all: add flush cache domains config

cmd/cli/cli.go

@@ -1831,6 +1831,11 @@ func fieldErrorMsg(fe validator.FieldError) string {
 			return fmt.Sprintf("must define at least %s element", fe.Param())
 		}
 		return fmt.Sprintf("minimum value: %q", fe.Param())
+	case "max":
+		if fe.Kind() == reflect.Map || fe.Kind() == reflect.Slice {
+			return fmt.Sprintf("exceeded maximum number of elements: %s", fe.Param())
+		}
+		return fmt.Sprintf("maximum value: %q", fe.Param())
 	case "len":
 		if fe.Kind() == reflect.Slice {
 			return fmt.Sprintf("must have at least %s element", fe.Param())

cmd/cli/dns_proxy.go

@@ -101,6 +101,10 @@ func (p *prog) serveDNS(listenerNum string) error {
 		go p.detectLoop(m)
 		q := m.Question[0]
 		domain := canonicalName(q.Name)
+		if _, ok := p.cacheFlushDomainsMap[domain]; ok && p.cache != nil {
+			p.cache.Purge()
+			ctrld.Log(ctx, mainLog.Load().Debug(), "received query %q, local cache is purged", domain)
+		}
 		remoteIP, _, _ := net.SplitHostPort(w.RemoteAddr().String())
 		ci := p.getClientInfo(remoteIP, m)
 		ci.ClientIDPref = p.cfg.Service.ClientIDPref

cmd/cli/prog.go

@@ -70,17 +70,18 @@ type prog struct {
 	logConn      net.Conn
 	cs           *controlServer
 
-	cfg            *ctrld.Config
+	cfg                  *ctrld.Config
-	localUpstreams []string
+	localUpstreams       []string
-	ptrNameservers []string
+	ptrNameservers       []string
-	appCallback    *AppCallback
+	appCallback          *AppCallback
-	cache          dnscache.Cacher
+	cache                dnscache.Cacher
-	sema           semaphore
+	cacheFlushDomainsMap map[string]struct{}
-	ciTable        *clientinfo.Table
+	sema                 semaphore
-	um             *upstreamMonitor
+	ciTable              *clientinfo.Table
-	router         router.Router
+	um                   *upstreamMonitor
-	ptrLoopGuard   *loopGuard
+	router               router.Router
-	lanLoopGuard   *loopGuard
+	ptrLoopGuard         *loopGuard
+	lanLoopGuard         *loopGuard
 
 	loopMu sync.Mutex
 	loop   map[string]bool
@@ -253,12 +254,17 @@ func (p *prog) run(reload bool, reloadCh chan struct{}) {
 	p.loop = make(map[string]bool)
 	p.lanLoopGuard = newLoopGuard()
 	p.ptrLoopGuard = newLoopGuard()
+	p.cacheFlushDomainsMap = nil
 	if p.cfg.Service.CacheEnable {
 		cacher, err := dnscache.NewLRUCache(p.cfg.Service.CacheSize)
 		if err != nil {
 			mainLog.Load().Error().Err(err).Msg("failed to create cacher, caching is disabled")
 		} else {
 			p.cache = cacher
+			p.cacheFlushDomainsMap = make(map[string]struct{}, 256)
+			for _, domain := range p.cfg.Service.CacheFlushDomains {
+				p.cacheFlushDomainsMap[canonicalName(domain)] = struct{}{}
+			}
 		}
 	}
 

config.go

@@ -179,26 +179,27 @@ func (c *Config) FirstUpstream() *UpstreamConfig {
 
 // ServiceConfig specifies the general ctrld config.
 type ServiceConfig struct {
-	LogLevel                string `mapstructure:"log_level" toml:"log_level,omitempty"`
+	LogLevel                string   `mapstructure:"log_level" toml:"log_level,omitempty"`
-	LogPath                 string `mapstructure:"log_path" toml:"log_path,omitempty"`
+	LogPath                 string   `mapstructure:"log_path" toml:"log_path,omitempty"`
-	CacheEnable             bool   `mapstructure:"cache_enable" toml:"cache_enable,omitempty"`
+	CacheEnable             bool     `mapstructure:"cache_enable" toml:"cache_enable,omitempty"`
-	CacheSize               int    `mapstructure:"cache_size" toml:"cache_size,omitempty"`
+	CacheSize               int      `mapstructure:"cache_size" toml:"cache_size,omitempty"`
-	CacheTTLOverride        int    `mapstructure:"cache_ttl_override" toml:"cache_ttl_override,omitempty"`
+	CacheTTLOverride        int      `mapstructure:"cache_ttl_override" toml:"cache_ttl_override,omitempty"`
-	CacheServeStale         bool   `mapstructure:"cache_serve_stale" toml:"cache_serve_stale,omitempty"`
+	CacheServeStale         bool     `mapstructure:"cache_serve_stale" toml:"cache_serve_stale,omitempty"`
-	MaxConcurrentRequests   *int   `mapstructure:"max_concurrent_requests" toml:"max_concurrent_requests,omitempty" validate:"omitempty,gte=0"`
+	CacheFlushDomains       []string `mapstructure:"cache_flush_domains" toml:"cache_flush_domains" validate:"max=256"`
-	DHCPLeaseFile           string `mapstructure:"dhcp_lease_file_path" toml:"dhcp_lease_file_path" validate:"omitempty,file"`
+	MaxConcurrentRequests   *int     `mapstructure:"max_concurrent_requests" toml:"max_concurrent_requests,omitempty" validate:"omitempty,gte=0"`
-	DHCPLeaseFileFormat     string `mapstructure:"dhcp_lease_file_format" toml:"dhcp_lease_file_format" validate:"required_unless=DHCPLeaseFile '',omitempty,oneof=dnsmasq isc-dhcp"`
+	DHCPLeaseFile           string   `mapstructure:"dhcp_lease_file_path" toml:"dhcp_lease_file_path" validate:"omitempty,file"`
-	DiscoverMDNS            *bool  `mapstructure:"discover_mdns" toml:"discover_mdns,omitempty"`
+	DHCPLeaseFileFormat     string   `mapstructure:"dhcp_lease_file_format" toml:"dhcp_lease_file_format" validate:"required_unless=DHCPLeaseFile '',omitempty,oneof=dnsmasq isc-dhcp"`
-	DiscoverARP             *bool  `mapstructure:"discover_arp" toml:"discover_arp,omitempty"`
+	DiscoverMDNS            *bool    `mapstructure:"discover_mdns" toml:"discover_mdns,omitempty"`
-	DiscoverDHCP            *bool  `mapstructure:"discover_dhcp" toml:"discover_dhcp,omitempty"`
+	DiscoverARP             *bool    `mapstructure:"discover_arp" toml:"discover_arp,omitempty"`
-	DiscoverPtr             *bool  `mapstructure:"discover_ptr" toml:"discover_ptr,omitempty"`
+	DiscoverDHCP            *bool    `mapstructure:"discover_dhcp" toml:"discover_dhcp,omitempty"`
-	DiscoverHosts           *bool  `mapstructure:"discover_hosts" toml:"discover_hosts,omitempty"`
+	DiscoverPtr             *bool    `mapstructure:"discover_ptr" toml:"discover_ptr,omitempty"`
-	DiscoverRefreshInterval int    `mapstructure:"discover_refresh_interval" toml:"discover_refresh_interval,omitempty"`
+	DiscoverHosts           *bool    `mapstructure:"discover_hosts" toml:"discover_hosts,omitempty"`
-	ClientIDPref            string `mapstructure:"client_id_preference" toml:"client_id_preference,omitempty" validate:"omitempty,oneof=host mac"`
+	DiscoverRefreshInterval int      `mapstructure:"discover_refresh_interval" toml:"discover_refresh_interval,omitempty"`
-	MetricsQueryStats       bool   `mapstructure:"metrics_query_stats" toml:"metrics_query_stats,omitempty"`
+	ClientIDPref            string   `mapstructure:"client_id_preference" toml:"client_id_preference,omitempty" validate:"omitempty,oneof=host mac"`
-	MetricsListener         string `mapstructure:"metrics_listener" toml:"metrics_listener,omitempty"`
+	MetricsQueryStats       bool     `mapstructure:"metrics_query_stats" toml:"metrics_query_stats,omitempty"`
-	Daemon                  bool   `mapstructure:"-" toml:"-"`
+	MetricsListener         string   `mapstructure:"metrics_listener" toml:"metrics_listener,omitempty"`
-	AllocateIP              bool   `mapstructure:"-" toml:"-"`
+	Daemon                  bool     `mapstructure:"-" toml:"-"`
+	AllocateIP              bool     `mapstructure:"-" toml:"-"`
 }
 
 // NetworkConfig specifies configuration for networks where ctrld will handle requests.

config_test.go

@@ -1,6 +1,7 @@
 package ctrld_test
 
 import (
+	"fmt"
 	"os"
 	"strings"
 	"testing"
@@ -103,6 +104,7 @@ func TestConfigValidation(t *testing.T) {
 		{"invalid doh/doh3 endpoint", configWithInvalidDoHEndpoint(t), true},
 		{"invalid client id pref", configWithInvalidClientIDPref(t), true},
 		{"doh endpoint without scheme", dohUpstreamEndpointWithoutScheme(t), false},
+		{"maximum number of flush cache domains", configWithInvalidFlushCacheDomain(t), true},
 	}
 
 	for _, tc := range tests {
@@ -275,3 +277,12 @@ func configWithInvalidClientIDPref(t *testing.T) *ctrld.Config {
 	cfg.Service.ClientIDPref = "foo"
 	return cfg
 }
+
+func configWithInvalidFlushCacheDomain(t *testing.T) *ctrld.Config {
+	cfg := defaultConfig(t)
+	cfg.Service.CacheFlushDomains = make([]string, 257)
+	for i := range cfg.Service.CacheFlushDomains {
+		cfg.Service.CacheFlushDomains[i] = fmt.Sprintf("%d.com", i)
+	}
+	return cfg
+}

docs/config.md

@@ -157,6 +157,13 @@ stale cached records (regardless of their TTLs) until upstream comes online.
 - Required: no
 - Default: false
 
+### cache_flush_domains
+When `ctrld` receives query with domain name in `cache_flush_domains`, the local cache will be discarded
+before serving the query.
+
+- Type: array of strings
+- Required: no
+
 ### max_concurrent_requests
 The number of concurrent requests that will be handled, must be a non-negative integer. 
 Tweaking this value depends on the capacity of your system.
@@ -531,7 +538,7 @@ And within each policy, the rules are processed from top to bottom.
 ### failover_rcodes
 For non success response, `failover_rcodes` allows the request to be forwarded to next upstream, if the response `RCODE` matches any value defined in `failover_rcodes`.
 
-- Type: array of string
+- Type: array of strings
 - Required: no
 - Default: []
 - 

internal/dnscache/cache.go

@@ -12,6 +12,7 @@ import (
 type Cacher interface {
 	Get(Key) *Value
 	Add(Key, *Value)
+	Purge()
 }
 
 // Key is the caching key for DNS message.
@@ -34,15 +35,22 @@ type LRUCache struct {
 	cacher *lru.ARCCache[Key, *Value]
 }
 
+// Get looks up key's value from cache.
 func (l *LRUCache) Get(key Key) *Value {
 	v, _ := l.cacher.Get(key)
 	return v
 }
 
+// Add adds a value to cache.
 func (l *LRUCache) Add(key Key, value *Value) {
 	l.cacher.Add(key, value)
 }
 
+// Purge clears the cache.
+func (l *LRUCache) Purge() {
+	l.cacher.Purge()
+}
+
 // NewLRUCache creates a new LRUCache instance with given size.
 func NewLRUCache(size int) (*LRUCache, error) {
 	cacher, err := lru.NewARC[Key, *Value](size)