Go through the loopback code with a broom..

Remove lots'o'hacks.
looutput is now static.

Other callers who want to use loopback to allow shortcutting
should call the special entrypoint for this, if_simloop(), which is
specifically designed for this purpose. Using looutput for this purpose
was problematic, particularly with bpf and trying to keep track
of whether one should be using the charateristics of the loopback interface
or the interface (e.g. if_ethersubr.c) that was requesting the loopback.
There was a whole class of errors due to this mis-use each of which had
hacks to cover them up.

Consists largly of hack removal :-)

1 files changed, 62 insertions, 27 deletions

diff --git a/sys/net/if_loop.c b/sys/net/if_loop.c
index f594525..c6f3832 100644
--- a/sys/net/if_loop.c
+++ b/sys/net/if_loop.c
@@ -31,7 +31,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)if_loop.c	8.1 (Berkeley) 6/10/93
- * $Id: if_loop.c,v 1.31 1998/04/30 19:37:00 phk Exp $
+ * $Id: if_loop.c,v 1.32 1998/06/07 17:12:03 dfr Exp $
  */
 
 /*
@@ -83,6 +83,9 @@
 #endif NETATALK
 
 #include "bpfilter.h"
+#if NBPFILTER > 0
+#include <net/bpfdesc.h>
+#endif
 
 static int loioctl __P((struct ifnet *, u_long, caddr_t));
 static void lortrequest __P((int, struct rtentry *, struct sockaddr *));
@@ -90,6 +93,9 @@ static void lortrequest __P((int, struct rtentry *, struct sockaddr *));
 static void loopattach __P((void *));
 PSEUDO_SET(loopattach, if_loop);
 
+static int looutput __P((struct ifnet *ifp,
+		struct mbuf *m, struct sockaddr *dst, struct rtentry *rt));
+
 #ifdef TINY_LOMTU
 #define	LOMTU	(1024+512)
 #else
@@ -121,18 +127,50 @@ loopattach(dummy)
 	}
 }
 
-int
+static int
 looutput(ifp, m, dst, rt)
 	struct ifnet *ifp;
 	register struct mbuf *m;
 	struct sockaddr *dst;
 	register struct rtentry *rt;
 {
+	if ((m->m_flags & M_PKTHDR) == 0)
+		panic("looutput no HDR");
+
+	if (rt && rt->rt_flags & (RTF_REJECT|RTF_BLACKHOLE)) {
+		m_freem(m);
+		return (rt->rt_flags & RTF_BLACKHOLE ? 0 :
+		        rt->rt_flags & RTF_HOST ? EHOSTUNREACH : ENETUNREACH);
+	}
+	ifp->if_opackets++;
+	ifp->if_obytes += m->m_pkthdr.len;
+	return(if_simloop(ifp, m, dst, 0));
+}
+
+/*
+ * if_simloop()
+ *
+ * This function is to support software emulation of hardware loopback,
+ * i.e., for interfaces with the IFF_SIMPLEX attribute. Since they can't
+ * hear their own broadcasts, we create a copy of the packet that we
+ * would normally receive via a hardware loopback.
+ *
+ * This function expects the packet to include the media header of length hlen.
+ */
+
+int
+if_simloop(ifp, m, dst, hlen)
+	struct ifnet *ifp;
+	register struct mbuf *m;
+	struct sockaddr *dst;
+	int hlen;
+{
 	int s, isr;
 	register struct ifqueue *ifq = 0;
 
 	if ((m->m_flags & M_PKTHDR) == 0)
-		panic("looutput no HDR");
+		panic("%s: no HDR", __FUNCTION__);
+	m->m_pkthdr.rcvif = ifp;
 #if NBPFILTER > 0
 	/* BPF write needs to be handled specially */
 	if (dst->sa_family == AF_UNSPEC) {
@@ -143,34 +181,31 @@ looutput(ifp, m, dst, rt)
 	}
 
 	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;
+		struct mbuf m0, *n = m;
 		u_int af = dst->sa_family;
 
-		m0.m_next = m;
-		m0.m_len = 4;
-		m0.m_data = (char *)&af;
-
-		bpf_mtap(ifp, &m0);
+		if (ifp->if_bpf->bif_dlt == DLT_NULL) {
+			/*
+			 * 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).
+			 */
+			m0.m_next = m;
+			m0.m_len = 4;
+			m0.m_data = (char *)&af;
+			n = &m0;
+		}
+		bpf_mtap(ifp, n);
 	}
 #endif
-	m->m_pkthdr.rcvif = ifp;
 
-	if (rt && rt->rt_flags & (RTF_REJECT|RTF_BLACKHOLE)) {
-		m_freem(m);
-		return (rt->rt_flags & RTF_BLACKHOLE ? 0 :
-		        rt->rt_flags & RTF_HOST ? EHOSTUNREACH : ENETUNREACH);
-	}
-	ifp->if_opackets++;
-	ifp->if_obytes += m->m_pkthdr.len;
-	switch (dst->sa_family) {
+	/* Strip away media header */
+	if (hlen > 0)
+		m_adj(m, hlen);
 
+	switch (dst->sa_family) {
 #ifdef INET
 	case AF_INET:
 		ifq = &ipintrq;
@@ -202,8 +237,8 @@ looutput(ifp, m, dst, rt)
 		break;
 #endif NETATALK
 	default:
-		printf("lo%d: can't handle af%d\n", ifp->if_unit,
-			dst->sa_family);
+		printf("%s: can't handle af=%d\n",
+		  __FUNCTION__, dst->sa_family);
 		m_freem(m);
 		return (EAFNOSUPPORT);
 	}