205 строки
6.6 KiB
C
205 строки
6.6 KiB
C
// SPDX-License-Identifier: GPL-2.0
|
|
#include <linux/tcp.h>
|
|
#include <net/tcp.h>
|
|
|
|
static void tcp_rack_mark_skb_lost(struct sock *sk, struct sk_buff *skb)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
tcp_skb_mark_lost_uncond_verify(tp, skb);
|
|
if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
|
|
/* Account for retransmits that are lost again */
|
|
TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
|
|
tp->retrans_out -= tcp_skb_pcount(skb);
|
|
NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPLOSTRETRANSMIT,
|
|
tcp_skb_pcount(skb));
|
|
}
|
|
}
|
|
|
|
static bool tcp_rack_sent_after(u64 t1, u64 t2, u32 seq1, u32 seq2)
|
|
{
|
|
return t1 > t2 || (t1 == t2 && after(seq1, seq2));
|
|
}
|
|
|
|
/* RACK loss detection (IETF draft draft-ietf-tcpm-rack-01):
|
|
*
|
|
* Marks a packet lost, if some packet sent later has been (s)acked.
|
|
* The underlying idea is similar to the traditional dupthresh and FACK
|
|
* but they look at different metrics:
|
|
*
|
|
* dupthresh: 3 OOO packets delivered (packet count)
|
|
* FACK: sequence delta to highest sacked sequence (sequence space)
|
|
* RACK: sent time delta to the latest delivered packet (time domain)
|
|
*
|
|
* The advantage of RACK is it applies to both original and retransmitted
|
|
* packet and therefore is robust against tail losses. Another advantage
|
|
* is being more resilient to reordering by simply allowing some
|
|
* "settling delay", instead of tweaking the dupthresh.
|
|
*
|
|
* When tcp_rack_detect_loss() detects some packets are lost and we
|
|
* are not already in the CA_Recovery state, either tcp_rack_reo_timeout()
|
|
* or tcp_time_to_recover()'s "Trick#1: the loss is proven" code path will
|
|
* make us enter the CA_Recovery state.
|
|
*/
|
|
static void tcp_rack_detect_loss(struct sock *sk, u32 *reo_timeout)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
u32 min_rtt = tcp_min_rtt(tp);
|
|
struct sk_buff *skb, *n;
|
|
u32 reo_wnd;
|
|
|
|
*reo_timeout = 0;
|
|
/* To be more reordering resilient, allow min_rtt/4 settling delay
|
|
* (lower-bounded to 1000uS). We use min_rtt instead of the smoothed
|
|
* RTT because reordering is often a path property and less related
|
|
* to queuing or delayed ACKs.
|
|
*/
|
|
reo_wnd = 1000;
|
|
if ((tp->rack.reord || inet_csk(sk)->icsk_ca_state < TCP_CA_Recovery) &&
|
|
min_rtt != ~0U) {
|
|
reo_wnd = max((min_rtt >> 2) * tp->rack.reo_wnd_steps, reo_wnd);
|
|
reo_wnd = min(reo_wnd, tp->srtt_us >> 3);
|
|
}
|
|
|
|
list_for_each_entry_safe(skb, n, &tp->tsorted_sent_queue,
|
|
tcp_tsorted_anchor) {
|
|
struct tcp_skb_cb *scb = TCP_SKB_CB(skb);
|
|
s32 remaining;
|
|
|
|
/* Skip ones marked lost but not yet retransmitted */
|
|
if ((scb->sacked & TCPCB_LOST) &&
|
|
!(scb->sacked & TCPCB_SACKED_RETRANS))
|
|
continue;
|
|
|
|
if (!tcp_rack_sent_after(tp->rack.mstamp, skb->skb_mstamp,
|
|
tp->rack.end_seq, scb->end_seq))
|
|
break;
|
|
|
|
/* A packet is lost if it has not been s/acked beyond
|
|
* the recent RTT plus the reordering window.
|
|
*/
|
|
remaining = tp->rack.rtt_us + reo_wnd -
|
|
tcp_stamp_us_delta(tp->tcp_mstamp, skb->skb_mstamp);
|
|
if (remaining <= 0) {
|
|
tcp_rack_mark_skb_lost(sk, skb);
|
|
list_del_init(&skb->tcp_tsorted_anchor);
|
|
} else {
|
|
/* Record maximum wait time */
|
|
*reo_timeout = max_t(u32, *reo_timeout, remaining);
|
|
}
|
|
}
|
|
}
|
|
|
|
void tcp_rack_mark_lost(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
u32 timeout;
|
|
|
|
if (!tp->rack.advanced)
|
|
return;
|
|
|
|
/* Reset the advanced flag to avoid unnecessary queue scanning */
|
|
tp->rack.advanced = 0;
|
|
tcp_rack_detect_loss(sk, &timeout);
|
|
if (timeout) {
|
|
timeout = usecs_to_jiffies(timeout) + TCP_TIMEOUT_MIN;
|
|
inet_csk_reset_xmit_timer(sk, ICSK_TIME_REO_TIMEOUT,
|
|
timeout, inet_csk(sk)->icsk_rto);
|
|
}
|
|
}
|
|
|
|
/* Record the most recently (re)sent time among the (s)acked packets
|
|
* This is "Step 3: Advance RACK.xmit_time and update RACK.RTT" from
|
|
* draft-cheng-tcpm-rack-00.txt
|
|
*/
|
|
void tcp_rack_advance(struct tcp_sock *tp, u8 sacked, u32 end_seq,
|
|
u64 xmit_time)
|
|
{
|
|
u32 rtt_us;
|
|
|
|
rtt_us = tcp_stamp_us_delta(tp->tcp_mstamp, xmit_time);
|
|
if (rtt_us < tcp_min_rtt(tp) && (sacked & TCPCB_RETRANS)) {
|
|
/* If the sacked packet was retransmitted, it's ambiguous
|
|
* whether the retransmission or the original (or the prior
|
|
* retransmission) was sacked.
|
|
*
|
|
* If the original is lost, there is no ambiguity. Otherwise
|
|
* we assume the original can be delayed up to aRTT + min_rtt.
|
|
* the aRTT term is bounded by the fast recovery or timeout,
|
|
* so it's at least one RTT (i.e., retransmission is at least
|
|
* an RTT later).
|
|
*/
|
|
return;
|
|
}
|
|
tp->rack.advanced = 1;
|
|
tp->rack.rtt_us = rtt_us;
|
|
if (tcp_rack_sent_after(xmit_time, tp->rack.mstamp,
|
|
end_seq, tp->rack.end_seq)) {
|
|
tp->rack.mstamp = xmit_time;
|
|
tp->rack.end_seq = end_seq;
|
|
}
|
|
}
|
|
|
|
/* We have waited long enough to accommodate reordering. Mark the expired
|
|
* packets lost and retransmit them.
|
|
*/
|
|
void tcp_rack_reo_timeout(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
u32 timeout, prior_inflight;
|
|
|
|
prior_inflight = tcp_packets_in_flight(tp);
|
|
tcp_rack_detect_loss(sk, &timeout);
|
|
if (prior_inflight != tcp_packets_in_flight(tp)) {
|
|
if (inet_csk(sk)->icsk_ca_state != TCP_CA_Recovery) {
|
|
tcp_enter_recovery(sk, false);
|
|
if (!inet_csk(sk)->icsk_ca_ops->cong_control)
|
|
tcp_cwnd_reduction(sk, 1, 0);
|
|
}
|
|
tcp_xmit_retransmit_queue(sk);
|
|
}
|
|
if (inet_csk(sk)->icsk_pending != ICSK_TIME_RETRANS)
|
|
tcp_rearm_rto(sk);
|
|
}
|
|
|
|
/* Updates the RACK's reo_wnd based on DSACK and no. of recoveries.
|
|
*
|
|
* If DSACK is received, increment reo_wnd by min_rtt/4 (upper bounded
|
|
* by srtt), since there is possibility that spurious retransmission was
|
|
* due to reordering delay longer than reo_wnd.
|
|
*
|
|
* Persist the current reo_wnd value for TCP_RACK_RECOVERY_THRESH (16)
|
|
* no. of successful recoveries (accounts for full DSACK-based loss
|
|
* recovery undo). After that, reset it to default (min_rtt/4).
|
|
*
|
|
* At max, reo_wnd is incremented only once per rtt. So that the new
|
|
* DSACK on which we are reacting, is due to the spurious retx (approx)
|
|
* after the reo_wnd has been updated last time.
|
|
*
|
|
* reo_wnd is tracked in terms of steps (of min_rtt/4), rather than
|
|
* absolute value to account for change in rtt.
|
|
*/
|
|
void tcp_rack_update_reo_wnd(struct sock *sk, struct rate_sample *rs)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
if (sock_net(sk)->ipv4.sysctl_tcp_recovery & TCP_RACK_STATIC_REO_WND ||
|
|
!rs->prior_delivered)
|
|
return;
|
|
|
|
/* Disregard DSACK if a rtt has not passed since we adjusted reo_wnd */
|
|
if (before(rs->prior_delivered, tp->rack.last_delivered))
|
|
tp->rack.dsack_seen = 0;
|
|
|
|
/* Adjust the reo_wnd if update is pending */
|
|
if (tp->rack.dsack_seen) {
|
|
tp->rack.reo_wnd_steps = min_t(u32, 0xFF,
|
|
tp->rack.reo_wnd_steps + 1);
|
|
tp->rack.dsack_seen = 0;
|
|
tp->rack.last_delivered = tp->delivered;
|
|
tp->rack.reo_wnd_persist = TCP_RACK_RECOVERY_THRESH;
|
|
} else if (!tp->rack.reo_wnd_persist) {
|
|
tp->rack.reo_wnd_steps = 1;
|
|
}
|
|
}
|