update resolve.conf mode and resolver upstream

gravitl · Sep 26, 2024 · b3c6fc4 · b3c6fc4
1 parent 5ae1c40
commit b3c6fc4
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Showing 4 changed files with 102 additions and 44 deletions.
diff --git a/dns/config_linux.go b/dns/config_linux.go
@@ -7,12 +7,15 @@ import (
 	"os"
 	"slices"
 	"strings"
+	"sync"
 
 	"github.com/gravitl/netclient/config"
 	"github.com/gravitl/netclient/ncutils"
 	"golang.org/x/exp/slog"
 )
 
+var dnsConfigMutex = sync.Mutex{} // used to mutex functions of the DNS
+
 const (
 	resolvconfFilePath    = "/etc/resolv.conf"
 	resolvconfFileBkpPath = "/etc/netclient/resolv.conf.nm.bkp"
@@ -31,7 +34,8 @@ func isStubSupported() bool {
 // }
 
 func SetupDNSConfig() (err error) {
-
+	dnsConfigMutex.Lock()
+	defer dnsConfigMutex.Unlock()
 	if isStubSupported() {
 		err = setupResolvectl()
 	} else {
@@ -42,7 +46,8 @@ func SetupDNSConfig() (err error) {
 }
 
 func RestoreDNSConfig() (err error) {
-
+	dnsConfigMutex.Lock()
+	defer dnsConfigMutex.Unlock()
 	if isStubSupported() {
 
 	} else {
@@ -99,9 +104,8 @@ func getIpFromServerString(addrStr string) string {
 	return s
 }
 
-func setupResolveconf() error {
+func backupResolveconfFile() error {
 
-	// backup /etc/resolv.conf
 	_, err := os.Stat(resolvconfFileBkpPath)
 	if err != nil {
 		src_file, err := os.Open(resolvconfFilePath)
@@ -123,39 +127,29 @@ func setupResolveconf() error {
 			return err
 		}
 	}
+	return nil
+}
 
-	//get nameserver and search domain
-	dnsIp := GetDNSServerInstance().AddrStr
-	if dnsIp == "" {
-		return errors.New("no listener is running")
-	}
-	if len(config.GetNodes()) == 0 {
-		return errors.New("no network joint")
-	}
+func buildAddConfigContent() ([]string, error) {
 
-	domains := "search"
-	for _, v := range config.GetNodes() {
-		domains = domains + " " + v.Network
+	//get nameserver and search domain
+	ns, domains, err := getNSAndDomains()
+	if err != nil {
+		slog.Error("error in getting getNSAndDomains", "error", err.Error())
+		return []string{}, err
 	}
-	domains = domains + " " + config.Netclient().DNSSearch
-
-	dnsIp = getIpFromServerString(dnsIp)
-
-	ns := "nameserver"
-	ns = ns + " " + dnsIp
 
-	// add nameserver and search domain
 	f, err := os.Open(resolvconfFilePath)
 	if err != nil {
 		slog.Error("error opending file", "error", resolvconfFilePath, err.Error())
-		return err
+		return []string{}, err
 	}
 	defer f.Close()
 
 	rawBytes, err := io.ReadAll(f)
 	if err != nil {
 		slog.Error("error reading file", "error", resolvconfFilePath, err.Error())
-		return err
+		return []string{}, err
 	}
 	lines := strings.Split(string(rawBytes), "\n")
 	lNo := 0
@@ -169,7 +163,26 @@ func setupResolveconf() error {
 	lines = slices.Insert(lines, lNo, ns)
 	lines = slices.Insert(lines, lNo, domains)
 
-	f, err = os.OpenFile(resolvconfFilePath, os.O_CREATE|os.O_WRONLY, 0700)
+	return lines, nil
+}
+
+func setupResolveconf() error {
+
+	// backup /etc/resolv.conf
+	err := backupResolveconfFile()
+	if err != nil {
+		slog.Error("could not backup ", resolvconfFilePath, "error", err.Error())
+		return err
+	}
+
+	// add nameserver and search domain
+	lines, err := buildAddConfigContent()
+	if err != nil {
+		slog.Error("could not build config content", "error", err.Error())
+		return err
+	}
+
+	f, err := os.OpenFile(resolvconfFilePath, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0700)
 	if err != nil {
 		slog.Error("error opending file", "error", resolvconfFilePath, err.Error())
 		return err
@@ -187,33 +200,75 @@ func setupResolveconf() error {
 	return nil
 }
 
-func restoreResolveconf() error {
+func getNSAndDomains() (string, string, error) {
+
+	dnsIp := GetDNSServerInstance().AddrStr
+	if dnsIp == "" {
+		return "", "", errors.New("no listener is running")
+	}
+	if len(config.GetNodes()) == 0 {
+		return "", "", errors.New("no network joint")
+	}
+
+	domains := "search"
+	for _, v := range config.GetNodes() {
+		domains = domains + " " + v.Network
+	}
+	domains = domains + " " + config.Netclient().DNSSearch
+
+	dnsIp = getIpFromServerString(dnsIp)
+
+	ns := "nameserver"
+	ns = ns + " " + dnsIp
+
+	return ns, domains, nil
+}
 
+func buildDeleteConfigContent() ([]string, error) {
 	f, err := os.Open(resolvconfFilePath)
 	if err != nil {
 		slog.Error("error opending file", "error", resolvconfFilePath, err.Error())
-		return err
+		return []string{}, err
 	}
 	defer f.Close()
 
 	rawBytes, err := io.ReadAll(f)
 	if err != nil {
 		slog.Error("error reading file", "error", resolvconfFilePath, err.Error())
-		return err
+		return []string{}, err
 	}
 	lines := strings.Split(string(rawBytes), "\n")
+
+	//get nameserver and search domain
+	_, domains, err := getNSAndDomains()
+	if err != nil {
+		slog.Error("error in getting getNSAndDomains", "error", err.Error())
+		return []string{}, err
+	}
+
 	lNo := 0
 	for i, line := range lines {
-		if strings.HasPrefix(line, "nameserver") {
+		if strings.Contains(line, domains) {
 			lNo = i
 			break
 		}
 	}
 
-	//Delete the added search and nameserver two lines
-	lines = slices.Delete(lines, lNo-1, lNo)
+	lines = slices.Delete(lines, lNo, lNo+1)
+	lines = slices.Delete(lines, lNo, lNo+1)
+
+	return lines, nil
+}
+
+func restoreResolveconf() error {
+
+	lines, err := buildDeleteConfigContent()
+	if err != nil {
+		slog.Error("could not build config content", "error", err.Error())
+		return err
+	}
 
-	f, err = os.OpenFile(resolvconfFilePath, os.O_CREATE|os.O_WRONLY, 0700)
+	f, err := os.OpenFile(resolvconfFilePath, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0700)
 	if err != nil {
 		slog.Error("error opending file", "error", resolvconfFilePath, err.Error())
 		return err
@@ -239,7 +294,8 @@ func restoreResolveconf() error {
 }
 
 func InitDNSConfig() {
-
+	dnsConfigMutex.Lock()
+	defer dnsConfigMutex.Unlock()
 	f, err := os.Open(resolvconfFilePath)
 	if err != nil {
 		slog.Error("error opending file", "error", resolvconfFilePath, err.Error())

diff --git a/dns/listener.go b/dns/listener.go
@@ -97,6 +97,14 @@ func (dnsServer *DNSServer) Stop() {
 		return
 	}
 
+	//restore DNS config for Linux
+	if config.Netclient().Host.OS == "linux" {
+		err := RestoreDNSConfig()
+		if err != nil {
+			slog.Error("Restore DNS conig failed", "error", err.Error())
+		}
+	}
+
 	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
 	defer cancel()
 
@@ -107,12 +115,4 @@ func (dnsServer *DNSServer) Stop() {
 
 	dnsServer.AddrStr = ""
 	dnsServer.DnsServer = nil
-
-	//restore DNS config for Linux
-	if config.Netclient().Host.OS == "linux" {
-		err := RestoreDNSConfig()
-		if err != nil {
-			slog.Error("Restore DNS conig failed", "error", err.Error())
-		}
-	}
 }
diff --git a/dns/resolver.go b/dns/resolver.go
@@ -56,8 +56,10 @@ func handleDNSRequest(w dns.ResponseWriter, r *dns.Msg) {
 					continue
 				}
 
-				reply.Answer = append(reply.Answer, resp.Answer[0])
-				break
+				if len(resp.Answer) > 0 {
+					reply.Answer = append(reply.Answer, resp.Answer[0])
+					break
+				}
 			}
 		} else {
 			reply.Rcode = dns.RcodeNameError

diff --git a/functions/mqhandlers.go b/functions/mqhandlers.go
@@ -398,7 +398,7 @@ func resetInterfaceFunc() {
 	wireguard.SetRoutesFromCache()
 
 	//Setup resolveconf for Linux
-	if config.Netclient().Host.OS == "linux" && dns.GetDNSServerInstance().AddrStr != "" {
+	if config.Netclient().Host.OS == "linux" && dns.GetDNSServerInstance().AddrStr != "" && (config.Netclient().DNSManagerType == dns.DNS_MANAGER_STUB || config.Netclient().DNSManagerType == dns.DNS_MANAGER_UPLINK) {
 		dns.SetupDNSConfig()
 	}
 }