Fix some long standing bugs in writing to the BPF device attached to

a DLT_NULL interface. In particular:

        1) Consistently use type u_int32_t for the header of a
           DLT_NULL device - it continues to represent the address
           family as always.
        2) In the DLT_NULL case get bpf_movein to store the u_int32_t
           in a sockaddr rather than in the mbuf, to be consistent
           with all the DLT types.
        3) Consequently fix a bug in bpf_movein/bpfwrite which
           only permitted packets up to 4 bytes less than the MTU
           to be written.
        4) Fix all DLT_NULL devices to have the code required to
           allow writing to their bpf devices.
        5) Move the code to allow writing to if_lo from if_simloop
           to looutput, because it only applies to DLT_NULL devices
           but was being applied to other devices that use if_simloop
           possibly incorrectly.

PR:		82157
Submitted by:	Matthew Luckie <mjl@luckie.org.nz>
Approved by:	re (scottl)

1 files changed, 10 insertions, 10 deletions

diff --git a/sys/net/if_loop.c b/sys/net/if_loop.c
index d10d859..12231b2 100644
--- a/sys/net/if_loop.c
+++ b/sys/net/if_loop.c
@@ -156,7 +156,7 @@ lo_clone_create(ifc, unit)
 	ifp->if_snd.ifq_maxlen = ifqmaxlen;
 	ifp->if_softc = sc;
 	if_attach(ifp);
-	bpfattach(ifp, DLT_NULL, sizeof(u_int));
+	bpfattach(ifp, DLT_NULL, sizeof(u_int32_t));
 	mtx_lock(&lo_mtx);
 	LIST_INSERT_HEAD(&lo_list, sc, sc_next);
 	mtx_unlock(&lo_mtx);
@@ -199,6 +199,8 @@ looutput(ifp, m, dst, rt)
 	struct sockaddr *dst;
 	register struct rtentry *rt;
 {
+	u_int32_t af;
+
 	M_ASSERTPKTHDR(m); /* check if we have the packet header */
 
 	if (rt && rt->rt_flags & (RTF_REJECT|RTF_BLACKHOLE)) {
@@ -209,6 +211,13 @@ looutput(ifp, m, dst, rt)
 
 	ifp->if_opackets++;
 	ifp->if_obytes += m->m_pkthdr.len;
+
+	/* BPF writes need to be handled specially. */
+	if (dst->sa_family == AF_UNSPEC) {
+		bcopy(dst->sa_data, &af, sizeof(af));
+		dst->sa_family = af;
+	}
+
 #if 1	/* XXX */
 	switch (dst->sa_family) {
 	case AF_INET:
@@ -249,15 +258,6 @@ if_simloop(ifp, m, af, hlen)
 	m_tag_delete_nonpersistent(m);
 	m->m_pkthdr.rcvif = ifp;
 
-	/* BPF write needs to be handled specially */
-	if (af == AF_UNSPEC) {
-		KASSERT(m->m_len >= sizeof(int), ("if_simloop: m_len"));
-		af = *(mtod(m, int *));
-		m->m_len -= sizeof(int);
-		m->m_pkthdr.len -= sizeof(int);
-		m->m_data += sizeof(int);
-	}
-
 	/* Let BPF see incoming packet */
 	if (ifp->if_bpf) {
 		if (ifp->if_bpf->bif_dlt == DLT_NULL) {