From 4ff9852103f3a200762b84ed9109a44dcdede5b7 Mon Sep 17 00:00:00 2001
From: "Bjoern A. Zeeb" <bz@FreeBSD.org>
Date: Sat, 28 Nov 2009 21:40:57 +0000
Subject: [PATCH] Directly send data uncompressed if the packet payload size is
 lower than the compression algorithm threshold.

MFC after:	6 days
---
 sys/netipsec/xform_ipcomp.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/sys/netipsec/xform_ipcomp.c b/sys/netipsec/xform_ipcomp.c
index 4049154ac3ee..93a157e77ca1 100644
--- a/sys/netipsec/xform_ipcomp.c
+++ b/sys/netipsec/xform_ipcomp.c
@@ -343,6 +343,17 @@ ipcomp_output(
 	ipcompx = sav->tdb_compalgxform;
 	IPSEC_ASSERT(ipcompx != NULL, ("null compression xform"));
 
+	/*
+	 * Do not touch the packet in case our payload to compress
+	 * is lower than the minimal threshold of the compression
+	 * alogrithm.  We will just send out the data uncompressed.
+	 * See RFC 3173, 2.2. Non-Expansion Policy.
+	 */
+	if (m->m_pkthdr.len <= ipcompx->minlen) {
+		/* XXX-BZ V_ipcompstat.threshold++; */
+		return ipsec_process_done(m, isr);
+	}
+
 	ralen = m->m_pkthdr.len - skip;	/* Raw payload length before comp. */
 	hlen = IPCOMP_HLENGTH;