[src/trunk]: src/sys/net To cater for VLAN-aware layer 2 ethernet switches wh...

[scw <scw%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/ffac9be9ffad
branches:  trunk
changeset: 555996:ffac9be9ffad
user:      scw <scw%NetBSD.org@localhost>
date:      Fri Dec 05 19:35:43 2003 +0000

description:
To cater for VLAN-aware layer 2 ethernet switches which may need to strip
the tag before forwarding the packet, make sure the packet+tag is at least
68 bytes long.

This is necessary because our parent will only pad to 64 bytes (ETHER_MIN_LEN)
and some switches will not pad by themselves after deleting a tag.

diffstat:

 sys/net/if_vlan.c |  26 ++++++++++++++++++++++++--
 1 files changed, 24 insertions(+), 2 deletions(-)

diffs (54 lines):

diff -r 2facf25453e7 -r ffac9be9ffad sys/net/if_vlan.c
--- a/sys/net/if_vlan.c Fri Dec 05 19:00:07 2003 +0000
+++ b/sys/net/if_vlan.c Fri Dec 05 19:35:43 2003 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: if_vlan.c,v 1.37 2003/10/02 07:13:57 itojun Exp $      */
+/*     $NetBSD: if_vlan.c,v 1.38 2003/12/05 19:35:43 scw Exp $ */
 
 /*-
  * Copyright (c) 2000, 2001 The NetBSD Foundation, Inc.
@@ -85,7 +85,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: if_vlan.c,v 1.37 2003/10/02 07:13:57 itojun Exp $");
+__KERNEL_RCSID(0, "$NetBSD: if_vlan.c,v 1.38 2003/12/05 19:35:43 scw Exp $");
 
 #include "opt_inet.h"
 #include "bpfilter.h"
@@ -189,6 +189,9 @@
 struct if_clone vlan_cloner =
     IF_CLONE_INITIALIZER("vlan", vlan_clone_create, vlan_clone_destroy);
 
+/* Used to pad ethernet frames with < ETHER_MIN_LEN bytes */
+static char vlan_zero_pad_buff[ETHER_MIN_LEN];
+
 void
 vlanattach(int n)
 {
@@ -779,6 +782,25 @@
                                evl->evl_proto = evl->evl_encap_proto;
                                evl->evl_encap_proto = htons(ETHERTYPE_VLAN);
                                evl->evl_tag = htons(ifv->ifv_tag);
+
+                               /*
+                                * To cater for VLAN-aware layer 2 ethernet
+                                * switches which may need to strip the tag
+                                * before forwarding the packet, make sure
+                                * the packet+tag is at least 68 bytes long.
+                                * This is necessary because our parent will
+                                * only pad to 64 bytes (ETHER_MIN_LEN) and
+                                * some switches will not pad by themselves
+                                * after deleting a tag.
+                                */
+                               if (m->m_pkthdr.len <
+                                   (ETHER_MIN_LEN + ETHER_VLAN_ENCAP_LEN)) {
+                                       m_copyback(m, m->m_pkthdr.len,
+                                           (ETHER_MIN_LEN +
+                                            ETHER_VLAN_ENCAP_LEN) -
+                                            m->m_pkthdr.len,
+                                           vlan_zero_pad_buff);
+                               }
                                break;
                            }