcpy(v6 + 12, v4, 4);
}

/*
** Copy a hostent, and all of the memory that it refers to into
** (hopefully) stacked buffers.
*/
static PRStatus CopyHostent(
    struct hostent *from,
    char **buf,
    PRIntn *bufsize,
    _PRIPAddrConversion conversion,
    PRHostEnt *to)
{
    PRIntn len, na;
    char **ap;

    if (conversion != _PRIPAddrNoConversion
        && from->h_addrtype == AF_INET) {
        PR_ASSERT(from->h_length == 4);
        to->h_addrtype = PR_AF_INET6;
        to->h_length = 16;
    } else {
#if defined(_PR_INET6) || defined(_PR_INET6_PROBE)
        if (AF_INET6 == from->h_addrtype) {
            to->h_addrtype = PR_AF_INET6;
        }
        else
#endif
            to->h_addrtype = from->h_addrtype;
        to->h_length = from->h_length;
    }

    /* Copy the official name */
    if (!from->h_name) {
        return PR_FAILURE;
    }
    len = strlen(from->h_name) + 1;
    to->h_name = Alloc(len, buf, bufsize, 0);
    if (!to->h_name) {
        return PR_FAILURE;
    }
    memcpy(to->h_name, from->h_name, len);

    /* Count the aliases, then allocate storage for the pointers */
    if (!from->h_aliases) {
        na = 1;
    } else {
        for (na = 1, ap = from->h_aliases; *ap != 0; na++, ap++) {;} /* nothing to execute */
    }
    to->h_aliases = (char**)Alloc(
                        na * sizeof(char*), buf, bufsize, sizeof(char**));
    if (!to->h_aliases) {
        return PR_FAILURE;
    }

    /* Copy the aliases, one at a time */
    if (!from->h_aliases) {
        to->h_aliases[0] = 0;
    } else {
        for (na = 0, ap = from->h_aliases; *ap != 0; na++, ap++) {
            len = strlen(*ap) + 1;
            to->h_aliases[na] = Alloc(len, buf, bufsize, 0);
            if (!to->h_aliases[na]) {
                return PR_FAILURE;
            }
            memcpy(to->h_aliases[na], *ap, len);
        }
        to->h_aliases[na] = 0;
    }

    /* Count the addresses, then allocate storage for the pointers */
    for (na = 1, ap = from->h_addr_list; *ap != 0; na++, ap++) {;} /* nothing to execute */
    to->h_addr_list = (char**)Alloc(
                          na * sizeof(char*), buf, bufsize, sizeof(char**));
    if (!to->h_addr_list) {
        return PR_FAILURE;
    }

    /* Copy the addresses, one at a time */
    for (na = 0, ap = from->h_addr_list; *ap != 0; na++, ap++) {
        to->h_addr_list[na] = Alloc(to->h_length, buf, bufsize, 0);
        if (!to->h_addr_list[na]) {
            return PR_FAILURE;
        }
        if (conversion != _PRIPAddrNoConversion
            && from->h_addrtype == AF_INET) {
            if (conversion == _PRIPAddrIPv4Mapped) {
                MakeIPv4MappedAddr(*ap, to->h_addr_list[na]);
            } else {
                PR_ASSERT(conversion == _PRIPAddrIPv4Compat);
                MakeIPv4CompatAddr(*ap, to->h_addr_list[na]);
            }
        } else {
            memcpy(to->h_addr_list[na], *ap, to->h_length);
        }
    }
    to->h_addr_list[na] = 0;
    return PR_SUCCESS;
}

#if !defined(_PR_HAVE_GETPROTO_R)
/*
** Copy a protoent, and all of the memory that it refers to into
** (hopefully) stacked buffers.
*/
static PRStatus CopyProtoent(
    struct protoent *from, char *buf, PRIntn bufsize, PRProtoEnt *to)
{
    PRIntn len, na;
    char **ap;

    /* Do the easy stuff */
    to->p_num = from->p_proto;

    /* Copy the official name */
    if (!from->p_name) {
        return PR_FAILURE;
    }
    len = strlen(from->p_name) + 1;
    to->p_name = Alloc(len, &buf, &bufsize, 0);
    if (!to->p_name) {
        return PR_FAILURE;
    }
    memcpy(to->p_name, from->p_name, len);

    /* Count the aliases, then allocate storage for the pointers */
    for (na = 1, ap = from->p_aliases; *ap != 0; na++, ap++) {;} /* nothing to execute */
    to->p_aliases = (char**)Alloc(
                        na * sizeof(char*), &buf, &bufsize, sizeof(char**));
    if (!to->p_aliases) {
        return PR_FAILURE;
    }

    /* Copy the aliases, one at a time */
    for (na = 0, ap = from->p_aliases; *ap != 0; na++, ap++) {
        len = strlen(*ap) + 1;
        to->p_aliases[na] = Alloc(len, &buf, &bufsize, 0);
        if (!to->p_aliases[na]) {
            return PR_FAILURE;
        }
        memcpy(to->p_aliases[na], *ap, len);
    }
    to->p_aliases[na] = 0;

    return PR_SUCCESS;
}
#endif /* !defined(_PR_HAVE_GETPROTO_R) */

/*
 * #################################################################
 * NOTE: tmphe, tmpbuf, bufsize, h, and h_err are local variables
 * or arguments of PR_GetHostByName, PR_GetIPNodeByName, and
 * PR_GetHostByAddr.  DO NOT CHANGE THE NAMES OF THESE LOCAL
 * VARIABLES OR ARGUMENTS.
 * #################################################################
 */
#if defined(_PR_HAVE_GETHOST_R_INT)

#define GETHOSTBYNAME(name) \
    (gethostbyname_r(name, &tmphe, tmpbuf, bufsize, &h, &h_err), h)
#define GETHOSTBYNAME2(name, af) \
    (gethostbyname2_r(name, af, &tmphe, tmpbuf, bufsize, &h, &h_err), h)
#define GETHOSTBYADDR(addr, addrlen, af) \
    (gethostbyaddr_r(addr, addrlen, af, \
    &tmphe, tmpbuf, bufsize, &h, &h_err), h)

#elif defined(_PR_HAVE_GETHOST_R_POINTER)

#define GETHOSTBYNAME(name) \
    gethostbyname_r(name, &tmphe, tmpbuf, bufsize, &h_err)
#define GETHOSTBYNAME2(name, af) \
    gethostbyname2_r(name, af, &tmphe, tmpbuf, bufsize, &h_err)
#define GETHOSTBYADDR(addr, addrlen, af) \
    gethostbyaddr_r(addr, addrlen, af, &tmphe, tmpbuf, bufsize, &h_err)

#else

#define GETHOSTBYNAME(name) gethostbyname(name)
#define GETHOSTBYNAME2(name, af) gethostbyname2(name, af)
#define GETHOSTBYADDR(addr, addrlen, af) gethostbyaddr(addr, addrlen, af)

#endif  /* definition of GETHOSTBYXXX */

PR_IMPLEMENT(PRStatus) PR_GetHostByName(
    const char *name, char *buf, PRIntn bufsize, PRHostEnt *hp)
{
    struct hostent *h;
    PRStatus rv = PR_FAILURE;
#if defined(_PR_HAVE_GETHOST_R)
    char localbuf[PR_NETDB_BUF_SIZE];
    char *tmpbuf;
    struct hostent tmphe;
    int h_err;
#endif

    if (!_pr_initialized) {
        _PR_ImplicitInitialization();
    }

#if defined(_PR_HAVE_GETHOST_R)
    tmpbuf = localbuf;
    if (bufsize > sizeof(localbuf))
    {
        tmpbuf = (char *)PR_Malloc(bufsize);
        if (NULL == tmpbuf)
        {
            PR_SetError(PR_OUT_OF_MEMORY_ERROR, 0);
            return rv;
        }
    }
#endif

    LOCK_DNS();

    h = GETHOSTBYNAME(name);

    if (NULL == h)
    {
        PR_SetError(PR_DIRECTORY_LOOKUP_ERROR, _MD_GETHOST_ERRNO());
    }
    else
    {
        _PRIPAddrConversion conversion = _PRIPAddrNoConversion;
        rv = CopyHostent(h, &buf, &bufsize, conversion, hp);
        if (PR_SUCCESS != rv) {
            PR_SetError(PR_INSUFFICIENT_RESOURCES_ERROR, 0);
        }
    }
    UNLOCK_DNS();
#if defined(_PR_HAVE_GETHOST_R)
    if (tmpbuf != localbuf) {
        PR_Free(tmpbuf);
    }
#endif
    return rv;
}

#if !defined(_PR_INET6) && \
        defined(_PR_INET6_PROBE) && defined(_PR_HAVE_GETIPNODEBYNAME)
typedef struct hostent  * (*_pr_getipnodebyname_t)(const char *, int,
        int, int *);
typedef struct hostent  * (*_pr_getipnodebyaddr_t)(const void *, size_t,
        int, int *);
typedef void (*_pr_freehostent_t)(struct hostent *);
static void * _pr_getipnodebyname_fp;
static void * _pr_getipnodebyaddr_fp;
static void * _pr_freehostent_fp;

/*
 * Look up the addresses of getipnodebyname, getipnodebyaddr,
 * and freehostent.
 */
PRStatus
_pr_find_getipnodebyname(void)
{
    PRLibrary *lib;
    PRStatus rv;
#define GETIPNODEBYNAME "getipnodebyname"
#define GETIPNODEBYADDR "getipnodebyaddr"
#define FREEHOSTENT     "freehostent"

    _pr_getipnodebyname_fp = PR_FindSymbolAndLibrary(GETIPNODEBYNAME, &lib);
    if (NULL != _pr_getipnodebyname_fp) {
        _pr_freehostent_fp = PR_FindSymbol(lib, FREEHOSTENT);
        if (NULL != _pr_freehostent_fp) {
            _pr_getipnodebyaddr_fp = PR_FindSymbol(lib, GETIPNODEBYADDR);
            if (NULL != _pr_getipnodebyaddr_fp) {
                rv = PR_SUCCESS;
            }
            else {
                rv = PR_FAILURE;
            }
        } else {
            rv = PR_FAILURE;
        }
        (void)PR_UnloadLibrary(lib);
    } else {
        rv = PR_FAILURE;
    }
    return rv;
}
#endif

#if defined(_PR_INET6) && defined(_PR_HAVE_GETHOSTBYNAME2)
/*
** Append the V4 addresses to the end of the list
*/
static PRStatus AppendV4AddrsToHostent(
    struct hostent *from,
    char **buf,
    PRIntn *bufsize,
    PRHostEnt *to)
{
    PRIntn na, na_old;
    char **ap;
    char **new_addr_list;

    /* Count the addresses, then grow storage for the pointers */
    for (na_old = 0, ap = to->h_addr_list; *ap != 0; na_old++, ap++)
    {;} /* nothing to execute */
    for (na = na_old + 1, ap = from->h_addr_list; *ap != 0; na++, ap++)
    {;} /* nothing to execute */
    new_addr_list = (char**)Alloc(
                        na * sizeof(char*), buf, bufsize, sizeof(char**));
    if (!new_addr_list) {
        return PR_FAILURE;
    }

    /* Copy the V6 addresses, one at a time */
    for (na = 0, ap = to->h_addr_list; *ap != 0; na++, ap++) {
        new_addr_list[na] = to->h_addr_list[na];
    }
    to->h_addr_list = new_addr_list;

    /* Copy the V4 addresses, one at a time */
    for (ap = from->h_addr_list; *ap != 0; na++, ap++) {
        to->h_addr_list[na] = Alloc(to->h_length, buf, bufsize, 0);
        if (!to->h_addr_list[na]) {
            return PR_FAILURE;
        }
        MakeIPv4MappedAddr(*ap, to->h_addr_list[na]);
    }
    to->h_addr_list[na] = 0;
    return PR_SUCCESS;
}
#endif

PR_IMPLEMENT(PRStatus) PR_GetIPNodeByName(
    const char *name, PRUint16 af, PRIntn flags,
    char *buf, PRIntn bufsize, PRHostEnt *hp)
{
    struct hostent *h = 0;
    PRStatus rv = PR_FAILURE;
#if defined(_PR_HAVE_GETHOST_R)
    char localbuf[PR_NETDB_BUF_SIZE];
    char *tmpbuf;
    struct hostent tmphe;
    int h_err;
#endif
#if defined(_PR_HAVE_GETIPNODEBYNAME)
    PRUint16 md_af = af;
    int error_num;
    int tmp_flags = 0;
#endif
#if defined(_PR_HAVE_GETHOSTBYNAME2)
    PRBool did_af_inet = PR_FALSE;
#endif

    if (!_pr_initialized) {
        _PR_ImplicitInitialization();
    }

    if (af != PR_AF_INET && af != PR_AF_INET6) {
        PR_SetError(PR_INVALID_ARGUMENT_ERROR, 0);
        return PR_FAILURE;
    }

#if defined(_PR_INET6) && defined(_PR_HAVE_GETHOSTBYNAME2)
    PR_Lock(_pr_query_ifs_lock);
    /*
     * Keep querying the presence of IPv4 and IPv6 interfaces until
     * at least one is up.  This allows us to detect the local
     * machine going from offline to online.
     */
    if (!_pr_have_inet_if && !_pr_have_inet6_if) {
        _pr_QueryNetIfs();
#ifdef DEBUG_QUERY_IFS
        if (_pr_have_inet_if) {
            printf("Have IPv4 source address\n");
        }
        if (_pr_have_inet6_if) {
            printf("Have IPv6 source address\n");
        }
#endif
    }
    PR_Unlock(_pr_query_ifs_lock);
#endif

#if defined(_PR_HAVE_GETIPNODEBYNAME)
    if (flags & PR_AI_V4MAPPED) {
        tmp_flags |= AI_V4MAPPED;
    }
    if (flags & PR_AI_ADDRCONFIG) {
        tmp_flags |= AI_ADDRCONFIG;
    }
    if (flags & PR_AI_ALL) {
        tmp_flags |= AI_ALL;
    }
    if (af == PR_AF_INET6) {
        md_af = AF_INET6;
    }
    else {
        md_af = af;
    }
#endif

#if defined(_PR_HAVE_GETHOST_R)
    tmpbuf = localbuf;
    if (bufsize > sizeof(localbuf))
    {
        tmpbuf = (char *)PR_Malloc(bufsize);
        if (NULL == tmpbuf)
        {
            PR_SetError(PR_OUT_OF_MEMORY_ERROR, 0);
            return rv;
        }
    }
#endif

    /* Do not need to lock the DNS lock if getipnodebyname() is called */
#ifdef _PR_INET6
#ifdef _PR_HAVE_GETHOSTBYNAME2
    LOCK_DNS();
    if (af == PR_AF_INET6)
    {
        if ((flags & PR_AI_ADDRCONFIG) == 0 || _pr_have_inet6_if)
        {
#ifdef _PR_INET6_PROBE
            if (_pr_ipv6_is_present())
#endif
                h = GETHOSTBYNAME2(name, AF_INET6);
        }
        if ((NULL == h) && (flags & PR_AI_V4MAPPED)
            && ((flags & PR_AI_ADDRCONFIG) == 0 || _pr_have_inet_if))
        {
            did_af_inet = PR_TRUE;
            h = GETHOSTBYNAME2(name, AF_INET);
        }
    }
    else
    {
        if ((flags & PR_AI_ADDRCONFIG) == 0 || _pr_have_inet_if)
        {
            did_af_inet = PR_TRUE;
            h = GETHOSTBYNAME2(name, af);
        }
    }
#elif defined(_PR_HAVE_GETIPNODEBYNAME)
    h = getipnodebyname(name, md_af, tmp_flags, &error_num);
#else
#error "Unknown name-to-address translation function"
#endif  /* _PR_HAVE_GETHOSTBYNAME2 */
#elif defined(_PR_INET6_PROBE) && defined(_PR_HAVE_GETIPNODEBYNAME)
    if (_pr_ipv6_is_present())
    {
#ifdef PR_GETIPNODE_NOT_THREADSAFE
        LOCK_DNS();
#endif
        h = (*((_pr_getipnodebyname_t)_pr_getipnodebyname_fp))(name, md_af, tmp_flags, &error_num);
    }
    else
    {
        LOCK_DNS();
        h = GETHOSTBYNAME(name);
    }
#else /* _PR_INET6 */
    LOCK_DNS();
    h = GETHOSTBYNAME(name);
#endif /* _PR_INET6 */

    if (NULL == h)
    {
#if defined(_PR_INET6) && defined(_PR_HAVE_GETIPNODEBYNAME)
        PR_SetError(PR_DIRECTORY_LOOKUP_ERROR, error_num);
#elif defined(_PR_INET6_PROBE) && defined(_PR_HAVE_GETIPNODEBYNAME)
        if (_pr_ipv6_is_present()) {
            PR_SetError(PR_DIRECTORY_LOOKUP_ERROR, error_num);
        }
        else {
            PR_SetError(PR_DIRECTORY_LOOKUP_ERROR, _MD_GETHOST_ERRNO());
        }
#else
        PR_SetError(PR_DIRECTORY_LOOKUP_ERROR, _MD_GETHOST_ERRNO());
#endif
    }
    else
    {
        _PRIPAddrConversion conversion = _PRIPAddrNoConversion;

        if (af == PR_AF_INET6) {
            conversion = _PRIPAddrIPv4Mapped;
        }
        rv = CopyHostent(h, &buf, &bufsize, conversion, hp);
        if (PR_SUCCESS != rv) {
            PR_SetError(PR_INSUFFICIENT_RESOURCES_ERROR, 0);
        }
#if defined(_PR_INET6) && defined(_PR_HAVE_GETIPNODEBYNAME)
        freehostent(h);
#elif defined(_PR_INET6_PROBE) && defined(_PR_HAVE_GETIPNODEBYNAME)
        if (_pr_ipv6_is_present()) {
            (*((_pr_freehostent_t)_pr_freehostent_fp))(h);
        }
#endif
#if defined(_PR_INET6) && defined(_PR_HAVE_GETHOSTBYNAME2)
        if ((PR_SUCCESS == rv) && (flags & PR_AI_V4MAPPED)
            && ((flags & PR_AI_ALL)
                || ((flags & PR_AI_ADDRCONFIG) && _pr_have_inet_if))
            && !did_af_inet && (h = GETHOSTBYNAME2(name, AF_INET)) != 0) {
            rv = AppendV4AddrsToHostent(h, &buf, &bufsize, hp);
            if (PR_SUCCESS != rv) {
                PR_SetError(PR_INSUFFICIENT_RESOURCES_ERROR, 0);
            }
        }
#endif
    }

    /* Must match the convoluted logic above for LOCK_DNS() */
#ifdef _PR_INET6
#ifdef _PR_HAVE_GETHOSTBYNAME2
    UNLOCK_DNS();
#endif  /* _PR_HAVE_GETHOSTBYNAME2 */
#elif defined(_PR_INET6_PROBE) && defined(_PR_HAVE_GETIPNODEBYNAME)
#ifdef PR_GETIPNODE_NOT_THREADSAFE
    UNLOCK_DNS();
#else
    if (!_pr_ipv6_is_present()) {
        UNLOCK_DNS();
    }
#endif
#else /* _PR_INET6 */
    UNLOCK_DNS();
#endif /* _PR_INET6 */

#if defined(_PR_HAVE_GETHOST_R)
    if (tmpbuf != localbuf) {
        PR_Free(tmpbuf);
    }
#endif

    return rv;
}

PR_IMPLEMENT(PRStatus) PR_GetHostByAddr(
    const PRNetAddr *hostaddr, char *buf, PRIntn bufsize, PRHostEnt *hostentry)
{
    struct hostent *h;
    PRStatus rv = PR_FAILURE;
    const void *addr;
    PRUint32 tmp_ip;
    int addrlen;
    PRInt32 af;
#if defined(_PR_HAVE_GETHOST_R)
    char localbuf[PR_NETDB_BUF_SIZE];
    char *tmpbuf;
    struct hostent tmphe;
    int h_err;
#endif
#if defined(_PR_HAVE_GETIPNODEBYADDR)
    int error_num;
#endif

    if (!_pr_initialized) {
        _PR_ImplicitInitialization();
    }

    if (hostaddr->raw.family == PR_AF_INET6)
    {
#if defined(_PR_INET6_PROBE)
        af = _pr_ipv6_is_present() ? AF_INET6 : AF_INET;
#elif defined(_PR_INET6)
        af = AF_INET6;
#else
        af = AF_INET;
#endif
#if defined(_PR_GHBA_DISALLOW_V4MAPPED)
        if (_PR_IN6_IS_ADDR_V4MAPPED(&hostaddr->ipv6.ip)) {
            af = AF_INET;
        }
#endif
    }
    else
    {
        PR_ASSERT(hostaddr->raw.family == AF_INET);
        af = AF_INET;
    }
    if (hostaddr->raw.family == PR_AF_INET6) {
#if defined(_PR_INET6) || defined(_PR_INET6_PROBE)
        if (af == AF_INET6) {
            addr = &hostaddr->ipv6.ip;
            addrlen = sizeof(hostaddr->ipv6.ip);
        }
        else
#endif
        {
            PR_ASSERT(af == AF_INET);
            if (!_PR_IN6_IS_ADDR_V4MAPPED(&hostaddr->ipv6.ip)) {
                PR_SetError(PR_INVALID_ARGUMENT_ERROR, 0);
                return rv;
            }
            tmp_ip = _PR_IN6_V4MAPPED_TO_IPADDR((PRIPv6Addr *)
                                                &hostaddr->ipv6.ip);
            addr = &tmp_ip;
            addrlen = sizeof(tmp_ip);
        }
    } else {
        PR_ASSERT(hostaddr->raw.family == AF_INET);
        PR_ASSERT(af == AF_INET);
        addr = &hostaddr->inet.ip;
        addrlen = sizeof(hostaddr->inet.ip);
    }

#if defined(_PR_HAVE_GETHOST_R)
    tmpbuf = localbuf;
    if (bufsize > sizeof(localbuf))
    {
        tmpbuf = (char *)PR_Malloc(bufsize);
        if (NULL == tmpbuf)
        {
            PR_SetError(PR_OUT_OF_MEMORY_ERROR, 0);
            return rv;
        }
    }
#endif

    /* Do not need to lock the DNS lock if getipnodebyaddr() is called */
#if defined(_PR_HAVE_GETIPNODEBYADDR) && defined(_PR_INET6)
    h = getipnodebyaddr(addr, addrlen, af, &error_num);
#elif defined(_PR_HAVE_GETIPNODEBYADDR) && defined(_PR_INET6_PROBE)
    if (_pr_ipv6_is_present())
    {
#ifdef PR_GETIPNODE_NOT_THREADSAFE
        LOCK_DNS();
#endif
        h = (*((_pr_getipnodebyaddr_t)_pr_getipnodebyaddr_fp))(addr, addrlen,
                af, &error_num);
    }
    else
    {
        LOCK_DNS();
        h = GETHOSTBYADDR(addr, addrlen, af);
    }
#else   /* _PR_HAVE_GETIPNODEBYADDR */
    LOCK_DNS();
    h = GETHOSTBYADDR(addr, addrlen, af);
#endif /* _PR_HAVE_GETIPNODEBYADDR */
    if (NULL == h)
    {
#if defined(_PR_INET6) && defined(_PR_HAVE_GETIPNODEBYADDR)
        PR_SetError(PR_DIRECTORY_LOOKUP_ERROR, error_num);
#elif defined(_PR_INET6_PROBE) && defined(_PR_HAVE_GETIPNODEBYADDR)
        if (_pr_ipv6_is_present()) {
            PR_SetError(PR_DIRECTORY_LOOKUP_ERROR, error_num);
        }
        else {
            PR_SetError(PR_DIRECTORY_LOOKUP_ERROR, _MD_GETHOST_ERRNO());
        }
#else
        PR_SetError(PR_DIRECTORY_LOOKUP_ERROR, _MD_GETHOST_ERRNO());
#endif
    }
    else
    {
        _PRIPAddrConversion conversion = _PRIPAddrNoConversion;
        if (hostaddr->raw.family == PR_AF_INET6) {
            if (af == AF_INET) {
                if (_PR_IN6_IS_ADDR_V4MAPPED((PRIPv6Addr*)
                                             &hostaddr->ipv6.ip)) {
                    conversion = _PRIPAddrIPv4Mapped;
                } else if (_PR_IN6_IS_ADDR_V4COMPAT((PRIPv6Addr *)
                                                    &hostaddr->ipv6.ip)) {
                    conversion = _PRIPAddrIPv4Compat;
                }
            }
        }
        rv = CopyHostent(h, &buf, &bufsize, conversion, hostentry);
        if (PR_SUCCESS != rv) {
            PR_SetError(PR_INSUFFICIENT_RESOURCES_ERROR, 0);
        }
#if defined(_PR_INET6) && defined(_PR_HAVE_GETIPNODEBYADDR)
        freehostent(h);
#elif defined(_PR_INET6_PROBE) && defined(_PR_HAVE_GETIPNODEBYADDR)
        if (_pr_ipv6_is_present()) {
            (*((_pr_freehostent_t)_pr_freehostent_fp))(h);
        }
#endif
    }

    /* Must match the convoluted logic above for LOCK_DNS() */
#if defined(_PR_HAVE_GETIPNODEBYADDR) && defined(_PR_INET6)
#elif defined(_PR_HAVE_GETIPNODEBYADDR) && defined(_PR_INET6_PROBE)
#ifdef PR_GETIPNODE_NOT_THREADSAFE
    UNLOCK_DNS();
#else
    if (!_pr_ipv6_is_present()) {
        UNLOCK_DNS();
    }
#endif
#else   /* _PR_HAVE_GETIPNODEBYADDR */
    UNLOCK_DNS();
#endif /* _PR_HAVE_GETIPNODEBYADDR */

#if defined(_PR_HAVE_GETHOST_R)
    if (tmpbuf != localbuf) {
        PR_Free(tmpbuf);
    }
#endif

    return rv;
}

/******************************************************************************/
/*
 * Some systems define a reentrant version of getprotobyname(). Too bad
 * the signature isn't always the same. But hey, they tried. If there
 * is such a definition, use it. Otherwise, grab a lock and do it here.
 */
/******************************************************************************/

#if !defined(_PR_HAVE_GETPROTO_R)
/*
 * This may seem like a silly thing to do, but the compiler SHOULD
 * complain if getprotobyname_r() is implemented on some system and
 * we're not using it. For sure these signatures are different than
 * any usable implementation.
 */

#if defined(ANDROID)
/* Android's Bionic libc system includes prototypes for these in netdb.h,
 * but doesn't actually include implementations.  It uses the 5-arg form,
 * so these functions end up not matching the prototype.  So just rename
 * them if not found.
 */
#define getprotobyname_r _pr_getprotobyname_r
#define getprotobynumber_r _pr_getprotobynumber_r
#endif

static struct protoent *getprotobyname_r(const char* name)
{
    return getprotobyname(name);
} /* getprotobyname_r */

static struct protoent *getprotobynumber_r(PRInt32 number)
{
    return getprotobynumber(number);
} /* getprotobynumber_r */

#endif /* !defined(_PR_HAVE_GETPROTO_R) */

PR_IMPLEMENT(PRStatus) PR_GetProtoByName(
    const char* name, char* buffer, PRInt32 buflen, PRProtoEnt* result)
{
    PRStatus rv = PR_SUCCESS;
#if defined(_PR_HAVE_GETPROTO_R)
    struct protoent* res = (struct protoent*)result;
#endif

    if (!_pr_initialized) {
        _PR_ImplicitInitialization();
    }

#if defined(_PR_HAVE_GETPROTO_R_INT)
    {
        /*
        ** The protoent_data has a pointer as the first field.
        ** That implies the buffer better be aligned, and char*
        ** doesn't promise much.
        */
        PRUptrdiff aligned = (PRUptrdiff)buffer;
        if (0 != (aligned & (sizeof(struct protoent_data*) - 1)))
        {
            aligned += sizeof(struct protoent_data*) - 1;
            aligned &= ~(sizeof(struct protoent_data*) - 1);
            buflen -= (aligned - (PRUptrdiff)buffer);
            buffer = (char*)aligned;
        }
    }
#endif  /* defined(_PR_HAVE_GETPROTO_R_INT) */

    if (PR_MIN_NETDB_BUF_SIZE > buflen)
    {
        PR_SetError(PR_INVALID_ARGUMENT_ERROR, 0);
        return PR_FAILURE;
    }

#if defined(_PR_HAVE_GETPROTO_R_POINTER)
    if (NULL == getprotobyname_r(name, res, buffer, buflen))
    {
        PR_SetError(PR_DIRECTORY_LOOKUP_ERROR, _MD_ERRNO());
        return PR_FAILURE;
    }
#elif defined(_PR_HAVE_GETPROTO_R_INT)
    /*
    ** The buffer needs to be zero'd, and it should be
    ** at least the size of a struct protoent_data.
    */
    memset(buffer, 0, buflen);
    if (-1 == getprotobyname_r(name, res, (struct protoent_data*)buffer))
    {
        PR_SetError(PR_DIRECTORY_LOOKUP_ERROR, _MD_ERRNO());
        return PR_FAILURE;
    }
#elif defined(_PR_HAVE_5_ARG_GETPROTO_R)
    /* The 5th argument for getprotobyname_r() cannot be NULL */
    if (-1 == getprotobyname_r(name, res, buffer, buflen, &res))
    {
        PR_SetError(PR_DIRECTORY_LOOKUP_ERROR, _MD_ERRNO());
        return PR_FAILURE;
    }
#else  /* do it the hard way */
    {
        struct protoent *staticBuf;
        PR_Lock(_getproto_lock);
        staticBuf = getprotobyname_r(name);
        if (NULL == staticBuf)
        {
            rv = PR_FAILURE;
            PR_SetError(PR_DIRECTORY_LOOKUP_ERROR, _MD_ERRNO());
        }
        else
        {
            rv = CopyProtoent(staticBuf, buffer, buflen, result);
            if (PR_FAILURE == rv) {
                PR_SetError(PR_INSUFFICIENT_RESOURCES_ERROR, 0);
            }
        }
        PR_Unlock(_getproto_lock);
    }
#endif  /* all that */
    return rv;
}

PR_IMPLEMENT(PRStatus) PR_GetProtoByNumber(
    PRInt32 number, char* buffer, PRInt32 buflen, PRProtoEnt* result)
{
    PRStatus rv = PR_SUCCESS;
#if defined(_PR_HAVE_GETPROTO_R)
    struct protoent* res = (struct protoent*)result;
#endif

    if (!_pr_initialized) {
        _PR_ImplicitInitialization();
    }

#if defined(_PR_HAVE_GETPROTO_R_INT)
    {
        /*
        ** The protoent_data has a pointer as the first field.
        ** That implies the buffer better be aligned, and char*
        ** doesn't promise much.
        */
        PRUptrdiff aligned = (PRUptrdiff)buffer;
        if (0 != (aligned & (sizeof(struct protoent_data*) - 1)))
        {
            aligned += sizeof(struct protoent_data*) - 1;
            aligned &= ~(sizeof(struct protoent_data*) - 1);
            buflen -= (aligned - (PRUptrdiff)buffer);
            buffer = (char*)aligned;
        }
    }
#endif /* defined(_PR_HAVE_GETPROTO_R_INT) */

    if (PR_MIN_NETDB_BUF_SIZE > buflen)
    {
        PR_SetError(PR_INVALID_ARGUMENT_ERROR, 0);
        return PR_FAILURE;
    }

#if defined(_PR_HAVE_GETPROTO_R_POINTER)
    if (NULL == getprotobynumber_r(number, res, buffer, buflen))
    {
        PR_SetError(PR_DIRECTORY_LOOKUP_ERROR, _MD_ERRNO());
        return PR_FAILURE;
    }

#elif defined(_PR_HAVE_GETPROTO_R_INT)
    /*
    ** The buffer needs to be zero'd for these OS's.
    */
    memset(buffer, 0, buflen);
    if (-1 == getprotobynumber_r(number, res, (struct protoent_data*)buffer))
    {
        PR_SetError(PR_DIRECTORY_LOOKUP_ERROR, _MD_ERRNO());
        return PR_FAILURE;
    }
#elif defined(_PR_HAVE_5_ARG_GETPROTO_R)
    /* The 5th argument for getprotobynumber_r() cannot be NULL */
    if (-1 == getprotobynumber_r(number, res, buffer, buflen, &res))
    {
        PR_SetError(PR_DIRECTORY_LOOKUP_ERROR, _MD_ERRNO());
        return PR_FAILURE;
    }
#else  /* do it the hard way */
    {
        struct protoent *staticBuf;
        PR_Lock(_getproto_lock);
        staticBuf = getprotobynumber_r(number);
        if (NULL == staticBuf)
        {
            rv = PR_FAILURE;
            PR_SetError(PR_DIRECTORY_LOOKUP_ERROR, _MD_ERRNO());
        }
        else
        {
            rv = CopyProtoent(staticBuf, buffer, buflen, result);
            if (PR_FAILURE == rv) {
                PR_SetError(PR_INSUFFICIENT_RESOURCES_ERROR, 0);
            }
        }
        PR_Unlock(_getproto_lock);
    }
#endif  /* all that crap */
    return rv;

}

PRUintn _PR_NetAddrSize(const PRNetAddr* addr)
{
    PRUintn addrsize;

    /*
     * RFC 2553 added a new field (sin6_scope_id) to
     * struct sockaddr_in6.  PRNetAddr's ipv6 member has a
     * scope_id field to match the new field.  In order to
     * work with older implementations supporting RFC 2133,
     * we take the size of struct sockaddr_in6 instead of
     * addr->ipv6.
     */
    if (AF_INET == addr->raw.family) {
        addrsize = sizeof(addr->inet);
    }
    else if (PR_AF_INET6 == addr->raw.family)
#if defined(_PR_INET6)
        addrsize = sizeof(struct sockaddr_in6);
#else
        addrsize = sizeof(addr->ipv6);
#endif
#if defined(XP_UNIX) || defined(XP_OS2)
    else if (AF_UNIX == addr->raw.family)
    {
#if defined(LINUX)
        if (addr->local.path[0] == 0)
            /* abstract socket address is supported on Linux only */
            addrsize = strnlen(addr->local.path + 1,
                               sizeof(addr->local.path)) +
                       offsetof(struct sockaddr_un, sun_path) + 1;
        else
#endif
            addrsize = sizeof(addr->local);
    }
#endif
    else {
        addrsize = 0;
    }

    return addrsize;
}  /* _PR_NetAddrSize */

PR_IMPLEMENT(PRIntn) PR_EnumerateHostEnt(
    PRIntn enumIndex, const PRHostEnt *hostEnt, PRUint16 port, PRNetAddr *address)
{
    void *addr = hostEnt->h_addr_list[enumIndex++];
    memset(address, 0, sizeof(PRNetAddr));
    if (NULL == addr) {
        enumIndex = 0;
    }
    else
    {
        address->raw.family = hostEnt->h_addrtype;
        if (PR_AF_INET6 == hostEnt->h_addrtype)
        {
            address->ipv6.port = htons(port);
            address->ipv6.flowinfo = 0;
            address->ipv6.scope_id = 0;
            memcpy(&address->ipv6.ip, addr, hostEnt->h_length);
        }
        else
        {
            PR_ASSERT(AF_INET == hostEnt->h_addrtype);
            address->inet.port = htons(port);
            memcpy(&address->inet.ip, addr, hostEnt->h_length);
        }
    }
    return enumIndex;
}  /* PR_EnumerateHostEnt */

PR_IMPLEMENT(PRStatus) PR_InitializeNetAddr(
    PRNetAddrValue val, PRUint16 port, PRNetAddr *addr)
{
    PRStatus rv = PR_SUCCESS;
    if (!_pr_initialized) {
        _PR_ImplicitInitialization();
    }

    if (val != PR_IpAddrNull) {
        memset(addr, 0, sizeof(*addr));
    }
    addr->inet.family = AF_INET;
    addr->inet.port = htons(port);
    switch (val)
    {
        case PR_IpAddrNull:
            break;  /* don't overwrite the address */
        case PR_IpAddrAny:
            addr->inet.ip = htonl(INADDR_ANY);
            break;
        case PR_IpAddrLoopback:
            addr->inet.ip = htonl(INADDR_LOOPBACK);
            break;
        default:
            PR_SetError(PR_INVALID_ARGUMENT_ERROR, 0);
            rv = PR_FAILURE;
    }
    return rv;
}  /* PR_InitializeNetAddr */

PR_IMPLEMENT(PRStatus) PR_SetNetAddr(
    PRNetAddrValue val, PRUint16 af, PRUint16 port, PRNetAddr *addr)
{
    PRStatus rv = PR_SUCCESS;
    if (!_pr_initialized) {
        _PR_ImplicitInitialization();
    }

    if (af == PR_AF_INET6)
    {
        if (val != PR_IpAddrNull) {
            memset(addr, 0, sizeof(addr->ipv6));
        }
        addr->ipv6.family = af;
        addr->ipv6.port = htons(port);
        addr->ipv6.flowinfo = 0;
        addr->ipv6.scope_id = 0;
        switch (val)
        {
            case PR_IpAddrNull:
                break;  /* don't overwrite the address */
            case PR_IpAddrAny:
                addr->ipv6.ip = _pr_in6addr_any;
                break;
            case PR_IpAddrLoopback:
                addr->ipv6.ip = _pr_in6addr_loopback;
                break;
            default:
                PR_SetError(PR_INVALID_ARGUMENT_ERROR, 0);
                rv = PR_FAILURE;
        }
    }
    else
    {
        if (val != PR_IpAddrNull) {
            memset(addr, 0, sizeof(addr->inet));
        }
        addr->inet.family = af;
        addr->inet.port = htons(port);
        switch (val)
        {
            case PR_IpAddrNull:
                break;  /* don't overwrite the address */
            case PR_IpAddrAny:
                addr->inet.ip = htonl(INADDR_ANY);
                break;
            case PR_IpAddrLoopback:
                addr->inet.ip = htonl(INADDR_LOOPBACK);
                break;
            default:
                PR_SetError(PR_INVALID_ARGUMENT_ERROR, 0);
                rv = PR_FAILURE;
        }
    }
    return rv;
}  /* PR_SetNetAddr */

PR_IMPLEMENT(PRBool)
PR_IsNetAddrType(const PRNetAddr *addr, PRNetAddrValue val)
{
    if (addr->raw.family == PR_AF_INET6) {
        if (val == PR_IpAddrAny) {
            if (_PR_IN6_IS_ADDR_UNSPECIFIED((PRIPv6Addr *)&addr->ipv6.ip)) {
                return PR_TRUE;
            }
            if (_PR_IN6_IS_ADDR_V4MAPPED((PRIPv6Addr *)&addr->ipv6.ip)
                && _PR_IN6_V4MAPPED_TO_IPADDR((PRIPv6Addr *)&addr->ipv6.ip)
                == htonl(INADDR_ANY)) {
                return PR_TRUE;
            }
        } else if (val == PR_IpAddrLoopback) {
            if (_PR_IN6_IS_ADDR_LOOPBACK((PRIPv6Addr *)&addr->ipv6.ip)) {
                return PR_TRUE;
            }
            if (_PR_IN6_IS_ADDR_V4MAPPED((PRIPv6Addr *)&addr->ipv6.ip)
                && _PR_IN6_V4MAPPED_TO_IPADDR((PRIPv6Addr *)&addr->ipv6.ip)
                == htonl(INADDR_LOOPBACK)) {
                return PR_TRUE;
            }
        } else if (val == PR_IpAddrV4Mapped
                   && _PR_IN6_IS_ADDR_V4MAPPED((PRIPv6Addr *)&addr->ipv6.ip)) {
            return PR_TRUE;
        }
    } else {
        if (addr->raw.family == AF_INET) {
            if (val == PR_IpAddrAny && addr->inet.ip == htonl(INADDR_ANY)) {
                return PR_TRUE;
            }
            if (val == PR_IpAddrLoopback
                && addr->inet.ip == htonl(INADDR_LOOPBACK)) {
                return PR_TRUE;
            }
        }
    }
    return PR_FALSE;
}

extern int pr_inet_aton(const char *cp, PRUint32 *addr);

#define XX 127
static const unsigned char index_hex[256] = {
    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
    0, 1, 2, 3,  4, 5, 6, 7,  8, 9,XX,XX, XX,XX,XX,XX,
    XX,10,11,12, 13,14,15,XX, XX,XX,XX,XX, XX,XX,XX,XX,
    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
    XX,10,11,12, 13,14,15,XX, XX,XX,XX,XX, XX,XX,XX,XX,
    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
};

/*
 * StringToV6Addr() returns 1 if the conversion succeeds,
 * or 0 if the input is not a valid IPv6 address string.
 * (Same as inet_pton(AF_INET6, string, addr).)
 */
static int StringToV6Addr(const char *string, PRIPv6Addr *addr)
{
    const unsigned char *s = (const unsigned char *)string;
    int section = 0;        /* index of the current section (a 16-bit
                             * piece of the address */
    int double_colon = -1;  /* index of the section after the first
                             * 16-bit group of zeros represented by
                             * the double colon */
    unsigned int val;
    int len;

    /* Handle initial (double) colon */
    if (*s == ':') {
        if (s[1] != ':') {
            return 0;
        }
        s += 2;
        addr->pr_s6_addr16[0] = 0;
        section = double_colon = 1;
    }

    while (*s) {
        if (section == 8) {
            return 0;    /* too long */
        }
        if (*s == ':') {
            if (double_colon != -1) {
                return 0;    /* two double colons */
            }
            addr->pr_s6_addr16[section++] = 0;
            double_colon = section;
            s++;
            continue;
        }
        for (len = val = 0; len < 4 && index_hex[*s] != XX; len++) {
            val = (val << 4) + index_hex[*s++];
        }
        if (*s == '.') {
            if (len == 0) {
                return 0;    /* nothing between : and . */
            }
            break;
        }
        if (*s == ':') {
            s++;
            if (!*s) {
                return 0;    /* cannot end with single colon */
            }
        } else if (*s) {
            return 0; /* bad character */
        }
        addr->pr_s6_addr16[section++] = htons((unsigned short)val);
    }

    if (*s == '.') {
        /* Have a trailing v4 format address */
        if (section > 6) {
            return 0;    /* not enough room */
        }

        /*
         * The number before the '.' is decimal, but we parsed it
         * as hex.  That means it is in BCD.  Check it for validity
         * and convert it to binary.
         */
        if (val > 0x0255 || (val & 0xf0) > 0x90 || (val & 0xf) > 9) {
            return 0;
        }
        val = (val >> 8) * 100 + ((val >> 4) & 0xf) * 10 + (val & 0xf);
        addr->pr_s6_addr[2 * section] = val;

        s++;
        val = index_hex[*s++];
        if (val > 9) {
            return 0;
        }
        while (*s >= '0' && *s <= '9') {
            val = val * 10 + *s++ - '0';
            if (val > 255) {
                return 0;
            }
        }
        if (*s != '.') {
            return 0;    /* must have exactly 4 decimal numbers */
        }
        addr->pr_s6_addr[2 * section + 1] = val;
        section++;

        s++;
        val = index_hex[*s++];
        if (val > 9) {
            return 0;
        }
        while (*s >= '0' && *s <= '9') {
            val = val * 10 + *s++ - '0';
            if (val > 255) {
                return 0;
            }
        }
        if (*s != '.') {
            return 0;    /* must have exactly 4 decimal numbers */
        }
        addr->pr_s6_addr[2 * section] = val;

        s++;
        val = index_hex[*s++];
        if (val > 9) {
            return 0;
        }
        while (*s >= '0' && *s <= '9') {
            val = val * 10 + *s++ - '0';
            if (val > 255) {
                return 0;
            }
        }
        if (*s) {
            return 0;    /* must have exactly 4 decimal numbers */
        }
        addr->pr_s6_addr[2 * section + 1] = val;
        section++;
    }

    if (double_colon != -1) {
        /* Stretch the double colon */
        int tosection;
        int ncopy = section - double_colon;
        for (tosection = 7; ncopy--; tosection--) {
            addr->pr_s6_addr16[tosection] =
                addr->pr_s6_addr16[double_colon + ncopy];
        }
        while (tosection >= double_colon) {
            addr->pr_s6_addr16[tosection--] = 0;
        }
    } else if (section != 8) {
        return 0; /* too short */
    }
    return 1;
}
#undef XX

#ifndef _PR_HAVE_INET_NTOP
static const char *basis_hex = "0123456789abcdef";

/*
 * V6AddrToString() returns a pointer to the buffer containing
 * the text string if the conversion succeeds, and NULL otherwise.
 * (Same as inet_ntop(AF_INET6, addr, buf, size), except that errno
 * is not set on failure.)
 */
static const char *V6AddrToString(
    const PRIPv6Addr *addr, char *buf, PRUint32 size)
{
#define STUFF(c) do { \
    if (!size--) return NULL; \
    *buf++ = (c); \
} while (0)

    int double_colon = -1;          /* index of the first 16-bit
                                     * group of zeros represented
                                     * by the double colon */
    int double_colon_length = 1;    /* use double colon only if
                                     * there are two or more 16-bit
                                     * groups of zeros */
    int zero_length;
    int section;
    unsigned int val;
    const char *bufcopy = buf;

    /* Scan to find the placement of the double colon */
    for (section = 0; section < 8; section++) {
        if (addr->pr_s6_addr16[section] == 0) {
            zero_length = 1;
            section++;
            while (section < 8 && addr->pr_s6_addr16[section] == 0) {
                zero_length++;
                section++;
            }
            /* Select the longest sequence of zeros */
            if (zero_length > double_colon_length) {
                double_colon = section - zero_length;
                double_colon_length = zero_length;
            }
        }
    }

    /* Now start converting to a string */
    section = 0;

    if (double_colon == 0) {
        if (double_colon_length == 6 ||
            (double_colon_length == 5 && addr->pr_s6_addr16[5] == 0xffff)) {
            /* ipv4 format address */
            STUFF(':');
            STUFF(':');
            if (double_colon_length == 5) {
                STUFF('f');
                STUFF('f');
                STUFF('f');
                STUFF('f');
                STUFF(':');
            }
            if (addr->pr_s6_addr[12] > 99) {
                STUFF(addr->pr_s6_addr[12]/100 + '0');
            }
            if (addr->pr_s6_addr[12] > 9) {
                STUFF((addr->pr_s6_addr[12]%100)/10 + '0');
            }
            STUFF(addr->pr_s6_addr[12]%10 + '0');
            STUFF('.');
            if (addr->pr_s6_addr[13] > 99) {
                STUFF(addr->pr_s6_addr[13]/100 + '0');
            }
            if (addr->pr_s6_addr[13] > 9) {
                STUFF((addr->pr_s6_addr[13]%100)/10 + '0');
            }
            STUFF(addr->pr_s6_addr[13]%10 + '0');
            STUFF('.');
            if (addr->pr_s6_addr[14] > 99) {
                STUFF(addr->pr_s6_addr[14]/100 + '0');
            }
            if (addr->pr_s6_addr[14] > 9) {
                STUFF((addr->pr_s6_addr[14]%100)/10 + '0');
            }
            STUFF(addr->pr_s6_addr[14]%10 + '0');
            STUFF('.');
            if (addr->pr_s6_addr[15] > 99) {
                STUFF(addr->pr_s6_addr[15]/100 + '0');
            }
            if (addr->pr_s6_addr[15] > 9) {
                STUFF((addr->pr_s6_addr[15]%100)/10 + '0');
            }
            STUFF(addr->pr_s6_addr[15]%10 + '0');
            STUFF('\0');
            return bufcopy;
        }
    }

    while (section < 8) {
        if (section == double_colon) {
            STUFF(':');
            STUFF(':');
            section += double_colon_length;
            continue;
        }
        val = ntohs(addr->pr_s6_addr16[section]);
        if (val > 0xfff) {
            STUFF(basis_hex[val >> 12]);
        }
        if (val > 0xff) {
            STUFF(basis_hex[(val >> 8) & 0xf]);
        }
        if (val > 0xf) {
            STUFF(basis_hex[(val >> 4) & 0xf]);
        }
        STUFF(basis_hex[val & 0xf]);
        section++;
        if (section < 8 && section != double_colon) {
            STUFF(':');
        }
    }
    STUFF('\0');
    return bufcopy;
#undef STUFF
}
#endif /* !_PR_HAVE_INET_NTOP */

/*
 * Convert an IPv4 addr to an (IPv4-mapped) IPv6 addr
 */
PR_IMPLEMENT(void) PR_ConvertIPv4AddrToIPv6(PRUint32 v4addr, PRIPv6Addr *v6addr)
{
    PRUint8 *dstp;
    dstp = v6addr->pr_s6_addr;
    memset(dstp, 0, 10);
    memset(dstp + 10, 0xff, 2);
    memcpy(dstp + 12,(char *) &v4addr, 4);
}

PR_IMPLEMENT(PRUint16) PR_ntohs(PRUint16 n) {
    return ntohs(n);
}
PR_IMPLEMENT(PRUint32) PR_ntohl(PRUint32 n) {
    return ntohl(n);
}
PR_IMPLEMENT(PRUint16) PR_htons(PRUint16 n) {
    return htons(n);
}
PR_IMPLEMENT(PRUint32) PR_htonl(PRUint32 n) {
    return htonl(n);
}
PR_IMPLEMENT(PRUint64) PR_ntohll(PRUint64 n)
{
#ifdef IS_BIG_ENDIAN
    return n;
#else
    PRUint32 hi, lo;
    lo = (PRUint32)n;
    hi = (PRUint32)(n >> 32);
    hi = PR_ntohl(hi);
    lo = PR_ntohl(lo);
    return ((PRUint64)lo << 32) + (PRUint64)hi;
#endif
}  /* ntohll */

PR_IMPLEMENT(PRUint64) PR_htonll(PRUint64 n)
{
#ifdef IS_BIG_ENDIAN
    return n;
#else
    PRUint32 hi, lo;
    lo = (PRUint32)n;
    hi = (PRUint32)(n >> 32);
    hi = htonl(hi);
    lo = htonl(lo);
    return ((PRUint64)lo << 32) + (PRUint64)hi;
#endif
}  /* htonll */


/*
 * Implementation of PR_GetAddrInfoByName and friends
 *
 * Compile-time options:
 *
 *  _PR_HAVE_GETADDRINFO  Define this macro if the target system provides
 *                        getaddrinfo. With this defined, NSPR will require
 *                        getaddrinfo at run time. If this if not defined,
 *                        then NSPR will attempt to dynamically resolve
 *                        getaddrinfo, falling back to PR_GetHostByName if
 *                        getaddrinfo does not exist on the target system.
 *
 * Since getaddrinfo is a relatively new system call on many systems,
 * we are forced to dynamically resolve it at run time in most cases.
 * The exception includes any system (such as Mac OS X) that is known to
 * provide getaddrinfo in all versions that NSPR cares to support.
 */

#if defined(_PR_HAVE_GETADDRINFO)

#if defined(_PR_INET6)

typedef struct addrinfo PRADDRINFO;
#define GETADDRINFO getaddrinfo
#define FREEADDRINFO freeaddrinfo
#define GETNAMEINFO getnameinfo

#elif defined(_PR_INET6_PROBE)

typedef struct addrinfo PRADDRINFO;

/* getaddrinfo/freeaddrinfo/getnameinfo prototypes */
#if defined(WIN32)
#define FUNC_MODIFIER __stdcall
#else
#define FUNC_MODIFIER
#endif
typedef int (FUNC_MODIFIER * FN_GETADDRINFO)
(const char *nodename,
 const char *servname,
 const PRADDRINFO *hints,
 PRADDRINFO **res);
typedef int (FUNC_MODIFIER * FN_FREEADDRINFO)
(PRADDRINFO *ai);
typedef int (FUNC_MODIFIER * FN_GETNAMEINFO)
(const struct sockaddr *addr, int addrlen,
 char *host, int hostlen,
 char *serv, int servlen, int flags);

/* global state */
static FN_GETADDRINFO   _pr_getaddrinfo   = NULL;
static FN_FREEADDRINFO  _pr_freeaddrinfo  = NULL;
static FN_GETNAMEINFO   _pr_getnameinfo   = NULL;

#define GETADDRINFO_SYMBOL "getaddrinfo"
#define FREEADDRINFO_SYMBOL "freeaddrinfo"
#define GETNAMEINFO_SYMBOL "getnameinfo"

PRStatus
_pr_find_getaddrinfo(void)
{
    PRLibrary *lib;
#ifdef WIN32
    /*
     * On windows, we need to search ws2_32.dll or wship6.dll
     * (Microsoft IPv6 Technology Preview for Windows 2000) for
     * getaddrinfo and freeaddrinfo.  These libraries might not
     * be loaded yet.
     */
    const char *libname[] = { "ws2_32.dll", "wship6.dll" };
    int i;

    for (i = 0; i < sizeof(libname)/sizeof(libname[0]); i++) {
        lib = PR_LoadLibrary(libname[i]);
        if (!lib) {
            continue;
        }
        _pr_getaddrinfo = (FN_GETADDRINFO)
                          PR_FindFunctionSymbol(lib, GETADDRINFO_SYMBOL);
        if (!_pr_getaddrinfo) {
            PR_UnloadLibrary(lib);
            continue;
        }
        _pr_freeaddrinfo = (FN_FREEADDRINFO)
                           PR_FindFunctionSymbol(lib, FREEADDRINFO_SYMBOL);
        _pr_getnameinfo = (FN_GETNAMEINFO)
                          PR_FindFunctionSymbol(lib, GETNAMEINFO_SYMBOL);
        if (!_pr_freeaddrinfo || !_pr_getnameinfo) {
            PR_UnloadLibrary(lib);
            continue;
        }
        /* Keep the library loaded. */
        return PR_SUCCESS;
    }
    return PR_FAILURE;
#else
    /*
     * Resolve getaddrinfo by searching all loaded libraries.  Then
     * search library containing getaddrinfo for freeaddrinfo.
     */
    _pr_getaddrinfo = (FN_GETADDRINFO)
                      PR_FindFunctionSymbolAndLibrary(GETADDRINFO_SYMBOL, &lib);
    if (!_pr_getaddrinfo) {
        return PR_FAILURE;
    }
    _pr_freeaddrinfo = (FN_FREEADDRINFO)
                       PR_FindFunctionSymbol(lib, FREEADDRINFO_SYMBOL);
    _pr_getnameinfo = (FN_GETNAMEINFO)
                      PR_FindFunctionSymbol(lib, GETNAMEINFO_SYMBOL);
    PR_UnloadLibrary(lib);
    if (!_pr_freeaddrinfo || !_pr_getnameinfo) {
        return PR_FAILURE;
    }
    return PR_SUCCESS;
#endif
}

#define GETADDRINFO (*_pr_getaddrinfo)
#define FREEADDRINFO (*_pr_freeaddrinfo)
#define GETNAMEINFO (*_pr_getnameinfo)

#endif /* _PR_INET6 */

#endif /* _PR_HAVE_GETADDRINFO */

#if !defined(_PR_HAVE_GETADDRINFO) || defined(_PR_INET6_PROBE)
/*
 * If getaddrinfo does not exist, then we will fall back on
 * PR_GetHostByName, which requires that we allocate a buffer for the
 * PRHostEnt data structure and its members.
 */
typedef struct PRAddrInfoFB {
    char      buf[PR_NETDB_BUF_SIZE];
    PRHostEnt hostent;
    PRBool    has_cname;
} PRAddrInfoFB;

static PRAddrInfo *
pr_GetAddrInfoByNameFB(const char  *hostname,
                       PRUint16     af,
                       PRIntn       flags)
{
    PRStatus rv;
    PRAddrInfoFB *ai;
    /* fallback on PR_GetHostByName */
    ai = PR_NEW(PRAddrInfoFB);
    if (!ai) {
        PR_SetError(PR_OUT_OF_MEMORY_ERROR, 0);
        return NULL;
    }
    rv = PR_GetHostByName(hostname, ai->buf, sizeof ai->buf, &ai->hostent);
    if (rv == PR_FAILURE) {
        PR_Free(ai);
        return NULL;
    }
    ai->has_cname = !(flags & PR_AI_NOCANONNAME);

    return (PRAddrInfo *) ai;
}
#endif /* !_PR_HAVE_GETADDRINFO || _PR_INET6_PROBE */

PR_IMPLEMENT(PRAddrInfo *) PR_GetAddrInfoByName(const char  *hostname,
        PRUint16     af,
        PRIntn       flags)
{
    /* restrict input to supported values */
    if ((af != PR_AF_INET && af != PR_AF_UNSPEC) ||
        (flags & ~ PR_AI_NOCANONNAME) != PR_AI_ADDRCONFIG) {
        PR_SetError(PR_INVALID_ARGUMENT_ERROR, 0);
        return NULL;
    }

    if (!_pr_initialized) {
        _PR_ImplicitInitialization();
    }

#if !defined(_PR_HAVE_GETADDRINFO)
    return pr_GetAddrInfoByNameFB(hostname, af, flags);
#else
#if defined(_PR_INET6_PROBE)
    if (!_pr_ipv6_is_present()) {
        return pr_GetAddrInfoByNameFB(hostname, af, flags);
    }
#endif
    {
        PRADDRINFO *res, hints;
        int rv;

        /*
         * we assume a RFC 2553 compliant getaddrinfo.  this may at some
         * point need to be customized as platforms begin to adopt the
         * RFC 3493.
         */

        memset(&hints, 0, sizeof(hints));
        if (!(flags & PR_AI_NOCANONNAME)) {
            hints.ai_flags |= AI_CANONNAME;
        }
#ifdef AI_ADDRCONFIG
        /*
         * Propagate AI_ADDRCONFIG to the GETADDRINFO call if PR_AI_ADDRCONFIG
         * is set.
         *
         * Need a workaround for loopback host addresses:
         * The problem is that in glibc and Windows, AI_ADDRCONFIG applies the
         * existence of an outgoing network interface to IP addresses of the
         * loopback interface, due to a strict interpretation of the
         * specification.  For example, if a computer does not have any
         * outgoing IPv6 network interface, but its loopback network interface
         * supports IPv6, a getaddrinfo call on "localhost" with AI_ADDRCONFIG
         * won't return the IPv6 loopback address "::1", because getaddrinfo
         * thinks the computer cannot connect to any IPv6 destination,
         * ignoring the remote vs. local/loopback distinction.
         */
        if ((flags & PR_AI_ADDRCONFIG) &&
            strcmp(hostname, "localhost") != 0 &&
            strcmp(hostname, "localhost.localdomain") != 0 &&
            strcmp(hostname, "localhost6") != 0 &&
            strcmp(hostname, "localhost6.localdomain6") != 0) {
            hints.ai_flags |= AI_ADDRCONFIG;
        }
#endif
        hints.ai_family = (af == PR_AF_INET) ? AF_INET : AF_UNSPEC;

        /*
         * it is important to select a socket type in the hints, otherwise we
         * will get back repetitive entries: one for each socket type.  since
         * we do not expose ai_socktype through our API, it is okay to do this
         * here.  the application may still choose to create a socket of some
         * other type.
         */
        hints.ai_socktype = SOCK_STREAM;

        rv = GETADDRINFO(hostname, NULL, &hints, &res);
#ifdef AI_ADDRCONFIG
        if (rv == EAI_BADFLAGS && (hints.ai_flags & AI_ADDRCONFIG)) {
            hints.ai_flags &= ~AI_ADDRCONFIG;
            rv = GETADDRINFO(hostname, NULL, &hints, &res);
        }
#endif
        if (rv == 0) {
            return (PRAddrInfo *) res;
        }

        PR_SetError(PR_DIRECTORY_LOOKUP_ERROR, rv);
    }
    return NULL;
#endif
}

PR_IMPLEMENT(PRStatus)
PR_GetPrefLoopbackAddrInfo(PRNetAddr *result,
                           PRUint16 port)
{
    char          tmpBuf[ 40 ];
    const int     tmpBufSize = sizeof( tmpBuf );

    if (!result) {
        PR_SetError(PR_INVALID_ARGUMENT_ERROR, 0);
        return PR_FAILURE;
    }

    if (!_pr_initialized) _PR_ImplicitInitialization();

    PR_snprintf(tmpBuf, tmpBufSize, "%u", port );

#if !defined(_PR_HAVE_GETADDRINFO) || !defined(AI_PASSIVE)
    PR_SetError(PR_NOT_IMPLEMENTED_ERROR, 0);
    return PR_FAILURE;
#else

    PRADDRINFO *res, hints;
    PRStatus rv;

    memset(&hints, 0, sizeof(hints));

    rv = GETADDRINFO(NULL, tmpBuf, &hints, &res);
    if (rv == 0) {
        PRBool result_still_empty = PR_TRUE;
        PRADDRINFO *ai = res;
        do {
            PRNetAddr aNetAddr;

            while (ai && ai->ai_addrlen > sizeof(PRNetAddr))
                ai = ai->ai_next;

            if (ai) {
                /* copy sockaddr to PRNetAddr */
                memcpy(&aNetAddr, ai->ai_addr, ai->ai_addrlen);
                aNetAddr.raw.family = ai->ai_addr->sa_family;
#ifdef _PR_INET6
                if (AF_INET6 == aNetAddr.raw.family)
                    aNetAddr.raw.family = PR_AF_INET6;
#endif
                if (ai->ai_addrlen < sizeof(PRNetAddr))
                    memset(((char*)result)+ai->ai_addrlen, 0,
                           sizeof(PRNetAddr) - ai->ai_addrlen);
            }

            /* If we obtain more than one result, prefer IPv6. */
            if (result_still_empty || aNetAddr.raw.family == PR_AF_INET6) {
                memcpy(result, &aNetAddr, sizeof(PRNetAddr));
            }
            result_still_empty = PR_FALSE;
            ai = ai->ai_next;
        }
        while (ai);

        FREEADDRINFO(res);
        return PR_SUCCESS;
    }

    PR_SetError(PR_DIRECTORY_LOOKUP_ERROR, rv);
    return PR_FAILURE;
#endif
}

PR_IMPLEMENT(void) PR_FreeAddrInfo(PRAddrInfo *ai)
{
#if defined(_PR_HAVE_GETADDRINFO)
#if defined(_PR_INET6_PROBE)
    if (!_pr_ipv6_is_present()) {
        PR_Free((PRAddrInfoFB *) ai);
    }
    else
#endif
        FREEADDRINFO((PRADDRINFO *) ai);
#else
    PR_Free((PRAddrInfoFB *) ai);
#endif
}

PR_IMPLEMENT(void *) PR_EnumerateAddrInfo(void             *iterPtr,
        const PRAddrInfo *base,
        PRUint16          port,
        PRNetAddr        *result)
{
#if defined(_PR_HAVE_GETADDRINFO)
    PRADDRINFO *ai;
#if defined(_PR_INET6_PROBE)
    if (!_pr_ipv6_is_present()) {
        /* using PRAddrInfoFB */
        PRIntn iter = (PRIntn)(PRPtrdiff) iterPtr;
        iter = PR_EnumerateHostEnt(iter, &((PRAddrInfoFB *) base)->hostent, port, result);
        if (iter < 0) {
            iter = 0;
        }
        return (void *)(PRPtrdiff) iter;
    }
#endif

    if (iterPtr) {
        ai = ((PRADDRINFO *) iterPtr)->ai_next;
    }
    else {
        ai = (PRADDRINFO *) base;
    }

    while (ai && ai->ai_addrlen > sizeof(PRNetAddr)) {
        ai = ai->ai_next;
    }

    if (ai) {
        /* copy sockaddr to PRNetAddr */
        memcpy(result, ai->ai_addr, ai->ai_addrlen);
        result->raw.family = ai->ai_addr->sa_family;
#ifdef _PR_INET6
        if (AF_INET6 == result->raw.family) {
            result->raw.family = PR_AF_INET6;
        }
#endif
        if (ai->ai_addrlen < sizeof(PRNetAddr)) {
            memset(((char*)result)+ai->ai_addrlen, 0, sizeof(PRNetAddr) - ai->ai_addrlen);
        }

        if (result->raw.family == PR_AF_INET) {
            result->inet.port = htons(port);
        }
        else {
            result->ipv6.port = htons(port);
        }
    }

    return ai;
#else
    /* using PRAddrInfoFB */
    PRIntn iter = (PRIntn) iterPtr;
    iter = PR_EnumerateHostEnt(iter, &((PRAddrInfoFB *) base)->hostent, port, result);
    if (iter < 0) {
        iter = 0;
    }
    return (void *) iter;
#endif
}

PR_IMPLEMENT(const char *) PR_GetCanonNameFromAddrInfo(const PRAddrInfo *ai)
{
#if defined(_PR_HAVE_GETADDRINFO)
#if defined(_PR_INET6_PROBE)
    if (!_pr_ipv6_is_present()) {
        const PRAddrInfoFB *fb = (const PRAddrInfoFB *) ai;
        return fb->has_cname ? fb->hostent.h_name : NULL;
    }
#endif
    return ((const PRADDRINFO *) ai)->ai_canonname;
#else
    const PRAddrInfoFB *fb = (const PRAddrInfoFB *) ai;
    return fb->has_cname ? fb->hostent.h_name : NULL;
#endif
}

#if defined(_PR_HAVE_GETADDRINFO)
static PRStatus pr_StringToNetAddrGAI(const char *string, PRNetAddr *addr)
{
    PRADDRINFO *res, hints;
    int rv;  /* 0 for success, or the error code EAI_xxx */
    PRNetAddr laddr;
    PRStatus status = PR_SUCCESS;

    memset(&hints, 0, sizeof(hints));
    hints.ai_flags = AI_NUMERICHOST;
    hints.ai_family = AF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;

    rv = GETADDRINFO(string, NULL, &hints, &res);
    if (rv != 0)
    {
        PR_SetError(PR_INVALID_ARGUMENT_ERROR, rv);
        return PR_FAILURE;
    }

    /* pick up the first addr */
    memcpy(&laddr, res->ai_addr, res->ai_addrlen);
    if (AF_INET6 == res->ai_addr->sa_family)
    {
        addr->ipv6.family = PR_AF_INET6;
        addr->ipv6.ip = laddr.ipv6.ip;
        addr->ipv6.scope_id = laddr.ipv6.scope_id;
    }
    else if (AF_INET == res->ai_addr->sa_family)
    {
        addr->inet.family = PR_AF_INET;
        addr->inet.ip = laddr.inet.ip;
    }
    else
    {
        PR_SetError(PR_INVALID_ARGUMENT_ERROR, 0);
        status = PR_FAILURE;
    }

    FREEADDRINFO(res);
    return status;
}
#endif  /* _PR_HAVE_GETADDRINFO */

static PRStatus pr_StringToNetAddrFB(const char *string, PRNetAddr *addr)
{
    PRIntn rv;

    rv = pr_inet_aton(string, &addr->inet.ip);
    if (1 == rv)
    {
        addr->raw.family = AF_INET;
        return PR_SUCCESS;
    }

    PR_ASSERT(0 == rv);
    /* clean up after the failed call */
    memset(&addr->inet.ip, 0, sizeof(addr->inet.ip));

    rv = StringToV6Addr(string, &addr->ipv6.ip);
    if (1 == rv)
    {
        addr->raw.family = PR_AF_INET6;
        return PR_SUCCESS;
    }

    PR_ASSERT(0 == rv);
    PR_SetError(PR_INVALID_ARGUMENT_ERROR, 0);
    return PR_FAILURE;
}

PR_IMPLEMENT(PRStatus) PR_StringToNetAddr(const char *string, PRNetAddr *addr)
{
    if (!_pr_initialized) {
        _PR_ImplicitInitialization();
    }

    if (!addr || !string || !*string)
    {
        PR_SetError(PR_INVALID_ARGUMENT_ERROR, 0);
        return PR_FAILURE;
    }

#if !defined(_PR_HAVE_GETADDRINFO)
    return pr_StringToNetAddrFB(string, addr);
#else
    /*
     * getaddrinfo with AI_NUMERICHOST is much slower than pr_inet_aton on some
     * platforms, such as Mac OS X (bug 404399), Linux glibc 2.10 (bug 344809),
     * and most likely others. So we only use it to convert literal IP addresses
     * that contain IPv6 scope IDs, which pr_inet_aton cannot convert.
     */
    if (!strchr(string, '%')) {
        return pr_StringToNetAddrFB(string, addr);
    }

#if defined(_PR_INET6_PROBE)
    if (!_pr_ipv6_is_present()) {
        return pr_StringToNetAddrFB(string, addr);
    }
#endif

    return pr_StringToNetAddrGAI(string, addr);
#endif
}

#if defined(_PR_HAVE_GETADDRINFO)
static PRStatus pr_NetAddrToStringGNI(
    const PRNetAddr *addr, char *string, PRUint32 size)
{
    int addrlen;
    const PRNetAddr *addrp = addr;
#if defined(_PR_HAVE_SOCKADDR_LEN) || defined(_PR_INET6)
    PRUint16 md_af = addr->raw.family;
    PRNetAddr addrcopy;
#endif
    int rv;  /* 0 for success, or the error code EAI_xxx */

#ifdef _PR_INET6
    if (addr->raw.family == PR_AF_INET6)
    {
        md_af = AF_INET6;
#ifndef _PR_HAVE_SOCKADDR_LEN
        addrcopy = *addr;
        addrcopy.raw.family = md_af;
        addrp = &addrcopy;
#endif
    }
#endif

    addrlen = PR_NETADDR_SIZE(addr);
#ifdef _PR_HAVE_SOCKADDR_LEN
    addrcopy = *addr;
    ((struct sockaddr*)&addrcopy)->sa_len = addrlen;
    ((struct sockaddr*)&addrcopy)->sa_family = md_af;
    addrp = &addrcopy;
#endif
    rv = GETNAMEINFO((const struct sockaddr *)addrp, addrlen,
                     string, size, NULL, 0, NI_NUMERICHOST);
    if (rv != 0)
    {
        PR_SetError(PR_INVALID_ARGUMENT_ERROR, rv);
        return PR_FAILURE;
    }
    return PR_SUCCESS;
}
#endif  /* _PR_HAVE_GETADDRINFO */

#if !defined(_PR_HAVE_GETADDRINFO) || defined(_PR_INET6_PROBE)
static PRStatus pr_NetAddrToStringFB(
    const PRNetAddr *addr, char *string, PRUint32 size)
{
    if (PR_AF_INET6 == addr->raw.family)
    {
#if defined(_PR_HAVE_INET_NTOP)
        if (NULL == inet_ntop(AF_INET6, &addr->ipv6.ip, string, size))
#else
        if (NULL == V6AddrToString(&addr->ipv6.ip, string, size))
#endif
        {
            /* the size of the result buffer is inadequate */
            PR_SetError(PR_BUFFER_OVERFLOW_ERROR, 0);
            return PR_FAILURE;
        }
    }
    else
    {
        if (size < 16) {
            goto failed;
        }
        if (AF_INET != addr->raw.family) {
            goto failed;
        }
        else
        {
            unsigned char *byte = (unsigned char*)&addr->inet.ip;
            PR_snprintf(string, size, "%u.%u.%u.%u",
                        byte[0], byte[1], byte[2], byte[3]);
        }
    }

    return PR_SUCCESS;

failed:
    PR_SetError(PR_INVALID_ARGUMENT_ERROR, 0);
    return PR_FAILURE;

}  /* pr_NetAddrToStringFB */
#endif  /* !_PR_HAVE_GETADDRINFO || _PR_INET6_PROBE */

PR_IMPLEMENT(PRStatus) PR_NetAddrToString(
    const PRNetAddr *addr, char *string, PRUint32 size)
{
    if (!_pr_initialized) {
        _PR_ImplicitInitialization();
    }

#if !defined(_PR_HAVE_GETADDRINFO)
    return pr_NetAddrToStringFB(addr, string, size);
#else
#if defined(_PR_INET6_PROBE)
    if (!_pr_ipv6_is_present()) {
        return pr_NetAddrToStringFB(addr, string, size);
    }
#endif
    return pr_NetAddrToStringGNI(addr, string, size);
#endif
}  /* PR_NetAddrToString */