Documentation: netlink: specs: tc: Add DualPI2 specification

Introduce the specification of tc qdisc DualPI2 stats and attributes,
which is the reference implementation of IETF RFC9332 DualQ Coupled AQM
(https://datatracker.ietf.org/doc/html/rfc9332) providing two different
queues: low latency queue (L-queue) and classic queue (C-queue).

Signed-off-by: Chia-Yu Chang <chia-yu.chang@nokia-bell-labs.com>
Link: https://patch.msgid.link/20250722095915.24485-7-chia-yu.chang@nokia-bell-labs.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 149 insertions, 2 deletions

diff --git a/Documentation/netlink/specs/tc.yaml b/Documentation/netlink/specs/tc.yaml
index e983c0c82eb9..b1afc7ab3539 100644
--- a/Documentation/netlink/specs/tc.yaml
+++ b/Documentation/netlink/specs/tc.yaml
@@ -57,6 +57,23 @@ definitions:
       - tunoam
       - tuncrit
   -
+    name: dualpi2-drop-overload
+    type: enum
+    entries: [overflow, drop]
+  -
+    name: dualpi2-drop-early
+    type: enum
+    entries: [drop-dequeue, drop-enqueue]
+  -
+    name: dualpi2-ecn-mask
+    type: enum
+    value-start: 1
+    entries: [l4s-ect, cla-ect, any-ect]
+  -
+    name: dualpi2-split-gso
+    type: enum
+    entries: [no-split-gso, split-gso]
+  -
     name: tc-stats
     type: struct
     members:
@@ -826,6 +843,58 @@ definitions:
         name: drop-overmemory
         type: u32
   -
+    name: tc-dualpi2-xstats
+    type: struct
+    members:
+      -
+        name: prob
+        type: u32
+        doc: Current base PI probability
+      -
+        name: delay-c
+        type: u32
+        doc: Current C-queue delay in microseconds
+      -
+        name: delay-l
+        type: u32
+        doc: Current L-queue delay in microseconds
+      -
+        name: pkts-in-c
+        type: u32
+        doc: Number of packets enqueued in the C-queue
+      -
+        name: pkts-in-l
+        type: u32
+        doc: Number of packets enqueued in the L-queue
+      -
+        name: maxq
+        type: u32
+        doc: Maximum number of packets seen by the DualPI2
+      -
+        name: ecn-mark
+        type: u32
+        doc: All packets marked with ECN
+      -
+        name: step-mark
+        type: u32
+        doc: Only packets marked with ECN due to L-queue step AQM
+      -
+        name: credit
+        type: s32
+        doc: Current credit value for WRR
+      -
+        name: memory-used
+        type: u32
+        doc: Memory used in bytes by the DualPI2
+      -
+        name: max-memory-used
+        type: u32
+        doc: Maximum memory used in bytes by the DualPI2
+      -
+        name: memory-limit
+        type: u32
+        doc: Memory limit in bytes
+  -
     name: tc-fq-pie-xstats
     type: struct
     members:
@@ -848,7 +917,7 @@ definitions:
       -
         name: ecn-mark
         type: u32
-        doc: Packets marked with ecn
+        doc: Packets marked with ECN
       -
         name: new-flow-count
         type: u32
@@ -991,7 +1060,7 @@ definitions:
       -
         name: ecn-mark
         type: u32
-        doc: Packets marked with ecn
+        doc: Packets marked with ECN
   -
     name: tc-red-xstats
     type: struct
@@ -2285,6 +2354,78 @@ attribute-sets:
         name: quantum
         type: u32
   -
+    name: dualpi2-attrs
+    name-prefix: tca-dualpi2-
+    attributes:
+      -
+        name: limit
+        type: u32
+        doc: Limit of total number of packets in queue
+      -
+        name: memory-limit
+        type: u32
+        doc: Memory limit of total number of packets in queue
+      -
+        name: target
+        type: u32
+        doc: Classic target delay in microseconds
+      -
+        name: tupdate
+        type: u32
+        doc: Drop probability update interval time in microseconds
+      -
+        name: alpha
+        type: u32
+        doc: Integral gain factor in Hz for PI controller
+      -
+        name: beta
+        type: u32
+        doc: Proportional gain factor in Hz for PI controller
+      -
+        name: step-thresh-pkts
+        type: u32
+        doc: L4S step marking threshold in packets
+      -
+        name: step-thresh-us
+        type: u32
+        doc: L4S Step marking threshold in microseconds
+      -
+        name: min-qlen-step
+        type: u32
+        doc: Packets enqueued to the L-queue can apply the step threshold
+             when the queue length of L-queue is larger than this value.
+             (0 is recommended)
+      -
+        name: coupling
+        type: u8
+        doc: Probability coupling factor between Classic and L4S
+             (2 is recommended)
+      -
+        name: drop-overload
+        type: u8
+        doc: Control the overload strategy (drop to preserve latency or
+             let the queue overflow)
+        enum: dualpi2-drop-overload
+      -
+        name: drop-early
+        type: u8
+        doc: Decide where the Classic packets are PI-based dropped or marked
+        enum: dualpi2-drop-early
+      -
+        name: c-protection
+        type: u8
+        doc: Classic WRR weight in percentage (from 0 to 100)
+      -
+        name: ecn-mask
+        type: u8
+        doc: Configure the L-queue ECN classifier
+        enum: dualpi2-ecn-mask
+      -
+        name: split-gso
+        type: u8
+        doc: Split aggregated skb or not
+        enum: dualpi2-split-gso
+  -
     name: ematch-attrs
     name-prefix: tca-ematch-
     attr-max-name: tca-ematch-tree-max
@@ -3709,6 +3850,9 @@ sub-messages:
         value: drr
         attribute-set: drr-attrs
       -
+        value: dualpi2
+        attribute-set: dualpi2-attrs
+      -
         value: etf
         attribute-set: etf-attrs
       -
@@ -3876,6 +4020,9 @@ sub-messages:
         value: codel
         fixed-header: tc-codel-xstats
       -
+        value: dualpi2
+        fixed-header: tc-dualpi2-xstats
+      -
         value: fq
         fixed-header: tc-fq-qd-stats
       -