tcp_metrics: add netlink protocol spec in YAML

Add a protocol spec for tcp_metrics, so that it's accessible via YNL.
Useful at the very least for testing fixes.

In this episode of "10,000 ways to complicate netlink" the metric
nest has defines which are off by 1. iproute2 does:

        struct rtattr *m[TCP_METRIC_MAX + 1 + 1];

        parse_rtattr_nested(m, TCP_METRIC_MAX + 1, a);

        for (i = 0; i < TCP_METRIC_MAX + 1; i++) {
                // ...
                attr = m[i + 1];

This is too weird to support in YNL, add a new set of defines
with _correct_ values to the official kernel header.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Donald Hunter <donald.hunter@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 169 insertions, 0 deletions

diff --git a/Documentation/netlink/specs/tcp_metrics.yaml b/Documentation/netlink/specs/tcp_metrics.yaml
new file mode 100644
index 000000000000..1bd94f43e526
--- /dev/null
+++ b/Documentation/netlink/specs/tcp_metrics.yaml
@@ -0,0 +1,169 @@
+# SPDX-License-Identifier: ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause)
+
+name: tcp_metrics
+
+protocol: genetlink-legacy
+
+doc: |
+  Management interface for TCP metrics.
+
+c-family-name: tcp-metrics-genl-name
+c-version-name: tcp-metrics-genl-version
+max-by-define: true
+kernel-policy: global
+
+definitions:
+  -
+    name: tcp-fastopen-cookie-max
+    type: const
+    value: 16
+
+attribute-sets:
+  -
+    name: tcp-metrics
+    name-prefix: tcp-metrics-attr-
+    attributes:
+      -
+        name: addr-ipv4
+        type: u32
+        byte-order: big-endian
+        display-hint: ipv4
+      -
+        name: addr-ipv6
+        type: binary
+        checks:
+          min-len: 16
+        byte-order: big-endian
+        display-hint: ipv6
+      -
+        name: age
+        type: u64
+      -
+        name: tw-tsval
+        type: u32
+        doc: unused
+      -
+        name: tw-ts-stamp
+        type: s32
+        doc: unused
+      -
+        name: vals
+        type: nest
+        nested-attributes: metrics
+      -
+        name: fopen-mss
+        type: u16
+      -
+        name: fopen-syn-drops
+        type: u16
+      -
+        name: fopen-syn-drop-ts
+        type: u64
+      -
+        name: fopen-cookie
+        type: binary
+        checks:
+          min-len: tcp-fastopen-cookie-max
+      -
+        name: saddr-ipv4
+        type: u32
+        byte-order: big-endian
+        display-hint: ipv4
+      -
+        name: saddr-ipv6
+        type: binary
+        checks:
+          min-len: 16
+        byte-order: big-endian
+        display-hint: ipv6
+      -
+        name: pad
+        type: pad
+
+  -
+    name: metrics
+    # Intentionally don't define the name-prefix, see below.
+    doc: |
+      Attributes with metrics. Note that the values here do not match
+      the TCP_METRIC_* defines in the kernel, because kernel defines
+      are off-by one (e.g. rtt is defined as enum 0, while netlink carries
+      attribute type 1).
+    attributes:
+      -
+        name: rtt
+        type: u32
+        doc: |
+          Round Trip Time (RTT), in msecs with 3 bits fractional
+          (left-shift by 3 to get the msec value).
+      -
+        name: rttvar
+        type: u32
+        doc: |
+          Round Trip Time VARiance (RTT), in msecs with 2 bits fractional
+          (left-shift by 2 to get the msec value).
+      -
+        name: ssthresh
+        type: u32
+        doc: Slow Start THRESHold.
+      -
+        name: cwnd
+        type: u32
+        doc: Congestion Window.
+      -
+        name: reodering
+        type: u32
+        doc: Reodering metric.
+      -
+        name: rtt-us
+        type: u32
+        doc: |
+          Round Trip Time (RTT), in usecs, with 3 bits fractional
+          (left-shift by 3 to get the msec value).
+      -
+        name: rttvar-us
+        type: u32
+        doc: |
+          Round Trip Time (RTT), in usecs, with 2 bits fractional
+          (left-shift by 3 to get the msec value).
+
+operations:
+  list:
+    -
+      name: get
+      doc: Retrieve metrics.
+      attribute-set: tcp-metrics
+
+      dont-validate: [ strict, dump ]
+
+      do:
+        request: &sel_attrs
+          attributes:
+            - addr-ipv4
+            - addr-ipv6
+            - saddr-ipv4
+            - saddr-ipv6
+        reply: &all_attrs
+          attributes:
+            - addr-ipv4
+            - addr-ipv6
+            - saddr-ipv4
+            - saddr-ipv6
+            - age
+            - vals
+            - fopen-mss
+            - fopen-syn-drops
+            - fopen-syn-drop-ts
+            - fopen-cookie
+      dump:
+        reply: *all_attrs
+
+    -
+      name: del
+      doc: Delete metrics.
+      attribute-set: tcp-metrics
+
+      dont-validate: [ strict, dump ]
+      flags: [ admin-perm ]
+
+      do:
+        request: *sel_attrs