When using TSO and sending more than TCP_MAXWIN sendalot is set

and we loop back to 'again'.  If the remainder is less or equal
to one full segment, the TSO flag was not cleared even though
it isn't necessary anymore.  Enabling the TSO flag on a segment
that doesn't require any offloaded segmentation by the NIC may
cause confusion in the driver or hardware.

Reset the internal tso flag in tcp_output() on every iteration
of sendalot.

PR:		kern/132832
Submitted by:	Renaud Lienhart <renaud-at-vmware com>
MFC after:	1 week

1 files changed, 5 insertions, 2 deletions

diff --git a/sys/netinet/tcp_output.c b/sys/netinet/tcp_output.c
index 50973c4..4327c7e 100644
--- a/sys/netinet/tcp_output.c
+++ b/sys/netinet/tcp_output.c
@@ -153,7 +153,7 @@ tcp_output(struct tcpcb *tp)
 	int idle, sendalot;
 	int sack_rxmit, sack_bytes_rxmt;
 	struct sackhole *p;
-	int tso = 0;
+	int tso;
 	struct tcpopt to;
 #if 0
 	int maxburst = TCP_MAXBURST;
@@ -211,6 +211,7 @@ again:
 	    SEQ_LT(tp->snd_nxt, tp->snd_max))
 		tcp_sack_adjust(tp);
 	sendalot = 0;
+	tso = 0;
 	off = tp->snd_nxt - tp->snd_una;
 	sendwin = min(tp->snd_wnd, tp->snd_cwnd);
 	sendwin = min(sendwin, tp->snd_bwnd);
@@ -490,9 +491,9 @@ after_sack_rexmit:
 		} else {
 			len = tp->t_maxseg;
 			sendalot = 1;
-			tso = 0;
 		}
 	}
+
 	if (sack_rxmit) {
 		if (SEQ_LT(p->rxmit + len, tp->snd_una + so->so_snd.sb_cc))
 			flags &= ~TH_FIN;
@@ -1051,6 +1052,8 @@ send:
 	 * XXX: Fixme: This is currently not the case for IPv6.
 	 */
 	if (tso) {
+		KASSERT(len > tp->t_maxopd - optlen,
+		    ("%s: len <= tso_segsz", __func__));
 		m->m_pkthdr.csum_flags |= CSUM_TSO;
 		m->m_pkthdr.tso_segsz = tp->t_maxopd - optlen;
 	}