[PATCH v2 3/3] samples/landlock: Clarify option parsing behaviour

From: Matthieu Buffet
Date: Wed Oct 02 2024 - 20:50:43 EST


- Clarify which environment variables are optional, which ones are
mandatory
- Clarify the difference between unset variables and empty ones

Signed-off-by: Matthieu Buffet <matthieu@xxxxxxxxx>
---
samples/landlock/sandboxer.c | 22 +++++++++++++---------
1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c
index f16994d35d9e..a28e4a9c5f87 100644
--- a/samples/landlock/sandboxer.c
+++ b/samples/landlock/sandboxer.c
@@ -298,24 +298,27 @@ static bool check_ruleset_scope(const char *const env_var,
static void print_help(const char *argv0)
{
fprintf(stderr,
- "usage: %s=\"...\" %s=\"...\" %s=\"...\" %s=\"...\" %s=\"...\" %s "
+ "usage: %s=\"...\" %s=\"...\" [other environment variables] %s "
"<cmd> [args]...\n\n",
- ENV_FS_RO_NAME, ENV_FS_RW_NAME, ENV_TCP_BIND_NAME,
- ENV_TCP_CONNECT_NAME, ENV_SCOPED_NAME, argv0);
+ ENV_FS_RO_NAME, ENV_FS_RW_NAME, argv0);
fprintf(stderr,
"Execute a command in a restricted environment.\n\n");
fprintf(stderr,
- "Environment variables containing paths and ports "
- "each separated by a colon:\n");
+ "All environment variables can be multi-valued, with a "
+ "colon delimiter.\n"
+ "\n"
+ "Mandatory settings:\n");
fprintf(stderr,
"* %s: list of paths allowed to be used in a read-only way.\n",
ENV_FS_RO_NAME);
fprintf(stderr,
- "* %s: list of paths allowed to be used in a read-write way.\n\n",
+ "* %s: list of paths allowed to be used in a read-write way.\n",
ENV_FS_RW_NAME);
fprintf(stderr,
- "Environment variables containing ports are optional "
- "and could be skipped.\n");
+ "\n"
+ "Optional settings (when not set, their associated access "
+ "check is always allowed, which is different from an empty "
+ "string which means an empty list)\n");
fprintf(stderr,
"* %s: list of ports allowed to bind (server).\n",
ENV_TCP_BIND_NAME);
@@ -325,7 +328,8 @@ static void print_help(const char *argv0)
fprintf(stderr, "* %s: list of scoped IPCs.\n",
ENV_SCOPED_NAME);
fprintf(stderr,
- "\nexample:\n"
+ "\n"
+ "Example:\n"
"%s=\"${PATH}:/lib:/usr:/proc:/etc:/dev/urandom\" "
"%s=\"/dev/null:/dev/full:/dev/zero:/dev/pts:/tmp\" "
"%s=\"9418\" "
--
2.39.2