Merge pull request #438 from redoste/fix-ipv6-dns

Fix DNS not being accessible with slirp4netns on hosts with IPv6-only nameservers
rootless-containers · May 14, 2024 · e484dd6 · e484dd6
2 parents af744bc + ada96bd
commit e484dd6
Show file tree

Hide file tree

Showing 6 changed files with 30 additions and 11 deletions.
diff --git a/pkg/child/resolvconf.go b/pkg/child/resolvconf.go
@@ -1,5 +1,12 @@
 package child
 
-func generateResolvConf(dns string) []byte {
-	return []byte("nameserver " + dns + "\n")
+import "strings"
+
+func generateResolvConf(dns []string) []byte {
+	var sb strings.Builder
+
+	for _, nameserver := range dns {
+		sb.WriteString("nameserver " + nameserver + "\n")
+	}
+	return []byte(sb.String())
 }
diff --git a/pkg/messages/messages.go b/pkg/messages/messages.go
@@ -59,7 +59,7 @@ type ParentInitNetworkDriverCompleted struct {
 	IP      string
 	Netmask int
 	Gateway string
-	DNS     string
+	DNS     []string
 	MTU     int
 	// NetworkDriverOpaque strings are specific to driver
 	NetworkDriverOpaque map[string]string

diff --git a/pkg/network/lxcusernic/lxcusernic.go b/pkg/network/lxcusernic/lxcusernic.go
@@ -184,7 +184,7 @@ func (d *childDriver) ConfigureNetworkChild(netmsg *messages.ParentInitNetworkDr
 	netmask, _ := p.SubnetMask().Size()
 	netmsg.Netmask = netmask
 	netmsg.Gateway = p.Router()[0].To4().String()
-	netmsg.DNS = p.DNS()[0].To4().String()
+	netmsg.DNS = []string{p.DNS()[0].To4().String()}
 	go dhcpRenewRoutine(c, dev, p.YourIPAddr.To4(), p.IPAddressLeaseTime(time.Hour), detachedNetNSPath)
 	return dev, nil
 }

diff --git a/pkg/network/pasta/pasta.go b/pkg/network/pasta/pasta.go
@@ -169,13 +169,13 @@ func (d *parentDriver) ConfigureNetwork(childPID int, stateDir, detachedNetNSPat
 	netmsg.IP = address.String()
 	netmsg.Netmask = netmask
 	netmsg.Gateway = gateway.String()
-	netmsg.DNS = dns.String()
+	netmsg.DNS = []string{dns.String()}
 
 	d.infoMu.Lock()
 	d.info = func() *api.NetworkDriverInfo {
 		return &api.NetworkDriverInfo{
 			Driver:         DriverName,
-			DNS:            []net.IP{net.ParseIP(netmsg.DNS)},
+			DNS:            []net.IP{net.ParseIP(netmsg.DNS[0])},
 			ChildIP:        net.ParseIP(netmsg.IP),
 			DynamicChildIP: false,
 		}

diff --git a/pkg/network/slirp4netns/slirp4netns.go b/pkg/network/slirp4netns/slirp4netns.go
@@ -243,6 +243,7 @@ func (d *parentDriver) ConfigureNetwork(childPID int, stateDir, detachedNetNSPat
 	}
 	netmsg := messages.ParentInitNetworkDriverCompleted{
 		Dev: tap,
+		DNS: make([]string, 0, 2),
 		MTU: d.mtu,
 	}
 	if d.ipnet != nil {
@@ -262,19 +263,30 @@ func (d *parentDriver) ConfigureNetwork(childPID int, stateDir, detachedNetNSPat
 		if err != nil {
 			return nil, common.Seq(cleanups), err
 		}
-		netmsg.DNS = x.String()
+		netmsg.DNS = append(netmsg.DNS, x.String())
 	} else {
 		netmsg.IP = "10.0.2.100"
 		netmsg.Netmask = 24
 		netmsg.Gateway = "10.0.2.2"
-		netmsg.DNS = "10.0.2.3"
+		netmsg.DNS = append(netmsg.DNS, "10.0.2.3")
+	}
+
+	if d.enableIPv6 {
+		// for now slirp4netns only supports fd00::3 as v6 nameserver
+		// https://github.com/rootless-containers/slirp4netns/blob/ee1542e1532e6a7f266b8b6118973ab3b10a8bb5/slirp4netns.c#L272
+		netmsg.DNS = append(netmsg.DNS, "fd00::3")
+	}
+
+	apiDNS := make([]net.IP, 0, cap(netmsg.DNS))
+	for _, nameserver := range netmsg.DNS {
+		apiDNS = append(apiDNS, net.ParseIP(nameserver))
 	}
 
 	d.infoMu.Lock()
 	d.info = func() *api.NetworkDriverInfo {
 		return &api.NetworkDriverInfo{
 			Driver:         DriverName,
-			DNS:            []net.IP{net.ParseIP(netmsg.DNS)},
+			DNS:            apiDNS,
 			ChildIP:        net.ParseIP(netmsg.IP),
 			DynamicChildIP: false,
 		}

diff --git a/pkg/network/vpnkit/vpnkit.go b/pkg/network/vpnkit/vpnkit.go
@@ -127,7 +127,7 @@ func (d *parentDriver) ConfigureNetwork(childPID int, stateDir, detachedNetNSPat
 		IP:      vif.IP.String(),
 		Netmask: 24,
 		Gateway: "192.168.65.1",
-		DNS:     "192.168.65.1",
+		DNS:     []string{"192.168.65.1"},
 		MTU:     d.mtu,
 		NetworkDriverOpaque: map[string]string{
 			opaqueMAC:    vif.ClientMAC.String(),
@@ -139,7 +139,7 @@ func (d *parentDriver) ConfigureNetwork(childPID int, stateDir, detachedNetNSPat
 	d.info = func() *api.NetworkDriverInfo {
 		return &api.NetworkDriverInfo{
 			Driver:         DriverName,
-			DNS:            []net.IP{net.ParseIP(netmsg.DNS)},
+			DNS:            []net.IP{net.ParseIP(netmsg.DNS[0])},
 			ChildIP:        net.ParseIP(netmsg.IP),
 			DynamicChildIP: false,
 		}