Commit 2fba2eae authored by David S. Miller's avatar David S. Miller

Merge branch 'tcp-rack'

Neal Cardwell says:

====================
more accurate DSACK processing for RACK-TLP

This patch series includes two minor improvements to tighten up the accuracy of
the processing of incoming DSACK information, so that RACK-TLP behavior is
faster and more precise: first, to ensure we detect packet loss in some extra
corner cases; and second, to avoid growing the RACK reordering window (and
delaying fast recovery) in cases where it seems clear we don't need to.
====================
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parents 409f386b a657db03
......@@ -100,6 +100,7 @@ int sysctl_tcp_max_orphans __read_mostly = NR_FILE;
#define FLAG_UPDATE_TS_RECENT 0x4000 /* tcp_replace_ts_recent() */
#define FLAG_NO_CHALLENGE_ACK 0x8000 /* do not call tcp_send_challenge_ack() */
#define FLAG_ACK_MAYBE_DELAYED 0x10000 /* Likely a delayed ACK */
#define FLAG_DSACK_TLP 0x20000 /* DSACK for tail loss probe */
#define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
#define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
......@@ -991,6 +992,8 @@ static u32 tcp_dsack_seen(struct tcp_sock *tp, u32 start_seq,
return 0;
if (seq_len > tp->mss_cache)
dup_segs = DIV_ROUND_UP(seq_len, tp->mss_cache);
else if (tp->tlp_high_seq && tp->tlp_high_seq == end_seq)
state->flag |= FLAG_DSACK_TLP;
tp->dsack_dups += dup_segs;
/* Skip the DSACK if dup segs weren't retransmitted by sender */
......@@ -998,6 +1001,13 @@ static u32 tcp_dsack_seen(struct tcp_sock *tp, u32 start_seq,
return 0;
tp->rx_opt.sack_ok |= TCP_DSACK_SEEN;
/* We increase the RACK ordering window in rounds where we receive
* DSACKs that may have been due to reordering causing RACK to trigger
* a spurious fast recovery. Thus RACK ignores DSACKs that happen
* without having seen reordering, or that match TLP probes (TLP
* is timer-driven, not triggered by RACK).
*/
if (tp->reord_seen && !(state->flag & FLAG_DSACK_TLP))
tp->rack.dsack_seen = 1;
state->flag |= FLAG_DSACKING_ACK;
......@@ -3650,7 +3660,7 @@ static void tcp_process_tlp_ack(struct sock *sk, u32 ack, int flag)
if (!tp->tlp_retrans) {
/* TLP of new data has been acknowledged */
tp->tlp_high_seq = 0;
} else if (flag & FLAG_DSACKING_ACK) {
} else if (flag & FLAG_DSACK_TLP) {
/* This DSACK means original and TLP probe arrived; no loss */
tp->tlp_high_seq = 0;
} else if (after(ack, tp->tlp_high_seq)) {
......
......@@ -172,7 +172,8 @@ void tcp_rack_reo_timeout(struct sock *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
* If a DSACK is received that seems like it may have been due to reordering
* triggering fast recovery, 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.
*
......
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