func configureIface(ifname string, ipn ip.IP4Net, mtu int) error {
iface, err := netlink.LinkByName(ifname)
if err != nil {
return fmt.Errorf("failed to lookup interface %v", ifname)
}
err = netlink.AddrAdd(iface, &netlink.Addr{ipn.ToIPNet(), ""})
if err != nil {
return fmt.Errorf("failed to add IP address %v to %v: %v", ipn.String(), ifname, err)
}
err = netlink.LinkSetMTU(iface, mtu)
if err != nil {
return fmt.Errorf("failed to set MTU for %v: %v", ifname, err)
}
err = netlink.LinkSetUp(iface)
if err != nil {
return fmt.Errorf("failed to set interface %v to UP state: %v", ifname, err)
}
// explicitly add a route since there might be a route for a subnet already
// installed by Docker and then it won't get auto added
err = netlink.RouteAdd(&netlink.Route{
LinkIndex: iface.Attrs().Index,
Scope: netlink.SCOPE_UNIVERSE,
Dst: ipn.Network().ToIPNet(),
})
if err != nil && err != syscall.EEXIST {
return fmt.Errorf("Failed to add route (%v -> %v): %v", ipn.Network().String(), ifname, err)
}
return nil
}
func setupIPMasq(ipn ip.IP4Net) error {
ipt, err := iptables.New()
if err != nil {
return fmt.Errorf("failed to setup IP Masquerade. iptables was not found")
}
err = ipt.ClearChain("nat", "FLANNEL")
if err != nil {
return fmt.Errorf("Failed to create/clear FLANNEL chain in NAT table: %v", err)
}
rules := [][]string{
// This rule makes sure we don't NAT traffic within overlay network (e.g. coming out of docker0)
{"FLANNEL", "-d", ipn.String(), "-j", "ACCEPT"},
// NAT if it's not multicast traffic
{"FLANNEL", "!", "-d", "224.0.0.0/4", "-j", "MASQUERADE"},
// This rule will take everything coming from overlay and sent it to FLANNEL chain
{"POSTROUTING", "-s", ipn.String(), "-j", "FLANNEL"},
}
for _, rule := range rules {
log.Info("Adding iptables rule: ", strings.Join(rule, " "))
chain := rule[0]
args := rule[1:len(rule)]
err = ipt.AppendUnique("nat", chain, args...)
if err != nil {
return fmt.Errorf("Failed to insert IP masquerade rule: %v", err)
}
}
return nil
}
func rules(ipn ip.IP4Net) [][]string {
n := ipn.String()
return [][]string{
// This rule makes sure we don't NAT traffic within overlay network (e.g. coming out of docker0)
{"-s", n, "-d", n, "-j", "RETURN"},
// NAT if it's not multicast traffic
{"-s", n, "!", "-d", "224.0.0.0/4", "-j", "MASQUERADE"},
// Masquerade anything headed towards flannel from the host
{"!", "-s", n, "-d", n, "-j", "MASQUERADE"},
}
}