internal/router: use max-cache-ttl=0 on some routers

On some routers, dnsmasq config may change cache-size dynamically after
ctrld starts, causing dnsmasq crashes.

Fixing this by using max-cache-ttl, which have the same effect with
setting cache-size=0 but won't conflict with existing routers config.

internal/router/dnsmasq/dnsmasq.go

@@ -1,12 +1,9 @@
 package dnsmasq
 
 import (
-	"bytes"
 	"errors"
-	"fmt"
 	"html/template"
 	"net"
-	"os"
 	"path/filepath"
 	"strings"
 
@@ -24,6 +21,8 @@ add-subnet=32,128
 {{- end}}
 {{- if .CacheDisabled}}
 cache-size=0
+{{- else}}
+max-cache-ttl=0
 {{- end}}
 `
 
@@ -72,11 +71,18 @@ type Upstream struct {
 	Port int
 }
 
+// ConfTmpl generates dnsmasq configuration from ctrld config.
 func ConfTmpl(tmplText string, cfg *ctrld.Config) (string, error) {
-	return ConfTmplWitchCacheDisabled(tmplText, cfg, true)
+	return ConfTmplWithCacheDisabled(tmplText, cfg, true)
 }
 
-func ConfTmplWitchCacheDisabled(tmplText string, cfg *ctrld.Config, cacheDisabled bool) (string, error) {
+// ConfTmplWithCacheDisabled is like ConfTmpl, but the caller can control whether
+// dnsmasq cache is disabled using cacheDisabled parameter.
+//
+// Generally, the caller should use ConfTmpl, but on some routers which dnsmasq config may be changed
+// after ctrld started (like EdgeOS/Ubios, Firewalla ...), dnsmasq cache should not be disabled because
+// the cache-size=0 generated by ctrld will conflict with router's generated config.
+func ConfTmplWithCacheDisabled(tmplText string, cfg *ctrld.Config, cacheDisabled bool) (string, error) {
 	listener := cfg.FirstListener()
 	if listener == nil {
 		return "", errors.New("missing listener")
@@ -89,11 +95,14 @@ func ConfTmplWitchCacheDisabled(tmplText string, cfg *ctrld.Config, cacheDisable
 	return confTmpl(tmplText, upstreams, cfg.HasUpstreamSendClientInfo(), cacheDisabled)
 }
 
+// FirewallaConfTmpl generates dnsmasq config for Firewalla routers.
 func FirewallaConfTmpl(tmplText string, cfg *ctrld.Config) (string, error) {
+	// If ctrld listen on all interfaces, generating config for all of them.
 	if lc := cfg.FirstListener(); lc != nil && (lc.IP == "0.0.0.0" || lc.IP == "") {
-		return confTmpl(tmplText, firewallaUpstreams(lc.Port), cfg.HasUpstreamSendClientInfo(), true)
+		return confTmpl(tmplText, firewallaUpstreams(lc.Port), cfg.HasUpstreamSendClientInfo(), false)
 	}
-	return ConfTmpl(tmplText, cfg)
+	// Otherwise, generating config for the specific listener from ctrld's config.
+	return ConfTmplWithCacheDisabled(tmplText, cfg, false)
 }
 
 func confTmpl(tmplText string, upstreams []Upstream, sendClientInfo, cacheDisabled bool) (string, error) {
@@ -136,20 +145,6 @@ func firewallaDnsmasqConfFiles() ([]string, error) {
 	return filepath.Glob("/home/pi/firerouter/etc/dnsmasq.dns.*.conf")
 }
 
-// firewallUpdateConf updates all firewall config files using given function.
-func firewallUpdateConf(update func(conf string) error) error {
-	confFiles, err := firewallaDnsmasqConfFiles()
-	if err != nil {
-		return err
-	}
-	for _, conf := range confFiles {
-		if err := update(conf); err != nil {
-			return fmt.Errorf("%s: %w", conf, err)
-		}
-	}
-	return nil
-}
-
 // FirewallaSelfInterfaces returns list of interfaces that will be configured with default dnsmasq setup on Firewalla.
 func FirewallaSelfInterfaces() []*net.Interface {
 	matches, err := firewallaDnsmasqConfFiles()
@@ -166,32 +161,3 @@ func FirewallaSelfInterfaces() []*net.Interface {
 	}
 	return ifaces
 }
-
-// FirewallaDisableCache comments out "cache-size" line in all firewalla dnsmasq config files.
-func FirewallaDisableCache() error {
-	return firewallUpdateConf(DisableCache)
-}
-
-// FirewallaEnableCache un-comments out "cache-size" line in all firewalla dnsmasq config files.
-func FirewallaEnableCache() error {
-	return firewallUpdateConf(EnableCache)
-}
-
-// DisableCache comments out "cache-size" line in dnsmasq config file.
-func DisableCache(conf string) error {
-	return replaceFileContent(conf, "\ncache-size=", "\n#cache-size=")
-}
-
-// EnableCache un-comments "cache-size" line in dnsmasq config file.
-func EnableCache(conf string) error {
-	return replaceFileContent(conf, "\n#cache-size=", "\ncache-size=")
-}
-
-func replaceFileContent(filename, old, new string) error {
-	content, err := os.ReadFile(filename)
-	if err != nil {
-		return err
-	}
-	content = bytes.ReplaceAll(content, []byte(old), []byte(new))
-	return os.WriteFile(filename, content, 0644)
-}

internal/router/edgeos/edgeos.go

@@ -109,7 +109,7 @@ func (e *EdgeOS) setupUSG() error {
 		sb.WriteString(line)
 	}
 
-	data, err := dnsmasq.ConfTmplWitchCacheDisabled(dnsmasq.ConfigContentTmpl, e.cfg, false)
+	data, err := dnsmasq.ConfTmplWithCacheDisabled(dnsmasq.ConfigContentTmpl, e.cfg, false)
 	if err != nil {
 		return err
 	}
@@ -127,7 +127,7 @@ func (e *EdgeOS) setupUSG() error {
 }
 
 func (e *EdgeOS) setupUDM() error {
-	data, err := dnsmasq.ConfTmplWitchCacheDisabled(dnsmasq.ConfigContentTmpl, e.cfg, false)
+	data, err := dnsmasq.ConfTmplWithCacheDisabled(dnsmasq.ConfigContentTmpl, e.cfg, false)
 	if err != nil {
 		return err
 	}

internal/router/firewalla/firewalla.go

@@ -65,11 +65,6 @@ func (f *Firewalla) Setup() error {
 		return fmt.Errorf("writing ctrld config: %w", err)
 	}
 
-	// Disable dnsmasq cache.
-	if err := dnsmasq.FirewallaDisableCache(); err != nil {
-		return err
-	}
-
 	// Restart dnsmasq service.
 	if err := restartDNSMasq(); err != nil {
 		return fmt.Errorf("restartDNSMasq: %w", err)
@@ -87,11 +82,6 @@ func (f *Firewalla) Cleanup() error {
 		return fmt.Errorf("removing ctrld config: %w", err)
 	}
 
-	// Enable dnsmasq cache.
-	if err := dnsmasq.FirewallaEnableCache(); err != nil {
-		return err
-	}
-
 	// Restart dnsmasq service.
 	if err := restartDNSMasq(); err != nil {
 		return fmt.Errorf("restartDNSMasq: %w", err)

internal/router/ubios/ubios.go

@@ -51,17 +51,13 @@ func (u *Ubios) Setup() error {
 	if u.cfg.FirstListener().IsDirectDnsListener() {
 		return nil
 	}
-	data, err := dnsmasq.ConfTmpl(dnsmasq.ConfigContentTmpl, u.cfg)
+	data, err := dnsmasq.ConfTmplWithCacheDisabled(dnsmasq.ConfigContentTmpl, u.cfg, false)
 	if err != nil {
 		return err
 	}
 	if err := os.WriteFile(ubiosDNSMasqConfigPath, []byte(data), 0600); err != nil {
 		return err
 	}
-	// Disable dnsmasq cache.
-	if err := dnsmasq.DisableCache(ubiosDNSMasqDnsConfigPath); err != nil {
-		return err
-	}
 	// Restart dnsmasq service.
 	if err := restartDNSMasq(); err != nil {
 		return err
@@ -77,10 +73,6 @@ func (u *Ubios) Cleanup() error {
 	if err := os.Remove(ubiosDNSMasqConfigPath); err != nil {
 		return err
 	}
-	// Enable dnsmasq cache.
-	if err := dnsmasq.EnableCache(ubiosDNSMasqDnsConfigPath); err != nil {
-		return err
-	}
 	// Restart dnsmasq service.
 	if err := restartDNSMasq(); err != nil {
 		return err