From: treysis <trey...@gmx.net>

Intented for IPv6 only installations
that have to deal with software that prefers IPv4 above IPv6.
---
 src/dnsmasq.h |  3 ++-
 src/option.c  |  3 +++
 src/rfc1035.c | 11 +++++++++++
 3 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/src/dnsmasq.h b/src/dnsmasq.h
index 95dc8ae..7eae110 100644
--- a/src/dnsmasq.h
+++ b/src/dnsmasq.h
@@ -272,7 +272,8 @@ struct event_desc {
 #define OPT_LOG_DEBUG      62
 #define OPT_UMBRELLA       63
 #define OPT_UMBRELLA_DEVID 64
-#define OPT_LAST           65
+#define OPT_FILTER_A       65
+#define OPT_LAST           66
 
 #define OPTION_BITS (sizeof(unsigned int)*8)
 #define OPTION_SIZE ( (OPT_LAST/OPTION_BITS)+((OPT_LAST%OPTION_BITS)!=0) )
diff --git a/src/option.c b/src/option.c
index 23cf058..a81aa1f 100644
--- a/src/option.c
+++ b/src/option.c
@@ -171,6 +171,7 @@ struct myoption {
 #define LOPT_DYNHOST       362
 #define LOPT_LOG_DEBUG     363
 #define LOPT_UMBRELLA     364
+#define LOPT_FILTER_A      365
  
 #ifdef HAVE_GETOPT_LONG
 static const struct option opts[] =  
@@ -347,6 +348,7 @@ static const struct myoption opts[] =
     { "dynamic-host", 1, 0, LOPT_DYNHOST },
     { "log-debug", 0, 0, LOPT_LOG_DEBUG },
        { "umbrella", 2, 0, LOPT_UMBRELLA },
+    { "filter-a", 0, 0, LOPT_FILTER_A },
     { NULL, 0, 0, 0 }
   };
 
@@ -530,6 +532,7 @@ static struct {
   { LOPT_DUMPMASK, ARG_ONE, "<hex>", gettext_noop("Mask which packets to 
dump"), NULL },
   { LOPT_SCRIPT_TIME, OPT_LEASE_RENEW, NULL, gettext_noop("Call dhcp-script 
when lease expiry changes."), NULL },
   { LOPT_UMBRELLA, ARG_ONE, "[=<optspec>]", gettext_noop("Send Cisco Umbrella 
identifiers including remote IP."), NULL },
+  { LOPT_FILTER_A, OPT_FILTER_A, NULL, gettext_noop("Filter all A requests."), 
NULL },
   { 0, 0, NULL, NULL, NULL }
 }; 
 
diff --git a/src/rfc1035.c b/src/rfc1035.c
index 5a961b8..a7f83f2 100644
--- a/src/rfc1035.c
+++ b/src/rfc1035.c
@@ -1895,6 +1895,17 @@ size_t answer_request(struct dns_header *header, char 
*limit, size_t qlen,
            }
        }
 
+       /* filter a forwards */
+       if (qtype == T_A && option_bool(OPT_FILTER_A))
+         {
+           /* return a null reply */
+               ans = 1;
+               if (!dryrun)
+                 log_query(F_CONFIG | F_IPV6 | F_NEG, name, &addr, NULL);
+               break;
+         }
+       /* end of filtering a */
+
       if (!ans)
        return 0; /* failed to answer a question */
     }
-- 
2.1.4


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