Thu, Aug 18, 2016 at 08:22:49AM CEST, had...@dev.mellanox.co.il wrote:
>On Wed, Aug 17, 2016 at 4:02 PM, Jiri Pirko <j...@resnulli.us> wrote:
>> Wed, Aug 17, 2016 at 01:05:33PM CEST, had...@dev.mellanox.co.il wrote:
>>>On Wed, Aug 17, 2016 at 1:46 PM, Jiri Pirko <j...@resnulli.us> wrote:
>>>> Wed, Aug 17, 2016 at 12:36:10PM 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 stripped vlan packets correctly.
>>>>>In some flows, vlan doesn't exist in skb->data anymore when applying
>>>>>flow dissection on the skb, fix that.
>>>>>
>>>>>In case vlan info wasn't stripped before applying flow_dissector (RPS
>>>>>flow for example), or in case of skb with multiple vlans (e.g. 802.1ad),
>>>>>get the vlan info from skb->data. The flow_dissector correctly skips
>>>>>any number of vlans and stores only the first level vlan.
>>>>>
>>>>>Fixes: 0744dd00c1b1 ('net: introduce skb_flow_dissect()')
>>>>>Signed-off-by: Hadar Hen Zion <had...@mellanox.com>
>>>>>---
>>>>> net/core/flow_dissector.c | 34 ++++++++++++++++++++++++++--------
>>>>> 1 file changed, 26 insertions(+), 8 deletions(-)
>>>>>
>>>>>diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
>>>>>index 91028ae..362d693 100644
>>>>>--- a/net/core/flow_dissector.c
>>>>>+++ b/net/core/flow_dissector.c
>>>>>@@ -119,12 +119,14 @@ bool __skb_flow_dissect(const struct sk_buff *skb,
>>>>> struct flow_dissector_key_ports *key_ports;
>>>>> struct flow_dissector_key_tags *key_tags;
>>>>> struct flow_dissector_key_keyid *key_keyid;
>>>>>+ bool skip_vlan = false;
>>>>> u8 ip_proto = 0;
>>>>> bool ret = false;
>>>>>
>>>>> 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);
>>>>> }
>>>>>@@ -243,23 +245,39 @@ 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 (skb_vlan_tag_present(skb))
>>>>>+ proto = skb->protocol;
>>>>>+
>>>>>+ if (!skb_vlan_tag_present(skb) ||
>>>>>+ proto == cpu_to_be16(ETH_P_8021Q) ||
>>>>>+ proto == cpu_to_be16(ETH_P_8021AD)) {
>>>>
>>>> How this can happen? Could you give me an example?
>>>>
>>>
>>>This can happen in 2 cases:
>>>
>>>1. vlan wasn't stripped yet from the skb.
>>>In RPS flow for example, get_rps_cpu function is using flow-dissector
>>>before vlan_untag is called by __netif_receive_skb_core.
>>
>> right, sigh...
>>
>>
>>>
>>>2. skb with multiple vlan tags.
>>>Only the first vlan is stripped while the inner vlans are still in skb->data.
>>>In this case skb->vlan_proto is 802.1AD and skb->protocol is 802.1Q
>>>(for example) so I have to take the next header from skb->data.
>>
>> Hmm I think that whoever removes the outermost vlan from skb->vlan_*
>> should strip the next header into skb->vlan_*
>
>The outermost vlan isn't removed from skb->vlan_* it stays there.
No I didn't mean in your code. But other code that removes it should
ensure that next vlan header is stripped so the rest of the code (like
yours) can count with it.
