func (daemon *Daemon) checkLocaldns() error {
resolvConf, err := resolvconf.Get()
if err != nil {
return err
}
if len(daemon.config.Dns) == 0 && utils.CheckLocalDns(resolvConf) {
log.Printf("Local (127.0.0.1) DNS resolver found in resolv.conf and containers can't use it. Using default external servers : %v\n", DefaultDns)
daemon.config.Dns = DefaultDns
}
return nil
}
func (container *Container) setupContainerDns() error {
if container.ResolvConfPath != "" {
return nil
}
var (
config = container.hostConfig
daemon = container.daemon
)
if config.NetworkMode == "host" {
container.ResolvConfPath = "/etc/resolv.conf"
return nil
}
resolvConf, err := resolvconf.Get()
if err != nil {
return err
}
// If custom dns exists, then create a resolv.conf for the container
if len(config.Dns) > 0 || len(daemon.config.Dns) > 0 || len(config.DnsSearch) > 0 || len(daemon.config.DnsSearch) > 0 {
var (
dns = resolvconf.GetNameservers(resolvConf)
dnsSearch = resolvconf.GetSearchDomains(resolvConf)
)
if len(config.Dns) > 0 {
dns = config.Dns
} else if len(daemon.config.Dns) > 0 {
dns = daemon.config.Dns
}
if len(config.DnsSearch) > 0 {
dnsSearch = config.DnsSearch
} else if len(daemon.config.DnsSearch) > 0 {
dnsSearch = daemon.config.DnsSearch
}
resolvConfPath, err := container.getRootResourcePath("resolv.conf")
if err != nil {
return err
}
container.ResolvConfPath = resolvConfPath
return resolvconf.Build(container.ResolvConfPath, dns, dnsSearch)
} else {
container.ResolvConfPath = "/etc/resolv.conf"
}
return nil
}
// CreateBridgeIface creates a network bridge interface on the host system with the name `ifaceName`,
// and attempts to configure it with an address which doesn't conflict with any other interface on the host.
// If it can't find an address which doesn't conflict, it will return an error.
func createBridge(bridgeIP string) error {
nameservers := []string{}
resolvConf, _ := resolvconf.Get()
// we don't check for an error here, because we don't really care
// if we can't read /etc/resolv.conf. So instead we skip the append
// if resolvConf is nil. It either doesn't exist, or we can't read it
// for some reason.
if resolvConf != nil {
nameservers = append(nameservers, resolvconf.GetNameserversAsCIDR(resolvConf)...)
}
var ifaceAddr string
if len(bridgeIP) != 0 {
_, _, err := net.ParseCIDR(bridgeIP)
if err != nil {
return err
}
ifaceAddr = bridgeIP
} else {
for _, addr := range addrs {
_, dockerNetwork, err := net.ParseCIDR(addr)
if err != nil {
return err
}
if err := networkdriver.CheckNameserverOverlaps(nameservers, dockerNetwork); err == nil {
if err := networkdriver.CheckRouteOverlaps(dockerNetwork); err == nil {
ifaceAddr = addr
break
} else {
utils.Debugf("%s %s", addr, err)
}
}
}
}
if ifaceAddr == "" {
return fmt.Errorf("Could not find a free IP address range for interface '%s'. Please configure its address manually and run 'docker -b %s'", bridgeIface, bridgeIface)
}
utils.Debugf("Creating bridge %s with network %s", bridgeIface, ifaceAddr)
if err := createBridgeIface(bridgeIface); err != nil {
return err
}
iface, err := net.InterfaceByName(bridgeIface)
if err != nil {
return err
}
ipAddr, ipNet, err := net.ParseCIDR(ifaceAddr)
if err != nil {
return err
}
if netlink.NetworkLinkAddIp(iface, ipAddr, ipNet); err != nil {
return fmt.Errorf("Unable to add private network: %s", err)
}
if err := netlink.NetworkLinkUp(iface); err != nil {
return fmt.Errorf("Unable to start network bridge: %s", err)
}
return nil
}