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Rewrite of tcp_update_sack_list() to make it simpler and more readable

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than our original OpenBSD derived version.

Submitted by:	Noritoshi Demizu
Reviewed by:	Mohan Srinivasan, Raja Mukerji
This commit is contained in:
Paul Saab 2005-04-18 18:10:56 +00:00
parent ac5c6dad08
commit b7c755717c
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=145244
1 changed files with 67 additions and 74 deletions
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141
sys/netinet/tcp_sack.c
View File

@ -181,14 +181,13 @@ static int tcp_sack_globalholes = 0;
SYSCTL_INT(_net_inet_tcp_sack, OID_AUTO, globalholes, CTLFLAG_RD,
&tcp_sack_globalholes, 0,
"Global number of TCP SACK holes currently allocated");
/*
* This function is called upon receipt of new valid data (while not in header
* prediction mode), and it updates the ordered list of sacks.
*/
void
tcp_update_sack_list(tp, rcv_laststart, rcv_lastend)
struct tcpcb *tp;
tcp_seq rcv_laststart, rcv_lastend;
tcp_update_sack_list(struct tcpcb *tp, tcp_seq rcv_start, tcp_seq rcv_end)
{
/*
* First reported block MUST be the most recent one. Subsequent
@ -196,86 +195,79 @@ tcp_update_sack_list(tp, rcv_laststart, rcv_lastend)
* receiver. These two conditions make the implementation fully
* compliant with RFC 2018.
*/
int i, j = 0, count = 0, lastpos = -1;
struct sackblk sack, firstsack, temp[MAX_SACK_BLKS];
struct sackblk head_blk, saved_blks[MAX_SACK_BLKS];
int num_head, num_saved, i;
INP_LOCK_ASSERT(tp->t_inpcb);
/* First clean up current list of sacks */
for (i = 0; i < tp->rcv_numsacks; i++) {
sack = tp->sackblks[i];
if (sack.start == 0 && sack.end == 0) {
count++; /* count = number of blocks to be discarded */
continue;
}
if (SEQ_LEQ(sack.end, tp->rcv_nxt)) {
tp->sackblks[i].start = tp->sackblks[i].end = 0;
count++;
} else {
temp[j].start = tp->sackblks[i].start;
temp[j++].end = tp->sackblks[i].end;
}
}
tp->rcv_numsacks -= count;
if (tp->rcv_numsacks == 0) { /* no sack blocks currently (fast path) */
tcp_clean_sackreport(tp);
if (SEQ_LT(tp->rcv_nxt, rcv_laststart)) {
/* ==> need first sack block */
tp->sackblks[0].start = rcv_laststart;
tp->sackblks[0].end = rcv_lastend;
tp->rcv_numsacks = 1;
}
return;
}
/* Otherwise, sack blocks are already present. */
for (i = 0; i < tp->rcv_numsacks; i++)
tp->sackblks[i] = temp[i]; /* first copy back sack list */
if (SEQ_GEQ(tp->rcv_nxt, rcv_lastend))
return; /* sack list remains unchanged */
/* Check arguments */
KASSERT(SEQ_LT(rcv_start, rcv_end), ("rcv_start < rcv_end"));
/* SACK block for the received segment. */
head_blk.start = rcv_start;
head_blk.end = rcv_end;
/*
* From here, segment just received should be (part of) the 1st sack.
* Go through list, possibly coalescing sack block entries.
* Merge updated SACK blocks into head_blk, and
* save unchanged SACK blocks into saved_blks[].
* num_saved will have the number of the saved SACK blocks.
*/
firstsack.start = rcv_laststart;
firstsack.end = rcv_lastend;
num_saved = 0;
for (i = 0; i < tp->rcv_numsacks; i++) {
sack = tp->sackblks[i];
if (SEQ_LT(sack.end, firstsack.start) ||
SEQ_GT(sack.start, firstsack.end))
continue; /* no overlap */
if (sack.start == firstsack.start && sack.end == firstsack.end){
tcp_seq start = tp->sackblks[i].start;
tcp_seq end = tp->sackblks[i].end;
if (SEQ_GEQ(start, end) || SEQ_LEQ(start, tp->rcv_nxt)) {
/*
* identical block; delete it here since we will
* move it to the front of the list.
* Discard this SACK block.
*/
tp->sackblks[i].start = tp->sackblks[i].end = 0;
lastpos = i; /* last posn with a zero entry */
continue;
} else if (SEQ_LEQ(head_blk.start, end) &&
SEQ_GEQ(head_blk.end, start)) {
/*
* Merge this SACK block into head_blk.
* This SACK block itself will be discarded.
*/
if (SEQ_GT(head_blk.start, start))
head_blk.start = start;
if (SEQ_LT(head_blk.end, end))
head_blk.end = end;
} else {
/*
* Save this SACK block.
*/
saved_blks[num_saved].start = start;
saved_blks[num_saved].end = end;
num_saved++;
}
if (SEQ_LEQ(sack.start, firstsack.start))
firstsack.start = sack.start; /* merge blocks */
if (SEQ_GEQ(sack.end, firstsack.end))
firstsack.end = sack.end; /* merge blocks */
tp->sackblks[i].start = tp->sackblks[i].end = 0;
lastpos = i; /* last posn with a zero entry */
}
if (lastpos != -1) { /* at least one merge */
for (i = 0, j = 1; i < tp->rcv_numsacks; i++) {
sack = tp->sackblks[i];
if (sack.start == 0 && sack.end == 0)
continue;
temp[j++] = sack;
}
tp->rcv_numsacks = j; /* including first blk (added later) */
for (i = 1; i < tp->rcv_numsacks; i++) /* now copy back */
tp->sackblks[i] = temp[i];
} else { /* no merges -- shift sacks by 1 */
if (tp->rcv_numsacks < MAX_SACK_BLKS)
tp->rcv_numsacks++;
for (i = tp->rcv_numsacks-1; i > 0; i--)
tp->sackblks[i] = tp->sackblks[i-1];
/*
* Update SACK list in tp->sackblks[].
*/
num_head = 0;
if (SEQ_GT(head_blk.start, tp->rcv_nxt)) {
/*
* The received data segment is an out-of-order segment.
* Put head_blk at the top of SACK list.
*/
tp->sackblks[0] = head_blk;
num_head = 1;
/*
* If the number of saved SACK blocks exceeds its limit,
* discard the last SACK block.
*/
if (num_saved >= MAX_SACK_BLKS)
num_saved--;
}
tp->sackblks[0] = firstsack;
return;
if (num_saved > 0) {
/*
* Copy the saved SACK blocks back.
*/
bcopy(saved_blks, &tp->sackblks[num_head],
sizeof(struct sackblk) * num_saved);
}
/* Save the number of SACK blocks. */
tp->rcv_numsacks = num_head + num_saved;
}
/*
@ -608,8 +600,9 @@ tcp_sack_output(struct tcpcb *tp, int *sack_bytes_rexmt)
void
tcp_sack_adjust(struct tcpcb *tp)
{
INP_LOCK_ASSERT(tp->t_inpcb);
struct sackhole *cur = tp->snd_holes;
INP_LOCK_ASSERT(tp->t_inpcb);
if (cur == NULL)
return; /* No holes */
if (SEQ_GEQ(tp->snd_nxt, tp->rcv_lastsack))