make allocation universal, given a network

add.go

@@ -62,7 +62,8 @@ func Add() {
 	privateKey := GenerateJSONPrivateKey()
 	publicKey := privateKey.PublicKey()
 
-	IP := conf.MustAllocateIP()
+	IP := conf.MustAllocateIP(conf.Network.IPNet)
+	//IP6 := conf.MustAllocateIP(conf.Network6.IPNet)
 
 	peer := PeerConfig{
 		Owner:        owner,
@@ -73,6 +74,7 @@ func Add() {
 		PrivateKey:   privateKey, // omitted from server config JSON!
 		PresharedKey: GenerateJSONKey(),
 		IP:           IP,
+		//IP6:          IP6,
 		Networks:     []JSONIPNet{},
 	}
 

configtypes.go

@@ -154,12 +154,15 @@ func (conf DsnetConfig) IPAllocated(IP net.IP) bool {
 }
 
 // choose a free IP for a new Peer
-func (conf DsnetConfig) MustAllocateIP() net.IP {
-	network := conf.Network.IPNet
+func (conf DsnetConfig) MustAllocateIP(network net.IPNet) net.IP {
 	ones, bits := network.Mask.Size()
 	zeros := bits - ones
-	min := 1                // avoids network addr
-	max := (1 << zeros) - 2 // avoids broadcast addr + overflow
+
+	// avoids network addr
+	min := 1
+	// avoids broadcast addr + overflow. Note there is no broadcast addr with
+	// IPv6, but I don't care about losing one when there are so many!
+	max := (1 << zeros) - 2
 
 	for i := min; i <= max; i++ {
 		IP := make(net.IP, len(network.IP))

init.go

@@ -31,8 +31,9 @@ func Init() {
 		Networks:      []JSONIPNet{},
 	}
 
-	IP := conf.MustAllocateIP()
-	conf.IP = IP
+	conf.IP = conf.MustAllocateIP(conf.Network.IPNet)
+	//conf.IP6 = conf.MustAllocateIP(conf.Network6.IPNet)
+
 	// DNS not set by default
 	//conf.DNS = IP