[PATCH v2] util: Don't stop on unrelated values when looking for --fd in close_open_files()

21 Aug 2024

Seen with krun: we get a file descriptor via --fd, but we close it and
happily use the same number for TCP files.

The issue is that if we also get other options before --fd, with
arguments, getopt_long() stops parsing them because it sees them as
non-option values.

Use the - modifier at the beginning of optstring (before :, which is
needed to avoid printing errors) instead of +, which means we'll
continue parsing after finding unrelated option values, but
getopt_long() won't reorder them anyway: they'll be passed with option
value '1', which we can ignore.

By the way, we also need to add : after F in the optstring, so that
we're able to parse the option when given as short name as well.

Now that we change the parsing mode between close_open_files() and
conf(), we need to reset optind to 0, not to 1, whenever we call
getopt_long() again in conf(), so that the internal initialisation
of getopt_long() evaluating GNU extensions is re-triggered.

Link: https://github.com/slp/krun/issues/17#issuecomment-2294943828
Fixes: baccfb95ce0e ("conf: Stop parsing options at first non-option argument")
Fixes: 09603cab28f9 ("passt, util: Close any open file that the parent might have leaked")
Signed-off-by: Stefano Brivio 
---
v2: Reset optind to 0 before any further call to getopt_long() in
    conf()

 conf.c | 6 +++---
 util.c | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/conf.c b/conf.c
index ed097bd..ba82696 100644
--- a/conf.c
+++ b/conf.c
@@ -1261,7 +1261,7 @@ void conf(struct ctx *c, int argc, char **argv)
 	c->tcp.fwd_in.mode = c->tcp.fwd_out.mode = FWD_UNSET;
 	c->udp.fwd_in.mode = c->udp.fwd_out.mode = FWD_UNSET;
 
-	optind = 1;
+	optind = 0;
 	do {
 		name = getopt_long(argc, argv, optstring, options, NULL);
 
@@ -1648,7 +1648,7 @@ void conf(struct ctx *c, int argc, char **argv)
 	 * settings)
 	 */
 	udp_portmap_clear();
-	optind = 1;
+	optind = 0;
 	do {
 		name = getopt_long(argc, argv, optstring, options, NULL);
 
@@ -1720,7 +1720,7 @@ void conf(struct ctx *c, int argc, char **argv)
 		nl_sock_init(c, true);
 
 	/* ...and outbound port options now that namespaces are set up. */
-	optind = 1;
+	optind = 0;
 	do {
 		name = getopt_long(argc, argv, optstring, options, NULL);
 
diff --git a/util.c b/util.c
index 0b41404..3fce3c2 100644
--- a/util.c
+++ b/util.c
@@ -710,7 +710,7 @@ void close_open_files(int argc, char **argv)
 	int name, rc;
 
 	do {
-		name = getopt_long(argc, argv, "+:F", optfd, NULL);
+		name = getopt_long(argc, argv, "-:F:", optfd, NULL);
 
 		if (name == 'F') {
 			errno = 0;
-- 
2.43.0

    

Stefano Brivio

David Gibson

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