Re: [PATCH net-next 1/4] flow_dissector: Get vlan info from skb->vlan_tci instead of skb->data

[Jiri Pirko]

Mon, Aug 15, 2016 at 05:51:38PM CEST, had...@dev.mellanox.co.il wrote:
>On Mon, Aug 15, 2016 at 5:38 AM, Toshiaki Makita
> wrote:
>> On 16/08/14 (日) 23:58, Hadar Hen Zion wrote:
>>>
>>> On Fri, Aug 12, 2016 at 9:36 AM, Toshiaki Makita
>>>  wrote:

 On 2016/08/10 22:32, Hadar Hen Zion wrote:
>
> Early in the datapath skb_vlan_untag function is called, stripped
> the vlan from the skb and set skb->vlan_tci and skb->vlan_proto fields.
>
> The current dissection doesn't handle vlan packets correctly.  Vlan
> doesn't exist in skb->data anymore when applying flow dissection on the
> skb, fix that.


 RPS (and flow-dissector called in RPS) is performed before vlan-strip in
 __netif_receive_skb_core().
>>>
>>>
>>> right, I'll fix it to v2.
>>>
 Also, in cases skb is tagged with multiple vlan headers (typical when
 using 802.1ad), the second level vlan tag is in skb->data.
>>>
>>>
>>> Currently, flow_dissector doesn't support multiple vlan headers, only
>>> one vlan_id field is present.
>>> There aren't any flow_dissector "customers" yet for multiple vlan support.
>>
>>
>> Sure, no need to store second level vlan tag information for now.
>> The point is that current flow-dissector correctly skips any number of vlan
>> tags and get hash value from IP/TCP/UDP headers, so RPS works for multiple
>> vlan tagged packets.
>>
>> Thanks,
>> Toshiaki Makita
>
>ok, so we are on the same page.
>The flow dissector will correctly skip any number of vlans regardless
>if the first vlan is stripped or not.


On RX the first vlan is always stripped either by hw or by skb_vlan_untag.
On TX the first vlan is also stripped as validate_xmit_skb_list which
pushes vlan header is called just before dev_hard_start_xmit.

So I believe you can safely work just with skb->vlan_*

Re: [PATCH net-next 1/4] flow_dissector: Get vlan info from skb->vlan_tci instead of skb->data

[Hadar Hen Zion]

On Mon, Aug 15, 2016 at 5:38 AM, Toshiaki Makita
 wrote:
> On 16/08/14 (日) 23:58, Hadar Hen Zion wrote:
>>
>> On Fri, Aug 12, 2016 at 9:36 AM, Toshiaki Makita
>>  wrote:
>>>
>>> On 2016/08/10 22:32, Hadar Hen Zion wrote:

 Early in the datapath skb_vlan_untag function is called, stripped
 the vlan from the skb and set skb->vlan_tci and skb->vlan_proto fields.

 The current dissection doesn't handle vlan packets correctly.  Vlan
 doesn't exist in skb->data anymore when applying flow dissection on the
 skb, fix that.
>>>
>>>
>>> RPS (and flow-dissector called in RPS) is performed before vlan-strip in
>>> __netif_receive_skb_core().
>>
>>
>> right, I'll fix it to v2.
>>
>>> Also, in cases skb is tagged with multiple vlan headers (typical when
>>> using 802.1ad), the second level vlan tag is in skb->data.
>>
>>
>> Currently, flow_dissector doesn't support multiple vlan headers, only
>> one vlan_id field is present.
>> There aren't any flow_dissector "customers" yet for multiple vlan support.
>
>
> Sure, no need to store second level vlan tag information for now.
> The point is that current flow-dissector correctly skips any number of vlan
> tags and get hash value from IP/TCP/UDP headers, so RPS works for multiple
> vlan tagged packets.
>
> Thanks,
> Toshiaki Makita

ok, so we are on the same page.
The flow dissector will correctly skip any number of vlans regardless
if the first vlan is stripped or not.

I also found a dependency between my vlan addition to flower and mlx5
tc offload support so I'm working to fix it for V2.

Thanks,
Hadar

Re: [PATCH net-next 1/4] flow_dissector: Get vlan info from skb->vlan_tci instead of skb->data

[Toshiaki Makita]

On 16/08/14 (日) 23:58, Hadar Hen Zion wrote:

On Fri, Aug 12, 2016 at 9:36 AM, Toshiaki Makita
 wrote:

On 2016/08/10 22:32, Hadar Hen Zion wrote:

Early in the datapath skb_vlan_untag function is called, stripped
the vlan from the skb and set skb->vlan_tci and skb->vlan_proto fields.

The current dissection doesn't handle vlan packets correctly.  Vlan
doesn't exist in skb->data anymore when applying flow dissection on the
skb, fix that.


RPS (and flow-dissector called in RPS) is performed before vlan-strip in
__netif_receive_skb_core().


right, I'll fix it to v2.


Also, in cases skb is tagged with multiple vlan headers (typical when
using 802.1ad), the second level vlan tag is in skb->data.


Currently, flow_dissector doesn't support multiple vlan headers, only
one vlan_id field is present.
There aren't any flow_dissector "customers" yet for multiple vlan support.


Sure, no need to store second level vlan tag information for now.
The point is that current flow-dissector correctly skips any number of 
vlan tags and get hash value from IP/TCP/UDP headers, so RPS works for 
multiple vlan tagged packets.


Thanks,
Toshiaki Makita

Re: [PATCH net-next 1/4] flow_dissector: Get vlan info from skb->vlan_tci instead of skb->data

[Hadar Hen Zion]

On Fri, Aug 12, 2016 at 9:36 AM, Toshiaki Makita
 wrote:
> On 2016/08/10 22:32, Hadar Hen Zion wrote:
>> Early in the datapath skb_vlan_untag function is called, stripped
>> the vlan from the skb and set skb->vlan_tci and skb->vlan_proto fields.
>>
>> The current dissection doesn't handle vlan packets correctly.  Vlan
>> doesn't exist in skb->data anymore when applying flow dissection on the
>> skb, fix that.
>
> RPS (and flow-dissector called in RPS) is performed before vlan-strip in
> __netif_receive_skb_core().

right, I'll fix it to v2.

> Also, in cases skb is tagged with multiple vlan headers (typical when
> using 802.1ad), the second level vlan tag is in skb->data.

Currently, flow_dissector doesn't support multiple vlan headers, only
one vlan_id field is present.
There aren't any flow_dissector "customers" yet for multiple vlan support.


> So I think you should handle both of skb->vlan_tci and skb->data cases.

Sure, will do it.


>
> Thanks,
> Toshiaki Makita
>
>

Re: [PATCH net-next 1/4] flow_dissector: Get vlan info from skb->vlan_tci instead of skb->data

[Toshiaki Makita]

On 2016/08/10 22:32, Hadar Hen Zion wrote:
> Early in the datapath skb_vlan_untag function is called, stripped
> the vlan from the skb and set skb->vlan_tci and skb->vlan_proto fields.
> 
> The current dissection doesn't handle vlan packets correctly.  Vlan
> doesn't exist in skb->data anymore when applying flow dissection on the
> skb, fix that.

RPS (and flow-dissector called in RPS) is performed before vlan-strip in
__netif_receive_skb_core().
Also, in cases skb is tagged with multiple vlan headers (typical when
using 802.1ad), the second level vlan tag is in skb->data.
So I think you should handle both of skb->vlan_tci and skb->data cases.

Thanks,
Toshiaki Makita

Re: [PATCH net-next 1/4] flow_dissector: Get vlan info from skb->vlan_tci instead of skb->data

[Jiri Pirko]

Wed, Aug 10, 2016 at 03:32:20PM CEST, had...@mellanox.com wrote:
>Early in the datapath skb_vlan_untag function is called, stripped
>the vlan from the skb and set skb->vlan_tci and skb->vlan_proto fields.
>
>The current dissection doesn't handle vlan packets correctly.  Vlan
>doesn't exist in skb->data anymore when applying flow dissection on the
>skb, fix that.
>
>Fixes: 0744dd00c1b1 ('net: introduce skb_flow_dissect()')
>Signed-off-by: Hadar Hen Zion 

Acked-by: Jiri Pirko 

[PATCH net-next 1/4] flow_dissector: Get vlan info from skb->vlan_tci instead of skb->data

[Hadar Hen Zion]

Early in the datapath skb_vlan_untag function is called, stripped
the vlan from the skb and set skb->vlan_tci and skb->vlan_proto fields.

The current dissection doesn't handle vlan packets correctly.  Vlan
doesn't exist in skb->data anymore when applying flow dissection on the
skb, fix that.

Fixes: 0744dd00c1b1 ('net: introduce skb_flow_dissect()')
Signed-off-by: Hadar Hen Zion 
---
 net/core/flow_dissector.c | 13 +++--
 1 file changed, 3 insertions(+), 10 deletions(-)

diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index 61ad43f..6060fc2 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -122,7 +122,8 @@ bool __skb_flow_dissect(const struct sk_buff *skb,
 
if (!data) {
data = skb->data;
-   proto = skb->protocol;
+   proto = skb_vlan_tag_present(skb) ?
+skb->vlan_proto : skb->protocol;
nhoff = skb_network_offset(skb);
hlen = skb_headlen(skb);
}
@@ -240,13 +241,6 @@ ipv6:
}
case htons(ETH_P_8021AD):
case htons(ETH_P_8021Q): {
-   const struct vlan_hdr *vlan;
-   struct vlan_hdr _vlan;
-
-   vlan = __skb_header_pointer(skb, nhoff, sizeof(_vlan), data, 
hlen, &_vlan);
-   if (!vlan)
-   goto out_bad;
-
if (dissector_uses_key(flow_dissector,
   FLOW_DISSECTOR_KEY_VLANID)) {
key_tags = skb_flow_dissector_target(flow_dissector,
@@ -256,8 +250,7 @@ ipv6:
key_tags->vlan_id = skb_vlan_tag_get_id(skb);
}
 
-   proto = vlan->h_vlan_encapsulated_proto;
-   nhoff += sizeof(*vlan);
+   proto = skb->protocol;
goto again;
}
case htons(ETH_P_PPP_SES): {
-- 
1.8.3.1