From 3390d47670b18dbdd6f618cc7df61a233cb1e914 Mon Sep 17 00:00:00 2001
From: Mike Silbersack <silby@FreeBSD.org>
Date: Mon, 1 Sep 2003 05:55:37 +0000
Subject: [PATCH] Implement MBUF_STRESS_TEST mark II.

Changes from the original implementation:

- Fragmentation is handled by the function m_fragment, which can
be called from whereever fragmentation is needed.  Note that this
function is wrapped in #ifdef MBUF_STRESS_TEST to discourage non-testing
use.

- m_fragment works slightly differently from the old fragmentation
code in that it allocates a seperate mbuf cluster for each fragment.
This defeats dma_map_load_mbuf/buffer's feature of coalescing adjacent
fragments.  While that is a nice feature in practice, it nerfed the
usefulness of mbuf_stress_test.

- Add two modes of random fragmentation.  Chains with fragments all of
the same random length and chains with fragments that are each uniquely
random in length may now be requested.
---
 sys/kern/uipc_mbuf.c    | 84 +++++++++++++++++++++++++++++++++++++++++
 sys/netinet/ip_output.c | 20 +---------
 sys/sys/mbuf.h          |  1 +
 3 files changed, 87 insertions(+), 18 deletions(-)

diff --git a/sys/kern/uipc_mbuf.c b/sys/kern/uipc_mbuf.c
index c3e8856f5c45..3dfee6954a67 100644
--- a/sys/kern/uipc_mbuf.c
+++ b/sys/kern/uipc_mbuf.c
@@ -883,3 +883,87 @@ m_defrag(struct mbuf *m0, int how)
 		m_freem(m_final);
 	return (NULL);
 }
+
+#ifdef MBUF_STRESS_TEST
+
+/*
+ * Fragment an mbuf chain.  There's no reason you'd ever want to do
+ * this in normal usage, but it's great for stress testing various
+ * mbuf consumers.
+ *
+ * If fragmentation is not possible, the original chain will be
+ * returned.
+ *
+ * Possible length values:
+ * 0	 no fragmentation will occur
+ * > 0	each fragment will be of the specified length
+ * -1	each fragment will be the same random value in length
+ * -2	each fragment's length will be entirely random
+ * (Random values range from 1 to 256)
+ */
+struct mbuf *
+m_fragment(struct mbuf *m0, int how, int length)
+{
+	struct mbuf	*m_new = NULL, *m_final = NULL;
+	int		progress = 0;
+
+	if (!(m0->m_flags & M_PKTHDR))
+		return (m0);
+	
+	if ((length == 0) || (length < -2))
+		return (m0);
+
+	m_fixhdr(m0); /* Needed sanity check */
+
+	m_final = m_getcl(how, MT_DATA, M_PKTHDR);
+
+	if (m_final == NULL)
+		goto nospace;
+
+	if (m_dup_pkthdr(m_final, m0, how) == NULL)
+		goto nospace;
+
+	m_new = m_final;
+
+	if (length == -1)
+		length = 1 + (arc4random() & 255);
+
+	while (progress < m0->m_pkthdr.len) {
+		int fraglen;
+
+		if (length > 0)
+			fraglen = length;
+		else
+			fraglen = 1 + (arc4random() & 255);
+		if (fraglen > m0->m_pkthdr.len - progress)
+			fraglen = m0->m_pkthdr.len - progress;
+
+		if (fraglen > MCLBYTES)
+			fraglen = MCLBYTES;
+
+		if (m_new == NULL) {
+			m_new = m_getcl(how, MT_DATA, 0);
+			if (m_new == NULL)
+				goto nospace;
+		}
+
+		m_copydata(m0, progress, fraglen, mtod(m_new, caddr_t));
+		progress += fraglen;
+		m_new->m_len = fraglen;
+		if (m_new != m_final)
+			m_cat(m_final, m_new);
+		m_new = NULL;
+	}
+	m_freem(m0);
+	m0 = m_final;
+	return (m0);
+nospace:
+	if (m_new)
+		m_free(m_new);
+	if (m_final)
+		m_freem(m_final);
+	/* Return the original chain on failure */
+	return (m0);
+}
+
+#endif
diff --git a/sys/netinet/ip_output.c b/sys/netinet/ip_output.c
index 4a507cf8224b..f6a70efc9e5a 100644
--- a/sys/netinet/ip_output.c
+++ b/sys/netinet/ip_output.c
@@ -1030,24 +1030,8 @@ ip_output(struct mbuf *m0, struct mbuf *opt, struct route *ro,
 #endif
 
 #ifdef MBUF_STRESS_TEST
-		if (mbuf_frag_size && m->m_pkthdr.len > mbuf_frag_size) {
-			struct mbuf *m1, *m2;
-			int length, tmp;
-
-			tmp = length = m->m_pkthdr.len;
-
-			while ((length -= mbuf_frag_size) >= 1) {
-				m1 = m_split(m, length, M_DONTWAIT);
-				if (m1 == NULL)
-					break;
-				m1->m_flags &= ~M_PKTHDR;
-				m2 = m;
-				while (m2->m_next != NULL)
-					m2 = m2->m_next;
-				m2->m_next = m1;
-				m->m_pkthdr.len = tmp;
-			}
-		}
+		if (mbuf_frag_size && m->m_pkthdr.len > mbuf_frag_size)
+			m = m_fragment(m, M_DONTWAIT, mbuf_frag_size);
 #endif
 		error = (*ifp->if_output)(ifp, m,
 				(struct sockaddr *)dst, ro->ro_rt);
diff --git a/sys/sys/mbuf.h b/sys/sys/mbuf.h
index a0e4b47b982a..abdd6625f06b 100644
--- a/sys/sys/mbuf.h
+++ b/sys/sys/mbuf.h
@@ -443,6 +443,7 @@ struct	mbuf	*m_devget(char *, int, int, struct ifnet *,
 struct	mbuf	*m_dup(struct mbuf *, int);
 int		 m_dup_pkthdr(struct mbuf *, struct mbuf *, int);
 u_int		 m_fixhdr(struct mbuf *);
+struct	mbuf	*m_fragment(struct mbuf *, int, int);
 struct	mbuf	*m_free(struct mbuf *);
 void		 m_freem(struct mbuf *);
 struct	mbuf	*m_get(int, short);