From 7ae3d4bf547fbeb9dda13fb8136ad92ae909ae21 Mon Sep 17 00:00:00 2001
From: Sepherosa Ziehau <sephe@FreeBSD.org>
Date: Thu, 18 Feb 2016 04:58:34 +0000
Subject: [PATCH] tcp/lro: Allow drivers to set the TCP ACK/data segment
 aggregation limit

ACK aggregation limit is append count based, while the TCP data segment
aggregation limit is length based.  Unless the network driver sets these
two limits, it's an NO-OP.

Reviewed by:	adrian, gallatin (previous version), hselasky (previous version)
Approved by:	adrian (mentor)
MFC after:	1 week
Sponsored by:	Microsoft OSTC
Differential Revision:	https://reviews.freebsd.org/D5185
---
 sys/netinet/tcp_lro.c | 15 +++++++++++++--
 sys/netinet/tcp_lro.h |  5 +++++
 sys/sys/param.h       |  2 +-
 3 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/sys/netinet/tcp_lro.c b/sys/netinet/tcp_lro.c
index 62d8595c3f70..7067abe6840f 100644
--- a/sys/netinet/tcp_lro.c
+++ b/sys/netinet/tcp_lro.c
@@ -88,6 +88,8 @@ tcp_lro_init_args(struct lro_ctrl *lc, struct ifnet *ifp,
 	lc->lro_mbuf_count = 0;
 	lc->lro_mbuf_max = lro_mbufs;
 	lc->lro_cnt = lro_entries;
+	lc->lro_ackcnt_lim = TCP_LRO_ACKCNT_MAX;
+	lc->lro_length_lim = TCP_LRO_LENGTH_MAX;
 	lc->ifp = ifp;
 	SLIST_INIT(&lc->lro_free);
 	SLIST_INIT(&lc->lro_active);
@@ -610,7 +612,7 @@ tcp_lro_rx(struct lro_ctrl *lc, struct mbuf *m, uint32_t csum)
 		}
 
 		/* Flush now if appending will result in overflow. */
-		if (le->p_len > (65535 - tcp_data_len)) {
+		if (le->p_len > (lc->lro_length_lim - tcp_data_len)) {
 			SLIST_REMOVE(&lc->lro_active, le, lro_entry, next);
 			tcp_lro_flush(lc, le);
 			break;
@@ -648,6 +650,15 @@ tcp_lro_rx(struct lro_ctrl *lc, struct mbuf *m, uint32_t csum)
 
 		if (tcp_data_len == 0) {
 			m_freem(m);
+			/*
+			 * Flush this LRO entry, if this ACK should not
+			 * be further delayed.
+			 */
+			if (le->append_cnt >= lc->lro_ackcnt_lim) {
+				SLIST_REMOVE(&lc->lro_active, le, lro_entry,
+				    next);
+				tcp_lro_flush(lc, le);
+			}
 			return (0);
 		}
 
@@ -668,7 +679,7 @@ tcp_lro_rx(struct lro_ctrl *lc, struct mbuf *m, uint32_t csum)
 		 * If a possible next full length packet would cause an
 		 * overflow, pro-actively flush now.
 		 */
-		if (le->p_len > (65535 - lc->ifp->if_mtu)) {
+		if (le->p_len > (lc->lro_length_lim - lc->ifp->if_mtu)) {
 			SLIST_REMOVE(&lc->lro_active, le, lro_entry, next);
 			tcp_lro_flush(lc, le);
 		} else
diff --git a/sys/netinet/tcp_lro.h b/sys/netinet/tcp_lro.h
index 48c679dec340..3fc627c31500 100644
--- a/sys/netinet/tcp_lro.h
+++ b/sys/netinet/tcp_lro.h
@@ -91,11 +91,16 @@ struct lro_ctrl {
 	unsigned	lro_cnt;
 	unsigned	lro_mbuf_count;
 	unsigned	lro_mbuf_max;
+	unsigned short	lro_ackcnt_lim;		/* max # of aggregated ACKs */
+	unsigned 	lro_length_lim;		/* max len of aggregated data */
 
 	struct lro_head	lro_active;
 	struct lro_head	lro_free;
 };
 
+#define	TCP_LRO_LENGTH_MAX	65535
+#define	TCP_LRO_ACKCNT_MAX	65535		/* unlimited */
+
 int tcp_lro_init(struct lro_ctrl *);
 int tcp_lro_init_args(struct lro_ctrl *, struct ifnet *, unsigned, unsigned);
 void tcp_lro_free(struct lro_ctrl *);
diff --git a/sys/sys/param.h b/sys/sys/param.h
index bb53a93170f3..f9b4b280d2bd 100644
--- a/sys/sys/param.h
+++ b/sys/sys/param.h
@@ -58,7 +58,7 @@
  *		in the range 5 to 9.
  */
 #undef __FreeBSD_version
-#define __FreeBSD_version 1100098	/* Master, propagated to newvers */
+#define __FreeBSD_version 1100099	/* Master, propagated to newvers */
 
 /*
  * __FreeBSD_kernel__ indicates that this system uses the kernel of FreeBSD,