Merge pull request #650 from rancher-sandbox/hosts

Allow adding static names to hostresolver

Author: AkihiroSuda

cmd/limactl/debug.go

@@ -47,7 +47,7 @@ func debugDNSAction(cmd *cobra.Command, args []string) error {
 			return err
 		}
 	}
-	srv, err := dns.Start(udpLocalPort, tcpLocalPort, ipv6)
+	srv, err := dns.Start(udpLocalPort, tcpLocalPort, ipv6, map[string]string{})
 	if err != nil {
 		return err
 	}

examples/docker.yaml

@@ -23,6 +23,10 @@ containerd:
   user: false
 provision:
 - mode: system
+  # This script defines the host.docker.internal hostname when hostResolver is disabled.
+  # It is also needed for lima 0.8.2 and earlier, which does not support hostResolver.hosts.
+  # Names defined in /etc/hosts inside the VM are not resolved inside containers when
+  # using the hostResolver; use hostResolver.hosts instead (requires lima 0.8.3 or later).
   script: |
     #!/bin/sh
     sed -i 's/host.lima.internal.*/host.lima.internal host.docker.internal/' /etc/hosts
@@ -56,6 +60,11 @@ probes:
       exit 1
     fi
   hint: See "/var/log/cloud-init-output.log". in the guest
+hostResolver:
+  # hostResolver.hosts requires lima 0.8.3 or later. Names defined here will also
+  # resolve inside containers, and not just inside the VM itself.
+  hosts:
+    host.docker.internal: host.lima.internal
 portForwards:
 - guestSocket: "/run/user/{{.UID}}/docker.sock"
   hostSocket: "{{.Dir}}/sock/docker.sock"

pkg/cidata/cidata.TEMPLATE.d/boot/06-etc-hosts.sh

@@ -1,5 +1,8 @@
 #!/bin/bash
 set -eux -o pipefail
 
+# Define host.lima.internal in case the hostResolver is disabled. When using
+# the hostResolver, the name is provided by the lima resolver itself because
+# it doesn't have access to /etc/hosts inside the VM.
 sed -i '/host.lima.internal/d' /etc/hosts
 echo -e "${LIMA_CIDATA_SLIRP_GATEWAY}\thost.lima.internal" >>/etc/hosts

pkg/hostagent/dns/dns.go

@@ -7,6 +7,7 @@ import (
 	"net"
 	"strings"
 
+	"github.com/lima-vm/lima/pkg/limayaml"
 	"github.com/miekg/dns"
 	"github.com/sirupsen/logrus"
 )
@@ -19,6 +20,8 @@ type Handler struct {
 	clientConfig *dns.ClientConfig
 	clients      []*dns.Client
 	IPv6         bool
+	cname        map[string]string
+	ip           map[string]net.IP
 }
 
 type Server struct {
@@ -44,7 +47,7 @@ func newStaticClientConfig(ips []net.IP) (*dns.ClientConfig, error) {
 	return dns.ClientConfigFromReader(r)
 }
 
-func newHandler(IPv6 bool) (dns.Handler, error) {
+func newHandler(IPv6 bool, hosts map[string]string) (dns.Handler, error) {
 	cc, err := dns.ClientConfigFromFile("/etc/resolv.conf")
 	if err != nil {
 		fallbackIPs := []net.IP{net.ParseIP("8.8.8.8"), net.ParseIP("1.1.1.1")}
@@ -62,6 +65,15 @@ func newHandler(IPv6 bool) (dns.Handler, error) {
 		clientConfig: cc,
 		clients:      clients,
 		IPv6:         IPv6,
+		cname:        make(map[string]string),
+		ip:           make(map[string]net.IP),
+	}
+	for host, address := range hosts {
+		if ip := net.ParseIP(address); ip != nil {
+			h.ip[host] = ip
+		} else {
+			h.cname[host] = limayaml.Cname(address)
+		}
 	}
 	return h, nil
 }
@@ -82,14 +94,32 @@ func (h *Handler) handleQuery(w dns.ResponseWriter, req *dns.Msg) {
 		switch q.Qtype {
 		case dns.TypeAAAA:
 			if !h.IPv6 {
+				handled = true
 				break
 			}
 			fallthrough
 		case dns.TypeCNAME, dns.TypeA:
-			cname, err := net.LookupCNAME(q.Name)
-			if err != nil {
+			cname := q.Name
+			seen := make(map[string]bool)
+			for {
+				// break cyclic definition
+				if seen[cname] {
+					break
+				}
+				if _, ok := h.cname[cname]; ok {
+					seen[cname] = true
+					cname = h.cname[cname]
+					continue
+				}
 				break
 			}
+			var err error
+			if _, ok := h.ip[cname]; !ok {
+				cname, err = net.LookupCNAME(cname)
+				if err != nil {
+					break
+				}
+			}
 			if cname != "" && cname != q.Name {
 				hdr.Rrtype = dns.TypeCNAME
 				a := &dns.CNAME{
@@ -103,7 +133,13 @@ func (h *Handler) handleQuery(w dns.ResponseWriter, req *dns.Msg) {
 				break
 			}
 			hdr.Name = cname
-			addrs, err := net.LookupIP(q.Name)
+			var addrs []net.IP
+			if _, ok := h.ip[cname]; ok {
+				addrs = []net.IP{h.ip[cname]}
+				err = nil
+			} else {
+				addrs, err = net.LookupIP(cname)
+			}
 			if err == nil && len(addrs) > 0 {
 				for _, ip := range addrs {
 					var a dns.RR
@@ -219,8 +255,8 @@ func (h *Handler) ServeDNS(w dns.ResponseWriter, req *dns.Msg) {
 	}
 }
 
-func Start(udpLocalPort, tcpLocalPort int, IPv6 bool) (*Server, error) {
-	h, err := newHandler(IPv6)
+func Start(udpLocalPort, tcpLocalPort int, IPv6 bool, hosts map[string]string) (*Server, error) {
+	h, err := newHandler(IPv6, hosts)
 	if err != nil {
 		return nil, err
 	}

pkg/hostagent/hostagent.go

@@ -27,6 +27,7 @@ import (
 	"github.com/lima-vm/lima/pkg/hostagent/events"
 	"github.com/lima-vm/lima/pkg/limayaml"
 	"github.com/lima-vm/lima/pkg/qemu"
+	qemuconst "github.com/lima-vm/lima/pkg/qemu/const"
 	"github.com/lima-vm/lima/pkg/sshutil"
 	"github.com/lima-vm/lima/pkg/store"
 	"github.com/lima-vm/lima/pkg/store/filenames"
@@ -40,6 +41,7 @@ type HostAgent struct {
 	udpDNSLocalPort int
 	tcpDNSLocalPort int
 	instDir         string
+	instName        string
 	sshConfig       *ssh.SSHConfig
 	portForwarder   *portForwarder
 	onClose         []func() error // LIFO
@@ -145,6 +147,7 @@ func New(instName string, stdout io.Writer, sigintCh chan os.Signal, opts ...Opt
 		udpDNSLocalPort: udpDNSLocalPort,
 		tcpDNSLocalPort: tcpDNSLocalPort,
 		instDir:         inst.Dir,
+		instName:        instName,
 		sshConfig:       sshConfig,
 		portForwarder:   newPortForwarder(sshConfig, sshLocalPort, rules),
 		qExe:            qExe,
@@ -249,7 +252,10 @@ func (a *HostAgent) Run(ctx context.Context) error {
 	}()
 
 	if *a.y.HostResolver.Enabled {
-		dnsServer, err := dns.Start(a.udpDNSLocalPort, a.tcpDNSLocalPort, *a.y.HostResolver.IPv6)
+		hosts := a.y.HostResolver.Hosts
+		hosts["host.lima.internal."] = qemuconst.SlirpGateway
+		hosts[fmt.Sprintf("lima-%s.", a.instName)] = qemuconst.SlirpIPAddress
+		dnsServer, err := dns.Start(a.udpDNSLocalPort, a.tcpDNSLocalPort, *a.y.HostResolver.IPv6, hosts)
 		if err != nil {
 			return fmt.Errorf("cannot start DNS server: %w", err)
 		}

pkg/limayaml/default.yaml

@@ -264,6 +264,12 @@ hostResolver:
   enabled: null
   # Default: false
   ipv6: null
+  # Static names can be defined here as an alternative to adding them to the hosts /etc/hosts.
+  # Values can be either other hostnames, or IP addresses. The host.lima.internal name is
+  # predefined to specify the gateway address to the host.
+  hosts:
+    # guest.name: 127.1.1.1
+    # host.name: host.lima.internal
 
 # If useHostResolver is false, then the following rules apply for configuring dns:
 # Explicitly set DNS addresses for qemu user-mode networking. By default qemu picks *one*

pkg/limayaml/defaults.go

@@ -10,6 +10,7 @@ import (
 	"path/filepath"
 	"runtime"
 	"strconv"
+	"strings"
 	"text/template"
 
 	"github.com/lima-vm/lima/pkg/guestagent/api"
@@ -188,6 +189,19 @@ func FillDefault(y, d, o *LimaYAML, filePath string) {
 		y.SSH.ForwardAgent = pointer.Bool(false)
 	}
 
+	hosts := make(map[string]string)
+	// Values can be either names or IP addresses. Name values are canonicalized in the hostResolver.
+	for k, v := range d.HostResolver.Hosts {
+		hosts[Cname(k)] = v
+	}
+	for k, v := range y.HostResolver.Hosts {
+		hosts[Cname(k)] = v
+	}
+	for k, v := range o.HostResolver.Hosts {
+		hosts[Cname(k)] = v
+	}
+	y.HostResolver.Hosts = hosts
+
 	y.Provision = append(append(o.Provision, y.Provision...), d.Provision...)
 	for i := range y.Provision {
 		provision := &y.Provision[i]
@@ -498,3 +512,11 @@ func IsNativeArch(arch Arch) bool {
 	nativeAARCH64 := arch == AARCH64 && runtime.GOARCH == "arm64"
 	return nativeX8664 || nativeAARCH64
 }
+
+func Cname(host string) string {
+	host = strings.ToLower(host)
+	if !strings.HasSuffix(host, ".") {
+		host += "."
+	}
+	return host
+}

pkg/limayaml/defaults_test.go

@@ -93,6 +93,11 @@ func TestFillDefault(t *testing.T) {
 	// All these slices and maps are empty in "builtin". Add minimal entries here to see that
 	// their values are retained and defaults for their fields are applied correctly.
 	y = LimaYAML{
+		HostResolver: HostResolver{
+			Hosts: map[string]string{
+				"MY.Host": "host.lima.internal",
+			},
+		},
 		Mounts: []Mount{
 			{Location: "/tmp"},
 		},
@@ -123,6 +128,10 @@ func TestFillDefault(t *testing.T) {
 	}
 
 	expect := builtin
+	expect.HostResolver.Hosts = map[string]string{
+		"my.host.": "host.lima.internal",
+	}
+
 	expect.Mounts = y.Mounts
 	expect.Mounts[0].Writable = pointer.Bool(false)
 	expect.Mounts[0].SSHFS.Cache = pointer.Bool(true)
@@ -202,6 +211,9 @@ func TestFillDefault(t *testing.T) {
 		HostResolver: HostResolver{
 			Enabled: pointer.Bool(false),
 			IPv6:    pointer.Bool(true),
+			Hosts: map[string]string{
+				"default": "localhost",
+			},
 		},
 		PropagateProxyEnv: pointer.Bool(false),
 
@@ -255,6 +267,9 @@ func TestFillDefault(t *testing.T) {
 	expect.Containerd.Archives[0].Arch = *d.Arch
 	expect.Mounts[0].SSHFS.Cache = pointer.Bool(true)
 	expect.Mounts[0].SSHFS.FollowSymlinks = pointer.Bool(false)
+	expect.HostResolver.Hosts = map[string]string{
+		"default.": d.HostResolver.Hosts["default"],
+	}
 
 	y = LimaYAML{}
 	FillDefault(&y, &d, &LimaYAML{}, filePath)
@@ -277,6 +292,8 @@ func TestFillDefault(t *testing.T) {
 	expect.Mounts = append(d.Mounts, y.Mounts...)
 	expect.Networks = append(d.Networks, y.Networks...)
 
+	expect.HostResolver.Hosts["default."] = d.HostResolver.Hosts["default"]
+
 	// d.DNS will be ignored, and not appended to y.DNS
 
 	// "TWO" does not exist in filledDefaults.Env, so is set from d.Env
@@ -322,6 +339,9 @@ func TestFillDefault(t *testing.T) {
 		HostResolver: HostResolver{
 			Enabled: pointer.Bool(false),
 			IPv6:    pointer.Bool(false),
+			Hosts: map[string]string{
+				"override.": "underflow",
+			},
 		},
 		PropagateProxyEnv: pointer.Bool(false),
 
@@ -386,6 +406,9 @@ func TestFillDefault(t *testing.T) {
 	expect.PortForwards = append(append(o.PortForwards, y.PortForwards...), d.PortForwards...)
 	expect.Containerd.Archives = append(append(o.Containerd.Archives, y.Containerd.Archives...), d.Containerd.Archives...)
 
+	expect.HostResolver.Hosts["default."] = d.HostResolver.Hosts["default"]
+	expect.HostResolver.Hosts["my.host."] = d.HostResolver.Hosts["host.lima.internal"]
+
 	// o.Mounts just makes d.Mounts[0] writable because the Location matches
 	expect.Mounts = append(d.Mounts, y.Mounts...)
 	expect.Mounts[0].Writable = pointer.Bool(true)

pkg/limayaml/limayaml.go

@@ -137,8 +137,9 @@ type Network struct {
 }
 
 type HostResolver struct {
-	Enabled *bool `yaml:"enabled,omitempty" json:"enabled,omitempty"`
-	IPv6    *bool `yaml:"ipv6,omitempty" json:"ipv6,omitempty"`
+	Enabled *bool             `yaml:"enabled,omitempty" json:"enabled,omitempty"`
+	IPv6    *bool             `yaml:"ipv6,omitempty" json:"ipv6,omitempty"`
+	Hosts   map[string]string `yaml:"hosts,omitempty" json:"hosts,omitempty"`
 }
 
 // DEPRECATED types below