/*
* If the ack type is CC_ACK, and the inferred queueing delay is greater than
* the Qmin threshold, cwnd is reduced probabilistically. When backing off due
* to delay, HD behaves like NewReno when an ECN signal is received. HD behaves
* as NewReno in all other circumstances.
*/
static void
hd_ack_received(struct cc_var *ccv, uint16_t ack_type)
{
struct ertt *e_t;
int qdly;
if (ack_type == CC_ACK) {
//ScenSim-Port// e_t = khelp_get_osd(CCV(ccv, osd), ertt_id);
e_t = &ccv->ertt_porting; //ScenSim-Port//
if (e_t->rtt && e_t->minrtt && V_hd_qthresh > 0) {
qdly = e_t->rtt - e_t->minrtt;
if (qdly > V_hd_qmin &&
!IN_RECOVERY(CCV(ccv, t_flags))) {
/* Probabilistic backoff of cwnd. */
if (should_backoff(qdly,
e_t->maxrtt - e_t->minrtt)) {
/*
* Update cwnd and ssthresh update to
* half cwnd and behave like an ECN (ie
* not a packet loss).
*/
newreno_cc_algo.cong_signal(ccv,
CC_ECN);
return;
}
}
}
}
newreno_cc_algo.ack_received(ccv, ack_type); /* As for NewReno. */
}
static void
newreno_ack_received(struct cc_var *ccv, uint16_t type)
{
if (type == CC_ACK && !IN_RECOVERY(CCV(ccv, t_flags)) &&
(ccv->flags & CCF_CWND_LIMITED)) {
u_int cw = CCV(ccv, snd_cwnd);
u_int incr = CCV(ccv, t_maxseg);
/*
* Regular in-order ACK, open the congestion window.
* Method depends on which congestion control state we're
* in (slow start or cong avoid) and if ABC (RFC 3465) is
* enabled.
*
* slow start: cwnd <= ssthresh
* cong avoid: cwnd > ssthresh
*
* slow start and ABC (RFC 3465):
* Grow cwnd exponentially by the amount of data
* ACKed capping the max increment per ACK to
* (abc_l_var * maxseg) bytes.
*
* slow start without ABC (RFC 5681):
* Grow cwnd exponentially by maxseg per ACK.
*
* cong avoid and ABC (RFC 3465):
* Grow cwnd linearly by maxseg per RTT for each
* cwnd worth of ACKed data.
*
* cong avoid without ABC (RFC 5681):
* Grow cwnd linearly by approximately maxseg per RTT using
* maxseg^2 / cwnd per ACK as the increment.
* If cwnd > maxseg^2, fix the cwnd increment at 1 byte to
* avoid capping cwnd.
*/
if (cw > CCV(ccv, snd_ssthresh)) {
if (V_tcp_do_rfc3465) {
if (ccv->flags & CCF_ABC_SENTAWND)
ccv->flags &= ~CCF_ABC_SENTAWND;
else
incr = 0;
} else
incr = max((incr * incr / cw), 1);
} else if (V_tcp_do_rfc3465) {
/*
* In slow-start with ABC enabled and no RTO in sight?
* (Must not use abc_l_var > 1 if slow starting after
* an RTO. On RTO, snd_nxt = snd_una, so the
* snd_nxt == snd_max check is sufficient to
* handle this).
*
* XXXLAS: Find a way to signal SS after RTO that
* doesn't rely on tcpcb vars.
*/
if (CCV(ccv, snd_nxt) == CCV(ccv, snd_max))
incr = min(ccv->bytes_this_ack,
V_tcp_abc_l_var * CCV(ccv, t_maxseg));
else
incr = min(ccv->bytes_this_ack, CCV(ccv, t_maxseg));
}
/* ABC is on by default, so incr equals 0 frequently. */
if (incr > 0)
CCV(ccv, snd_cwnd) = min(cw + incr,
TCP_MAXWIN << CCV(ccv, snd_scale));
}
}
