| Message ID | cfc3e476bc30c1e15506e80955bf43563de3c16c.1475583870.git.jbenc@redhat.com |
|---|---|
| State | Changes Requested, archived |
| Delegated to: | David Miller |
| Headers | show |
Hi Jiri, On Tue, Oct 04, 2016 at 02:30:01PM +0200, Jiri Benc wrote: > It can never happen that there's a vlan tag in the packet but not in > skb->vlan_tci. This is ensured in __netif_receive_skb_core and honored by > skb_vlan_push and skb_vlan_pop. The code dealing with such case is a dead > code. > This code is also called for packets passed back down from userspace (after the flow key miss and upcall). So it does happen that we have a skb without skb->vlan_tci set. See the chain: ovs_packet_cmd_execute() ovs_flow_key_extract_userspace() key_extract() parse_vlan() > Moreover, the likely() statement around skb_vlan_tag_present is bogus. This > code is called whenever flow key is being extracted from the packet. The > packet may be as likely vlan tagged as not. > I guess the unlikely scenario is the one I mention above.
On Tue, 4 Oct 2016 20:06:18 -0400, Eric Garver wrote: > This code is also called for packets passed back down from userspace > (after the flow key miss and upcall). So it does happen that we have a > skb without skb->vlan_tci set. That sucks. The vlan handling should be really consistent, Jiri Pirko and others put great effort to unify it in the stack, we should make use of that effort. I'll respin this patchset and add a patch to make the vlan handling consistent. > See the chain: > ovs_packet_cmd_execute() > ovs_flow_key_extract_userspace() > key_extract() > parse_vlan() > > > Moreover, the likely() statement around skb_vlan_tag_present is bogus. This > > code is called whenever flow key is being extracted from the packet. The > > packet may be as likely vlan tagged as not. > > I guess the unlikely scenario is the one I mention above. But it's wrong. It's also called via ovs_vport_receive() ovs_flow_key_extract() key_extract() parse_vlan() and in that path, both cases (vlan vs. non-vlan) are equally possible. Jiri
diff --git a/net/openvswitch/flow.c b/net/openvswitch/flow.c index c8c82e109c68..d88c0a55b783 100644 --- a/net/openvswitch/flow.c +++ b/net/openvswitch/flow.c @@ -308,9 +308,7 @@ static bool icmp6hdr_ok(struct sk_buff *skb) /** * Parse vlan tag from vlan header. - * Returns ERROR on memory error. - * Returns 0 if it encounters a non-vlan or incomplete packet. - * Returns 1 after successfully parsing vlan tag. + * Returns ERROR on memory error, 0 otherwise. */ static int parse_vlan_tag(struct sk_buff *skb, struct vlan_head *key_vh) { @@ -331,34 +329,24 @@ static int parse_vlan_tag(struct sk_buff *skb, struct vlan_head *key_vh) key_vh->tpid = vh->tpid; __skb_pull(skb, sizeof(struct vlan_head)); - return 1; + return 0; } static int parse_vlan(struct sk_buff *skb, struct sw_flow_key *key) { - int res; - key->eth.vlan.tci = 0; key->eth.vlan.tpid = 0; key->eth.cvlan.tci = 0; key->eth.cvlan.tpid = 0; - if (likely(skb_vlan_tag_present(skb))) { - key->eth.vlan.tci = htons(skb->vlan_tci); - key->eth.vlan.tpid = skb->vlan_proto; - } else { - /* Parse outer vlan tag in the non-accelerated case. */ - res = parse_vlan_tag(skb, &key->eth.vlan); - if (res <= 0) - return res; - } + if (!skb_vlan_tag_present(skb)) + return 0; - /* Parse inner vlan tag. */ - res = parse_vlan_tag(skb, &key->eth.cvlan); - if (res <= 0) - return res; + key->eth.vlan.tci = htons(skb->vlan_tci); + key->eth.vlan.tpid = skb->vlan_proto; - return 0; + /* Parse inner vlan tag. */ + return parse_vlan_tag(skb, &key->eth.cvlan); } static __be16 parse_ethertype(struct sk_buff *skb)
It can never happen that there's a vlan tag in the packet but not in skb->vlan_tci. This is ensured in __netif_receive_skb_core and honored by skb_vlan_push and skb_vlan_pop. The code dealing with such case is a dead code. Moreover, the likely() statement around skb_vlan_tag_present is bogus. This code is called whenever flow key is being extracted from the packet. The packet may be as likely vlan tagged as not. Fixes: 018c1dda5ff1 ("openvswitch: 802.1AD Flow handling, actions, vlan parsing, netlink attributes") Signed-off-by: Jiri Benc <jbenc@redhat.com> --- net/openvswitch/flow.c | 28 ++++++++-------------------- 1 file changed, 8 insertions(+), 20 deletions(-)