From aab3beeede3032eef69a9bf581707f4ea77affe3 Mon Sep 17 00:00:00 2001
From: Brian Somers <brian@FreeBSD.org>
Date: Fri, 6 Aug 1999 13:53:03 +0000
Subject: [PATCH] Define IF_MAXMTU and IF_MINMTU and don't allow MTUs with
 out-of-range values.

``comparison is always 0'' warnings are silly !

Ok'd by:	wollman, dg
Advised by:	bde
---
 sys/net/if.c      |  8 ++------
 sys/net/if_loop.c |  7 +++++--
 sys/net/if_ppp.c  | 10 +++++++---
 sys/net/if_tun.c  | 11 ++++++++---
 sys/net/if_var.h  | 10 +++++++++-
 5 files changed, 31 insertions(+), 15 deletions(-)

diff --git a/sys/net/if.c b/sys/net/if.c
index c6f5c5ee823..1887c91a9c7 100644
--- a/sys/net/if.c
+++ b/sys/net/if.c
@@ -31,7 +31,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)if.c	8.3 (Berkeley) 1/4/94
- *	$Id: if.c,v 1.72 1999/06/06 09:28:01 phk Exp $
+ *	$Id: if.c,v 1.73 1999/06/19 18:42:26 phk Exp $
  */
 
 #include "opt_compat.h"
@@ -685,11 +685,7 @@ ifioctl(so, cmd, data, p)
 			return (error);
 		if (ifp->if_ioctl == NULL)
 			return (EOPNOTSUPP);
-		/*
-		 * 72 was chosen below because it is the size of a TCP/IP
-		 * header (40) + the minimum mss (32).
-		 */
-		if (ifr->ifr_mtu < 72 || ifr->ifr_mtu > 65535)
+		if (ifr->ifr_mtu < IF_MINMTU || ifr->ifr_mtu > IF_MAXMTU)
 			return (EINVAL);
 		error = (*ifp->if_ioctl)(ifp, cmd, data);
 		if (error == 0)
diff --git a/sys/net/if_loop.c b/sys/net/if_loop.c
index 55abbf500f1..bc4b5449a12 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 1.38 1999/02/20 21:03:53 dt Exp $
+ * $Id: if_loop.c,v 1.39 1999/07/06 19:23:13 des Exp $
  */
 
 /*
@@ -346,7 +346,10 @@ loioctl(ifp, cmd, data)
 		break;
 
 	case SIOCSIFMTU:
-		ifp->if_mtu = ifr->ifr_mtu;
+		if (ifr->ifr_mtu < IF_MINMTU || ifr->ifr_mtu > IF_MAXMTU)
+			error = EINVAL;
+		else
+			ifp->if_mtu = ifr->ifr_mtu;
 		break;
 
 	case SIOCSIFFLAGS:
diff --git a/sys/net/if_ppp.c b/sys/net/if_ppp.c
index a1490bbe653..9598d2185a3 100644
--- a/sys/net/if_ppp.c
+++ b/sys/net/if_ppp.c
@@ -69,7 +69,7 @@
  * Paul Mackerras (paulus@cs.anu.edu.au).
  */
 
-/* $Id: if_ppp.c,v 1.60 1999/04/27 11:17:00 phk Exp $ */
+/* $Id: if_ppp.c,v 1.61 1999/07/06 19:23:13 des Exp $ */
 /* from if_sl.c,v 1.11 84/10/04 12:54:47 rick Exp */
 /* from NetBSD: if_ppp.c,v 1.15.2.2 1994/07/28 05:17:58 cgd Exp */
 
@@ -618,9 +618,13 @@ pppsioctl(ifp, cmd, data)
 	if (ifr->ifr_mtu > PPP_MAXMTU)
 	    error = EINVAL;
 	else {
-	    sc->sc_if.if_mtu = ifr->ifr_mtu;
-	    if (sc->sc_setmtu)
+	    if (ifr->ifr_mtu < IF_MINMTU || ifr->ifr_mtu > IF_MAXMTU)
+		error = EINVAL;
+	    else {
+		sc->sc_if.if_mtu = ifr->ifr_mtu;
+		if (sc->sc_setmtu)
 		    (*sc->sc_setmtu)(sc);
+	    }
 	}
 	break;
 
diff --git a/sys/net/if_tun.c b/sys/net/if_tun.c
index 16542dec0f4..3cb8f6bab69 100644
--- a/sys/net/if_tun.c
+++ b/sys/net/if_tun.c
@@ -302,9 +302,12 @@ tunifioctl(ifp, cmd, data)
 			 ifp->if_name, ifp->if_unit);
 		break;
 	case SIOCSIFMTU:
-		ifp->if_mtu = ifr->ifr_mtu;
-		TUNDEBUG("%s%d: mtu set\n",
-			 ifp->if_name, ifp->if_unit);
+		if (ifr->ifr_mtu < IF_MINMTU || ifr->ifr_mtu > IF_MAXMTU)
+			error = EINVAL;
+		else {
+			ifp->if_mtu = ifr->ifr_mtu;
+			TUNDEBUG("%s%d: mtu set\n", ifp->if_name, ifp->if_unit);
+		}
 		break;
 	case SIOCADDMULTI:
 	case SIOCDELMULTI:
@@ -435,6 +438,8 @@ tunioctl(dev, cmd, data, flag, p)
 	switch (cmd) {
  	case TUNSIFINFO:
  	        tunp = (struct tuninfo *)data;
+		if (tunp->mtu < IF_MINMTU || tunp->mtu > IF_MAXMTU)
+			return (EINVAL);
  		tp->tun_if.if_mtu = tunp->mtu;
  		tp->tun_if.if_type = tunp->type;
  		tp->tun_if.if_baudrate = tunp->baudrate;
diff --git a/sys/net/if_var.h b/sys/net/if_var.h
index 35780d6e71e..8163f60e2fc 100644
--- a/sys/net/if_var.h
+++ b/sys/net/if_var.h
@@ -31,7 +31,7 @@
  * SUCH DAMAGE.
  *
  *	From: @(#)if.h	8.1 (Berkeley) 6/10/93
- *	$Id: if_var.h,v 1.12 1999/05/06 18:12:55 peter Exp $
+ *	$Id: if_var.h,v 1.13 1999/05/16 17:09:20 pb Exp $
  */
 
 #ifndef	_NET_IF_VAR_H_
@@ -231,6 +231,14 @@ int	if_enq_drop __P((struct ifqueue *, struct mbuf *));
 #endif
 
 #endif
+
+/*
+ * 72 was chosen below because it is the size of a TCP/IP
+ * header (40) + the minimum mss (32).
+ */
+#define	IF_MINMTU	72
+#define	IF_MAXMTU	65535
+
 #endif /* KERNEL */
 
 /*