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

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

[Stefano Brivio]

...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>
---
 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;
 			}
 
-- 
@@ -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;
 			}
 
-- 
2.39.2

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

[Paul Holzinger]

On 12/03/2024 08:21, 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>
Tested-by: Paul Holzinger <pholzing@redhat.com>

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

[David Gibson]

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

[Stefano Brivio]

On Thu, 14 Mar 2024 13:17:02 +1100
David Gibson <david@gibson.dropbear.id.au> wrote:

> 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.

Right, yes. But as we introduced the feature, the man page said, from
the beginning:

  -D, --dns addr
      Use addr (IPv4 or IPv6) for DHCP, DHCPv6, NDP or DNS forwarding [...]

so we have to change/fix semantics, I guess.

-- 
Stefano

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

[David Gibson]

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On Thu, Mar 14, 2024 at 05:54:10AM +0100, Stefano Brivio wrote:
> On Thu, 14 Mar 2024 13:17:02 +1100
> David Gibson <david@gibson.dropbear.id.au> wrote:
> 
> > 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.
> 
> Right, yes. But as we introduced the feature, the man page said, from
> the beginning:
> 
>   -D, --dns addr
>       Use addr (IPv4 or IPv6) for DHCP, DHCPv6, NDP or DNS forwarding [...]
> 
> so we have to change/fix semantics, I guess.

Right, it's not really clear from the man page whether it's a host or
guest address.

-- 
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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