feat(network): add support for forward guest localhost DNS for unikraft

pkg/unikontainers/types/types.go

@@ -45,12 +45,13 @@ type VMM interface {
 }
 
 type NetDevParams struct {
-	IP      string // The veth device IP
-	Mask    string // The veth device mask
-	Gateway string // The veth device gateway
-	MAC     string // The MAC address of the guest network device
-	TapDev  string // The tap device name
-	MTU     int    // The MTU value of the tap device
+	IP        string // The veth device IP
+	Mask      string // The veth device mask
+	Gateway   string // The veth device gateway
+	MAC       string // The MAC address of the guest network device
+	TapDev    string // The tap device name
+	MTU       int    // The MTU value of the tap device
+	DNSServer string // The resolver IP the guest should be configured with, empty if unset
 }
 
 type BlockDevParams struct {

pkg/unikontainers/unikernels/unikraft.go

@@ -27,6 +27,10 @@ import (
 const UnikraftUnikernel string = "unikraft"
 const UnikraftCompatVersion string = "0.16.1"
 
+// defaultDNSServer is used when no DNS forwarding resolver IP was set up by
+// the network manager.
+const defaultDNSServer string = "8.8.8.8"
+
 var ErrUndefinedVersion = errors.New("version is undefined, using default version")
 var ErrVersionParsing = errors.New("failed to parse provided version, using default version")
 
@@ -107,10 +111,14 @@ func (u *Unikraft) Init(data types.UnikernelParams) error {
 	u.Monitor = data.Monitor
 	u.Command = strings.Join(data.CmdLine, " ")
 
-	return u.configureUnikraftArgs(data.Rootfs.Type, data.Net.IP, data.Net.Gateway, data.Net.Mask)
+	return u.configureUnikraftArgs(data.Rootfs.Type, data.Net.IP, data.Net.Gateway, data.Net.Mask, data.Net.DNSServer)
 }
 
-func (u *Unikraft) configureUnikraftArgs(rootFsType, ethDeviceIP, ethDeviceGateway, ethDeviceMask string) error {
+func (u *Unikraft) configureUnikraftArgs(rootFsType, ethDeviceIP, ethDeviceGateway, ethDeviceMask, dnsServer string) error {
+	if dnsServer == "" {
+		dnsServer = defaultDNSServer
+	}
+
 	setCompatArgs := func() {
 		u.Net.Address = "netdev.ipv4_addr=" + ethDeviceIP
 		u.Net.Gateway = "netdev.ipv4_gw_addr=" + ethDeviceGateway
@@ -125,7 +133,7 @@ func (u *Unikraft) configureUnikraftArgs(rootFsType, ethDeviceIP, ethDeviceGatew
 	}
 
 	setCurrentArgs := func() {
-		u.Net.Address = "netdev.ip=" + ethDeviceIP + "/24:" + ethDeviceGateway + ":8.8.8.8"
+		u.Net.Address = "netdev.ip=" + ethDeviceIP + "/24:" + ethDeviceGateway + ":" + dnsServer
 		switch rootFsType {
 		case "initrd":
 			// TODO: This needs better handling. We need to revisit this

tests/e2e/test_cases.go

@@ -1241,5 +1241,22 @@ func dockerTestCases() []containerTestArgs {
 			Skippable:      false,
 			TestFunc:       namespaceTest,
 		},
+		{
+			Image:          "ghcr.io/alimx07/dns-test-qemu-unikraft-initrd:latest",
+			Name:           "Qemu-unikraft-dns-external",
+			Devmapper:      false,
+			Seccomp:        true,
+			UID:            0,
+			GID:            0,
+			Groups:         []int64{},
+			Memory:         "",
+			Cli:            "",
+			Volumes:        []containerVolume{},
+			StaticNet:      false,
+			SideContainers: []string{},
+			Skippable:      true,
+			ExpectOut:      "Address: 8.8.8.8",
+			TestFunc:       matchTest,
+		},
 	}
 }