make the bpf tap functions take const struct mbuf *

this makes it more obvious that the bpf code should only read
packets, never modify them.

now possible because the paths that care about M_FILDROP set it
after calling bpf_mtap.

ok mpi@ visa@ deraadt@

2 files changed, 17 insertions, 26 deletions

diff --git a/sys/net/bpf.c b/sys/net/bpf.c
index db871b31756..9a8273114bf 100644
--- a/sys/net/bpf.c
+++ b/sys/net/bpf.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: bpf.c,v 1.139 2016/04/14 08:27:24 natano Exp $	*/
+/*	$OpenBSD: bpf.c,v 1.140 2016/05/10 23:48:07 dlg Exp $	*/
 /*	$NetBSD: bpf.c,v 1.33 1997/02/21 23:59:35 thorpej Exp $	*/
 
 /*
@@ -93,7 +93,7 @@ LIST_HEAD(, bpf_d) bpf_d_list;
 void	bpf_allocbufs(struct bpf_d *);
 void	bpf_freed(struct bpf_d *);
 void	bpf_ifname(struct ifnet *, struct ifreq *);
-int	_bpf_mtap(caddr_t, struct mbuf *, u_int,
+int	_bpf_mtap(caddr_t, const struct mbuf *, u_int,
 	    void (*)(const void *, void *, size_t));
 void	bpf_mcopy(const void *, void *, size_t);
 int	bpf_movein(struct uio *, u_int, struct mbuf **,
@@ -1210,14 +1210,14 @@ bpf_mcopy(const void *src_arg, void *dst_arg, size_t len)
  * like bpf_mtap, but copy fn can be given. used by various bpf_mtap*
  */
 int
-_bpf_mtap(caddr_t arg, struct mbuf *m, u_int direction,
+_bpf_mtap(caddr_t arg, const struct mbuf *m, u_int direction,
     void (*cpfn)(const void *, void *, size_t))
 {
 	struct bpf_if *bp = (struct bpf_if *)arg;
 	struct srpl_iter i;
 	struct bpf_d *d;
 	size_t pktlen, slen;
-	struct mbuf *m0;
+	const struct mbuf *m0;
 	struct timeval tv;
 	int gottime = 0;
 	int drop = 0;
@@ -1271,9 +1271,6 @@ _bpf_mtap(caddr_t arg, struct mbuf *m, u_int direction,
 	}
 	SRPL_LEAVE(&i, d);
 
-	if (drop)
-		m->m_flags |= M_FILDROP;
-
 	return (drop);
 }
 
@@ -1281,7 +1278,7 @@ _bpf_mtap(caddr_t arg, struct mbuf *m, u_int direction,
  * Incoming linkage from device drivers, when packet is in an mbuf chain.
  */
 int
-bpf_mtap(caddr_t arg, struct mbuf *m, u_int direction)
+bpf_mtap(caddr_t arg, const struct mbuf *m, u_int direction)
 {
 	return _bpf_mtap(arg, m, direction, NULL);
 }
@@ -1296,28 +1293,22 @@ bpf_mtap(caddr_t arg, struct mbuf *m, u_int direction)
  * it or keep a pointer to it.
  */
 int
-bpf_mtap_hdr(caddr_t arg, caddr_t data, u_int dlen, struct mbuf *m,
+bpf_mtap_hdr(caddr_t arg, caddr_t data, u_int dlen, const struct mbuf *m,
     u_int direction, void (*cpfn)(const void *, void *, size_t))
 {
-	struct m_hdr	 mh;
-	struct mbuf	*m0;
-	int		drop;
+	struct m_hdr mh;
+	const struct mbuf *m0;
 
 	if (dlen > 0) {
 		mh.mh_flags = 0;
-		mh.mh_next = m;
+		mh.mh_next = (struct mbuf *)m;
 		mh.mh_len = dlen;
 		mh.mh_data = data;
 		m0 = (struct mbuf *)&mh;
 	} else 
 		m0 = m;
 
-	drop = _bpf_mtap(arg, m0, direction, cpfn);
-
-	if (m0 != m)
-		m->m_flags |= m0->m_flags & M_FILDROP;
-
-	return (drop);
+	return _bpf_mtap(arg, m0, direction, cpfn);
 }
 
 /*
@@ -1330,7 +1321,7 @@ bpf_mtap_hdr(caddr_t arg, caddr_t data, u_int dlen, struct mbuf *m,
  * it or keep a pointer to it.
  */
 int
-bpf_mtap_af(caddr_t arg, u_int32_t af, struct mbuf *m, u_int direction)
+bpf_mtap_af(caddr_t arg, u_int32_t af, const struct mbuf *m, u_int direction)
 {
 	u_int32_t    afh;
 
@@ -1350,7 +1341,7 @@ bpf_mtap_af(caddr_t arg, u_int32_t af, struct mbuf *m, u_int direction)
  * it or keep a pointer to it.
  */
 int
-bpf_mtap_ether(caddr_t arg, struct mbuf *m, u_int direction)
+bpf_mtap_ether(caddr_t arg, const struct mbuf *m, u_int direction)
 {
 #if NVLAN > 0
 	struct ether_vlan_header evh;
diff --git a/sys/net/bpf.h b/sys/net/bpf.h
index 09ad1902ce7..c23d69a5e99 100644
--- a/sys/net/bpf.h
+++ b/sys/net/bpf.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: bpf.h,v 1.55 2016/04/03 01:37:26 dlg Exp $	*/
+/*	$OpenBSD: bpf.h,v 1.56 2016/05/10 23:48:07 dlg Exp $	*/
 /*	$NetBSD: bpf.h,v 1.15 1996/12/13 07:57:33 mikel Exp $	*/
 
 /*
@@ -289,11 +289,11 @@ struct mbuf;
 
 int	 bpf_validate(struct bpf_insn *, int);
 int	 bpf_tap(caddr_t, u_char *, u_int, u_int);
-int	 bpf_mtap(caddr_t, struct mbuf *, u_int);
-int	 bpf_mtap_hdr(caddr_t, caddr_t, u_int, struct mbuf *, u_int,
+int	 bpf_mtap(caddr_t, const struct mbuf *, u_int);
+int	 bpf_mtap_hdr(caddr_t, caddr_t, u_int, const struct mbuf *, u_int,
 	    void (*)(const void *, void *, size_t));
-int	 bpf_mtap_af(caddr_t, u_int32_t, struct mbuf *, u_int);
-int	 bpf_mtap_ether(caddr_t, struct mbuf *, u_int);
+int	 bpf_mtap_af(caddr_t, u_int32_t, const struct mbuf *, u_int);
+int	 bpf_mtap_ether(caddr_t, const struct mbuf *, u_int);
 void	 bpfattach(caddr_t *, struct ifnet *, u_int, u_int);
 void	 bpfdetach(struct ifnet *);
 void	 bpfilterattach(int);