--- Net2/net/if_loop.c	2018/04/24 18:04:02	1.1.1.1
+++ Net2/net/if_loop.c	2018/04/24 18:21:40	1.1.1.3
@@ -30,7 +30,8 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	@(#)if_loop.c	7.13 (Berkeley) 4/26/91
+ *	from: @(#)if_loop.c	7.13 (Berkeley) 4/26/91
+ *	if_loop.c,v 1.6 1993/06/27 06:02:27 andrew Exp
  */
 
 /*
@@ -43,6 +44,9 @@
 #include "socket.h"
 #include "errno.h"
 #include "ioctl.h"
+#include "protosw.h"
+
+#include "loop.h"
 
 #include "../net/if.h"
 #include "../net/if_types.h"
@@ -68,24 +72,41 @@
 #include "../netiso/iso_var.h"
 #endif
 
+#include "bpfilter.h"
+#if NBPFILTER > 0
+#include <sys/time.h>
+#include <net/bpf.h>
+static caddr_t lo_bpf;
+#endif
+
 #define	LOMTU	(1024+512)
 
-struct	ifnet loif;
+struct	ifnet loif[NLOOP];
 int	looutput(), loioctl();
 
+void
 loattach()
 {
-	register struct ifnet *ifp = &loif;
+	register int i;
+	register struct ifnet *ifp;
 
-	ifp->if_name = "lo";
-	ifp->if_mtu = LOMTU;
-	ifp->if_flags = IFF_LOOPBACK;
-	ifp->if_ioctl = loioctl;
-	ifp->if_output = looutput;
-	ifp->if_type = IFT_LOOP;
-	ifp->if_hdrlen = 0;
-	ifp->if_addrlen = 0;
-	if_attach(ifp);
+	for (i = 0; i < NLOOP; i++)
+	{
+		ifp = &loif[i];
+		ifp->if_unit = i;
+		ifp->if_name = "lo";
+		ifp->if_mtu = LOMTU;
+		ifp->if_flags = IFF_LOOPBACK;
+		ifp->if_ioctl = loioctl;
+		ifp->if_output = looutput;
+		ifp->if_type = IFT_LOOP;
+		ifp->if_hdrlen = 0;
+		ifp->if_addrlen = 0;
+		if_attach(ifp);
+#if NBPFILTER > 0
+		bpfattach(&lo_bpf, ifp, DLT_NULL, sizeof(u_int));
+#endif
+	}
 }
 
 looutput(ifp, m, dst, rt)
@@ -99,6 +120,25 @@ looutput(ifp, m, dst, rt)
 
 	if ((m->m_flags & M_PKTHDR) == 0)
 		panic("looutput no HDR");
+#if NBPFILTER > 0
+	if (lo_bpf) {
+		/*
+		 * We need to prepend the address family as
+		 * a four byte field.  Cons up a dummy header
+		 * to pacify bpf.  This is safe because bpf
+		 * will only read from the mbuf (i.e., it won't
+		 * try to free it or keep a pointer to it).
+		 */
+		struct mbuf m0;
+		u_int af = dst->sa_family;
+
+		m0.m_next = m;
+		m0.m_len = 4;
+		m0.m_data = (char *)&af;
+
+		bpf_mtap(lo_bpf, &m0);
+	}
+#endif
 	m->m_pkthdr.rcvif = ifp;
 
 	if (rt && rt->rt_flags & RTF_REJECT) {