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.
