Re: [PATCH] conf: Handle addresses passed via --dns just like the ones from resolv.conf

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

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On Tue, Mar 12, 2024 at 08:21:36AM +0100, Stefano Brivio wrote:
> ...that is, call add_dns4() and add_dns6() instead of simply adding
> those to the list of servers we advertise.
> 
> Most importantly, this will set the 'dns_host' field for the matching
> IP version, so that, as mentioned in the man page, servers passed via
> --dns are used for DNS mapping as well, if used in combination with
> --dns-forward.
> 
> Reported-by: Paul Holzinger <pholzing@redhat.com>
> Link: https://bugs.passt.top/show_bug.cgi?id=82
> Fixes: 89678c515755 ("conf, udp: Introduce basic DNS forwarding")
> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

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

This does subtly change semantics: addresses given to --dns are now
host addresses, rather than guest addresses.  I think the new meaning
is less cryptic, though.

> ---
>  conf.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/conf.c b/conf.c
> index c50c039..17c667a 100644
> --- a/conf.c
> +++ b/conf.c
> @@ -1164,11 +1164,11 @@ void conf(struct ctx *c, int argc, char **argv)
>  	};
>  	char userns[PATH_MAX] = { 0 }, netns[PATH_MAX] = { 0 };
>  	bool copy_addrs_opt = false, copy_routes_opt = false;
> +	struct in6_addr *dns6 = c->ip6.dns, dns6_tmp;
> +	struct in_addr *dns4 = c->ip4.dns, dns4_tmp;
>  	enum fwd_ports_mode fwd_default = FWD_NONE;
>  	bool v4_only = false, v6_only = false;
> -	struct in6_addr *dns6 = c->ip6.dns;
>  	struct fqdn *dnss = c->dns_search;
> -	struct in_addr *dns4 = c->ip4.dns;
>  	unsigned int ifi4 = 0, ifi6 = 0;
>  	const char *logfile = NULL;
>  	const char *optstring;
> @@ -1554,14 +1554,14 @@ void conf(struct ctx *c, int argc, char **argv)
>  				die("Conflicting DNS options");
>  
>  			if (dns4 - &c->ip4.dns[0] < ARRAY_SIZE(c->ip4.dns) &&
> -			    inet_pton(AF_INET, optarg, dns4)) {
> -				dns4++;
> +			    inet_pton(AF_INET, optarg, &dns4_tmp)) {
> +				add_dns4(c, &dns4_tmp, &dns4);
>  				break;
>  			}
>  
>  			if (dns6 - &c->ip6.dns[0] < ARRAY_SIZE(c->ip6.dns) &&
> -			    inet_pton(AF_INET6, optarg, dns6)) {
> -				dns6++;
> +			    inet_pton(AF_INET6, optarg, &dns6_tmp)) {
> +				add_dns6(c, &dns6_tmp, &dns6);
>  				break;
>  			}
>  

-- 
David Gibson			| 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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