Patchwork : Keep the "state" match as alias [Re: state match is obsolete 1.4.17]

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Submitter Jozsef Kadlecsik
Date Jan. 15, 2013, 5:28 p.m.
Message ID <alpine.DEB.2.00.1301151820230.12091@blackhole.kfki.hu>
Download mbox | patch
Permalink /patch/212259/
State Superseded
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Comments

Jozsef Kadlecsik - Jan. 15, 2013, 5:28 p.m.
On Tue, 15 Jan 2013, Jozsef Kadlecsik wrote:

> With passing one more internal flag, indicating that the "state" alias is 
> used, the "conntrack" module can remain completely hidden and the user can 
> list/save exactly the same command as the issued one.

Here follows the patch which introduces match module aliases (the same can 
be done for targets as well). The alias is handled as it were a real 
extension while it's actually handled by another module. Listing/saving 
keeps the alias name and options.

The "state" extension is the first example of such an alias.

 
Best regards,
Jozsef
-
E-mail  : kadlec@blackhole.kfki.hu, kadlecsik.jozsef@wigner.mta.hu
PGP key : http://www.kfki.hu/~kadlec/pgp_public_key.txt
Address : Wigner Research Centre for Physics, Hungarian Academy of Sciences
          H-1525 Budapest 114, POB. 49, Hungary
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Pablo Neira - Jan. 18, 2013, 12:28 a.m.
Hi Jozsef,

On Tue, Jan 15, 2013 at 06:28:11PM +0100, Jozsef Kadlecsik wrote:
> On Tue, 15 Jan 2013, Jozsef Kadlecsik wrote:
> 
> > With passing one more internal flag, indicating that the "state" alias is 
> > used, the "conntrack" module can remain completely hidden and the user can 
> > list/save exactly the same command as the issued one.
> 
> Here follows the patch which introduces match module aliases (the same can 
> be done for targets as well). The alias is handled as it were a real 
> extension while it's actually handled by another module. Listing/saving 
> keeps the alias name and options.
> 
> The "state" extension is the first example of such an alias.

I like this symmetrical aliasing approach.

The aim is to get rid of redundant things in the kernel. And with
this, we can get that without disturbing users.

Would you do the same for the NOTRACK target?

Thanks.
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Jozsef Kadlecsik - Jan. 22, 2013, 9:47 p.m.
On Fri, 18 Jan 2013, Pablo Neira Ayuso wrote:

> On Tue, Jan 15, 2013 at 06:28:11PM +0100, Jozsef Kadlecsik wrote:
> > On Tue, 15 Jan 2013, Jozsef Kadlecsik wrote:
> > 
> > > With passing one more internal flag, indicating that the "state" alias is 
> > > used, the "conntrack" module can remain completely hidden and the user can 
> > > list/save exactly the same command as the issued one.
> > 
> > Here follows the patch which introduces match module aliases (the same can 
> > be done for targets as well). The alias is handled as it were a real 
> > extension while it's actually handled by another module. Listing/saving 
> > keeps the alias name and options.
> > 
> > The "state" extension is the first example of such an alias.
> 
> I like this symmetrical aliasing approach.
> 
> The aim is to get rid of redundant things in the kernel. And with
> this, we can get that without disturbing users.
> 
> Would you do the same for the NOTRACK target?

Yes, but looking through the modules, I see a lot of inconsistencies: in 
listing match names capitalized, some match/target doesn't print its name, 
missing whitespaces, etc.

I'm going to fix those, but quite a lot of simplification could be 
achieved if the options at listing and saving could be generated by the 
same function in a match/target. Like instead of

	ttl match TTL == xxx

I propose to list the match as

	ttl eq xxx

(That is generate listings by striping off the dashes and the match/target 
name prefix from the options.)

The question is: do we have a "stable API" in listings, at this level?

Best regards,
Jozsef
-
E-mail  : kadlec@blackhole.kfki.hu, kadlecsik.jozsef@wigner.mta.hu
PGP key : http://www.kfki.hu/~kadlec/pgp_public_key.txt
Address : Wigner Research Centre for Physics, Hungarian Academy of Sciences
          H-1525 Budapest 114, POB. 49, Hungary
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Jan Engelhardt - Jan. 22, 2013, 9:58 p.m.
On Tuesday 2013-01-22 22:47, Jozsef Kadlecsik wrote:
>
>I'm going to fix those, but quite a lot of simplification could be 
>achieved if the options at listing and saving could be generated by the 
>same function in a match/target. Like instead of
>
>	ttl match TTL == xxx
>
>I propose to list the match as
>
>	ttl eq xxx
>
>(That is generate listings by striping off the dashes and the match/target 
>name prefix from the options.)
>
>The question is: do we have a "stable API" in listings, at this level?

Only with -S/iptables-save, IMO.
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Pablo Neira - Jan. 23, 2013, 3:03 a.m.
Hi Jozsef,

On Tue, Jan 22, 2013 at 10:47:35PM +0100, Jozsef Kadlecsik wrote:
> On Fri, 18 Jan 2013, Pablo Neira Ayuso wrote:
> 
> > On Tue, Jan 15, 2013 at 06:28:11PM +0100, Jozsef Kadlecsik wrote:
> > > On Tue, 15 Jan 2013, Jozsef Kadlecsik wrote:
> > > 
> > > > With passing one more internal flag, indicating that the "state" alias is 
> > > > used, the "conntrack" module can remain completely hidden and the user can 
> > > > list/save exactly the same command as the issued one.
> > > 
> > > Here follows the patch which introduces match module aliases (the same can 
> > > be done for targets as well). The alias is handled as it were a real 
> > > extension while it's actually handled by another module. Listing/saving 
> > > keeps the alias name and options.
> > > 
> > > The "state" extension is the first example of such an alias.
> > 
> > I like this symmetrical aliasing approach.
> > 
> > The aim is to get rid of redundant things in the kernel. And with
> > this, we can get that without disturbing users.
> > 
> > Would you do the same for the NOTRACK target?
> 
> Yes, but looking through the modules, I see a lot of inconsistencies: in 
> listing match names capitalized, some match/target doesn't print its name, 
> missing whitespaces, etc.
> 
> I'm going to fix those, but quite a lot of simplification could be 
> achieved if the options at listing and saving could be generated by the 
> same function in a match/target. Like instead of
> 
> 	ttl match TTL == xxx
> 
> I propose to list the match as
> 
> 	ttl eq xxx
> 
> (That is generate listings by striping off the dashes and the match/target 
> name prefix from the options.)
> 
> The question is: do we have a "stable API" in listings, at this level?

I remember that, while discussing nfacct, some people mentioned that
they were using scripts to parse iptables -L -n to digest counters.

I have also found some perl extension [1] that parses `iptables -L -n'
output.

[1] http://search.cpan.org/dist/IPTables-Parse/
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Jozsef Kadlecsik - Jan. 23, 2013, 9 a.m.
On Wed, 23 Jan 2013, Pablo Neira Ayuso wrote:

> On Tue, Jan 22, 2013 at 10:47:35PM +0100, Jozsef Kadlecsik wrote:
> > On Fri, 18 Jan 2013, Pablo Neira Ayuso wrote:
> > 
> > > On Tue, Jan 15, 2013 at 06:28:11PM +0100, Jozsef Kadlecsik wrote:
> > > > On Tue, 15 Jan 2013, Jozsef Kadlecsik wrote:
> > > > 
> > > > > With passing one more internal flag, indicating that the "state" alias is 
> > > > > used, the "conntrack" module can remain completely hidden and the user can 
> > > > > list/save exactly the same command as the issued one.
> > > > 
> > > > Here follows the patch which introduces match module aliases (the same can 
> > > > be done for targets as well). The alias is handled as it were a real 
> > > > extension while it's actually handled by another module. Listing/saving 
> > > > keeps the alias name and options.
> > > > 
> > > > The "state" extension is the first example of such an alias.
> > > 
> > > I like this symmetrical aliasing approach.
> > > 
> > > The aim is to get rid of redundant things in the kernel. And with
> > > this, we can get that without disturbing users.
> > > 
> > > Would you do the same for the NOTRACK target?
> > 
> > Yes, but looking through the modules, I see a lot of inconsistencies: in 
> > listing match names capitalized, some match/target doesn't print its name, 
> > missing whitespaces, etc.
> > 
> > I'm going to fix those, but quite a lot of simplification could be 
> > achieved if the options at listing and saving could be generated by the 
> > same function in a match/target. Like instead of
> > 
> > 	ttl match TTL == xxx
> > 
> > I propose to list the match as
> > 
> > 	ttl eq xxx
> > 
> > (That is generate listings by striping off the dashes and the match/target 
> > name prefix from the options.)
> > 
> > The question is: do we have a "stable API" in listings, at this level?
> 
> I remember that, while discussing nfacct, some people mentioned that
> they were using scripts to parse iptables -L -n to digest counters.

The counters part is not affected.
 
> I have also found some perl extension [1] that parses `iptables -L -n'
> output.
> 
> [1] http://search.cpan.org/dist/IPTables-Parse/

Sigh. Why 'iptables -L -n' is used and not 'iptables-save -c'?

Looking at the perl module, the proposed changes would break the parsing 
of the options of the SNAT/DNAT targets. It'd be not hard to prepare the 
module to handle current/proposed formats.

Best regards,
Jozsef
-
E-mail  : kadlec@blackhole.kfki.hu, kadlecsik.jozsef@wigner.mta.hu
PGP key : http://www.kfki.hu/~kadlec/pgp_public_key.txt
Address : Wigner Research Centre for Physics, Hungarian Academy of Sciences
          H-1525 Budapest 114, POB. 49, Hungary
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Jozsef Kadlecsik - Jan. 23, 2013, 9:06 a.m.
On Tue, 22 Jan 2013, Jan Engelhardt wrote:

> On Tuesday 2013-01-22 22:47, Jozsef Kadlecsik wrote:
> >
> >I'm going to fix those, but quite a lot of simplification could be 
> >achieved if the options at listing and saving could be generated by the 
> >same function in a match/target. Like instead of
> >
> >	ttl match TTL == xxx
> >
> >I propose to list the match as
> >
> >	ttl eq xxx
> >
> >(That is generate listings by striping off the dashes and the match/target 
> >name prefix from the options.)
> >
> >The question is: do we have a "stable API" in listings, at this level?
> 
> Only with -S/iptables-save, IMO.

Yes, I believe so too. Still, better not break something important.

Best regards,
Jozsef
-
E-mail  : kadlec@blackhole.kfki.hu, kadlecsik.jozsef@wigner.mta.hu
PGP key : http://www.kfki.hu/~kadlec/pgp_public_key.txt
Address : Wigner Research Centre for Physics, Hungarian Academy of Sciences
          H-1525 Budapest 114, POB. 49, Hungary
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Pablo Neira - Jan. 23, 2013, 10:08 a.m.
On Wed, Jan 23, 2013 at 10:00:19AM +0100, Jozsef Kadlecsik wrote:
> On Wed, 23 Jan 2013, Pablo Neira Ayuso wrote:
> 
> > On Tue, Jan 22, 2013 at 10:47:35PM +0100, Jozsef Kadlecsik wrote:
> > > On Fri, 18 Jan 2013, Pablo Neira Ayuso wrote:
> > > 
> > > > On Tue, Jan 15, 2013 at 06:28:11PM +0100, Jozsef Kadlecsik wrote:
> > > > > On Tue, 15 Jan 2013, Jozsef Kadlecsik wrote:
> > > > > 
> > > > > > With passing one more internal flag, indicating that the "state" alias is 
> > > > > > used, the "conntrack" module can remain completely hidden and the user can 
> > > > > > list/save exactly the same command as the issued one.
> > > > > 
> > > > > Here follows the patch which introduces match module aliases (the same can 
> > > > > be done for targets as well). The alias is handled as it were a real 
> > > > > extension while it's actually handled by another module. Listing/saving 
> > > > > keeps the alias name and options.
> > > > > 
> > > > > The "state" extension is the first example of such an alias.
> > > > 
> > > > I like this symmetrical aliasing approach.
> > > > 
> > > > The aim is to get rid of redundant things in the kernel. And with
> > > > this, we can get that without disturbing users.
> > > > 
> > > > Would you do the same for the NOTRACK target?
> > > 
> > > Yes, but looking through the modules, I see a lot of inconsistencies: in 
> > > listing match names capitalized, some match/target doesn't print its name, 
> > > missing whitespaces, etc.
> > > 
> > > I'm going to fix those, but quite a lot of simplification could be 
> > > achieved if the options at listing and saving could be generated by the 
> > > same function in a match/target. Like instead of
> > > 
> > > 	ttl match TTL == xxx
> > > 
> > > I propose to list the match as
> > > 
> > > 	ttl eq xxx
> > > 
> > > (That is generate listings by striping off the dashes and the match/target 
> > > name prefix from the options.)
> > > 
> > > The question is: do we have a "stable API" in listings, at this level?
> > 
> > I remember that, while discussing nfacct, some people mentioned that
> > they were using scripts to parse iptables -L -n to digest counters.
> 
> The counters part is not affected.
>  
> > I have also found some perl extension [1] that parses `iptables -L -n'
> > output.
> > 
> > [1] http://search.cpan.org/dist/IPTables-Parse/
> 
> Sigh. Why 'iptables -L -n' is used and not 'iptables-save -c'?

Good question :-). I don't have an answer for that, probably the
author.

> Looking at the perl module, the proposed changes would break the parsing 
> of the options of the SNAT/DNAT targets. It'd be not hard to prepare the 
> module to handle current/proposed formats.

Yes. That will fix that module for latest iptables, but would still
break with old iptables versions unless you add some workaround to
that script.

Don't get me wrong, I don't like those inconsistencies either. We have
to decide if we care to likely break existing applications parsing
iptables -L -n.
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Patch

diff --git a/extensions/libxt_conntrack.c b/extensions/libxt_conntrack.c
index c37f14d..92a42dc 100644
--- a/extensions/libxt_conntrack.c
+++ b/extensions/libxt_conntrack.c
@@ -794,6 +794,15 @@  conntrack_dump_ports(const char *prefix, const char *opt,
 		printf(" %s%s %u:%u", prefix, opt, port_low, port_high);
 }
 
+static const char *
+print_name_alias(const struct xt_entry_match *match)
+{
+	struct xt_conntrack_mtinfo1 *info = (void *)match->data;
+	
+	return info->match_flags & XT_CONNTRACK_STATE_ALIAS
+		? "state" : "conntrack";	
+}
+
 static void
 conntrack_dump(const struct xt_conntrack_mtinfo3 *info, const char *prefix,
                unsigned int family, bool numeric, bool v3)
@@ -801,7 +810,9 @@  conntrack_dump(const struct xt_conntrack_mtinfo3 *info, const char *prefix,
 	if (info->match_flags & XT_CONNTRACK_STATE) {
 		if (info->invert_flags & XT_CONNTRACK_STATE)
 			printf(" !");
-		printf(" %sctstate", prefix);
+		printf(" %s%s", prefix,
+		       info->match_flags & XT_CONNTRACK_STATE_ALIAS
+		       ? "state" : "ctstate");
 		print_state(info->state_mask);
 	}
 
@@ -1083,7 +1094,7 @@  static void state_ct1_parse(struct xt_option_call *cb)
 	struct xt_conntrack_mtinfo1 *sinfo = cb->data;
 
 	xtables_option_parse(cb);
-	sinfo->match_flags = XT_CONNTRACK_STATE;
+	sinfo->match_flags = XT_CONNTRACK_STATE | XT_CONNTRACK_STATE_ALIAS;
 	sinfo->state_mask = state_parse_states(cb->arg);
 	if (cb->invert)
 		sinfo->invert_flags |= XT_CONNTRACK_STATE;
@@ -1094,7 +1105,7 @@  static void state_ct23_parse(struct xt_option_call *cb)
 	struct xt_conntrack_mtinfo3 *sinfo = cb->data;
 
 	xtables_option_parse(cb);
-	sinfo->match_flags = XT_CONNTRACK_STATE;
+	sinfo->match_flags = XT_CONNTRACK_STATE | XT_CONNTRACK_STATE_ALIAS;
 	sinfo->state_mask = state_parse_states(cb->arg);
 	if (cb->invert)
 		sinfo->invert_flags |= XT_CONNTRACK_STATE;
@@ -1172,6 +1183,7 @@  static struct xtables_match conntrack_mt_reg[] = {
 		.x6_fcheck     = conntrack_mt_check,
 		.print         = conntrack1_mt4_print,
 		.save          = conntrack1_mt4_save,
+		.alias	       = print_name_alias,
 		.x6_options    = conntrack2_mt_opts,
 	},
 	{
@@ -1186,6 +1198,7 @@  static struct xtables_match conntrack_mt_reg[] = {
 		.x6_fcheck     = conntrack_mt_check,
 		.print         = conntrack1_mt6_print,
 		.save          = conntrack1_mt6_save,
+		.alias	       = print_name_alias,
 		.x6_options    = conntrack2_mt_opts,
 	},
 	{
@@ -1200,6 +1213,7 @@  static struct xtables_match conntrack_mt_reg[] = {
 		.x6_fcheck     = conntrack_mt_check,
 		.print         = conntrack2_mt_print,
 		.save          = conntrack2_mt_save,
+		.alias	       = print_name_alias,
 		.x6_options    = conntrack2_mt_opts,
 	},
 	{
@@ -1214,6 +1228,7 @@  static struct xtables_match conntrack_mt_reg[] = {
 		.x6_fcheck     = conntrack_mt_check,
 		.print         = conntrack2_mt6_print,
 		.save          = conntrack2_mt6_save,
+		.alias	       = print_name_alias,
 		.x6_options    = conntrack2_mt_opts,
 	},
 	{
@@ -1228,6 +1243,7 @@  static struct xtables_match conntrack_mt_reg[] = {
 		.x6_fcheck     = conntrack_mt_check,
 		.print         = conntrack3_mt_print,
 		.save          = conntrack3_mt_save,
+		.alias	       = print_name_alias,
 		.x6_options    = conntrack3_mt_opts,
 	},
 	{
@@ -1242,6 +1258,7 @@  static struct xtables_match conntrack_mt_reg[] = {
 		.x6_fcheck     = conntrack_mt_check,
 		.print         = conntrack3_mt6_print,
 		.save          = conntrack3_mt6_save,
+		.alias	       = print_name_alias,
 		.x6_options    = conntrack3_mt_opts,
 	},
 	{
@@ -1249,6 +1266,7 @@  static struct xtables_match conntrack_mt_reg[] = {
 		.name          = "state",
 		.real_name     = "conntrack",
 		.revision      = 1,
+		.ext_flags     = XTABLES_EXT_ALIAS,
 		.version       = XTABLES_VERSION,
 		.size          = XT_ALIGN(sizeof(struct xt_conntrack_mtinfo1)),
 		.userspacesize = XT_ALIGN(sizeof(struct xt_conntrack_mtinfo1)),
@@ -1261,6 +1279,7 @@  static struct xtables_match conntrack_mt_reg[] = {
 		.name          = "state",
 		.real_name     = "conntrack",
 		.revision      = 2,
+		.ext_flags     = XTABLES_EXT_ALIAS,
 		.version       = XTABLES_VERSION,
 		.size          = XT_ALIGN(sizeof(struct xt_conntrack_mtinfo2)),
 		.userspacesize = XT_ALIGN(sizeof(struct xt_conntrack_mtinfo2)),
@@ -1273,6 +1292,7 @@  static struct xtables_match conntrack_mt_reg[] = {
 		.name          = "state",
 		.real_name     = "conntrack",
 		.revision      = 3,
+		.ext_flags     = XTABLES_EXT_ALIAS,
 		.version       = XTABLES_VERSION,
 		.size          = XT_ALIGN(sizeof(struct xt_conntrack_mtinfo3)),
 		.userspacesize = XT_ALIGN(sizeof(struct xt_conntrack_mtinfo3)),
diff --git a/extensions/libxt_state.man b/extensions/libxt_state.man
index bd60468..ec096ca 100644
--- a/extensions/libxt_state.man
+++ b/extensions/libxt_state.man
@@ -1,4 +1,4 @@ 
-The "state" module is an obsolete version of "conntrack".
+The "state" extension is a subset of the "conntrack" module.
 "state" allows access to the connection tracking state for this packet.
 .TP
 [\fB!\fP] \fB\-\-state\fP \fIstate\fP
diff --git a/include/linux/netfilter/xt_conntrack.h b/include/linux/netfilter/xt_conntrack.h
index 74b904d..e971501 100644
--- a/include/linux/netfilter/xt_conntrack.h
+++ b/include/linux/netfilter/xt_conntrack.h
@@ -30,6 +30,7 @@  enum {
 	XT_CONNTRACK_REPLSRC_PORT = 1 << 10,
 	XT_CONNTRACK_REPLDST_PORT = 1 << 11,
 	XT_CONNTRACK_DIRECTION    = 1 << 12,
+	XT_CONNTRACK_STATE_ALIAS  = 1 << 13,
 };
 
 struct xt_conntrack_mtinfo1 {
diff --git a/include/xtables.h b/include/xtables.h
index 75de958..892c0b9 100644
--- a/include/xtables.h
+++ b/include/xtables.h
@@ -201,6 +201,10 @@  struct xtables_lmap {
 	struct xtables_lmap *next;
 };
 
+enum xtables_ext_flags {
+	XTABLES_EXT_ALIAS = 1 << 0,
+};
+
 /* Include file for additions: new matches and targets. */
 struct xtables_match
 {
@@ -217,6 +221,9 @@  struct xtables_match
 
 	/* Revision of match (0 by default). */
 	u_int8_t revision;
+	
+	/* Extension flags */
+	u_int8_t ext_flags;
 
 	u_int16_t family;
 
@@ -251,6 +258,9 @@  struct xtables_match
 	/* ip is struct ipt_ip * for example */
 	void (*save)(const void *ip, const struct xt_entry_match *match);
 
+	/* Print match name or alias*/
+	const char *(*alias)(const struct xt_entry_match *match);
+
 	/* Pointer to list of extra command-line options */
 	const struct option *extra_opts;
 
diff --git a/iptables/ip6tables.c b/iptables/ip6tables.c
index 556647f..a5bcca3 100644
--- a/iptables/ip6tables.c
+++ b/iptables/ip6tables.c
@@ -1000,7 +1000,8 @@  static int print_match_save(const struct xt_entry_match *e,
 		xtables_find_match(e->u.user.name, XTF_TRY_LOAD, NULL);
 
 	if (match) {
-		printf(" -m %s", e->u.user.name);
+		printf(" -m %s",
+		       match->alias ? match->alias(e) : e->u.user.name);
 
 		/* some matches don't provide a save function */
 		if (match->save)
@@ -1265,8 +1266,9 @@  static void command_match(struct iptables_command_state *cs)
 		strcpy(m->m->u.user.name, m->name);
 	} else {
 		strcpy(m->m->u.user.name, m->real_name);
-		fprintf(stderr, "WARNING: The %s match is obsolete. "
-		        "Use %s instead.\n", m->name, m->real_name);
+		if (!(m->ext_flags & XTABLES_EXT_ALIAS))
+			fprintf(stderr, "WARNING: The %s match is obsolete. "
+			        "Use %s instead.\n", m->name, m->real_name);
 	}
 	m->m->u.user.revision = m->revision;
 
diff --git a/iptables/iptables.c b/iptables/iptables.c
index 00e3f01..6c53c54 100644
--- a/iptables/iptables.c
+++ b/iptables/iptables.c
@@ -991,7 +991,8 @@  static int print_match_save(const struct xt_entry_match *e,
 		xtables_find_match(e->u.user.name, XTF_TRY_LOAD, NULL);
 
 	if (match) {
-		printf(" -m %s", e->u.user.name);
+		printf(" -m %s",
+		       match->alias ? match->alias(e) : e->u.user.name);
 
 		/* some matches don't provide a save function */
 		if (match->save)
@@ -1259,8 +1260,9 @@  static void command_match(struct iptables_command_state *cs)
 		strcpy(m->m->u.user.name, m->name);
 	} else {
 		strcpy(m->m->u.user.name, m->real_name);
-		fprintf(stderr, "WARNING: The %s match is obsolete. "
-		        "Use %s instead.\n", m->name, m->real_name);
+		if (!(m->ext_flags & XTABLES_EXT_ALIAS))
+			fprintf(stderr, "WARNING: The %s match is obsolete. "
+			        "Use %s instead.\n", m->name, m->real_name);
 	}
 	m->m->u.user.revision = m->revision;