add support for 'exact-len' validation on netlink attributes.

Link: https://github.com/multipath-tcp/mptcp_net-next/issues/340
Signed-off-by: Davide Caratti <dcaratti@redhat.com>
---
 Documentation/netlink/genetlink-c.yaml      |  3 +++
 Documentation/netlink/genetlink-legacy.yaml |  3 +++
 Documentation/netlink/genetlink.yaml        |  3 +++
 Documentation/netlink/netlink-raw.yaml      |  3 +++
 tools/net/ynl/ynl-gen-c.py                  | 28 +++++++++++++--------
 5 files changed, 29 insertions(+), 11 deletions(-)

diff --git a/Documentation/netlink/genetlink-c.yaml b/Documentation/netlink/genetlink-c.yaml
index 9806c44f604c..812113280148 100644
--- a/Documentation/netlink/genetlink-c.yaml
+++ b/Documentation/netlink/genetlink-c.yaml
@@ -194,6 +194,9 @@ properties:
                   max-len:
                     description: Max length for a string or a binary attribute.
                     $ref: '#/$defs/len-or-define'
+                  exact-len:
+                    description: Exact length for a string or a binary attribute.
+                    $ref: '#/$defs/len-or-define'
               sub-type: *attr-type
               display-hint: &display-hint
                 description: |
diff --git a/Documentation/netlink/genetlink-legacy.yaml b/Documentation/netlink/genetlink-legacy.yaml
index c08e5e3a0aaa..aa32649e20e9 100644
--- a/Documentation/netlink/genetlink-legacy.yaml
+++ b/Documentation/netlink/genetlink-legacy.yaml
@@ -233,6 +233,9 @@ properties:
                   max-len:
                     description: Max length for a string or a binary attribute.
                     $ref: '#/$defs/len-or-define'
+                  exact-len:
+                    description: Exact length for a string or a binary attribute.
+                    $ref: '#/$defs/len-or-define'
               sub-type: *attr-type
               display-hint: *display-hint
               # Start genetlink-c
diff --git a/Documentation/netlink/genetlink.yaml b/Documentation/netlink/genetlink.yaml
index 3d338c48bf21..3f179f8b95b3 100644
--- a/Documentation/netlink/genetlink.yaml
+++ b/Documentation/netlink/genetlink.yaml
@@ -167,6 +167,9 @@ properties:
                   max-len:
                     description: Max length for a string or a binary attribute.
                     $ref: '#/$defs/len-or-define'
+                  exact-len:
+                    description: Exact length for a string or a binary attribute.
+                    $ref: '#/$defs/len-or-define'
               sub-type: *attr-type
               display-hint: &display-hint
                 description: |
diff --git a/Documentation/netlink/netlink-raw.yaml b/Documentation/netlink/netlink-raw.yaml
index 896797876414..96913857ac71 100644
--- a/Documentation/netlink/netlink-raw.yaml
+++ b/Documentation/netlink/netlink-raw.yaml
@@ -240,6 +240,9 @@ properties:
                   max-len:
                     description: Max length for a string or a binary attribute.
                     $ref: '#/$defs/len-or-define'
+                  exact-len:
+                    description: Exact length for a string or a binary attribute.
+                    $ref: '#/$defs/len-or-define'
               sub-type: *attr-type
               display-hint: *display-hint
               # Start genetlink-c
diff --git a/tools/net/ynl/ynl-gen-c.py b/tools/net/ynl/ynl-gen-c.py
index 897af958cee8..c58bca967fc1 100755
--- a/tools/net/ynl/ynl-gen-c.py
+++ b/tools/net/ynl/ynl-gen-c.py
@@ -355,10 +355,13 @@ class TypeString(Type):
         return f'.type = YNL_PT_NUL_STR, '
 
     def _attr_policy(self, policy):
-        mem = '{ .type = ' + policy
-        if 'max-len' in self.checks:
-            mem += ', .len = ' + str(self.checks['max-len'])
-        mem += ', }'
+        if 'exact-len' in self.checks:
+            mem = 'NLA_POLICY_EXACT_LEN(' + str(self.checks['exact-len']) + ')'
+        else:
+            mem = '{ .type = ' + policy
+            if 'max-len' in self.checks:
+                mem += ', .len = ' + str(self.checks['max-len'])
+            mem += ', }'
         return mem
 
     def attr_policy(self, cw):
@@ -404,14 +407,17 @@ class TypeBinary(Type):
         return f'.type = YNL_PT_BINARY,'
 
     def _attr_policy(self, policy):
-        mem = '{ '
-        if len(self.checks) == 1 and 'min-len' in self.checks:
-            mem += '.len = ' + str(self.checks['min-len'])
-        elif len(self.checks) == 0:
-            mem += '.type = NLA_BINARY'
+        if 'exact-len' in self.checks:
+            mem = 'NLA_POLICY_EXACT_LEN(' + str(self.checks['exact-len']) + ')'
         else:
-            raise Exception('One or more of binary type checks not implemented, yet')
-        mem += ', }'
+            mem = '{ '
+            if len(self.checks) == 1 and 'min-len' in self.checks:
+                mem += '.len = ' + str(self.checks['min-len'])
+            elif len(self.checks) == 0:
+                mem += '.type = NLA_BINARY'
+            else:
+                raise Exception('One or more of binary type checks not implemented, yet')
+            mem += ', }'
         return mem
 
     def attr_put(self, ri, var):
-- 
2.41.0