Thread (12 messages) 12 messages, 3 authors, 2020-01-06

Re: [dpdk-dev] [RFC PATCH] mbuf: fix to update documentation of PKT_RX_QINQ_STRIPPED

From: Andrew Rybchenko <hidden>
Date: 2019-12-24 09:53:55

On 12/24/19 6:16 AM, Somnath Kotur wrote:
Given that we haven't heard any objection from anyone in a while on
this ...can we get this in please?
I'm sorry, but have you seen below?
It means that PKT_RX_QINQ_STRIPPED, PKT_RX_QINQ, PKT_RX_VLAN
and PKT_RX_VLAN_STRIPPED must be clarified.

It sounds like change of semantics in order to resolve the
problem, but anyway it is still a small change of semantics.

BTW, it is better to make summary human readable and avoid
PKT_RX_QINQ_STRIPPED (I guess check-git-log.sh yells on it).

Also RFC patch cannot be applied, non-RFC version is required.

CC main tree maintainers.
Thanks

On Mon, Dec 16, 2019 at 2:43 PM Andrew Rybchenko
[off-list ref] wrote:
quoted
On 12/16/19 11:47 AM, Somnath Kotur wrote:
quoted
On Mon, Dec 16, 2019 at 12:01 PM Andrew Rybchenko
[off-list ref] wrote:
quoted
On 12/16/19 6:16 AM, Somnath Kotur wrote:
quoted
Certain hardware may be able to strip and/or save only the outermost
VLAN instead of both the VLANs in the mbuf in a QinQ scenario.
To handle such cases, we could re-interpret setting of just PKT_RX_QINQ_STRIPPED
to indicate that only the outermost VLAN has been stripped by the hardware and
saved in mbuf->vlan_tci_outer.
Only When both PKT_RX_QINQ_STRIPPED and PKT_RX_VLAN_STRIPPED are set, the 2 vlans
have been stripped by the hardware and their tci are saved in mbuf->vlan_tci (inner)
and mbuf->vlan_tci_outer (outer).

Signed-off-by: Somnath Kotur <redacted>
Signed-off-by: JP Lee <redacted>
---
 lib/librte_mbuf/rte_mbuf_core.h | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)
diff --git a/lib/librte_mbuf/rte_mbuf_core.h b/lib/librte_mbuf/rte_mbuf_core.h
index 9a8557d..db1070b 100644
--- a/lib/librte_mbuf/rte_mbuf_core.h
+++ b/lib/librte_mbuf/rte_mbuf_core.h
@@ -124,12 +124,19 @@
 #define PKT_RX_FDIR_FLX      (1ULL << 14)

 /**
- * The 2 vlans have been stripped by the hardware and their tci are
- * saved in mbuf->vlan_tci (inner) and mbuf->vlan_tci_outer (outer).
+ * The outer vlan has been stripped by the hardware and their tci are
+ * saved in mbuf->vlan_tci_outer (outer).
  * This can only happen if vlan stripping is enabled in the RX
  * configuration of the PMD.
- * When PKT_RX_QINQ_STRIPPED is set, the flags (PKT_RX_VLAN |
- * PKT_RX_VLAN_STRIPPED | PKT_RX_QINQ) must also be set.
+ * When PKT_RX_QINQ_STRIPPED is set, the flags (PKT_RX_VLAN |  PKT_RX_QINQ)
+ * must also be set.
+ * When both PKT_RX_QINQ_STRIPPED and PKT_RX_VLAN_STRIPPED are set, the 2 vlans
+ * have been stripped by the hardware and their tci are saved in
+ * mbuf->vlan_tci (inner) and mbuf->vlan_tci_outer (outer).
+ * This can only happen if vlan stripping is enabled in the RX configuration
+ * of the PMD.
+ * When PKT_RX_QINQ_STRIPPED and PKT_RX_VLAN_STRIPPED are set,
+ * (PKT_RX_VLAN | PKT_RX_QINQ) must also be set.
  */
 #define PKT_RX_QINQ_STRIPPED (1ULL << 15)
I always thought that PKT_RX_VLAN_STRIPPED means *one* VLAN
stripped regardless if it is outer (if the packet is double
tagged) or inner (if only one VLAN tag was present).

That's why PKT_RX_QINQ_STRIPPED description says that *two*
VLANs have been stripped.

What is the problem with such approach?
The problem is that RX_VLAN_STRIPPED implies that the stripped VLAN
(outer or inner) is saved in mbuf->vlan_tci, correct?
Yes.
quoted
There is no way to convey that it is in QinQ mode and yet only outer
VLAN has been stripped and saved in mbuf->vlan_tci_outer ?
Ah, it looks like I understand now that the problem is in
PKT_RX_QINQ description which claims that TCI is saved in
mbuf->vlan_tci_outer and PKT_RX_QINQ_STRIPPED means that
both VLAN tags are stripped regardless (PKT_RX_VLAN_STRIPPED).
Moreover PKT_RX_QINQ_STRIPPED requires PKT_RX_VLAN_STRIPPED.

It means that PKT_RX_QINQ_STRIPPED, PKT_RX_QINQ, PKT_RX_VLAN
and PKT_RX_VLAN_STRIPPED must be clarified.

I'm not sure, but it looks like it could affect net/dpaa2,
so I'm including driver maintainers in CC.
  
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