[PATCH xtables-nft v2] extensions: xt_socket: add txlate support for socket match

[PATCH xtables-nft v2] extensions: xt_socket: add txlate support for socket match

[Florian Westphal]

v2: document the match semantics of -m socket.

Ignore --nowildcard if used with other options when translating
and add "wildcard 0" if the option is missing.

"-m socket" will ignore sockets bound to 0.0.0.0/:: by default,
unless --nowildcard is given.

So, xlate must always append "wildcard 0", can elide "wildcard"
if other options are present along with --nowildcard.

To emulate "-m socket --nowildcard", check for "wildcard <= 1" to
get a "socket exists" type matching.

Signed-off-by: Florian Westphal <fw@strlen.de>
---
 extensions/libxt_socket.c      | 39 ++++++++++++++++++++++++++++++++++
 extensions/libxt_socket.txlate | 17 +++++++++++++++
 2 files changed, 56 insertions(+)
 create mode 100644 extensions/libxt_socket.txlate

diff --git a/extensions/libxt_socket.c b/extensions/libxt_socket.c
index a99135cdfa0a..016ea3435339 100644
--- a/extensions/libxt_socket.c
+++ b/extensions/libxt_socket.c
@@ -159,6 +159,42 @@ socket_mt_print_v3(const void *ip, const struct xt_entry_match *match,
 	socket_mt_save_v3(ip, match);
 }
 
+static int socket_mt_xlate(struct xt_xlate *xl, const struct xt_xlate_mt_params *params)
+{
+	const struct xt_socket_mtinfo3 *info = (const void *)params->match->data;
+	const char *space = "";
+
+	/* ONLY --nowildcard: match if socket exists. It does not matter
+	 * to which address it is bound.
+	 */
+	if (info->flags == XT_SOCKET_NOWILDCARD) {
+		xt_xlate_add(xl, "%ssocket wildcard le 1", space);
+		return 1;
+	}
+
+	/* Without --nowildcard, restrict to sockets NOT bound to
+	 * the any address.
+	 */
+	if ((info->flags & XT_SOCKET_NOWILDCARD) == 0) {
+		xt_xlate_add(xl, "socket wildcard 0");
+		space = " ";
+	}
+
+	if (info->flags & XT_SOCKET_TRANSPARENT) {
+		xt_xlate_add(xl, "%ssocket transparent 1", space);
+		space = " ";
+	}
+
+	/* If --nowildcard was given, -m socket should not test
+	 * the bound address.  We can simply ignore this; its
+	 * equal to "wildcard <= 1".
+	 */
+	if (info->flags & XT_SOCKET_RESTORESKMARK)
+		xt_xlate_add(xl, "%smeta mark set socket mark", space);
+
+	return 1;
+}
+
 static struct xtables_match socket_mt_reg[] = {
 	{
 		.name          = "socket",
@@ -180,6 +216,7 @@ static struct xtables_match socket_mt_reg[] = {
 		.save          = socket_mt_save,
 		.x6_parse      = socket_mt_parse,
 		.x6_options    = socket_mt_opts,
+		.xlate	       = socket_mt_xlate,
 	},
 	{
 		.name          = "socket",
@@ -193,6 +230,7 @@ static struct xtables_match socket_mt_reg[] = {
 		.save          = socket_mt_save_v2,
 		.x6_parse      = socket_mt_parse_v2,
 		.x6_options    = socket_mt_opts_v2,
+		.xlate	       = socket_mt_xlate,
 	},
 	{
 		.name          = "socket",
@@ -206,6 +244,7 @@ static struct xtables_match socket_mt_reg[] = {
 		.save          = socket_mt_save_v3,
 		.x6_parse      = socket_mt_parse_v3,
 		.x6_options    = socket_mt_opts_v3,
+		.xlate	       = socket_mt_xlate,
 	},
 };
 
diff --git a/extensions/libxt_socket.txlate b/extensions/libxt_socket.txlate
new file mode 100644
index 000000000000..7731e42eabf7
--- /dev/null
+++ b/extensions/libxt_socket.txlate
@@ -0,0 +1,17 @@
+# old socket match, no options.  Matches if sk can be found and it is not bound to 0.0.0.0/::
+iptables-translate -A INPUT -m socket
+nft 'add rule ip filter INPUT socket wildcard 0 counter'
+
+iptables-translate -A INPUT -m socket --transparent
+nft 'add rule ip filter INPUT socket wildcard 0 socket transparent 1 counter'
+
+# Matches if sk can be found.  Doesn't matter as to what addess it is bound to.
+# therefore, emulate "exists".
+iptables-translate -A INPUT -m socket --nowildcard
+nft 'add rule ip filter INPUT socket wildcard le 1 counter'
+
+iptables-translate -A INPUT -m socket --restore-skmark
+nft 'add rule ip filter INPUT socket wildcard 0 meta mark set socket mark counter'
+
+iptables-translate -A INPUT -m socket --transparent --nowildcard --restore-skmark
+nft 'add rule ip filter INPUT socket transparent 1 meta mark set socket mark counter'
-- 
2.44.0

Re: [PATCH xtables-nft v2] extensions: xt_socket: add txlate support for socket match

[Phil Sutter]

On Wed, Mar 06, 2024 at 11:11:25AM +0100, Florian Westphal wrote:
> v2: document the match semantics of -m socket.
> 
> Ignore --nowildcard if used with other options when translating
> and add "wildcard 0" if the option is missing.
> 
> "-m socket" will ignore sockets bound to 0.0.0.0/:: by default,
> unless --nowildcard is given.
> 
> So, xlate must always append "wildcard 0", can elide "wildcard"
> if other options are present along with --nowildcard.
> 
> To emulate "-m socket --nowildcard", check for "wildcard <= 1" to
> get a "socket exists" type matching.
> 
> Signed-off-by: Florian Westphal <fw@strlen.de>
> ---
>  extensions/libxt_socket.c      | 39 ++++++++++++++++++++++++++++++++++
>  extensions/libxt_socket.txlate | 17 +++++++++++++++
>  2 files changed, 56 insertions(+)
>  create mode 100644 extensions/libxt_socket.txlate
> 
> diff --git a/extensions/libxt_socket.c b/extensions/libxt_socket.c
> index a99135cdfa0a..016ea3435339 100644
> --- a/extensions/libxt_socket.c
> +++ b/extensions/libxt_socket.c
> @@ -159,6 +159,42 @@ socket_mt_print_v3(const void *ip, const struct xt_entry_match *match,
>  	socket_mt_save_v3(ip, match);
>  }
>  
> +static int socket_mt_xlate(struct xt_xlate *xl, const struct xt_xlate_mt_params *params)
> +{
> +	const struct xt_socket_mtinfo3 *info = (const void *)params->match->data;
> +	const char *space = "";

The whole "leading space or not" handling is not necessary, I made
xt_xlate_add() insert leading space automatically if the first
character is alpha-numeric or a brace.

Thanks, Phil

Re: [PATCH xtables-nft v2] extensions: xt_socket: add txlate support for socket match

[Florian Westphal]

Phil Sutter <phil@nwl.cc> wrote:
> On Wed, Mar 06, 2024 at 11:11:25AM +0100, Florian Westphal wrote:
> > +static int socket_mt_xlate(struct xt_xlate *xl, const struct xt_xlate_mt_params *params)
> > +{
> > +	const struct xt_socket_mtinfo3 *info = (const void *)params->match->data;
> > +	const char *space = "";
> 
> The whole "leading space or not" handling is not necessary, I made
> xt_xlate_add() insert leading space automatically if the first
> character is alpha-numeric or a brace.

Perfect, I'll push this out after removing the extra handling.

Re: [PATCH xtables-nft v2] extensions: xt_socket: add txlate support for socket match

[Phil Sutter]

On Wed, Mar 06, 2024 at 04:42:07PM +0100, Florian Westphal wrote:
> Phil Sutter <phil@nwl.cc> wrote:
> > On Wed, Mar 06, 2024 at 11:11:25AM +0100, Florian Westphal wrote:
> > > +static int socket_mt_xlate(struct xt_xlate *xl, const struct xt_xlate_mt_params *params)
> > > +{
> > > +	const struct xt_socket_mtinfo3 *info = (const void *)params->match->data;
> > > +	const char *space = "";
> > 
> > The whole "leading space or not" handling is not necessary, I made
> > xt_xlate_add() insert leading space automatically if the first
> > character is alpha-numeric or a brace.
> 
> Perfect, I'll push this out after removing the extra handling.

Acked-by: Phil Sutter <phil@nwl.cc>