*** /tmp/,RCSt1a01575	Wed Jan 29 03:06:11 1992
--- if_loop.c	Wed Jan 29 02:35:15 1992
***************
*** 70,75 ****
--- 70,82 ----
  #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;
***************
*** 88,93 ****
--- 95,103 ----
  	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)
***************
*** 101,106 ****
--- 111,135 ----
  
  	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 a 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) {