Different SYN retransmit backoff between active and passive connections

[Karim Fodil-Lemelin]

Greetings,

When doing an active connect and assuming that SYN packets are lost. The 
next retransmit timeout will trigger retransmissions of the SYN 
according to this code (in tcp_timer_rexmt):

rexmt = TCP_REXMTVAL(tp) * tcp_syn_backoff[tp->t_rxtshift];


Now, when doing passive connections the syncache handles sending the 
SYN-ACK and assuming again the SYN-ACK is lost the next retransmit 
timeout will be calculated using this code:

sc->sc_rxttime = ticks + TCPTV_RTOBASE * (tcp_backoff[sc->sc_rxmits]);

Is there a reason why FreeBSD is not using the tcp_syn_backoff array in 
syncache_timeout?

Regards,

Karim.