libpod: move slirp magic IPs to consts

Signed-off-by: Giuseppe Scrivano <[email protected]>

libpod/container_internal_linux.go

@@ -1527,7 +1527,7 @@ func (c *Container) generateResolvConf() (string, error) {
 		nameservers = resolvconf.GetNameservers(resolv.Content)
 		// slirp4netns has a built in DNS server.
 		if c.config.NetMode.IsSlirp4netns() {
-			nameservers = append([]string{"10.0.2.3"}, nameservers...)
+			nameservers = append([]string{slirp4netnsDNS}, nameservers...)
 		}
 	}
 
@@ -1607,7 +1607,7 @@ func (c *Container) getHosts() string {
 	if c.Hostname() != "" {
 		if c.config.NetMode.IsSlirp4netns() {
 			// When using slirp4netns, the interface gets a static IP
-			hosts += fmt.Sprintf("# used by slirp4netns\n%s\t%s %s\n", "10.0.2.100", c.Hostname(), c.config.Name)
+			hosts += fmt.Sprintf("# used by slirp4netns\n%s\t%s %s\n", slirp4netnsIP, c.Hostname(), c.config.Name)
 		} else {
 			hasNetNS := false
 			netNone := false

libpod/networking_linux.go

@@ -34,6 +34,15 @@ import (
 	"golang.org/x/sys/unix"
 )
 
+const (
+	// slirp4netnsIP is the IP used by slirp4netns to configure the tap device
+	// inside the network namespace.
+	slirp4netnsIP = "10.0.2.100"
+
+	// slirp4netnsDNS is the IP for the built-in DNS server in the slirp network
+	slirp4netnsDNS = "10.0.2.3"
+)
+
 // Get an OCICNI network config
 func (r *Runtime) getPodNetwork(id, name, nsPath string, networks []string, ports []ocicni.PortMapping, staticIP net.IP, staticMAC net.HardwareAddr, netDescriptions ContainerNetworkDescriptions) ocicni.PodNetwork {
 	var networkKey string
@@ -544,7 +553,7 @@ func (r *Runtime) setupRootlessPortMappingViaRLK(ctr *Container, netnsPath strin
 		ExitFD:    3,
 		ReadyFD:   4,
 		TmpDir:    ctr.runtime.config.Engine.TmpDir,
-		ChildIP:   "10.0.2.100",
+		ChildIP:   slirp4netnsIP,
 	}
 	cfgJSON, err := json.Marshal(cfg)
 	if err != nil {