o eliminate widespread on-stack mbuf use for bpf by introducing

  a new bpf_mtap2 routine that does the right thing for an mbuf
  and a variable-length chunk of data that should be prepended.
o while we're sweeping the drivers, use u_int32_t uniformly when
  when prepending the address family (several places were assuming
  sizeof(int) was 4)
o return M_ASSERTVALID to BPF_MTAP* now that all stack-allocated
  mbufs have been eliminated; this may better be moved to the bpf
  routines

Reviewed by:	arch@ and several others

1 files changed, 1 insertions, 14 deletions

diff --git a/sys/net/if_disc.c b/sys/net/if_disc.c
index 48935b3..bc1f0ad 100644
--- a/sys/net/if_disc.c
+++ b/sys/net/if_disc.c
@@ -164,21 +164,8 @@ discoutput(struct ifnet *ifp, struct mbuf *m, struct sockaddr *dst,
 	}
 
 	if (ifp->if_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 *)⁡
-
-		BPF_MTAP(ifp, &m0);
+		bpf_mtap2(ifp->if_bpf, &af, sizeof(af), m);
 	}
 	m->m_pkthdr.rcvif = ifp;