dnsmasq: add filter_a option

Signed-off-by: ZiMing Mo <msylgj@immortalwrt.org>

package/network/services/dnsmasq/files/dhcp.conf

@@ -20,6 +20,7 @@ config dnsmasq
 	#list notinterface	lo
 	#list bogusnxdomain     '64.94.110.11'
 	option localservice	1  # disable to allow DNS requests from non-local subnets
+	option filter_a		0
 	option filter_aaaa	0
 	option cachesize	8000
 	option mini_ttl		3600

package/network/services/dnsmasq/files/dnsmasq.init

@@ -944,6 +944,7 @@ dnsmasq_start()
 	append_bool "$cfg" rapidcommit "--dhcp-rapid-commit"
 	append_bool "$cfg" scriptarp "--script-arp"
 
+	append_bool "$cfg" filter_a "--filter-A"
 	append_bool "$cfg" filter_aaaa "--filter-AAAA"
 
 	append_parm "$cfg" logfacility "--log-facility"

package/network/services/dnsmasq/patches/911-dnsmasq-filter-a&aaaa.patch

@@ -1,18 +1,28 @@
 From 966471712184cfb3b067f2ae8dad9d8e2a896cae Mon Sep 17 00:00:00 2001
 From: Bearice Ren <bearice@icybear.net>
 Date: Tue, 20 Sep 2016 11:52:08 +0800
-Subject: [PATCH] add filter-aaaa option
+Subject: [PATCH] add filter-a & filter-aaaa option
 
 ---
- src/rfc1035.c | 10 ++++++++++
- 1 files changed, 104 insertions(+)
+ src/rfc1035.c | 20 ++++++++++
+ 1 files changed, 20 insertions(+)
 
 --- a/src/rfc1035.c
 +++ b/src/rfc1035.c
-@@ -2111,6 +2111,16 @@ size_t answer_request(struct dns_header
+@@ -2111,6 +2111,26 @@ size_t answer_request(struct dns_header
  	    }
  	}
  
++      /* patch to 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_IPV4 | F_NEG, name, &addr, NULL, 0);
++          break;
++        }
++
 +      /* patch to filter aaaa forwards */
 +      if (qtype == T_AAAA && option_bool(OPT_FILTER_AAAA))
 +        {