func GetDefaultMtu() (int, error) {
routes, err := netlink.NetworkGetRoutes()
if err != nil {
return -1, err
}
for _, r := range routes {
if r.Default {
return r.Iface.MTU, nil
}
}
return -1, ErrNoDefaultRoute
}
// RegisterNetwork registers a new network with the allocator
// and validates that it contains a valid ip that does not overlap
// with existing routes and nameservers
func RegisterNetwork(network *net.IPNet, nameservers []string) error {
lock.Lock()
defer lock.Unlock()
if err := checkExistingNetworkOverlaps(network); err != nil {
return err
}
routes, err := netlink.NetworkGetRoutes()
if err != nil {
return err
}
if err := checkRouteOverlaps(routes, network); err != nil {
return err
}
if err := checkNameserverOverlaps(nameservers, network); err != nil {
return err
}
return RegisterExistingNetwork(network)
}
// 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 CreateBridgeIface(config *DaemonConfig) error {
addrs := []string{
// Here we don't follow the convention of using the 1st IP of the range for the gateway.
// This is to use the same gateway IPs as the /24 ranges, which predate the /16 ranges.
// In theory this shouldn't matter - in practice there's bound to be a few scripts relying
// on the internal addressing or other stupid things like that.
// The shouldn't, but hey, let's not break them unless we really have to.
"172.17.42.1/16", // Don't use 172.16.0.0/16, it conflicts with EC2 DNS 172.16.0.23
"10.0.42.1/16", // Don't even try using the entire /8, that's too intrusive
"10.1.42.1/16",
"10.42.42.1/16",
"172.16.42.1/24",
"172.16.43.1/24",
"172.16.44.1/24",
"10.0.42.1/24",
"10.0.43.1/24",
"192.168.42.1/24",
"192.168.43.1/24",
"192.168.44.1/24",
}
nameservers := []string{}
resolvConf, _ := utils.GetResolvConf()
// 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, utils.GetNameserversAsCIDR(resolvConf)...)
}
var ifaceAddr string
if len(config.BridgeIp) != 0 {
_, _, err := net.ParseCIDR(config.BridgeIp)
if err != nil {
return err
}
ifaceAddr = config.BridgeIp
} else {
for _, addr := range addrs {
_, dockerNetwork, err := net.ParseCIDR(addr)
if err != nil {
return err
}
routes, err := netlink.NetworkGetRoutes()
if err != nil {
return err
}
if err := checkRouteOverlaps(routes, dockerNetwork); err == nil {
if err := checkNameserverOverlaps(nameservers, 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'", config.BridgeIface, config.BridgeIface)
}
utils.Debugf("Creating bridge %s with network %s", config.BridgeIface, ifaceAddr)
if err := createBridgeIface(config.BridgeIface); err != nil {
return err
}
iface, err := net.InterfaceByName(config.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
}