[PATCH v4 3/3] landlock.7: Give a pointer to how to implement a fallback mechanism

["Günther Noack" <gnoack3000@gmail.com>]

Signed-off-by: Günther Noack <gnoack3000@gmail.com>
---
 man7/landlock.7 | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/man7/landlock.7 b/man7/landlock.7
index 9c305edef..c173cbb98 100644
--- a/man7/landlock.7
+++ b/man7/landlock.7
@@ -393,12 +393,14 @@ accessible through these system call families:
 Future Landlock evolutions will enable to restrict them.
 .SH EXAMPLES
 We first need to create the ruleset that will contain our rules.
+.PP
 For this example,
 the ruleset will contain rules that only allow read actions,
 but write actions will be denied.
 The ruleset then needs to handle both of these kinds of actions.
-See below for the description of filesystem actions.
-.PP
+See the
+.B DESCRIPTION
+section for the description of filesystem actions.
 .in +4n
 .EX
 struct landlock_ruleset_attr attr = {0};
@@ -429,6 +431,16 @@ if (ruleset_fd == \-1) {
 .EE
 .in
 .PP
+The ruleset we have constructed requires Landlock ABI version 3 or higher.
+On kernels which do not provide that,
+the call to
+.BR landlock_create_ruleset (2)
+will fail.
+You can build a more graceful fallback mechanism
+by using the version compatibility table from the
+.B VERSIONS
+section.
+.PP
 We can now add a new rule to this ruleset thanks to the returned file
 descriptor referring to this ruleset.
 The rule will only allow reading the file hierarchy
-- 
2.39.2