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

[David Gibson <david@gibson.dropbear.id.au>]

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On Wed, Aug 21, 2024 at 12:28:38AM +0200, Stefano Brivio wrote:
> 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 <sbrivio@redhat.com>

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

> ---
> 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;

-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson

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