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- Retransmit just one segment on initiation of SACK recovery.

Browse Source 
Remove the SACK "initburst" sysctl.
- Fix bugs in SACK dupack and partialack handling that can cause
  large bursts while in SACK recovery.

Submitted by:	Mohan Srinivasan
This commit is contained in:
Paul Saab 2005-02-14 21:01:08 +00:00
parent a8127ebb5d
commit 8db456bf17
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=141928
3 changed files with 18 additions and 42 deletions
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12
sys/netinet/tcp_input.c
View File

@ -159,12 +159,6 @@ SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD,
&tcp_reass_overflows, 0,
"Global number of TCP Segment Reassembly Queue Overflows");
static int tcp_sack_recovery_initburst = 3;
SYSCTL_INT(_net_inet_tcp_sack, OID_AUTO,
initburst, CTLFLAG_RW,
&tcp_sack_recovery_initburst, 0,
"Initial Number of Rexmits when sack recovery is set up");
struct inpcbhead tcb;
#define tcb6 tcb /* for KAME src sync over BSD*'s */
struct inpcbinfo tcbinfo;
@ -1870,14 +1864,10 @@ tcp_input(m, off0)
if (tp->sack_enable) {
tcpstat.tcps_sack_recovery_episode++;
tp->sack_newdata = tp->snd_nxt;
tp->snd_cwnd =
tp->t_maxseg * tcp_sack_recovery_initburst;
tp->snd_cwnd = tp->t_maxseg;
(void) tcp_output(tp);
tp->snd_cwnd +=
tp->snd_ssthresh;
goto drop;
}
tp->snd_nxt = th->th_ack;
tp->snd_cwnd = tp->t_maxseg;
(void) tcp_output(tp);

12
sys/netinet/tcp_reass.c
View File

@ -159,12 +159,6 @@ SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD,
&tcp_reass_overflows, 0,
"Global number of TCP Segment Reassembly Queue Overflows");
static int tcp_sack_recovery_initburst = 3;
SYSCTL_INT(_net_inet_tcp_sack, OID_AUTO,
initburst, CTLFLAG_RW,
&tcp_sack_recovery_initburst, 0,
"Initial Number of Rexmits when sack recovery is set up");
struct inpcbhead tcb;
#define tcb6 tcb /* for KAME src sync over BSD*'s */
struct inpcbinfo tcbinfo;
@ -1870,14 +1864,10 @@ tcp_input(m, off0)
if (tp->sack_enable) {
tcpstat.tcps_sack_recovery_episode++;
tp->sack_newdata = tp->snd_nxt;
tp->snd_cwnd =
tp->t_maxseg * tcp_sack_recovery_initburst;
tp->snd_cwnd = tp->t_maxseg;
(void) tcp_output(tp);
tp->snd_cwnd +=
tp->snd_ssthresh;
goto drop;
}
tp->snd_nxt = th->th_ack;
tp->snd_cwnd = tp->t_maxseg;
(void) tcp_output(tp);

36
sys/netinet/tcp_sack.c
View File

@ -481,9 +481,14 @@ tcp_free_sackholes(struct tcpcb *tp)
}
/*
* Checks for partial ack. If partial ack arrives, turn off retransmission
* timer, deflate the window, do not clear tp->t_dupacks, and return 1.
* If the ack advances at least to tp->snd_recover, return 0.
* Partial ack handling within a sack recovery episode.
* Keeping this very simple for now. When a partial ack
* is received, force snd_cwnd to a value that will allow
* the sender to transmit no more than 2 segments.
* If necessary, a better scheme can be adopted at a
* later point, but for now, the goal is to prevent the
* sender from bursting a large amount of data in the midst
* of sack recovery.
*/
void
tcp_sack_partialack(tp, th)
@ -491,28 +496,19 @@ tcp_sack_partialack(tp, th)
struct tcphdr *th;
{
INP_LOCK_ASSERT(tp->t_inpcb);
u_long ocwnd = tp->snd_cwnd;
int sack_bytes_rexmt = 0;
int num_segs = 1;
int sack_bytes_rxmt = 0;
callout_stop(tp->tt_rexmt);
tp->t_rtttime = 0;
/*
* Set cwnd so we can send one more segment (either rexmit based on
* scoreboard or new segment). Set cwnd to the amount of data
* rexmitted from scoreboard plus the amount of new data transmitted
* in this sack recovery episode plus one segment.
*/
(void)tcp_sack_output(tp, &sack_bytes_rexmt);
tp->snd_cwnd = sack_bytes_rexmt + (tp->snd_nxt - tp->sack_newdata) +
tp->t_maxseg;
/* send one or 2 segments based on how much new data was acked */
if (((th->th_ack - tp->snd_una) / tp->t_maxseg) > 2)
num_segs = 2;
(void)tcp_sack_output(tp, &sack_bytes_rxmt);
tp->snd_cwnd = sack_bytes_rxmt + (tp->snd_nxt - tp->sack_newdata) +
num_segs * tp->t_maxseg;
tp->t_flags |= TF_ACKNOW;
(void) tcp_output(tp);
tp->snd_cwnd = ocwnd;
/*
* Partial window deflation. Relies on fact that tp->snd_una
* not updated yet.
*/
tp->snd_cwnd -= (th->th_ack - tp->snd_una - tp->t_maxseg);
}
#ifdef TCP_SACK_DEBUG