From 7ac57605099d7c6f1605941b67a286778b250b7e Mon Sep 17 00:00:00 2001
From: Simon Zolin <s.zolin@adguard.com>
Date: Mon, 11 Nov 2019 19:34:47 +0300
Subject: [PATCH] + dns: add "aaaa_disabled" setting

---
 AGHTechDoc.md                 | 2 ++
 dnsforward/dnsforward.go      | 8 ++++++++
 dnsforward/dnsforward_http.go | 6 ++++++
 3 files changed, 16 insertions(+)

diff --git a/AGHTechDoc.md b/AGHTechDoc.md
index 4ed2c4e3..c3b4b249 100644
--- a/AGHTechDoc.md
+++ b/AGHTechDoc.md
@@ -823,6 +823,7 @@ Response:
 		"blocking_ipv4": "1.2.3.4",
 		"blocking_ipv6": "1:2:3::4",
 		"edns_cs_enabled": true | false,
+		"disable_ipv6": true | false,
 	}
 
 
@@ -839,6 +840,7 @@ Request:
 		"blocking_ipv4": "1.2.3.4",
 		"blocking_ipv6": "1:2:3::4",
 		"edns_cs_enabled": true | false,
+		"disable_ipv6": true | false,
 	}
 
 Response:
diff --git a/dnsforward/dnsforward.go b/dnsforward/dnsforward.go
index e94b47cc..c51a25b3 100644
--- a/dnsforward/dnsforward.go
+++ b/dnsforward/dnsforward.go
@@ -132,6 +132,9 @@ type FilteringConfig struct {
 
 	EnableEDNSClientSubnet bool `yaml:"edns_client_subnet"` // Enable EDNS Client Subnet option
 
+	// Respond with an empty answer to all AAAA requests
+	AAAADisabled bool `yaml:"aaaa_disabled"`
+
 	AllowedClients    []string `yaml:"allowed_clients"`    // IP addresses of whitelist clients
 	DisallowedClients []string `yaml:"disallowed_clients"` // IP addresses of clients that should be blocked
 	BlockedHosts      []string `yaml:"blocked_hosts"`      // hosts that should be blocked
@@ -426,6 +429,11 @@ func (s *Server) beforeRequestHandler(p *proxy.Proxy, d *proxy.DNSContext) (bool
 func (s *Server) handleDNSRequest(p *proxy.Proxy, d *proxy.DNSContext) error {
 	start := time.Now()
 
+	if s.conf.AAAADisabled && d.Req.Question[0].Qtype == dns.TypeAAAA {
+		_ = proxy.CheckDisabledAAAARequest(d, true)
+		return nil
+	}
+
 	if s.conf.OnDNSRequest != nil {
 		s.conf.OnDNSRequest(d)
 	}
diff --git a/dnsforward/dnsforward_http.go b/dnsforward/dnsforward_http.go
index 86bcdd3a..c20ac7fc 100644
--- a/dnsforward/dnsforward_http.go
+++ b/dnsforward/dnsforward_http.go
@@ -28,6 +28,7 @@ type dnsConfigJSON struct {
 	BlockingIPv4      string `json:"blocking_ipv4"`
 	BlockingIPv6      string `json:"blocking_ipv6"`
 	EDNSCSEnabled     bool   `json:"edns_cs_enabled"`
+	DisableIPv6       bool   `json:"disable_ipv6"`
 }
 
 func (s *Server) handleGetConfig(w http.ResponseWriter, r *http.Request) {
@@ -39,6 +40,7 @@ func (s *Server) handleGetConfig(w http.ResponseWriter, r *http.Request) {
 	resp.BlockingIPv6 = s.conf.BlockingIPv6
 	resp.RateLimit = s.conf.Ratelimit
 	resp.EDNSCSEnabled = s.conf.EnableEDNSClientSubnet
+	resp.DisableIPv6 = s.conf.AAAADisabled
 	s.RUnlock()
 
 	js, err := json.Marshal(resp)
@@ -117,6 +119,10 @@ func (s *Server) handleSetConfig(w http.ResponseWriter, r *http.Request) {
 		restart = true
 	}
 
+	if js.Exists("disable_ipv6") {
+		s.conf.AAAADisabled = req.DisableIPv6
+	}
+
 	s.Unlock()
 	s.conf.ConfigModified()