/*
- * Copyright (c) 2011 Nicira Networks.
- * Distributed under the terms of the GNU GPL version 2.
+ * Copyright (c) 2007-2011 Nicira, Inc.
*
- * Significant portions of this file may be copied from parts of the Linux
- * kernel, by Linus Torvalds and others.
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA
*/
#ifndef VLAN_H
#include <linux/skbuff.h>
#include <linux/version.h>
+/**
+ * DOC: VLAN tag manipulation.
+ *
+ * &struct sk_buff handling of VLAN tags has evolved over time:
+ *
+ * In 2.6.26 and earlier, VLAN tags did not have any generic representation in
+ * an skb, other than as a raw 802.1Q header inside the packet data.
+ *
+ * In 2.6.27 &struct sk_buff added a @vlan_tci member. Between 2.6.27 and
+ * 2.6.32, its value was the raw contents of the 802.1Q TCI field, or zero if
+ * no 802.1Q header was present. This worked OK except for the corner case of
+ * an 802.1Q header with an all-0-bits TCI, which could not be represented.
+ *
+ * In 2.6.33, @vlan_tci semantics changed. Now, if an 802.1Q header is
+ * present, then the VLAN_TAG_PRESENT bit is always set. This fixes the
+ * all-0-bits TCI corner case.
+ *
+ * For compatibility we emulate the 2.6.33+ behavior on earlier kernel
+ * versions. The client must not access @vlan_tci directly. Instead, use
+ * vlan_get_tci() to read it or vlan_set_tci() to write it, with semantics
+ * equivalent to those on 2.6.33+.
+ */
+
#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,27)
#define NEED_VLAN_FIELD
#endif
static inline u16 vlan_get_tci(struct sk_buff *skb)
{
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,33)
+ if (skb->vlan_tci)
+ return skb->vlan_tci | VLAN_TAG_PRESENT;
+#endif
return skb->vlan_tci;
}
static inline void vlan_set_tci(struct sk_buff *skb, u16 vlan_tci)
{
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,33)
+ vlan_tci &= ~VLAN_TAG_PRESENT;
+#endif
skb->vlan_tci = vlan_tci;
}
#else