lkml.org 
[lkml]   [2019]   [Jun]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH] flow_dissector: Fix vlan header offset in __skb_flow_dissect
From
Date
On 2019/6/20 2:39, Stanislav Fomichev wrote:
> On 06/20, YueHaibing wrote:
>> We build vlan on top of bonding interface, which vlan offload
>> is off, bond mode is 802.3ad (LACP) and xmit_hash_policy is
>> BOND_XMIT_POLICY_ENCAP34.
>>
>> __skb_flow_dissect() fails to get information from protocol headers
>> encapsulated within vlan, because 'nhoff' is points to IP header,
>> so bond hashing is based on layer 2 info, which fails to distribute
>> packets across slaves.
>>
>> Fixes: d5709f7ab776 ("flow_dissector: For stripped vlan, get vlan info from skb->vlan_tci")
>> Signed-off-by: YueHaibing <yuehaibing@huawei.com>
>> ---
>> net/core/flow_dissector.c | 3 +++
>> 1 file changed, 3 insertions(+)
>>
>> diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
>> index 415b95f..2a52abb 100644
>> --- a/net/core/flow_dissector.c
>> +++ b/net/core/flow_dissector.c
>> @@ -785,6 +785,9 @@ bool __skb_flow_dissect(const struct sk_buff *skb,
>> skb && skb_vlan_tag_present(skb)) {
>> proto = skb->protocol;
>> } else {
>> + if (dissector_vlan == FLOW_DISSECTOR_KEY_MAX)
>> + nhoff -= sizeof(*vlan);
>> +
> Should we instead fix the place where the skb is allocated to properly
> pull vlan (skb_vlan_untag)? I'm not sure this particular place is
> supposed to work with an skb. Having an skb with nhoff pointing to
> IP header but missing skb_vlan_tag_present() when with
> proto==ETH_P_8021xx seems weird.

The skb is a forwarded vxlan packet, it send through vlan interface like this:

vlan_dev_hard_start_xmit
--> __vlan_hwaccel_put_tag //vlan_tci and VLAN_TAG_PRESENT is set
--> dev_queue_xmit
--> validate_xmit_skb
--> validate_xmit_vlan // vlan_hw_offload_capable is false
--> __vlan_hwaccel_push_inside //here skb_push vlan_hlen, then clear skb->tci

--> bond_start_xmit
--> bond_xmit_hash
--> __skb_flow_dissect // nhoff point to IP header
--> case htons(ETH_P_8021Q)
// skb_vlan_tag_present is false, so
vlan = __skb_header_pointer(skb, nhoff, sizeof(_vlan), //vlan point to ip header wrongly

>
>> vlan = __skb_header_pointer(skb, nhoff, sizeof(_vlan),
>> data, hlen, &_vlan);
>> if (!vlan) {
>> --
>> 2.7.0
>>
>>
>
> .
>

\
 
 \ /
  Last update: 2019-06-20 12:03    [W:0.125 / U:0.256 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site