From 3728652303e1d58fe67b90dfa2a07668289902c8 Mon Sep 17 00:00:00 2001 From: Ben Pfaff Date: Wed, 23 Mar 2011 10:34:37 -0700 Subject: [PATCH] datapath: Add compatibility with sk_buff's vlan_tci before 2.6.33. Between 2.6.27 and 2.6.32, the vlan_tci member of struct sk_buff was the raw value of the 802.1Q header's TCI field, without the CFI bit being set. In 2.6.33 and later, the CFI bit is always set if an 802.1Q header is present, correcting a corner case. Until now, OVS has not consistently dealt with this. If a packet arrived at a datapath from a network device directly, or if it was set with an ODP_ACTION_ATTR_SET_DL_TCI action, then the CFI bit would not be set in vlan_tci. In flow_extract(), OVS copies vlan_tci directly to dl_tci in the flow structure (via vlan_get_tci()), so the CFI bit would also not be set in dl_tci. But if OVS had to send a packet up to userspace (converting the vlan_tci back to an 802.1Q header along the way) and got it back, then it would set the VLAN CFI bit in dl_tci when it parsed the 802.1Q header in parse_vlan(). This had the effect that a flow set up by userspace (with the CFI bit set) would never be matched by a packet arriving from a network device, because they would have different dl_tci values. This fixes the problem, by making the vlan_get_tci() and vlan_set_tci() interface consistent across kernel versions. Now, they always accept or return a value where the VLAN CFI bit is set if an 802.1Q header is present. Build-tested only. Problem isolated by Ethan Jackson Signed-off-by: Ben Pfaff Acked-by: Jesse Gross Reported-by: Ram Jothikumar Bug #4915. --- datapath/vlan.h | 30 ++++++++++++++++++++++++++++++ 1 file changed, 30 insertions(+) diff --git a/datapath/vlan.h b/datapath/vlan.h index 02a62909..7e1084e5 100644 --- a/datapath/vlan.h +++ b/datapath/vlan.h @@ -13,6 +13,29 @@ #include #include +/** + * 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 @@ -22,11 +45,18 @@ static inline void vlan_copy_skb_tci(struct sk_buff *skb) { } 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 -- 2.30.2