mosquitto_reconnect_delay_set() does not work according to specification

[karmagda]

Hello,
I noticed that reconnect back-off mechanism configured via mosquitto_reconnect_delay_set() does not work as stated in documentation.

According to documentation for: delay=3, delay_max=30, exponential_backoff=True
Delays would be: 3, 6, 12, 24, 30, 30, ...

But the tested behavior is different and for: delay=3, delay_max=30, exponential_backoff=True
Delays are: 3, 12, 27, 30, 30, ...

I noticed that the following formula is used for back-off calculation:
if(mosq->reconnect_exponential_backoff){
reconnect_delay = mosq->reconnect_delay*(mosq->reconnects+1)(mosq->reconnects+1);
}else{
reconnect_delay = mosq->reconnect_delay(mosq->reconnects+1);
}

Shouldn't the formula for the case when exponential_backoff=True look like that:
reconnect_delay = mosq->reconnect_delay*2^(mosq->reconnects-1)

I use mosquitto-1.6.7 but it seems that the same formula is stated in the newest version.