Add ASN as extended server ban, mask item, secgroup. Eg: GLINE ~asn:64496 0 Bye!

This also automatically adds it as a security group and mask item:

ban user {
        mask { asn 64496; }
        reason "Testing ASN ban";
}

And yeah, it is a normal extban too (in +b and +I). Users usually
don't know the AS Number of other users, though, unless you change
the default configuration (at the cost of privacy).

Updated release notes a bit... more will follow.

doc/RELEASE-NOTES.md

@@ -11,6 +11,20 @@ in progress and may not always be a stable version.
   [Mask item](https://www.unrealircd.org/docs/Mask_item).
   This means you can use all the power of mask items and security groups and
   multiple matching criteria.
+* The GeoIP module now contains info about 
+  [Autonomous system numbers](https://en.wikipedia.org/wiki/Autonomous_system_(Internet))
+  and this is exposed in:
+  * [Extended server ban](https://www.unrealircd.org/docs/Extended_server_bans)
+    so you can do things like `GLINE ~asn:64496 0 This ISP is banned`.
+  * In security groups and Mask items so you can do like:
+    ```
+    ban user {
+        mask { asn { 64496; 64497; 64498; } }
+        reason "Your ISP is banned.";
+       }
+    ```
+   * It is shown in the user connecting notice, WHOIS (for IRCOps) and
+     expanded in JSON data such as JSON Logging and JSON-RPC.
 * New option [set::tls::certificate-expiry-notification](https://www.unrealircd.org/docs/Set_block#set::tls::certificate-expiry-notification):
   since UnrealIRCd 5.0.8 we warn if a SSL/TLS certificate is (nearly) expired.
   This new option allows turning it off, it is (still) on by default.

doc/conf/modules.default.conf

@@ -221,6 +221,7 @@ loadmodule "extbans/securitygroup"; /* +b ~security-group (old ~G mode, security
 loadmodule "extbans/country"; /* +b ~country (country/geoip) */
 loadmodule "extbans/msgbypass"; /* +e ~msgbypass (old ~m mode, bypass message restrictions) */
 loadmodule "extbans/flood"; /* +e ~flood (flood exemption for chanmode +f/+F) */
+loadmodule "extbans/asn"; /* +b ~asn (country/asn) */
 
 
 /*** IRCv3 extensions ***/

src/modules/extbans/Makefile.in

@@ -35,7 +35,7 @@ R_MODULES= \
 	join.so quiet.so nickchange.so inchannel.so realname.so \
 	account.so operclass.so certfp.so textban.so msgbypass.so \
 	timedban.so partmsg.so securitygroup.so \
-	country.so flood.so
+	country.so asn.so flood.so
 
 MODULES=$(R_MODULES)
 MODULEFLAGS=@MODULEFLAGS@

src/modules/extbans/asn.c

@@ -0,0 +1,143 @@
+/*
+ * Extended ban to ban/exempt by asn/geoip info (+b ~asn:64496)
+ * (C) Copyright 2024 The UnrealIRCd Team
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 1, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+#include "unrealircd.h"
+
+ModuleHeader MOD_HEADER
+= {
+	"extbans/asn",
+	"6.0",
+	"ExtBan ~asn - Ban/exempt by ASN (geoip)",
+	"UnrealIRCd Team",
+	"unrealircd-6",
+};
+
+/* Forward declarations */
+int extban_asn_is_ok(BanContext *b);
+const char *extban_asn_conv_param(BanContext *b, Extban *extban);
+int extban_asn_is_banned(BanContext *b);
+
+Extban *register_asn_extban(ModuleInfo *modinfo)
+{
+	ExtbanInfo req;
+
+	memset(&req, 0, sizeof(req));
+	req.letter = 'A';
+	req.name = "asn";
+	req.is_ok = extban_asn_is_ok;
+	req.conv_param = extban_asn_conv_param;
+	req.is_banned = extban_asn_is_banned;
+	req.is_banned_events = BANCHK_ALL|BANCHK_TKL;
+	req.options = EXTBOPT_INVEX|EXTBOPT_TKL;
+	return ExtbanAdd(modinfo->handle, req);
+}
+
+/* Called upon module test */
+MOD_TEST()
+{
+	if (!register_asn_extban(modinfo))
+	{
+		config_error("could not register extended ban type");
+		return MOD_FAILED;
+	}
+
+	return MOD_SUCCESS;
+}
+
+/* Called upon module init */
+MOD_INIT()
+{
+	if (!register_asn_extban(modinfo))
+	{
+		config_error("could not register extended ban type");
+		return MOD_FAILED;
+	}
+
+	MARK_AS_OFFICIAL_MODULE(modinfo);
+
+	return MOD_SUCCESS;
+}
+
+/* Called upon module load */
+MOD_LOAD()
+{
+	return MOD_SUCCESS;
+}
+
+/* Called upon unload */
+MOD_UNLOAD()
+{
+	return MOD_SUCCESS;
+}
+
+int extban_asn_usage(Client *client)
+{
+	sendnotice(client, "ERROR: ExtBan ~asn expects the AS number (all digits). "
+	                   "For example: +b ~asn:64496");
+	return EX_DENY;
+}
+
+int extban_asn_is_ok(BanContext *b)
+{
+	if (b->is_ok_check == EXCHK_PARAM)
+	{
+		const char *p;
+
+		if (!strcmp(b->banstr, "*"))
+			return EX_ALLOW;
+
+		if (!*b->banstr)
+			return extban_asn_usage(b->client);
+
+		for (p = b->banstr; *p; p++)
+			if (!isdigit(*p))
+				return extban_asn_usage(b->client);
+
+		return EX_ALLOW;
+	}
+	return EX_ALLOW;
+}
+
+/* Obtain targeted asn from the ban string */
+const char *extban_asn_conv_param(BanContext *b, Extban *extban)
+{
+	static char retbuf[32];
+	unsigned int asn;
+	char *p=NULL;
+
+	if (!isdigit(b->banstr[0]))
+		return NULL;
+
+	asn = strtoul(b->banstr, &p, 10);
+	if (!BadPtr(p))
+		return NULL; /* contains invalid characters */
+
+	snprintf(retbuf, sizeof(retbuf), "%u", asn);
+	return retbuf;
+}
+
+int extban_asn_is_banned(BanContext *b)
+{
+	unsigned int banned_asn = strtoul(b->banstr, NULL, 10);
+	GeoIPResult *geo = geoip_client(b->client);
+
+	if (geo)
+		return banned_asn == geo->asn;
+
+	return banned_asn == 0; /* ASN 0 is for unknown */
+}

src/user.c

@@ -961,6 +961,7 @@ void free_geoip_result(GeoIPResult *r)
 		return;
 	safe_free(r->country_code);
 	safe_free(r->country_name);
+	safe_free(r->asname);
 	safe_free(r);
 }