Add the MBUF_FRAG_TEST option. When compiled in, this option

allows you to tell ip_output to fragment all outgoing packets
into mbuf fragments of size net.inet.ip.mbuf_frag_size bytes.
This is an excellent way to test if network drivers can properly
handle long mbuf chains being passed to them.

net.inet.ip.mbuf_frag_size defaults to 0 (no fragmentation)
so that you can at least boot before your network driver dies. :)

2 files changed, 31 insertions, 0 deletions

diff --git a/sys/conf/options b/sys/conf/options
index 1024a5d..82f2fce 100644
--- a/sys/conf/options
+++ b/sys/conf/options
@@ -360,6 +360,7 @@ SLIP_IFF_OPTS		opt_slip.h
 TCPDEBUG
 TCP_DROP_SYNFIN		opt_tcp_input.h
 XBONEHACK
+MBUF_FRAG_TEST		opt_mbuf_frag_test.h
 
 # Netgraph(4). Use option NETGRAPH to enable the base netgraph code.
 # Each netgraph node type can be either be compiled into the kernel
diff --git a/sys/netinet/ip_output.c b/sys/netinet/ip_output.c
index 9877964..02fb2d3 100644
--- a/sys/netinet/ip_output.c
+++ b/sys/netinet/ip_output.c
@@ -42,6 +42,7 @@
 #include "opt_mac.h"
 #include "opt_pfil_hooks.h"
 #include "opt_random_ip_id.h"
+#include "opt_mbuf_frag_test.h"
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -52,6 +53,7 @@
 #include <sys/protosw.h>
 #include <sys/socket.h>
 #include <sys/socketvar.h>
+#include <sys/sysctl.h>
 
 #include <net/if.h>
 #include <net/route.h>
@@ -94,6 +96,12 @@ static MALLOC_DEFINE(M_IPMOPTS, "ip_moptions", "internet multicast options");
 
 u_short ip_id;
 
+#ifdef MBUF_FRAG_TEST
+int mbuf_frag_size = 0;
+SYSCTL_INT(_net_inet_ip, OID_AUTO, mbuf_frag_size, CTLFLAG_RW,
+	&mbuf_frag_size, 0, "Fragment outgoing mbufs to this size");
+#endif
+
 static struct mbuf *ip_insertoptions(struct mbuf *, struct mbuf *, int *);
 static struct ifnet *ip_multicast_if(struct in_addr *, int *);
 static void	ip_mloopback
@@ -1012,6 +1020,28 @@ pass:
 		ipsec_delaux(m);
 #endif
 
+#ifdef MBUF_FRAG_TEST
+		if (mbuf_frag_size) {
+			struct mbuf *m1, *m2;
+			int length;
+
+			length = m->m_len;
+
+			while (1) {
+				length -= mbuf_frag_size;
+					if (length < 1)
+						break;
+				m1 = m_split(m, length, M_DONTWAIT);
+				m2 = m;
+				while (1) {
+					if (m2->m_next == NULL)
+						break;
+					m2 = m2->m_next;
+				}
+			m2->m_next = m1;
+			}
+		}
+#endif
 		error = (*ifp->if_output)(ifp, m,
 				(struct sockaddr *)dst, ro->ro_rt);
 		goto done;