From 352d050e790e3ee7e8441dfd38d23bbd62c337a8 Mon Sep 17 00:00:00 2001
From: Mike Silbersack <silby@FreeBSD.org>
Date: Tue, 15 Apr 2003 02:14:43 +0000
Subject: [PATCH] Add another MBUF_STRESS_TEST feature, m_defragrandomfailures.

When enabled, this causes m_defrag to randomly return NULL (following
its normal failure case so that extra memory leaks are not introduced.)

Code similar to this was used to find / fix a few bugs last week.
---
 sys/kern/uipc_mbuf.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/sys/kern/uipc_mbuf.c b/sys/kern/uipc_mbuf.c
index 08a7246409e..8810358ed9c 100644
--- a/sys/kern/uipc_mbuf.c
+++ b/sys/kern/uipc_mbuf.c
@@ -36,6 +36,7 @@
 
 #include "opt_mac.h"
 #include "opt_param.h"
+#include "opt_mbuf_stress_test.h"
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -56,6 +57,9 @@ int	m_defragpackets;
 int	m_defragbytes;
 int	m_defraguseless;
 int	m_defragfailure;
+#ifdef MBUF_STRESS_TEST
+int	m_defragrandomfailures;
+#endif
 
 /*
  * sysctl(8) exported objects
@@ -76,6 +80,10 @@ SYSCTL_INT(_kern_ipc, OID_AUTO, m_defraguseless, CTLFLAG_RD,
 	   &m_defraguseless, 0, "");
 SYSCTL_INT(_kern_ipc, OID_AUTO, m_defragfailure, CTLFLAG_RD,
 	   &m_defragfailure, 0, "");
+#ifdef MBUF_STRESS_TEST
+SYSCTL_INT(_kern_ipc, OID_AUTO, m_defragrandomfailures, CTLFLAG_RW,
+	   &m_defragrandomfailures, 0, "");
+#endif
 
 /*
  * "Move" mbuf pkthdr from "from" to "to".
@@ -802,6 +810,13 @@ m_defrag(struct mbuf *m0, int how)
 	if (!(m0->m_flags & M_PKTHDR))
 		return (m0);
 
+#ifdef MBUF_STRESS_TEST
+	if (m_defragrandomfailures) {
+		int temp = arc4random() & 0xff;
+		if (temp == 0xba)
+			goto nospace;
+	}
+#endif
 	
 	if (m0->m_pkthdr.len > MHLEN)
 		m_final = m_getcl(how, MT_DATA, M_PKTHDR);