krb5 commit [krb5-1.9]: Work around glibc getaddrinfo PTR lookups

[Tom Yu]

https://github.com/krb5/krb5/commit/e07cb2720551eaf1369ab388e8db61ee41c51c5b
commit e07cb2720551eaf1369ab388e8db61ee41c51c5b
Author: Greg Hudson <ghudson at mit.edu>
Date:   Thu Jun 23 04:13:38 2011 +0000

    Work around glibc getaddrinfo PTR lookups
    
    In krb5_sname_to_principal(), we always do a forward canonicalization
    using getaddrinfo() with AI_CANONNAME set.  Then, we do a reverse
    canonicalization with getnameinfo() if rdns isn't set to false in
    libdefaults.
    
    Current glibc (tested with eglibc 2.11.1) has the arguably buggy
    behavior of doing PTR lookups in getaddrinfo() to get the canonical
    name, if hints.ai_family is set to something other than AF_UNSPEC.
    This behavior defeats the ability to turn off rdns.  Work around this
    behavior by using AF_UNSPEC in krb5_sname_to_principal() from the
    start, instead of starting with AF_INET and falling back.  Specify
    AI_ADDRCONFIG to avoid AAAA lookups on hosts with no IPv6 addresses.
    
    (cherry picked from commit bc8594e7c388c8a5cfb9516a0980877cb1321d32)
    
    In sn2princ, getaddrinfo without AI_ADDRCONFIG
    
    When canonicalizing a principal, use AI_CANONNAME alone in the hint
    flags for getaddrinfo, for two reasons.  First, it works around a gnu
    libc bug where getaddrinfo does a PTR lookup for the canonical name
    (we tried to work around this in r24977 bug the addition of
    AI_ADDRCONFIG caused the same problem as the use of AF_INET).  Second,
    an IPv4-only host should be able create a principal for an IPv6-only
    host even if it can't contact the host.
    
    This does result in extra AAAA queries in the common case (IPv4-only
    host contacting IPv4-only service), which is unfortunate.  But we need
    to leave that optimization up to the platform at this point.
    
    (cherry picked from commit c3ab5fe0b01a68b14d5657740006488721b48b7b)
    
    ticket: 7164 (new)
    version_fixed: 1.9.4
    status: resolved

 src/lib/krb5/os/sn2princ.c |    7 -------
 1 files changed, 0 insertions(+), 7 deletions(-)

diff --git a/src/lib/krb5/os/sn2princ.c b/src/lib/krb5/os/sn2princ.c
index 9645fef..0a82161 100644
--- a/src/lib/krb5/os/sn2princ.c
+++ b/src/lib/krb5/os/sn2princ.c
@@ -107,19 +107,12 @@ krb5_sname_to_principal(krb5_context context, const char *hostname, const char *
                hostnames associated.  */
 
             memset(&hints, 0, sizeof(hints));
-            hints.ai_family = AF_INET;
             hints.ai_flags = AI_CANONNAME;
-        try_getaddrinfo_again:
             err = getaddrinfo(hostname, 0, &hints, &ai);
             if (err) {
 #ifdef DEBUG_REFERRALS
                 printf("sname_to_princ: probably punting due to bad hostname of %s\n",hostname);
 #endif
-                if (hints.ai_family == AF_INET) {
-                    /* Just in case it's an IPv6-only name.  */
-                    hints.ai_family = 0;
-                    goto try_getaddrinfo_again;
-                }
                 return KRB5_ERR_BAD_HOSTNAME;
             }
             remote_host = strdup(ai->ai_canonname ? ai->ai_canonname : hostname);