Merge f655b98db6 into f36eb81e61

net/dns/manager.go

@@ -400,7 +400,18 @@ func (m *Manager) compileConfig(cfg Config) (rcfg resolver.Config, ocfg OSConfig
 			defaultRoutes = append(defaultRoutes, &dnstype.Resolver{Addr: ip.String()})
 		}
 		rcfg.Routes["."] = defaultRoutes
-		ocfg.SearchDomains = append(ocfg.SearchDomains, baseCfg.SearchDomains...)
+
+		seen := map[dnsname.FQDN]bool{}
+		SearchDomains := append(ocfg.SearchDomains, baseCfg.SearchDomains...)
+		// deduplicate our list of SearchDomains
+		ocfg.SearchDomains = []dnsname.FQDN{}
+		for _, sd := range SearchDomains {
+			if seen[sd] {
+				continue
+			}
+			ocfg.SearchDomains = append(ocfg.SearchDomains, sd)
+			seen[sd] = true
+		}
 	}
 
 	return rcfg, ocfg, nil

net/dns/resolvd.go

@@ -38,11 +38,31 @@ func (m *resolvdManager) SetDNS(config OSConfig) error {
 		m.ifName,
 	}
 
-	origResolv, err := m.readAndCopy(resolvConf, backupConf, 0644)
+	// first, read in the resolvConf
+	origResolv, err := m.fs.ReadFile(resolvConf)
 	if err != nil {
 		return err
 	}
-	newResolvConf := removeSearchLines(origResolv)
+
+	// search for our sentinel in resolvConf, if it's not present
+	// it's our first call to SetDNS, and we should make backupConf
+	resolvConfOwned := bytes.Contains(origResolv, []byte("generated by tailscale"))
+	if !resolvConfOwned {
+		_, err = m.fs.Stat(backupConf)
+		if err != nil && os.IsNotExist(err) {
+			_, err = m.readAndCopy(resolvConf, backupConf, 0644)
+			if err != nil {
+				return err
+			}
+		}
+	}
+
+	// remove resolvd nameservers and search lines
+	origResolv = removeSearchLines(origResolv)
+	origResolv = removeResolvdNameserverLines(origResolv)
+	// and clean up whitespace
+	removeBlanks := regexp.MustCompile(`(?m)^\s*\n`)
+	origResolv = removeBlanks.ReplaceAll(origResolv, []byte(""))
 
 	for _, ns := range config.Nameservers {
 		args = append(args, ns.String())
@@ -55,6 +75,15 @@ func (m *resolvdManager) SetDNS(config OSConfig) error {
 		newSearch = append(newSearch, s.WithoutTrailingDot())
 	}
 
+	var resolvConfHeader = []byte("")
+	if !resolvConfOwned {
+		// if we don't have a header, insert one
+		resolvConfHeader = []byte(
+			"# resolv.conf(5) file generated by tailscale\n" +
+			"# For more info, see https://tailscale.com/s/resolvconf-overwrite\n" +
+			"# DO NOT EDIT THIS FILE BY HAND -- CHANGES WILL BE OVERWRITTEN\n\n")
+	}
+	newResolvConf := append(resolvConfHeader, origResolv...)
 	if len(newSearch) > 1 {
 		newResolvConf = append(newResolvConf, []byte(strings.Join(newSearch, " "))...)
 		newResolvConf = append(newResolvConf, '\n')
@@ -123,6 +152,11 @@ func (m resolvdManager) readResolvConf() (config OSConfig, err error) {
 	}, nil
 }
 
+func removeResolvdNameserverLines(orig []byte) []byte {
+	re := regexp.MustCompile(`(?m)^nameserver\s+[^\s]+\s+#\s+resolvd:.*$`)
+	return re.ReplaceAll(orig, []byte(""))
+}
+
 func removeSearchLines(orig []byte) []byte {
 	re := regexp.MustCompile(`(?ms)^search\s+.+$`)
 	return re.ReplaceAll(orig, []byte(""))