About commit 2d2abbab63f6726a147ae61ada39bf2c9ee0db9a:
It looks like this patch bypassed the enforcement of Karn's algorithm in
tcp_ack_no_tstamp() for the purposes of usec RTT sampling used by
congestion control modules. This will give them bad RTT data when there
are retransmits. I haven't actually observed this, but it seems like it
would be the case. ;) Please correct me if I'm wrong.
Here's a patch that should be a fix.
Signed-off-by: John Heffner <[EMAIL PROTECTED]>
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 159fa3f..725c868 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2306,8 +2306,6 @@ static int tcp_clean_rtx_queue(struct so
seq_rtt = -1;
} else if (seq_rtt < 0) {
seq_rtt = now - scb->when;
- if (rtt_sample)
- (*rtt_sample)(sk, tcp_usrtt(skb));
}
if (sacked & TCPCB_SACKED_ACKED)
tp->sacked_out -= tcp_skb_pcount(skb);
@@ -2320,8 +2318,6 @@ static int tcp_clean_rtx_queue(struct so
}
} else if (seq_rtt < 0) {
seq_rtt = now - scb->when;
- if (rtt_sample)
- (*rtt_sample)(sk, tcp_usrtt(skb));
}
tcp_dec_pcount_approx(&tp->fackets_out, skb);
tcp_packets_out_dec(tp, skb);
@@ -2333,6 +2329,8 @@ static int tcp_clean_rtx_queue(struct so
if (acked&FLAG_ACKED) {
tcp_ack_update_rtt(sk, acked, seq_rtt);
tcp_ack_packets_out(sk, tp);
+ if (rtt_sample && !(acked & FLAG_RETRANS_DATA_ACKED))
+ (*rtt_sample)(sk, tcp_usrtt(skb));
if (icsk->icsk_ca_ops->pkts_acked)
icsk->icsk_ca_ops->pkts_acked(sk, pkts_acked);
