// getRandomDevAddr returns a random free DevAddr. Note that the 7 MSB will be
// set to the NwkID (based on the configured NetID).
// TODO: handle collission with retry?
func getRandomDevAddr(p *redis.Pool, netID lorawan.NetID) (lorawan.DevAddr, error) {
var d lorawan.DevAddr
b := make([]byte, len(d))
if _, err := rand.Read(b); err != nil {
return d, fmt.Errorf("could not read from random reader: %s", err)
}
copy(d[:], b)
d[0] = d[0] & 1 // zero out 7 msb
d[0] = d[0] ^ (netID.NwkID() << 1) // set 7 msb to NwkID
c := p.Get()
defer c.Close()
key := "node_session_" + d.String()
val, err := redis.Int(c.Do("EXISTS", key))
if err != nil {
return lorawan.DevAddr{}, fmt.Errorf("test DevAddr %s exist error: %s", d, err)
}
if val == 1 {
return lorawan.DevAddr{}, fmt.Errorf("DevAddr %s already exists", d)
}
return d, nil
}
