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Date:      Sun, 14 Jul 2019 16:05:48 +0000 (UTC)
From:      Randall Stewart <rrs@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r349987 - in head/sys/netinet: . tcp_stacks
Message-ID:  <201907141605.x6EG5mGN013740@repo.freebsd.org>
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Author: rrs
Date: Sun Jul 14 16:05:47 2019
New Revision: 349987
URL: https://svnweb.freebsd.org/changeset/base/349987

Log:
  This is the second in a number of patches needed to
  get BBRv1 into the tree. This fixes the DSACK bug but
  is also needed by BBR. We have yet to go two more
  one will be for the pacing code (tcp_ratelimit.c) and
  the second will be for the new updated LRO code that
  allows a transport to know the arrival times of packets
  and (tcp_lro.c). After that we should finally be able
  to get BBRv1 into head.
  
  Sponsored by:	Netflix Inc
  Differential Revision:	https://reviews.freebsd.org/D20908

Modified:
  head/sys/netinet/tcp_output.c
  head/sys/netinet/tcp_sack.c
  head/sys/netinet/tcp_stacks/rack.c
  head/sys/netinet/tcp_var.h

Modified: head/sys/netinet/tcp_output.c
==============================================================================
--- head/sys/netinet/tcp_output.c	Sun Jul 14 12:04:39 2019	(r349986)
+++ head/sys/netinet/tcp_output.c	Sun Jul 14 16:05:47 2019	(r349987)
@@ -1508,7 +1508,13 @@ timer:
 		if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max))
 			tp->snd_max = tp->snd_nxt + xlen;
 	}
-
+	if ((error == 0) &&
+	    (TCPS_HAVEESTABLISHED(tp->t_state) &&
+	     (tp->t_flags & TF_SACK_PERMIT) &&
+	     tp->rcv_numsacks > 0)) {
+		    /* Clean up any DSACK's sent */
+		    tcp_clean_dsack_blocks(tp);
+	}
 	if (error) {
 		/* Record the error. */
 		TCP_LOG_EVENT(tp, NULL, &so->so_rcv, &so->so_snd, TCP_LOG_OUT,

Modified: head/sys/netinet/tcp_sack.c
==============================================================================
--- head/sys/netinet/tcp_sack.c	Sun Jul 14 12:04:39 2019	(r349986)
+++ head/sys/netinet/tcp_sack.c	Sun Jul 14 16:05:47 2019	(r349987)
@@ -279,6 +279,45 @@ tcp_update_sack_list(struct tcpcb *tp, tcp_seq rcv_sta
 	tp->rcv_numsacks = num_head + num_saved;
 }
 
+void
+tcp_clean_dsack_blocks(struct tcpcb *tp)
+{
+	struct sackblk saved_blks[MAX_SACK_BLKS];
+	int num_saved, i;
+
+	INP_WLOCK_ASSERT(tp->t_inpcb);
+	/*
+	 * Clean up any DSACK blocks that
+	 * are in our queue of sack blocks.
+	 * 
+	 */
+	num_saved = 0;
+	for (i = 0; i < tp->rcv_numsacks; i++) {
+		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)) {
+			/*
+			 * Discard this D-SACK block.
+			 */
+			continue;
+		}
+		/*
+		 * Save this SACK block.
+		 */
+		saved_blks[num_saved].start = start;
+		saved_blks[num_saved].end = end;
+		num_saved++;
+	}
+	if (num_saved > 0) {
+		/*
+		 * Copy the saved SACK blocks back.
+		 */
+		bcopy(saved_blks, &tp->sackblks[0],
+		      sizeof(struct sackblk) * num_saved);
+	}
+	tp->rcv_numsacks = num_saved;
+}
+
 /*
  * Delete all receiver-side SACK information.
  */

Modified: head/sys/netinet/tcp_stacks/rack.c
==============================================================================
--- head/sys/netinet/tcp_stacks/rack.c	Sun Jul 14 12:04:39 2019	(r349986)
+++ head/sys/netinet/tcp_stacks/rack.c	Sun Jul 14 16:05:47 2019	(r349987)
@@ -5087,9 +5087,8 @@ rack_do_fastnewdata(struct mbuf *m, struct tcphdr *th,
 
 
 	/* Clean receiver SACK report if present */
-/*	if (tp->rcv_numsacks)
+	if (tp->rcv_numsacks)
 	        tcp_clean_sackreport(tp);
-*/
 	TCPSTAT_INC(tcps_preddat);
 	tp->rcv_nxt += tlen;
 	/*
@@ -8537,10 +8536,10 @@ out:
 	 * retransmit.  In persist state, just set snd_max.
 	 */
 	if (error == 0) {
-/*		if (TCPS_HAVEESTABLISHED(tp->t_state) &&
+		if (TCPS_HAVEESTABLISHED(tp->t_state) &&
 		    (tp->t_flags & TF_SACK_PERMIT) &&
 		    tp->rcv_numsacks > 0)
-		    tcp_clean_dsack_blocks(tp);*/
+		    tcp_clean_dsack_blocks(tp);
 		if (len == 0)
 			counter_u64_add(rack_out_size[TCP_MSS_ACCT_SNDACK], 1);
 		else if (len == 1) {

Modified: head/sys/netinet/tcp_var.h
==============================================================================
--- head/sys/netinet/tcp_var.h	Sun Jul 14 12:04:39 2019	(r349986)
+++ head/sys/netinet/tcp_var.h	Sun Jul 14 16:05:47 2019	(r349987)
@@ -939,6 +939,7 @@ tcp_seq	 tcp_new_isn(struct in_conninfo *);
 
 int	 tcp_sack_doack(struct tcpcb *, struct tcpopt *, tcp_seq);
 void	 tcp_update_sack_list(struct tcpcb *tp, tcp_seq rcv_laststart, tcp_seq rcv_lastend);
+void	 tcp_clean_dsack_blocks(struct tcpcb *tp);
 void	 tcp_clean_sackreport(struct tcpcb *tp);
 void	 tcp_sack_adjust(struct tcpcb *tp);
 struct sackhole *tcp_sack_output(struct tcpcb *tp, int *sack_bytes_rexmt);

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