/* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
/*
 * Copyright (C) 2001,2002,2003,2004,2005,2006 by the Massachusetts Institute of Technology,
 * Cambridge, MA, USA.  All Rights Reserved.
 *
 * This software is being provided to you, the LICENSEE, by the
 * Massachusetts Institute of Technology (M.I.T.) under the following
 * license.  By obtaining, using and/or copying this software, you agree
 * that you have read, understood, and will comply with these terms and
 * conditions:
 *
 * Export of this software from the United States of America may
 * require a specific license from the United States Government.
 * It is the responsibility of any person or organization contemplating
 * export to obtain such a license before exporting.
 *
 * WITHIN THAT CONSTRAINT, permission to use, copy, modify and distribute
 * this software and its documentation for any purpose and without fee or
 * royalty is hereby granted, provided that you agree to comply with the
 * following copyright notice and statements, including the disclaimer, and
 * that the same appear on ALL copies of the software and documentation,
 * including modifications that you make for internal use or for
 * distribution:
 *
 * THIS SOFTWARE IS PROVIDED "AS IS", AND M.I.T. MAKES NO REPRESENTATIONS
 * OR WARRANTIES, EXPRESS OR IMPLIED.  By way of example, but not
 * limitation, M.I.T. MAKES NO REPRESENTATIONS OR WARRANTIES OF
 * MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE OR THAT THE USE OF
 * THE LICENSED SOFTWARE OR DOCUMENTATION WILL NOT INFRINGE ANY THIRD PARTY
 * PATENTS, COPYRIGHTS, TRADEMARKS OR OTHER RIGHTS.
 *
 * The name of the Massachusetts Institute of Technology or M.I.T. may NOT
 * be used in advertising or publicity pertaining to distribution of the
 * software.  Title to copyright in this software and any associated
 * documentation shall at all times remain with M.I.T., and USER agrees to
 * preserve same.
 *
 * Furthermore if you modify this software you must label
 * your software as modified software and not distribute it in such a
 * fashion that it might be confused with the original M.I.T. software.
 */

/*
 * Approach overview:
 *
 * If a system version is available but buggy, save handles to it,
 * redefine the names to refer to static functions defined here, and
 * in those functions, call the system versions and fix up the
 * returned data.  Use the native data structures and flag values.
 *
 * If no system version exists, use gethostby* and fake it.  Define
 * the data structures and flag values locally.
 *
 *
 * On macOS, getaddrinfo results aren't cached (though
 * gethostbyname results are), so we need to build a cache here.  Now
 * things are getting really messy.  Because the cache is in use, we
 * use getservbyname, and throw away thread safety.  (Not that the
 * cache is thread safe, but when we get locking support, that'll be
 * dealt with.)  This code needs tearing down and rebuilding, soon.
 *
 *
 * Note that recent Windows developers' code has an interesting hack:
 * When you include the right header files, with the right set of
 * macros indicating system versions, you'll get an inline function
 * that looks for getaddrinfo (or whatever) in the system library, and
 * calls it if it's there.  If it's not there, it fakes it with
 * gethostby* calls.
 *
 * We're taking a simpler approach: A system provides these routines or
 * it does not.
 *
 * Someday, we may want to take into account different versions (say,
 * different revs of GNU libc) where some are broken in one way, and
 * some work or are broken in another way.  Cross that bridge when we
 * come to it.
 */

/*
 * To do, maybe:
 *
 * + For AIX 4.3.3, using the RFC 2133 definition: Implement
 *   AI_NUMERICHOST.  It's not defined in the header file.
 *
 *   For certain (old?) versions of GNU libc, AI_NUMERICHOST is
 *   defined but not implemented.
 *
 * + Use gethostbyname2, inet_aton and other IPv6 or thread-safe
 *   functions if available.  But, see
 *   https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=135182 for one
 *   gethostbyname2 problem on Linux.  And besides, if a platform is
 *   supporting IPv6 at all, they really should be doing getaddrinfo
 *   by now.
 *
 * + inet_ntop, inet_pton
 *
 * + Conditionally export/import the function definitions, so a
 *   library can have a single copy instead of multiple.
 *
 * + Upgrade host requirements to include working implementations of
 *   these functions, and throw all this away.  Pleeease?  :-)
 */

#include "k5-platform.h"
#include "k5-thread.h"
#include "port-sockets.h"
#include "socket-utils.h"
#include "supp-int.h"

#define IMPLEMENT_FAKE_GETADDRINFO
#include "fake-addrinfo.h"

#ifdef S_SPLINT_S
/*@-incondefs@*/
extern int
getaddrinfo (/*@in@*/ /*@null@*/ const char *,
             /*@in@*/ /*@null@*/ const char *,
             /*@in@*/ /*@null@*/ const struct addrinfo *,
             /*@out@*/ struct addrinfo **)
    ;
extern void
freeaddrinfo (/*@only@*/ /*@out@*/ struct addrinfo *)
    ;
extern int
getnameinfo (const struct sockaddr *addr, socklen_t addrsz,
             /*@out@*/ /*@null@*/ char *h, socklen_t hsz,
             /*@out@*/ /*@null@*/ char *s, socklen_t ssz,
             int flags)
/*@requires (maxSet(h)+1) >= hsz /\ (maxSet(s)+1) >= ssz @*/
/* too hard: maxRead(addr) >= (addrsz-1) */
    /*@modifies *h, *s@*/;
extern /*@dependent@*/ char *gai_strerror (int code) /*@*/;
/*@=incondefs@*/
#endif


#include "cache-addrinfo.h"

#if (defined (__linux__) && defined(HAVE_GETADDRINFO)) || defined (_AIX)
/* See comments below.  */
#  define WRAP_GETADDRINFO
#endif

#if defined (__linux__) && defined(HAVE_GETADDRINFO)
/* Define COPY_FIRST_CANONNAME for glibc 2.3 and prior. */
#include <features.h>
# ifdef __GLIBC_PREREQ
#  if ! __GLIBC_PREREQ(2, 4)
#   define COPY_FIRST_CANONNAME
#  endif
# else
#   define COPY_FIRST_CANONNAME
# endif
#endif

#ifdef _AIX
# define NUMERIC_SERVICE_BROKEN
# define COPY_FIRST_CANONNAME
#endif


#ifdef COPY_FIRST_CANONNAME
# include <string.h>
#endif

#ifdef NUMERIC_SERVICE_BROKEN
# include <ctype.h>             /* isdigit */
# include <stdlib.h>            /* strtoul */
#endif


/* Do we actually have *any* systems we care about that don't provide
   either getaddrinfo or one of these two flavors of
   gethostbyname_r?  */
#if !defined(HAVE_GETHOSTBYNAME_R) || defined(THREADSAFE_GETHOSTBYNAME)
typedef struct hostent *GET_HOST_TMP;
#define GET_HOST_BY_NAME(NAME, HP, ERR, TMP)                            \
    { TMP = gethostbyname (NAME); (ERR) = h_errno; (HP) = TMP; }
#define GET_HOST_BY_ADDR(ADDR, ADDRLEN, FAMILY, HP, ERR, TMP)           \
    { TMP = gethostbyaddr ((ADDR), (ADDRLEN), (FAMILY)); (ERR) = h_errno; (HP) = TMP; }
#else
#ifdef _AIX /* XXX should have a feature test! */
typedef struct {
    struct hostent ent;
    struct hostent_data data;
} GET_HOST_TMP;
#define GET_HOST_BY_NAME(NAME, HP, ERR, TMP)                    \
    {                                                           \
        (HP) = (gethostbyname_r((NAME), &TMP.ent, &TMP.data)    \
                ? 0                                             \
                : &TMP.ent);                                    \
        (ERR) = h_errno;                                        \
    }
/*
  #define GET_HOST_BY_ADDR(ADDR, ADDRLEN, FAMILY, HP, ERR) \
  {                                                                     \
  struct hostent my_h_ent;                                      \
  struct hostent_data my_h_ent_data;                            \
  (HP) = (gethostbyaddr_r((ADDR), (ADDRLEN), (FAMILY), &my_h_ent,       \
  &my_h_ent_data)                               \
  ? 0                                                   \
  : &my_h_ent);                                         \
  (ERR) = my_h_err;                                             \
  }
*/
#else
#ifdef GETHOSTBYNAME_R_RETURNS_INT
typedef struct {
    struct hostent ent;
    char buf[8192];
} GET_HOST_TMP;
#define GET_HOST_BY_NAME(NAME, HP, ERR, TMP)                            \
    {                                                                   \
        struct hostent *my_hp = NULL;                                   \
        int my_h_err, my_ret;                                           \
        my_ret = gethostbyname_r((NAME), &TMP.ent,                      \
                                 TMP.buf, sizeof (TMP.buf), &my_hp,     \
                                 &my_h_err);                            \
        (HP) = (((my_ret != 0) || (my_hp != &TMP.ent))                  \
                ? 0                                                     \
                : &TMP.ent);                                            \
        (ERR) = my_h_err;                                               \
    }
#define GET_HOST_BY_ADDR(ADDR, ADDRLEN, FAMILY, HP, ERR, TMP)           \
    {                                                                   \
        struct hostent *my_hp;                                          \
        int my_h_err, my_ret;                                           \
        my_ret = gethostbyaddr_r((ADDR), (ADDRLEN), (FAMILY), &TMP.ent, \
                                 TMP.buf, sizeof (TMP.buf), &my_hp,     \
                                 &my_h_err);                            \
        (HP) = (((my_ret != 0) || (my_hp != &TMP.ent))                  \
                ? 0                                                     \
                : &TMP.ent);                                            \
        (ERR) = my_h_err;                                               \
    }
#else
typedef struct {
    struct hostent ent;
    char buf[8192];
} GET_HOST_TMP;
#define GET_HOST_BY_NAME(NAME, HP, ERR, TMP)                            \
    {                                                                   \
        int my_h_err;                                                   \
        (HP) = gethostbyname_r((NAME), &TMP.ent,                        \
                               TMP.buf, sizeof (TMP.buf), &my_h_err);   \
        (ERR) = my_h_err;                                               \
    }
#define GET_HOST_BY_ADDR(ADDR, ADDRLEN, FAMILY, HP, ERR, TMP)           \
    {                                                                   \
        int my_h_err;                                                   \
        (HP) = gethostbyaddr_r((ADDR), (ADDRLEN), (FAMILY), &TMP.ent,   \
                               TMP.buf, sizeof (TMP.buf), &my_h_err);   \
        (ERR) = my_h_err;                                               \
    }
#endif /* returns int? */
#endif /* _AIX */
#endif

/* Now do the same for getservby* functions.  */
#ifndef HAVE_GETSERVBYNAME_R
typedef struct servent *GET_SERV_TMP;
#define GET_SERV_BY_NAME(NAME, PROTO, SP, ERR, TMP)                     \
    (TMP = getservbyname (NAME, PROTO), (SP) = TMP, (ERR) = (SP) ? 0 : -1)
#define GET_SERV_BY_PORT(PORT, PROTO, SP, ERR, TMP)                     \
    (TMP = getservbyport (PORT, PROTO), (SP) = TMP, (ERR) = (SP) ? 0 : -1)
#else
#ifdef GETSERVBYNAME_R_RETURNS_INT
typedef struct {
    struct servent ent;
    char buf[8192];
} GET_SERV_TMP;
#define GET_SERV_BY_NAME(NAME, PROTO, SP, ERR, TMP)                     \
    {                                                                   \
        struct servent *my_sp;                                          \
        int my_s_err;                                                   \
        (SP) = (getservbyname_r((NAME), (PROTO), &TMP.ent,              \
                                TMP.buf, sizeof (TMP.buf), &my_sp,      \
                                &my_s_err)                              \
                ? 0                                                     \
                : &TMP.ent);                                            \
        (ERR) = my_s_err;                                               \
    }
#define GET_SERV_BY_PORT(PORT, PROTO, SP, ERR, TMP)                     \
    {                                                                   \
        struct servent *my_sp;                                          \
        int my_s_err;                                                   \
        (SP) = (getservbyport_r((PORT), (PROTO), &TMP.ent,              \
                                TMP.buf, sizeof (TMP.buf), &my_sp,      \
                                &my_s_err)                              \
                ? 0                                                     \
                : &TMP.ent);                                            \
        (ERR) = my_s_err;                                               \
    }
#else
/* returns ptr -- IRIX? */
typedef struct {
    struct servent ent;
    char buf[8192];
} GET_SERV_TMP;
#define GET_SERV_BY_NAME(NAME, PROTO, SP, ERR, TMP)             \
    {                                                           \
        (SP) = getservbyname_r((NAME), (PROTO), &TMP.ent,       \
                               TMP.buf, sizeof (TMP.buf));      \
        (ERR) = (SP) == NULL;                                   \
    }

#define GET_SERV_BY_PORT(PORT, PROTO, SP, ERR, TMP)             \
    {                                                           \
        struct servent *my_sp;                                  \
        my_sp = getservbyport_r((PORT), (PROTO), &TMP.ent,      \
                                TMP.buf, sizeof (TMP.buf));     \
        (SP) = my_sp;                                           \
        (ERR) = my_sp == 0;                                     \
        (ERR) = (ERR);  /* avoid "unused" warning */            \
    }
#endif
#endif

#if defined(WRAP_GETADDRINFO) || defined(FAI_CACHE)
static inline int
system_getaddrinfo (const char *name, const char *serv,
                    const struct addrinfo *hint,
                    struct addrinfo **res)
{
    return getaddrinfo(name, serv, hint, res);
}

static inline void
system_freeaddrinfo (struct addrinfo *ai)
{
    freeaddrinfo(ai);
}

#endif

#if !defined (HAVE_GETADDRINFO) || defined(WRAP_GETADDRINFO) || defined(FAI_CACHE)

#undef  getaddrinfo
#define getaddrinfo     my_fake_getaddrinfo
#undef  freeaddrinfo
#define freeaddrinfo    my_fake_freeaddrinfo

#endif

#if !defined (HAVE_GETADDRINFO)

#undef  gai_strerror
#define gai_strerror    my_fake_gai_strerror

#endif /* ! HAVE_GETADDRINFO */

#if (!defined (HAVE_GETADDRINFO) || defined (WRAP_GETADDRINFO)) && defined(DEBUG_ADDRINFO)
/* Some debug routines.  */

static const char *protoname (int p, char *buf, size_t bufsize) {
#define X(N) if (p == IPPROTO_ ## N) return #N

    X(TCP);
    X(UDP);
    X(ICMP);
    X(IPV6);
#ifdef IPPROTO_GRE
    X(GRE);
#endif
    X(NONE);
    X(RAW);
#ifdef IPPROTO_COMP
    X(COMP);
#endif
#ifdef IPPROTO_IGMP
    X(IGMP);
#endif

    snprintf(buf, bufsize, " %-2d", p);
    return buf;
}

static const char *socktypename (int t, char *buf, size_t bufsize) {
    switch (t) {
    case SOCK_DGRAM: return "DGRAM";
    case SOCK_STREAM: return "STREAM";
    case SOCK_RAW: return "RAW";
    case SOCK_RDM: return "RDM";
    case SOCK_SEQPACKET: return "SEQPACKET";
    }
    snprintf(buf, bufsize, " %-2d", t);
    return buf;
}

static const char *familyname (int f, char *buf, size_t bufsize) {
    switch (f) {
    default:
        snprintf(buf, bufsize, "AF %d", f);
        return buf;
    case AF_INET: return "AF_INET";
    case AF_INET6: return "AF_INET6";
#ifdef AF_UNIX
    case AF_UNIX: return "AF_UNIX";
#endif
    }
}

static void debug_dump_getaddrinfo_args (const char *name, const char *serv,
                                         const struct addrinfo *hint)
{
    const char *sep;
    fprintf(stderr,
            "getaddrinfo(hostname %s, service %s,\n"
            "            hints { ",
            name ? name : "(null)", serv ? serv : "(null)");
    if (hint) {
        char buf[30];
        sep = "";
#define Z(FLAG) if (hint->ai_flags & AI_##FLAG) fprintf(stderr, "%s%s", sep, #FLAG), sep = "|"
        Z(CANONNAME);
        Z(PASSIVE);
#ifdef AI_NUMERICHOST
        Z(NUMERICHOST);
#endif
        if (sep[0] == 0)
            fprintf(stderr, "no-flags");
        if (hint->ai_family)
            fprintf(stderr, " %s", familyname(hint->ai_family, buf,
                                              sizeof(buf)));
        if (hint->ai_socktype)
            fprintf(stderr, " SOCK_%s", socktypename(hint->ai_socktype, buf,
                                                     sizeof(buf)));
        if (hint->ai_protocol)
            fprintf(stderr, " IPPROTO_%s", protoname(hint->ai_protocol, buf,
                                                     sizeof(buf)));
    } else
        fprintf(stderr, "(null)");
    fprintf(stderr, " }):\n");
}

static void debug_dump_error (int err)
{
    fprintf(stderr, "error %d: %s\n", err, gai_strerror(err));
}

static void debug_dump_addrinfos (const struct addrinfo *ai)
{
    int count = 0;
    char buf[10];
    fprintf(stderr, "addrinfos returned:\n");
    while (ai) {
        fprintf(stderr, "%p...", ai);
        fprintf(stderr, " socktype=%s", socktypename(ai->ai_socktype, buf,
                                                     sizeof(buf)));
        fprintf(stderr, " ai_family=%s", familyname(ai->ai_family, buf,
                                                    sizeof(buf)));
        if (ai->ai_family != ai->ai_addr->sa_family)
            fprintf(stderr, " sa_family=%s",
                    familyname(ai->ai_addr->sa_family, buf, sizeof(buf)));
        fprintf(stderr, "\n");
        ai = ai->ai_next;
        count++;
    }
    fprintf(stderr, "end addrinfos returned (%d)\n");
}

#endif

#if !defined (HAVE_GETADDRINFO) || defined (WRAP_GETADDRINFO)

static
int getaddrinfo (const char *name, const char *serv,
                 const struct addrinfo *hint, struct addrinfo **result);

static
void freeaddrinfo (struct addrinfo *ai);

#endif

#if !defined (HAVE_GETADDRINFO)

#define HAVE_FAKE_GETADDRINFO /* was not originally HAVE_GETADDRINFO */
#define HAVE_GETADDRINFO
#define NEED_FAKE_GETNAMEINFO
#undef  HAVE_GETNAMEINFO
#define HAVE_GETNAMEINFO 1

#undef  getnameinfo
#define getnameinfo     my_fake_getnameinfo

static
char *gai_strerror (int code);

#endif

#if !defined (HAVE_GETADDRINFO)
static
int getnameinfo (const struct sockaddr *addr, socklen_t len,
                 char *host, socklen_t hostlen,
                 char *service, socklen_t servicelen,
                 int flags);
#endif

/* Fudge things on older gai implementations.  */
/* AIX 4.3.3 is based on RFC 2133; no AI_NUMERICHOST.  */
#ifndef AI_NUMERICHOST
# define AI_NUMERICHOST 0
#endif
/* Partial RFC 2553 implementations may not have AI_ADDRCONFIG and
   friends, which RFC 3493 says are now part of the getaddrinfo
   interface, and we'll want to use.  */
#ifndef AI_ADDRCONFIG
# define AI_ADDRCONFIG 0
#endif
#ifndef AI_V4MAPPED
# define AI_V4MAPPED 0
#endif
#ifndef AI_ALL
# define AI_ALL 0
#endif
#ifndef AI_DEFAULT
# define AI_DEFAULT (AI_ADDRCONFIG|AI_V4MAPPED)
#endif

#if defined(HAVE_FAKE_GETADDRINFO) || defined(FAI_CACHE)
#define NEED_FAKE_GETADDRINFO
#endif

#if defined(NEED_FAKE_GETADDRINFO) || defined(WRAP_GETADDRINFO)
#include <stdlib.h>
#endif

#ifdef NEED_FAKE_GETADDRINFO
#include <string.h> /* for strspn */

static inline int translate_h_errno (int h);

static inline int fai_add_entry (struct addrinfo **result, void *addr,
                                 int port, const struct addrinfo *template)
{
    struct addrinfo *n = malloc (sizeof (struct addrinfo));
    if (n == 0)
        return EAI_MEMORY;
    if (template->ai_family != AF_INET
        && template->ai_family != AF_INET6
    )
        return EAI_FAMILY;
    *n = *template;
    if (template->ai_family == AF_INET) {
        struct sockaddr_in *sin4;
        sin4 = malloc (sizeof (struct sockaddr_in));
        if (sin4 == 0)
            return EAI_MEMORY;
        memset (sin4, 0, sizeof (struct sockaddr_in)); /* for sin_zero */
        n->ai_addr = (struct sockaddr *) sin4;
        sin4->sin_family = AF_INET;
        sin4->sin_addr = *(struct in_addr *)addr;
        sin4->sin_port = port;
    }
    if (template->ai_family == AF_INET6) {
        struct sockaddr_in6 *sin6;
        sin6 = malloc (sizeof (struct sockaddr_in6));
        if (sin6 == 0)
            return EAI_MEMORY;
        memset (sin6, 0, sizeof (struct sockaddr_in6)); /* for sin_zero */
        n->ai_addr = (struct sockaddr *) sin6;
        sin6->sin6_family = AF_INET6;
        sin6->sin6_addr = *(struct in6_addr *)addr;
        sin6->sin6_port = port;
    }
    n->ai_next = *result;
    *result = n;
    return 0;
}

#ifdef FAI_CACHE
/* fake addrinfo cache entries */
#define CACHE_ENTRY_LIFETIME    15 /* seconds */

static void plant_face (const char *name, struct face *entry)
{
    entry->name = strdup(name);
    if (entry->name == NULL)
        /* @@ Wastes memory.  */
        return;
    k5_mutex_assert_locked(&krb5int_fac.lock);
    entry->next = krb5int_fac.data;
    entry->expiration = time(0) + CACHE_ENTRY_LIFETIME;
    krb5int_fac.data = entry;
#ifdef DEBUG_ADDRINFO
    printf("added cache entry '%s' at %p: %d ipv4, %d ipv6; expire %d\n",
           name, entry, entry->naddrs4, entry->naddrs6, entry->expiration);
#endif
}

static int find_face (const char *name, struct face **entry)
{
    struct face *fp, **fpp;
    time_t now = time(0);

    /* First, scan for expired entries and free them.
       (Future improvement: Integrate these two loops.)  */
#ifdef DEBUG_ADDRINFO
    printf("scanning cache at %d for '%s'...\n", now, name);
#endif
    k5_mutex_assert_locked(&krb5int_fac.lock);
    for (fpp = &krb5int_fac.data; *fpp; ) {
        fp = *fpp;
#ifdef DEBUG_ADDRINFO
        printf("  checking expiration time of @%p: %d\n",
               fp, fp->expiration);
#endif
        if (fp->expiration < now) {
#ifdef DEBUG_ADDRINFO
            printf("\texpiring cache entry\n");
#endif
            free(fp->name);
            free(fp->canonname);
            free(fp->addrs4);
            free(fp->addrs6);
            *fpp = fp->next;
            free(fp);
            /* Stay at this point in the list, and check again.  */
        } else
            /* Move forward.  */
            fpp = &(*fpp)->next;
    }

    for (fp = krb5int_fac.data; fp; fp = fp->next) {
#ifdef DEBUG_ADDRINFO
        printf("  comparing entry @%p\n", fp);
#endif
        if (!strcasecmp(fp->name, name)) {
#ifdef DEBUG_ADDRINFO
            printf("\tMATCH!\n");
#endif
            *entry = fp;
            return 1;
        }
    }
    return 0;
}

#endif

#ifdef FAI_CACHE
static int krb5int_lock_fac(void), krb5int_unlock_fac(void);
#endif

static inline int fai_add_hosts_by_name (const char *name,
                                         struct addrinfo *template,
                                         int portnum, int flags,
                                         struct addrinfo **result)
{
#ifdef FAI_CACHE

    struct face *ce;
    int i, r, err;

    err = krb5int_lock_fac();
    if (err) {
        errno = err;
        return EAI_SYSTEM;
    }
    if (!find_face(name, &ce)) {
        struct addrinfo myhints = { 0 }, *ai, *ai2;
        int i4, i6, aierr;

#ifdef DEBUG_ADDRINFO
        printf("looking up new data for '%s'...\n", name);
#endif
        myhints.ai_socktype = SOCK_STREAM;
        myhints.ai_flags = AI_CANONNAME;
        /* Don't set ai_family -- we want to cache all address types,
           because the next lookup may not use the same constraints as
           the current one.  We *could* cache them separately, so that
           we never have to look up an IPv6 address if we are always
           asked for IPv4 only, but let's deal with that later, if we
           have to.  */
        /* Try NULL for the service for now.

           It would be nice to use the requested service name, and not
           have to patch things up, but then we'd be doing multiple
           queries for the same host when we get different services.
           We were using "telnet" for a little more confidence that
           getaddrinfo would heed the hints to only give us stream
           socket types (with no socket type and null service name, we
           might get stream *and* dgram *and* raw, for each address,
           or only raw).  The RFC 3493 description of ai_socktype
           sometimes associates it with the specified service,
           sometimes not.

           But on macOS (10.3, 10.4) they've "extended" getaddrinfo
           to make SRV RR queries.  (Please, somebody, show me
           something in the specs that actually supports this?  RFC
           3493 says nothing about it, but it does say getaddrinfo is
           the new way to look up hostnames.  RFC 2782 says SRV
           records should *not* be used unless the application
           protocol spec says to do so.  The Telnet spec does not say
           to do it.)  And then they complain when our code
           "unexpectedly" seems to use this "extension" in cases where
           they don't want it to be used.

           Fortunately, it appears that if we specify ai_socktype as
           SOCK_STREAM and use a null service name, we only get one
           copy of each address on all the platforms I've tried,
           although it may not have ai_socktype filled in properly.
           So, we'll fudge it with that for now.  */
        aierr = system_getaddrinfo(name, NULL, &myhints, &ai);
        if (aierr) {
            krb5int_unlock_fac();
            return aierr;
        }
        ce = malloc(sizeof(struct face));
        memset(ce, 0, sizeof(*ce));
        ce->expiration = time(0) + 30;
        for (ai2 = ai; ai2; ai2 = ai2->ai_next) {
#ifdef DEBUG_ADDRINFO
            printf("  found an address in family %d...\n", ai2->ai_family);
#endif
            switch (ai2->ai_family) {
            case AF_INET:
                ce->naddrs4++;
                break;
            case AF_INET6:
                ce->naddrs6++;
                break;
            default:
                break;
            }
        }
        ce->addrs4 = calloc(ce->naddrs4, sizeof(*ce->addrs4));
        if (ce->addrs4 == NULL && ce->naddrs4 != 0) {
            krb5int_unlock_fac();
            system_freeaddrinfo(ai);
            return EAI_MEMORY;
        }
        ce->addrs6 = calloc(ce->naddrs6, sizeof(*ce->addrs6));
        if (ce->addrs6 == NULL && ce->naddrs6 != 0) {
            krb5int_unlock_fac();
            free(ce->addrs4);
            system_freeaddrinfo(ai);
            return EAI_MEMORY;
        }
        for (ai2 = ai, i4 = i6 = 0; ai2; ai2 = ai2->ai_next) {
            switch (ai2->ai_family) {
            case AF_INET:
                ce->addrs4[i4++] = ((struct sockaddr_in *)ai2->ai_addr)->sin_addr;
                break;
            case AF_INET6:
                ce->addrs6[i6++] = ((struct sockaddr_in6 *)ai2->ai_addr)->sin6_addr;
                break;
            default:
                break;
            }
        }
        ce->canonname = ai->ai_canonname ? strdup(ai->ai_canonname) : 0;
        system_freeaddrinfo(ai);
        plant_face(name, ce);
    }
    template->ai_family = AF_INET6;
    template->ai_addrlen = sizeof(struct sockaddr_in6);
    for (i = 0; i < ce->naddrs6; i++) {
        r = fai_add_entry (result, &ce->addrs6[i], portnum, template);
        if (r) {
            krb5int_unlock_fac();
            return r;
        }
    }
    template->ai_family = AF_INET;
    template->ai_addrlen = sizeof(struct sockaddr_in);
    for (i = 0; i < ce->naddrs4; i++) {
        r = fai_add_entry (result, &ce->addrs4[i], portnum, template);
        if (r) {
            krb5int_unlock_fac();
            return r;
        }
    }
    if (*result && (flags & AI_CANONNAME))
        (*result)->ai_canonname = (ce->canonname
                                   ? strdup(ce->canonname)
                                   : NULL);
    krb5int_unlock_fac();
    return 0;

#else

    struct hostent *hp;
    int i, r;
    int herr;
    GET_HOST_TMP htmp;

    GET_HOST_BY_NAME (name, hp, herr, htmp);
    if (hp == 0)
        return translate_h_errno (herr);
    for (i = 0; hp->h_addr_list[i]; i++) {
        r = fai_add_entry (result, hp->h_addr_list[i], portnum, template);
        if (r)
            return r;
    }
    if (*result && (flags & AI_CANONNAME))
        (*result)->ai_canonname = strdup (hp->h_name);
    return 0;

#endif
}

static inline void
fake_freeaddrinfo (struct addrinfo *ai)
{
    struct addrinfo *next;
    while (ai) {
        next = ai->ai_next;
        if (ai->ai_canonname)
            free (ai->ai_canonname);
        if (ai->ai_addr)
            free (ai->ai_addr);
        free (ai);
        ai = next;
    }
}

static inline int
fake_getaddrinfo (const char *name, const char *serv,
                  const struct addrinfo *hint, struct addrinfo **result)
{
    struct addrinfo *res = 0;
    int ret;
    int port = 0, socktype;
    int flags;
    struct addrinfo template;

#ifdef DEBUG_ADDRINFO
    debug_dump_getaddrinfo_args(name, serv, hint);
#endif

    if (hint != 0) {
        if (hint->ai_family != 0 && hint->ai_family != AF_INET)
            return EAI_NODATA;
        socktype = hint->ai_socktype;
        flags = hint->ai_flags;
    } else {
        socktype = 0;
        flags = 0;
    }

    if (serv) {
        size_t numlen = strspn (serv, "0123456789");
        if (serv[numlen] == '\0') {
            /* pure numeric */
            unsigned long p = strtoul (serv, 0, 10);
            if (p == 0 || p > 65535)
                return EAI_NONAME;
            port = htons (p);
        } else {
            struct servent *sp;
            int try_dgram_too = 0, s_err;
            GET_SERV_TMP stmp;

            if (socktype == 0) {
                try_dgram_too = 1;
                socktype = SOCK_STREAM;
            }
        try_service_lookup:
            GET_SERV_BY_NAME(serv, socktype == SOCK_STREAM ? "tcp" : "udp",
                             sp, s_err, stmp);
            if (sp == 0) {
                if (try_dgram_too) {
                    socktype = SOCK_DGRAM;
                    goto try_service_lookup;
                }
                return EAI_SERVICE;
            }
            port = sp->s_port;
        }
    }

    if (name == 0) {
        name = (flags & AI_PASSIVE) ? "0.0.0.0" : "127.0.0.1";
        flags |= AI_NUMERICHOST;
    }

    template.ai_family = AF_INET;
    template.ai_addrlen = sizeof (struct sockaddr_in);
    template.ai_socktype = socktype;
    template.ai_protocol = 0;
    template.ai_flags = 0;
    template.ai_canonname = 0;
    template.ai_next = 0;
    template.ai_addr = 0;

    /* If NUMERICHOST is set, parse a numeric address.
       If it's not set, don't accept such names.  */
    if (flags & AI_NUMERICHOST) {
        struct in_addr addr4;
        addr4.s_addr = inet_addr (name);
        if (addr4.s_addr == 0xffffffff || addr4.s_addr == -1)
            /* 255.255.255.255 or parse error, both bad */
            return EAI_NONAME;
        ret = fai_add_entry (&res, &addr4, port, &template);
    } else {
        ret = fai_add_hosts_by_name (name, &template, port, flags,
                                     &res);
    }

    if (ret && ret != NO_ADDRESS) {
        fake_freeaddrinfo (res);
        return ret;
    }
    if (res == 0)
        return NO_ADDRESS;
    *result = res;
    return 0;
}

#ifdef NEED_FAKE_GETNAMEINFO
static inline int
fake_getnameinfo (const struct sockaddr *sa, socklen_t len,
                  char *host, socklen_t hostlen,
                  char *service, socklen_t servicelen,
                  int flags)
{
    struct hostent *hp;
    const struct sockaddr_in *sinp;
    struct servent *sp;
    size_t hlen, slen;

    if (sa->sa_family != AF_INET) {
        return EAI_FAMILY;
    }
    sinp = (const struct sockaddr_in *) sa;

    hlen = hostlen;
    if (hostlen < 0 || hlen != hostlen) {
        errno = EINVAL;
        return EAI_SYSTEM;
    }
    slen = servicelen;
    if (servicelen < 0 || slen != servicelen) {
        errno = EINVAL;
        return EAI_SYSTEM;
    }

    if (host) {
        if (flags & NI_NUMERICHOST) {
#if (defined(__GNUC__) && defined(__mips__)) || 1 /* thread safety always */
            /* The inet_ntoa call, passing a struct, fails on IRIX 6.5
               using gcc 2.95; we get back "0.0.0.0".  Since this in a
               configuration still important at Athena, here's the
               workaround, which also happens to be thread-safe....  */
            const unsigned char *uc;
            char tmpbuf[20];
        numeric_host:
            uc = (const unsigned char *) &sinp->sin_addr;
            snprintf(tmpbuf, sizeof(tmpbuf), "%d.%d.%d.%d",
                     uc[0], uc[1], uc[2], uc[3]);
            strncpy(host, tmpbuf, hlen);
#else
            char *p;
        numeric_host:
            p = inet_ntoa (sinp->sin_addr);
            strncpy (host, p, hlen);
#endif
        } else {
            int herr;
            GET_HOST_TMP htmp;

            GET_HOST_BY_ADDR((const char *) &sinp->sin_addr,
                             sizeof (struct in_addr),
                             sa->sa_family, hp, herr, htmp);
            if (hp == 0) {
                if (herr == NO_ADDRESS && !(flags & NI_NAMEREQD)) /* ??? */
                    goto numeric_host;
                return translate_h_errno (herr);
            }
            /* According to the Open Group spec, getnameinfo can
               silently truncate, but must still return a
               null-terminated string.  */
            strncpy (host, hp->h_name, hlen);
        }
        host[hostlen-1] = 0;
    }

    if (service) {
        if (flags & NI_NUMERICSERV) {
            char numbuf[10];
            int port;
        numeric_service:
            port = ntohs (sinp->sin_port);
            if (port < 0 || port > 65535)
                return EAI_FAIL;
            snprintf (numbuf, sizeof(numbuf), "%d", port);
            strncpy (service, numbuf, slen);
        } else {
            int serr;
            GET_SERV_TMP stmp;

            GET_SERV_BY_PORT(sinp->sin_port,
                             (flags & NI_DGRAM) ? "udp" : "tcp",
                             sp, serr, stmp);
            if (sp == 0)
                goto numeric_service;
            strncpy (service, sp->s_name, slen);
        }
        service[servicelen-1] = 0;
    }

    return 0;
}
#endif

#if defined(HAVE_FAKE_GETADDRINFO) || defined(NEED_FAKE_GETNAMEINFO)

static inline
char *gai_strerror (int code)
{
    switch (code) {
    case EAI_ADDRFAMILY: return "address family for nodename not supported";
    case EAI_AGAIN:     return "temporary failure in name resolution";
    case EAI_BADFLAGS:  return "bad flags to getaddrinfo/getnameinfo";
    case EAI_FAIL:      return "non-recoverable failure in name resolution";
    case EAI_FAMILY:    return "ai_family not supported";
    case EAI_MEMORY:    return "out of memory";
    case EAI_NODATA:    return "no address associated with hostname";
    case EAI_NONAME:    return "name does not exist";
    case EAI_SERVICE:   return "service name not supported for specified socket type";
    case EAI_SOCKTYPE:  return "ai_socktype not supported";
    case EAI_SYSTEM:    return strerror (errno);
    default:            return "bogus getaddrinfo error?";
    }
}
#endif

static inline int translate_h_errno (int h)
{
    switch (h) {
    case 0:
        return 0;
#ifdef NETDB_INTERNAL
    case NETDB_INTERNAL:
        if (errno == ENOMEM)
            return EAI_MEMORY;
        return EAI_SYSTEM;
#endif
    case HOST_NOT_FOUND:
        return EAI_NONAME;
    case TRY_AGAIN:
        return EAI_AGAIN;
    case NO_RECOVERY:
        return EAI_FAIL;
    case NO_DATA:
#if NO_DATA != NO_ADDRESS
    case NO_ADDRESS:
#endif
        return EAI_NODATA;
    default:
        return EAI_SYSTEM;
    }
}

#if defined(HAVE_FAKE_GETADDRINFO) || defined(FAI_CACHE)
static inline
int getaddrinfo (const char *name, const char *serv,
                 const struct addrinfo *hint, struct addrinfo **result)
{
    return fake_getaddrinfo(name, serv, hint, result);
}

static inline
void freeaddrinfo (struct addrinfo *ai)
{
    fake_freeaddrinfo(ai);
}

#ifdef NEED_FAKE_GETNAMEINFO
static inline
int getnameinfo (const struct sockaddr *sa, socklen_t len,
                 char *host, socklen_t hostlen,
                 char *service, socklen_t servicelen,
                 int flags)
{
    return fake_getnameinfo(sa, len, host, hostlen, service, servicelen,
                            flags);
}
#endif /* NEED_FAKE_GETNAMEINFO */
#endif /* HAVE_FAKE_GETADDRINFO */
#endif /* NEED_FAKE_GETADDRINFO */


#ifdef WRAP_GETADDRINFO

static inline
int
getaddrinfo (const char *name, const char *serv, const struct addrinfo *hint,
             struct addrinfo **result)
{
    int aierr;
#if defined(_AIX) || defined(COPY_FIRST_CANONNAME)
    struct addrinfo *ai;
#endif
#ifdef NUMERIC_SERVICE_BROKEN
    int service_is_numeric = 0;
    int service_port = 0;
    int socket_type = 0;
#endif

#ifdef DEBUG_ADDRINFO
    debug_dump_getaddrinfo_args(name, serv, hint);
#endif

#ifdef NUMERIC_SERVICE_BROKEN
    /* AIX 4.3.3 is broken.  (Or perhaps out of date?)

       If a numeric service is provided, and it doesn't correspond to
       a known service name for tcp or udp (as appropriate), an error
       code (for "host not found") is returned.  If the port maps to a
       known service for both udp and tcp, all is well.  */
    if (serv && serv[0] && isdigit(serv[0])) {
        unsigned long lport;
        char *end;
        lport = strtoul(serv, &end, 10);
        if (!*end) {
            if (lport > 65535)
                return EAI_SOCKTYPE;
            service_is_numeric = 1;
            service_port = lport;
#ifdef AI_NUMERICSERV
            if (hint && hint->ai_flags & AI_NUMERICSERV)
                serv = "9";
            else
#endif
                serv = "discard";       /* defined for both udp and tcp */
            if (hint)
                socket_type = hint->ai_socktype;
        }
    }
#endif

    aierr = system_getaddrinfo (name, serv, hint, result);
    if (aierr || *result == 0) {
#ifdef DEBUG_ADDRINFO
        debug_dump_error(aierr);
#endif
        return aierr;
    }

    /* Linux libc version 6 prior to 2.3.4 is broken.

       RFC 2553 says that when AI_CANONNAME is set, the ai_canonname
       flag of the first returned structure has the canonical name of
       the host.  Instead, GNU libc sets ai_canonname in each returned
       structure to the name that the corresponding address maps to,
       if any, or a printable numeric form.

       RFC 2553 bis and the new Open Group spec say that field will be
       the canonical name if it can be determined, otherwise, the
       provided hostname or a copy of it.

       IMNSHO, "canonical name" means CNAME processing and not PTR
       processing, but I can see arguing it.  Using the numeric form
       when that's not the form provided is just wrong.  So, let's fix
       it.

       The glibc 2.2.5 sources indicate that the canonical name is
       *not* allocated separately, it's just some extra storage tacked
       on the end of the addrinfo structure.  So, let's try this
       approach: If getaddrinfo sets ai_canonname, we'll replace the
       *first* one with allocated storage, and free up that pointer in
       freeaddrinfo if it's set; the other ai_canonname fields will be
       left untouched.  And we'll just pray that the application code
       won't mess around with the list structure; if we start doing
       that, we'll have to start replacing and freeing all of the
       ai_canonname fields.

       Ref: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=133668 .

       Since it's dependent on the target hostname, it's hard to check
       for at configure time.  The bug was fixed in glibc 2.3.4.
       After the fix, the ai_canonname field is allocated, so our
       workaround leaks memory.  We disable the workaround for glibc
       >= 2.4, but there is no easy way to test for glibc patch
       versions, so we still leak memory under glibc 2.3.4 through
       2.3.6.

       Some Windows documentation says that even when AI_CANONNAME is
       set, the returned ai_canonname field can be null.  The NetBSD
       1.5 implementation also does this, if the input hostname is a
       numeric host address string.  That case isn't handled well at
       the moment.

       Libc version 5 didn't have getaddrinfo at all.  */

#ifdef COPY_FIRST_CANONNAME
    /*
     * This code must *always* return an error, return a null
     * ai_canonname, or return an ai_canonname allocated here using
     * malloc, so that freeaddrinfo can always free a non-null
     * ai_canonname.  Note that it really doesn't matter if the
     * AI_CANONNAME flag was set.
     */
    ai = *result;
    if (ai->ai_canonname) {
        struct hostent *hp;
        const char *name2 = 0;
        int i, herr;
        GET_HOST_TMP htmp;

        /*
         * Current versions of GET_HOST_BY_NAME will fail if the
         * target hostname has IPv6 addresses only.  Make sure it
         * fails fairly cleanly.
         */
        GET_HOST_BY_NAME (name, hp, herr, htmp);
        if (hp == 0) {
            /*
             * This case probably means it's an IPv6-only name.  If
             * ai_canonname is a numeric address, get rid of it.
             */
            if (ai->ai_canonname && strchr(ai->ai_canonname, ':'))
                ai->ai_canonname = 0;
            name2 = ai->ai_canonname ? ai->ai_canonname : name;
        } else {
            /*
             * Sometimes gethostbyname will be directed to /etc/hosts
             * first, and sometimes that file will have entries with
             * the unqualified name first.  So take the first entry
             * that looks like it could be a FQDN. Starting with h_name
             * and then all the aliases.
             */
            for (i = 0, name2 = hp->h_name; name2; i++) {
                if (strchr(name2, '.') != 0)
                    break;
                name2 = hp->h_aliases[i];
            }
            if (name2 == 0)
                name2 = hp->h_name;
        }

        ai->ai_canonname = strdup(name2);
        if (name2 != 0 && ai->ai_canonname == 0) {
            system_freeaddrinfo(ai);
            *result = 0;
#ifdef DEBUG_ADDRINFO
            debug_dump_error(EAI_MEMORY);
#endif
            return EAI_MEMORY;
        }
        /* Zap the remaining ai_canonname fields glibc fills in, in
           case the application messes around with the list
           structure.  */
        while ((ai = ai->ai_next) != NULL)
            ai->ai_canonname = 0;
    }
#endif

#ifdef NUMERIC_SERVICE_BROKEN
    if (service_port != 0) {
        for (ai = *result; ai; ai = ai->ai_next) {
            if (socket_type != 0 && ai->ai_socktype == 0)
                /* Is this check actually needed?  */
                ai->ai_socktype = socket_type;
            sa_setport(ai->ai_addr, service_port);
        }
    }
#endif

#ifdef _AIX
    for (ai = *result; ai; ai = ai->ai_next) {
        /* AIX 4.3.3 libc is broken.  It doesn't set the family or len
           fields of the sockaddr structures.  Usually, sa_family is
           zero, but I've seen it set to 1 in some cases also (maybe
           just leftover from previous contents of the memory
           block?).  So, always override what libc returned.  */
        ai->ai_addr->sa_family = ai->ai_family;
    }
#endif

    /* Not dealt with currently:

       - Some versions of GNU libc can lose some IPv4 addresses in
       certain cases when multiple IPv4 and IPv6 addresses are
       available.  */

#ifdef DEBUG_ADDRINFO
    debug_dump_addrinfos(*result);
#endif

    return 0;
}

static inline
void freeaddrinfo (struct addrinfo *ai)
{
#ifdef COPY_FIRST_CANONNAME
    if (ai) {
        free(ai->ai_canonname);
        ai->ai_canonname = 0;
        system_freeaddrinfo(ai);
    }
#else
    system_freeaddrinfo(ai);
#endif
}
#endif /* WRAP_GETADDRINFO */

#ifdef FAI_CACHE
static int krb5int_lock_fac (void)
{
    int err;
    err = krb5int_call_thread_support_init();
    if (err)
        return err;
    return k5_mutex_lock(&krb5int_fac.lock);
}

static int krb5int_unlock_fac (void)
{
    return k5_mutex_unlock(&krb5int_fac.lock);
}
#endif

/* Some systems don't define in6addr_any.  */
const struct in6_addr krb5int_in6addr_any = IN6ADDR_ANY_INIT;

int krb5int_getaddrinfo (const char *node, const char *service,
                         const struct addrinfo *hints,
                         struct addrinfo **aip)
{
    return getaddrinfo(node, service, hints, aip);
}

void krb5int_freeaddrinfo (struct addrinfo *ai)
{
    freeaddrinfo(ai);
}

const char *krb5int_gai_strerror(int err)
{
    return gai_strerror(err);
}

int krb5int_getnameinfo (const struct sockaddr *sa, socklen_t salen,
                         char *hbuf, size_t hbuflen,
                         char *sbuf, size_t sbuflen,
                         int flags)
{
    return getnameinfo(sa, salen, hbuf, hbuflen, sbuf, sbuflen, flags);
}
