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authorSiddhesh Poyarekar <siddhesh@redhat.com>2012-03-30 20:58:14 +0530
committerSiddhesh Poyarekar <siddhesh@redhat.com>2012-03-30 21:30:01 +0530
commit48c41d04ee06efc6ec97325ed6697c121b40865f (patch)
treed954e0201566cb3844d831217fd8753573ff51da /resolv
parent2f5a5ed02c346e5debc89b82a7c7e0eacc37a107 (diff)
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Consider TTL of CNAME record and return minimum TTL in the chain
[BZ #13928] A DNS request consists of multiple resources combined into
a single hostent, including multiple CNAME records that may have been
assigned different TTL values. In such a case, nscd should take the
least TTL among all of the resources as the timeout for the hostent
before it is reloaded in its cache so that the hostent remains stale
in the database for the least amount of time.
Diffstat (limited to 'resolv')
-rw-r--r--resolv/nss_dns/dns-host.c21
1 files changed, 18 insertions, 3 deletions
diff --git a/resolv/nss_dns/dns-host.c b/resolv/nss_dns/dns-host.c
index 3b287b717a..ba83c440cc 100644
--- a/resolv/nss_dns/dns-host.c
+++ b/resolv/nss_dns/dns-host.c
@@ -1,4 +1,4 @@
-/* Copyright (C) 1996-2004, 2007-2009, 2010, 2012 Free Software Foundation, Inc.
+/* Copyright (C) 1996-2004, 2007-2010, 2012 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
    Extended from original form by Ulrich Drepper <drepper@cygnus.com>, 1996.
 
@@ -744,6 +744,10 @@ getanswer_r (const querybuf *answer, int anslen, const char *qname, int qtype,
 
       if ((qtype == T_A || qtype == T_AAAA) && type == T_CNAME)
 	{
+	  /* A CNAME could also have a TTL entry.  */
+	  if (ttlp != NULL && ttl < *ttlp)
+	      *ttlp = ttl;
+
 	  if (ap >= &host_data->aliases[MAX_NR_ALIASES - 1])
 	    continue;
 	  n = dn_expand (answer->buf, end_of_message, cp, tbuf, sizeof tbuf);
@@ -905,7 +909,10 @@ getanswer_r (const querybuf *answer, int anslen, const char *qname, int qtype,
 	    {
 	      register int nn;
 
-	      if (ttlp != NULL)
+	      /* We compose a single hostent out of the entire chain of
+	         entries, so the TTL of the hostent is essentially the lowest
+		 TTL in the chain.  */
+	      if (ttlp != NULL && ttl < *ttlp)
 		*ttlp = ttl;
 	      if (canonp != NULL)
 		*canonp = bp;
@@ -1081,6 +1088,11 @@ gaih_getanswer_slice (const querybuf *answer, int anslen, const char *qname,
       if (type == T_CNAME)
 	{
 	  char tbuf[MAXDNAME];
+
+	  /* A CNAME could also have a TTL entry.  */
+	  if (ttlp != NULL && ttl < *ttlp)
+	      *ttlp = ttl;
+
 	  n = dn_expand (answer->buf, end_of_message, cp, tbuf, sizeof tbuf);
 	  if (__builtin_expect (n < 0 || res_hnok (tbuf) == 0, 0))
 	    {
@@ -1161,7 +1173,10 @@ gaih_getanswer_slice (const querybuf *answer, int anslen, const char *qname,
 
       if (*firstp)
 	{
-	  if (ttlp != NULL)
+	  /* We compose a single hostent out of the entire chain of
+	     entries, so the TTL of the hostent is essentially the lowest
+	     TTL in the chain.  */
+	  if (ttlp != NULL && ttl < *ttlp)
 	    *ttlp = ttl;
 
 	  (*pat)->name = canon ?: h_name;