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Receiver side DSACK implemenation.

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This adds initial support for RFC 2883.

Submitted by:		Richard Scheffenegger
Reviewed by:		rrs@
Differential Revision:	https://reviews.freebsd.org/D19334
This commit is contained in:
Michael Tuexen 2019-05-09 07:34:15 +00:00
parent 5cc11a89db
commit 5acfd95cbc
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=347382
2 changed files with 79 additions and 7 deletions
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36
sys/netinet/tcp_input.c
View File

@ -2258,6 +2258,17 @@ tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so,
TCPSTAT_INC(tcps_rcvpartduppack);
TCPSTAT_ADD(tcps_rcvpartdupbyte, todrop);
}
/*
* DSACK - add SACK block for dropped range
*/
if (tp->t_flags & TF_SACK_PERMIT) {
tcp_update_sack_list(tp, th->th_seq, th->th_seq+tlen);
/*
* ACK now, as the next in-sequence segment
* will clear the DSACK block again
*/
tp->t_flags |= TF_ACKNOW;
}
drop_hdrlen += todrop; /* drop from the top afterwards */
th->th_seq += todrop;
tlen -= todrop;
@ -2986,6 +2997,8 @@ tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so,
if ((tlen || (thflags & TH_FIN) || tfo_syn) &&
TCPS_HAVERCVDFIN(tp->t_state) == 0) {
tcp_seq save_start = th->th_seq;
tcp_seq save_rnxt = tp->rcv_nxt;
int save_tlen = tlen;
m_adj(m, drop_hdrlen); /* delayed header drop */
/*
* Insert segment which includes th into TCP reassembly queue
@ -3025,11 +3038,28 @@ tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so,
* m_adj() doesn't actually frees any mbufs
* when trimming from the head.
*/
thflags = tcp_reass(tp, th, &save_start, &tlen, m);
tcp_seq temp = save_start;
thflags = tcp_reass(tp, th, &temp, &tlen, m);
tp->t_flags |= TF_ACKNOW;
}
if (tlen > 0 && (tp->t_flags & TF_SACK_PERMIT))
tcp_update_sack_list(tp, save_start, save_start + tlen);
if (tp->t_flags & TF_SACK_PERMIT) {
if (((tlen == 0) && (save_tlen > 0) &&
(SEQ_LT(save_start, save_rnxt)))) {
// DSACK actually handled in the fastpath above
tcp_update_sack_list(tp, save_start, save_start + save_tlen);
} else
if ((tlen > 0) && SEQ_GT(tp->rcv_nxt, save_rnxt)) {
// cleaning sackblks by using zero length update
tcp_update_sack_list(tp, save_start, save_start);
} else
if ((tlen > 0) && (tlen >= save_tlen)) {
// update of sackblks
tcp_update_sack_list(tp, save_start, save_start + save_tlen);
} else
if (tlen > 0) {
tcp_update_sack_list(tp, save_start, save_start+tlen);
}
}
#if 0
/*
* Note the amount of data that peer has sent into

50
sys/netinet/tcp_sack.c
View File

@ -168,7 +168,7 @@ tcp_update_sack_list(struct tcpcb *tp, tcp_seq rcv_start, tcp_seq rcv_end)
INP_WLOCK_ASSERT(tp->t_inpcb);
/* Check arguments. */
KASSERT(SEQ_LT(rcv_start, rcv_end), ("rcv_start < rcv_end"));
KASSERT(SEQ_LEQ(rcv_start, rcv_end), ("rcv_start <= rcv_end"));
/* SACK block for the received segment. */
head_blk.start = rcv_start;
@ -193,11 +193,53 @@ tcp_update_sack_list(struct tcpcb *tp, tcp_seq rcv_start, tcp_seq rcv_end)
* Merge this SACK block into head_blk. This SACK
* block itself will be discarded.
*/
if (SEQ_GT(head_blk.start, start))
/*
* |-|
* |---| merge
*
* |-|
* |---| merge
*
* |-----|
* |-| DSACK smaller
*
* |-|
* |-----| DSACK smaller
*/
if (head_blk.start == end)
head_blk.start = start;
if (SEQ_LT(head_blk.end, end))
else if (head_blk.end == start)
head_blk.end = end;
else {
if (SEQ_LT(head_blk.start, start)) {
tcp_seq temp = start;
start = head_blk.start;
head_blk.start = temp;
}
if (SEQ_GT(head_blk.end, end)) {
tcp_seq temp = end;
end = head_blk.end;
head_blk.end = temp;
}
if ((head_blk.start != start) ||
(head_blk.end != end)) {
if ((num_saved >= 1) &&
SEQ_GEQ(saved_blks[num_saved-1].start, start) &&
SEQ_LEQ(saved_blks[num_saved-1].end, end))
num_saved--;
saved_blks[num_saved].start = start;
saved_blks[num_saved].end = end;
num_saved++;
}
}
} else {
/*
* This block supercedes the prior block
*/
if ((num_saved >= 1) &&
SEQ_GEQ(saved_blks[num_saved-1].start, start) &&
SEQ_LEQ(saved_blks[num_saved-1].end, end))
num_saved--;
/*
* Save this SACK block.
*/
@ -211,7 +253,7 @@ tcp_update_sack_list(struct tcpcb *tp, tcp_seq rcv_start, tcp_seq rcv_end)
* Update SACK list in tp->sackblks[].
*/
num_head = 0;
if (SEQ_GT(head_blk.start, tp->rcv_nxt)) {
if (SEQ_LT(rcv_start, rcv_end)) {
/*
* The received data segment is an out-of-order segment. Put
* head_blk at the top of SACK list.