kilo/pkg/mesh/ip.go
Lucas Servén Marín 51df7fc4e3
pkg/mesh: don't let hostname resolution stop mesh
If the hostname fails to resolve, this should not be considered a
blocking error. Most likely, it means that the hostname is simply not
resolvable, which should not be a requirement to run Kilo. In this case,
simply try to find a valid IP from other sources.
2019-05-17 18:09:31 +02:00

378 lines
9.5 KiB
Go

// Copyright 2019 the Kilo authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package mesh
import (
"errors"
"fmt"
"net"
"sort"
"github.com/vishvananda/netlink"
)
// getIP returns a private and public IP address for the local node.
// It selects the private IP address in the following order:
// - private IP to which hostname resolves
// - private IP assigned to interface of default route
// - private IP assigned to local interface
// - public IP to which hostname resolves
// - public IP assigned to interface of default route
// - public IP assigned to local interface
// It selects the public IP address in the following order:
// - public IP to which hostname resolves
// - public IP assigned to interface of default route
// - public IP assigned to local interface
// - private IP to which hostname resolves
// - private IP assigned to interface of default route
// - private IP assigned to local interface
// - if no IP was found, return nil and an error.
func getIP(hostname string, ignoreIfaces ...int) (*net.IPNet, *net.IPNet, error) {
ignore := make(map[string]struct{})
for i := range ignoreIfaces {
if ignoreIfaces[i] == 0 {
// Only ignore valid interfaces.
continue
}
iface, err := net.InterfaceByIndex(ignoreIfaces[i])
if err != nil {
return nil, nil, fmt.Errorf("failed to find interface %d: %v", ignoreIfaces[i], err)
}
ips, err := ipsForInterface(iface)
if err != nil {
return nil, nil, err
}
for _, ip := range ips {
ignore[ip.String()] = struct{}{}
ignore[oneAddressCIDR(ip.IP).String()] = struct{}{}
}
}
var hostPriv, hostPub []*net.IPNet
{
// Check IPs to which hostname resolves first.
ips := ipsForHostname(hostname)
for _, ip := range ips {
ok, mask, err := assignedToInterface(ip)
if err != nil {
return nil, nil, fmt.Errorf("failed to search locally assigned addresses: %v", err)
}
if !ok {
continue
}
ip.Mask = mask
if isPublic(ip) {
hostPub = append(hostPub, ip)
continue
}
hostPriv = append(hostPriv, ip)
}
sortIPs(hostPriv)
sortIPs(hostPub)
}
var defaultPriv, defaultPub []*net.IPNet
{
// Check IPs on interface for default route next.
iface, err := defaultInterface()
if err != nil {
return nil, nil, err
}
ips, err := ipsForInterface(iface)
if err != nil {
return nil, nil, err
}
for _, ip := range ips {
if isLocal(ip.IP) {
continue
}
if isPublic(ip) {
defaultPub = append(defaultPub, ip)
continue
}
defaultPriv = append(defaultPriv, ip)
}
sortIPs(defaultPriv)
sortIPs(defaultPub)
}
var interfacePriv, interfacePub []*net.IPNet
{
// Finally look for IPs on all interfaces.
ips, err := ipsForAllInterfaces()
if err != nil {
return nil, nil, err
}
for _, ip := range ips {
if isLocal(ip.IP) {
continue
}
if isPublic(ip) {
interfacePub = append(interfacePub, ip)
continue
}
interfacePriv = append(interfacePriv, ip)
}
sortIPs(interfacePriv)
sortIPs(interfacePub)
}
var priv, pub, tmpPriv, tmpPub []*net.IPNet
tmpPriv = append(tmpPriv, hostPriv...)
tmpPriv = append(tmpPriv, defaultPriv...)
tmpPriv = append(tmpPriv, interfacePriv...)
tmpPub = append(tmpPub, hostPub...)
tmpPub = append(tmpPub, defaultPub...)
tmpPub = append(tmpPub, interfacePub...)
for i := range tmpPriv {
if _, ok := ignore[tmpPriv[i].String()]; ok {
continue
}
priv = append(priv, tmpPriv[i])
}
for i := range tmpPub {
if _, ok := ignore[tmpPub[i].String()]; ok {
continue
}
pub = append(pub, tmpPub[i])
}
if len(priv) == 0 && len(pub) == 0 {
return nil, nil, errors.New("no valid IP was found")
}
if len(priv) == 0 {
priv = pub
}
if len(pub) == 0 {
pub = priv
}
return priv[0], pub[0], nil
}
// sortIPs sorts IPs so the result is stable.
// It will first sort IPs by type, to prefer selecting
// IPs of the same type, and then by value.
func sortIPs(ips []*net.IPNet) {
sort.Slice(ips, func(i, j int) bool {
i4, j4 := ips[i].IP.To4(), ips[j].IP.To4()
if i4 != nil && j4 == nil {
return true
}
if j4 != nil && i4 == nil {
return false
}
return ips[i].String() < ips[j].String()
})
}
func assignedToInterface(ip *net.IPNet) (bool, net.IPMask, error) {
links, err := netlink.LinkList()
if err != nil {
return false, nil, fmt.Errorf("failed to list interfaces: %v", err)
}
// Sort the links for stability.
sort.Slice(links, func(i, j int) bool {
return links[i].Attrs().Name < links[j].Attrs().Name
})
for _, link := range links {
addrs, err := netlink.AddrList(link, netlink.FAMILY_ALL)
if err != nil {
return false, nil, fmt.Errorf("failed to list addresses for %s: %v", link.Attrs().Name, err)
}
// Sort the IPs for stability.
sort.Slice(addrs, func(i, j int) bool {
return addrs[i].String() < addrs[j].String()
})
for i := range addrs {
if ip.IP.Equal(addrs[i].IP) {
return true, addrs[i].Mask, nil
}
}
}
return false, nil, nil
}
func isLocal(ip net.IP) bool {
return ip.IsLoopback() || ip.IsLinkLocalMulticast() || ip.IsLinkLocalUnicast()
}
func isPublic(ip *net.IPNet) bool {
// Check RFC 1918 addresses.
if ip4 := ip.IP.To4(); ip4 != nil {
switch true {
// Check for 10.0.0.0/8.
case ip4[0] == 10:
return false
// Check for 172.16.0.0/12.
case ip4[0] == 172 && ip4[1]&0xf0 == 0x01:
return false
// Check for 192.168.0.0/16.
case ip4[0] == 192 && ip4[1] == 168:
return false
default:
return true
}
}
// Check RFC 4193 addresses.
if len(ip.IP) == net.IPv6len {
switch true {
// Check for fd00::/8.
case ip.IP[0] == 0xfd && ip.IP[1] == 0x00:
return false
default:
return true
}
}
return false
}
// ipsForHostname returns a slice of IPs to which the
// given hostname resolves.
func ipsForHostname(hostname string) []*net.IPNet {
if ip := net.ParseIP(hostname); ip != nil {
return []*net.IPNet{oneAddressCIDR(ip)}
}
ips, err := net.LookupIP(hostname)
if err != nil {
// Most likely the hostname is not resolvable.
return nil
}
nets := make([]*net.IPNet, len(ips))
for i := range ips {
nets[i] = oneAddressCIDR(ips[i])
}
return nets
}
// ipsForAllInterfaces returns a slice of IPs assigned to all the
// interfaces on the host.
func ipsForAllInterfaces() ([]*net.IPNet, error) {
ifaces, err := net.Interfaces()
if err != nil {
return nil, fmt.Errorf("failed to list interfaces: %v", err)
}
var nets []*net.IPNet
for _, iface := range ifaces {
ips, err := ipsForInterface(&iface)
if err != nil {
return nil, fmt.Errorf("failed to list addresses for %s: %v", iface.Name, err)
}
nets = append(nets, ips...)
}
return nets, nil
}
// ipsForInterface returns a slice of IPs assigned to the given interface.
func ipsForInterface(iface *net.Interface) ([]*net.IPNet, error) {
link, err := netlink.LinkByIndex(iface.Index)
if err != nil {
return nil, fmt.Errorf("failed to get link: %s", err)
}
addrs, err := netlink.AddrList(link, netlink.FAMILY_ALL)
if err != nil {
return nil, fmt.Errorf("failed to list addresses for %s: %v", iface.Name, err)
}
var ips []*net.IPNet
for _, a := range addrs {
if a.IPNet != nil {
ips = append(ips, a.IPNet)
}
}
return ips, nil
}
// interfacesForIP returns a slice of interfaces withthe given IP.
func interfacesForIP(ip *net.IPNet) ([]net.Interface, error) {
ifaces, err := net.Interfaces()
if err != nil {
return nil, fmt.Errorf("failed to list interfaces: %v", err)
}
var interfaces []net.Interface
for _, iface := range ifaces {
ips, err := ipsForInterface(&iface)
if err != nil {
return nil, fmt.Errorf("failed to list addresses for %s: %v", iface.Name, err)
}
for i := range ips {
if ip.IP.Equal(ips[i].IP) {
interfaces = append(interfaces, iface)
break
}
}
}
if len(interfaces) == 0 {
return nil, fmt.Errorf("no interface has %s assigned", ip.String())
}
return interfaces, nil
}
// defaultInterface returns the interface for the default route of the host.
func defaultInterface() (*net.Interface, error) {
routes, err := netlink.RouteList(nil, netlink.FAMILY_ALL)
if err != nil {
return nil, err
}
for _, route := range routes {
if route.Dst == nil || route.Dst.String() == "0.0.0.0/0" || route.Dst.String() == "::/0" {
if route.LinkIndex <= 0 {
return nil, errors.New("failed to determine interface of route")
}
return net.InterfaceByIndex(route.LinkIndex)
}
}
return nil, errors.New("failed to find default route")
}
type allocator struct {
bits int
cidr *net.IPNet
current net.IP
}
func newAllocator(cidr net.IPNet) *allocator {
_, bits := cidr.Mask.Size()
current := make(net.IP, len(cidr.IP))
copy(current, cidr.IP)
if ip4 := current.To4(); ip4 != nil {
current = ip4
}
return &allocator{
bits: bits,
cidr: &cidr,
current: current,
}
}
func (a *allocator) next() *net.IPNet {
if a.current == nil {
return nil
}
for i := len(a.current) - 1; i >= 0; i-- {
a.current[i]++
// if we haven't overflowed, then we can exit.
if a.current[i] != 0 {
break
}
}
if !a.cidr.Contains(a.current) {
a.current = nil
}
ip := make(net.IP, len(a.current))
copy(ip, a.current)
return &net.IPNet{IP: ip, Mask: net.CIDRMask(a.bits, a.bits)}
}