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The TCP PAWS fix for kernels with fast tick rates (r231767) changed the TCP

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timestamp related stack variables to reference ms directly instead of ticks.
The h_ertt(4) Khelp module relies on TCP timestamp information in order to
calculate its enhanced RTT estimates, but was not updated as part of r231767.

Consequently, h_ertt has not been calculating correct RTT estimates since
r231767 was comitted, which in turn broke all delay-based congestion control
algorithms because they rely on the h_ertt RTT estimates.

Fix the breakage by switching h_ertt to use tcp_ts_getticks() in place of all
previous uses of the ticks variable. This ensures all timestamp related
variables in h_ertt use the same units as the TCP stack and therefore results in
meaningful comparisons and RTT estimate calculations.

Reported & tested by:	Naeem Khademi (naeemk at ifi uio no)
Discussed with:	bz
MFC after:	3 days
This commit is contained in:
lstewart 2012-08-17 01:49:51 +00:00
parent 8552821dd8
commit 71de2d67ba
1 changed files with 6 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
sys/netinet/khelp/h_ertt.c
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@ -151,11 +151,13 @@ marked_packet_rtt(struct txseginfo *txsi, struct ertt *e_t, struct tcpcb *tp,
*prtt_bytes_adjust += *pmeasurenext_len;
} else {
if (mflag & FORCED_MEASUREMENT) {
e_t->markedpkt_rtt = ticks - *pmeasurenext + 1;
e_t->markedpkt_rtt = tcp_ts_getticks() -
*pmeasurenext + 1;
e_t->bytes_tx_in_marked_rtt = e_t->bytes_tx_in_rtt +
*pmeasurenext_len - *prtt_bytes_adjust;
} else {
e_t->markedpkt_rtt = ticks - txsi->tx_ts + 1;
e_t->markedpkt_rtt = tcp_ts_getticks() -
txsi->tx_ts + 1;
e_t->bytes_tx_in_marked_rtt = e_t->bytes_tx_in_rtt -
*prtt_bytes_adjust;
}
@ -349,7 +351,7 @@ ertt_packet_measurement_hook(int hhook_type, int hhook_id, void *udata,
*/
if (!e_t->dlyack_rx || multiack || new_sacked_bytes) {
/* Make an accurate new measurement. */
e_t->rtt = ticks - txsi->tx_ts + 1;
e_t->rtt = tcp_ts_getticks() - txsi->tx_ts + 1;
if (e_t->rtt < e_t->minrtt || e_t->minrtt == 0)
e_t->minrtt = e_t->rtt;
@ -477,7 +479,7 @@ ertt_add_tx_segment_info_hook(int hhook_type, int hhook_id, void *udata,
tp->ts_offset;
txsi->rx_ts = ntohl(to->to_tsecr);
} else {
txsi->tx_ts = ticks;
txsi->tx_ts = tcp_ts_getticks();
txsi->rx_ts = 0; /* No received time stamp. */
}
TAILQ_INSERT_TAIL(&e_t->txsegi_q, txsi, txsegi_lnk);