+ dns: new settings for cache

Squashed commit of the following:

commit e5b488249a4d972efd63c6e96830d9f30829aee1
Author: Simon Zolin <s.zolin@adguard.com>
Date:   Tue Jun 16 15:38:27 2020 +0300

    + dns: new settings for cache

AGHTechDoc.md

@@ -894,6 +894,9 @@ Response:
 		"dnssec_enabled": true | false
 		"disable_ipv6": true | false,
 		"upstream_mode": "" | "parallel" | "fastest_addr"
+		"cache_size": 1234, // in bytes
+		"cache_ttl_min": 1234, // in seconds
+		"cache_ttl_max": 1234, // in seconds
 	}
 
 
@@ -916,6 +919,9 @@ Request:
 		"dnssec_enabled": true | false
 		"disable_ipv6": true | false,
 		"upstream_mode": "" | "parallel" | "fastest_addr"
+		"cache_size": 1234, // in bytes
+		"cache_ttl_min": 1234, // in seconds
+		"cache_ttl_max": 1234, // in seconds
 	}
 
 Response:

dnsforward/dnsforward_http.go

@@ -34,6 +34,9 @@ type dnsConfigJSON struct {
 	DNSSECEnabled     bool   `json:"dnssec_enabled"`
 	DisableIPv6       bool   `json:"disable_ipv6"`
 	UpstreamMode      string `json:"upstream_mode"`
+	CacheSize         uint32 `json:"cache_size"`
+	CacheMinTTL       uint32 `json:"cache_ttl_min"`
+	CacheMaxTTL       uint32 `json:"cache_ttl_max"`
 }
 
 func (s *Server) handleGetConfig(w http.ResponseWriter, r *http.Request) {
@@ -50,6 +53,9 @@ func (s *Server) handleGetConfig(w http.ResponseWriter, r *http.Request) {
 	resp.EDNSCSEnabled = s.conf.EnableEDNSClientSubnet
 	resp.DNSSECEnabled = s.conf.EnableDNSSEC
 	resp.DisableIPv6 = s.conf.AAAADisabled
+	resp.CacheSize = s.conf.CacheSize
+	resp.CacheMinTTL = s.conf.CacheMinTTL
+	resp.CacheMaxTTL = s.conf.CacheMaxTTL
 	if s.conf.FastestAddr {
 		resp.UpstreamMode = "fastest_addr"
 	} else if s.conf.AllServers {
@@ -126,6 +132,11 @@ func (s *Server) handleSetConfig(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	if req.CacheMinTTL > req.CacheMaxTTL {
+		httpError(r, w, http.StatusBadRequest, "cache_ttl_min must be less or equal than cache_ttl_max")
+		return
+	}
+
 	restart := false
 	s.Lock()
 
@@ -177,6 +188,21 @@ func (s *Server) handleSetConfig(w http.ResponseWriter, r *http.Request) {
 		s.conf.AAAADisabled = req.DisableIPv6
 	}
 
+	if js.Exists("cache_size") {
+		s.conf.CacheSize = req.CacheSize
+		restart = true
+	}
+
+	if js.Exists("cache_ttl_min") {
+		s.conf.CacheMinTTL = req.CacheMinTTL
+		restart = true
+	}
+
+	if js.Exists("cache_ttl_max") {
+		s.conf.CacheMaxTTL = req.CacheMaxTTL
+		restart = true
+	}
+
 	if js.Exists("upstream_mode") {
 		s.conf.FastestAddr = false
 		s.conf.AllServers = false

openapi/openapi.yaml

@@ -1016,6 +1016,12 @@ components:
                     type: boolean
                 dnssec_enabled:
                     type: boolean
+                cache_size:
+                    type: integer
+                cache_ttl_min:
+                    type: integer
+                cache_ttl_max:
+                    type: integer
                 upstream_mode:
                     enum:
                         - ""