netlink: specs: rt-route: describe lwtunnel IP options

Replace binary opts in lwtunnel-ip and lwtunnel-ip6 with a nested
lwtunnel-ip-opts set. Add attribute sets for geneve, vxlan, and erspan
IP options to match linux/lwtunnel.h.

Note the kernel encodes LWTUNNEL_IP_OPTS_GENEVE differently for requests
vs dumps. On the request path, the kernel iterates and reads one
CLASS/TYPE/DATA triplet per geneve option. On the dump path, the kernel
opens only one nested geneve option and writes a CLASS/TYPE/DATA triplet
for every option within it. Before there is a proper way to handle it,
I will just omit geneve options and use binary for it.

Signed-off-by: Hangbin Liu <liuhangbin@kylinos.cn>
Link: https://patch.msgid.link/20261008-ynl_rt_encap-v4-4-4ed2ccf7f949@kylinos.cn
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/netlink/specs/rt-route.yaml

@@ -377,7 +377,8 @@ attribute-sets:
         type: pad
       -
         name: opts
-        type: binary  # lwtunnel ip nest options
+        type: nest
+        nested-attributes: lwtunnel-ip-opts
   -
     name: ila-attrs
     name-prefix: ila-attr-
@@ -444,7 +445,8 @@ attribute-sets:
         type: pad
       -
         name: opts
-        type: binary  # lwtunnel ip nest options
+        type: nest
+        nested-attributes: lwtunnel-ip-opts
   -
     name: seg6-iptunnel
     name-prefix: seg6-iptunnel-
@@ -562,6 +564,45 @@ attribute-sets:
       -
         name: link
         type: u32
+  -
+    name: lwtunnel-ip-opts
+    name-prefix: lwtunnel-ip-opts-
+    attributes:
+      -
+        name: geneve
+        type: binary
+      -
+        name: vxlan
+        type: nest
+        nested-attributes: lwtunnel-ip-opt-vxlan
+      -
+        name: erspan
+        type: nest
+        nested-attributes: lwtunnel-ip-opt-erspan
+  -
+    name: lwtunnel-ip-opt-vxlan
+    name-prefix: lwtunnel-ip-opt-vxlan-
+    attributes:
+      -
+        name: gbp
+        type: u32
+  -
+    name: lwtunnel-ip-opt-erspan
+    name-prefix: lwtunnel-ip-opt-erspan-
+    attributes:
+      -
+        name: ver
+        type: u8
+      -
+        name: index
+        type: u32
+        byte-order: big-endian
+      -
+        name: dir
+        type: u8
+      -
+        name: hwid
+        type: u8
 
 operations:
   enum-model: directional