Switch tun(4) from encapsualting packets into a long mbuf chain over to use

mbuf clusters if the packet is big enough. This should speed up tun(4) and
may help in other cases where long mbuf chains hurt.
Additionally switch the default tun(4) MTU to a more sane 1500 bytes.
TUNMTU is kept because it is used in userland.
Input and OK from brad@ and djm@

1 files changed, 18 insertions, 2 deletions

diff --git a/sys/net/if_tun.c b/sys/net/if_tun.c
index aacce07d36c..e2bddf1183a 100644
--- a/sys/net/if_tun.c
+++ b/sys/net/if_tun.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: if_tun.c,v 1.76 2006/03/05 02:35:38 brad Exp $	*/
+/*	$OpenBSD: if_tun.c,v 1.77 2006/03/16 09:30:54 claudio Exp $	*/
 /*	$NetBSD: if_tun.c,v 1.24 1996/05/07 02:40:48 thorpej Exp $	*/
 
 /*
@@ -200,7 +200,7 @@ tun_create(struct if_clone *ifc, int unit, int flags)
 	IFQ_SET_READY(&ifp->if_snd);
 	if ((flags & TUN_LAYER2) == 0) {
 		tp->tun_flags &= ~TUN_LAYER2;
-		ifp->if_mtu = TUNMTU;
+		ifp->if_mtu = ETHERMTU;
 		ifp->if_flags = IFF_POINTOPOINT;
 		ifp->if_type = IFT_TUNNEL;
 		ifp->if_hdrlen = sizeof(u_int32_t);
@@ -828,6 +828,14 @@ tunwrite(dev_t dev, struct uio *uio, int ioflag)
 	if (m == NULL)
 		return (ENOBUFS);
 	mlen = MHLEN;
+	if (uio->uio_resid >= MINCLSIZE) {
+		MCLGET(m, M_DONTWAIT);
+		if (!(m->m_flags & M_EXT)) {
+			m_freem(m);
+			return (ENOBUFS);
+		}
+		mlen = MCLBYTES;
+	}
 
 	top = NULL;
 	mp = ⊤
@@ -851,6 +859,14 @@ tunwrite(dev_t dev, struct uio *uio, int ioflag)
 				break;
 			}
 			mlen = MLEN;
+			if (uio->uio_resid >= MINCLSIZE) {
+				MCLGET(m, M_DONTWAIT);
+				if (!(m->m_flags & M_EXT)) {
+					error = ENOBUFS;
+					break;
+				}
+				mlen = MCLBYTES;
+			}
 		}
 	}
 	if (error) {