Reject a link for anope or atheme if there is no ulines { } for it.

This is checked for both local and remote services linking in.

Naturally, the list can be expanded to include more services that
really need ulines { }, and not statistical services or some other
purpose non-unrealircd servers, which is the reason why cannot
blindly assume all non-unrealircd servers require ulines.

This should hopefully help users a lot with "mysterious" issues
with services that we see too often in the support channel.
Suggested in https://bugs.unrealircd.org/view.php?id=5742

Note that this does require services to communicate their software
version via EAUTH. Anope does this for years already, but atheme only
does so since 10 days ago (git only, presumably not released yet)
after Valware filed a PR.

include/h.h

@@ -820,6 +820,7 @@ extern MODVAR int (*do_remote_nick_name)(char *nick);
 extern MODVAR const char *(*charsys_get_current_languages)(void);
 extern MODVAR void (*broadcast_sinfo)(Client *acptr, Client *to, Client *except);
 extern MODVAR void (*connect_server)(ConfigItem_link *aconf, Client *by, struct hostent *hp);
+extern MODVAR int (*is_services_but_not_ulined)(Client *client);
 extern MODVAR void (*parse_message_tags)(Client *cptr, char **str, MessageTag **mtag_list);
 extern MODVAR const char *(*mtags_to_string)(MessageTag *m, Client *acptr);
 extern MODVAR int (*can_send_to_channel)(Client *cptr, Channel *channel, const char **msgtext, const char **errmsg, int notice);

include/modules.h

@@ -2507,6 +2507,7 @@ enum EfunctionType {
 	EFUNC_CHARSYS_GET_CURRENT_LANGUAGES,
 	EFUNC_BROADCAST_SINFO,
 	EFUNC_CONNECT_SERVER,
+	EFUNC_IS_SERVICES_BUT_NOT_ULINED,
 	EFUNC_PARSE_MESSAGE_TAGS,
 	EFUNC_MTAGS_TO_STRING,
 	EFUNC_TKL_CHARTOTYPE,

src/api-efunctions.c

@@ -106,6 +106,7 @@ int (*do_remote_nick_name)(char *nick);
 const char *(*charsys_get_current_languages)(void);
 void (*broadcast_sinfo)(Client *client, Client *to, Client *except);
 void (*connect_server)(ConfigItem_link *aconf, Client *by, struct hostent *hp);
+int (*is_services_but_not_ulined)(Client *client);
 void (*parse_message_tags)(Client *client, char **str, MessageTag **mtag_list);
 const char *(*mtags_to_string)(MessageTag *m, Client *client);
 int (*can_send_to_channel)(Client *client, Channel *channel, const char **msgtext, const char **errmsg, int notice);
@@ -389,6 +390,7 @@ void efunctions_init(void)
 	efunc_init_function(EFUNC_CHARSYS_GET_CURRENT_LANGUAGES, charsys_get_current_languages, NULL);
 	efunc_init_function(EFUNC_BROADCAST_SINFO, broadcast_sinfo, NULL);
 	efunc_init_function(EFUNC_CONNECT_SERVER, connect_server, NULL);
+	efunc_init_function(EFUNC_IS_SERVICES_BUT_NOT_ULINED, is_services_but_not_ulined, NULL);
 	efunc_init_function(EFUNC_PARSE_MESSAGE_TAGS, parse_message_tags, &parse_message_tags_default_handler);
 	efunc_init_function(EFUNC_MTAGS_TO_STRING, mtags_to_string, &mtags_to_string_default_handler);
 	efunc_init_function(EFUNC_TKL_CHARTOTYPE, tkl_chartotype, NULL);

src/modules/protoctl.c

@@ -277,6 +277,11 @@ CMD_FUNC(cmd_protoctl)
 				client->server->features.protocol = atoi(protocol);
 			if (software)
 				safe_strdup(client->server->features.software, software);
+			if (is_services_but_not_ulined(client))
+			{
+				exit_client_fmt(client, NULL, "Services detected but no ulines { } for server name %s", client->name);
+				return;
+			}
 			if (!IsHandshake(client) && aconf) /* Send PASS early... */
 				sendto_one(client, NULL, "PASS :%s", (aconf->auth->type == AUTHTYPE_PLAINTEXT) ? aconf->auth->data : "*");
 		}

src/modules/server.c

@@ -57,6 +57,7 @@ void server_generic_free(ModData *m);
 int server_post_connect(Client *client);
 void _connect_server(ConfigItem_link *aconf, Client *by, struct hostent *hp);
 static int connect_server_helper(ConfigItem_link *, Client *);
+int _is_services_but_not_ulined(Client *client);
 
 /* Global variables */
 static cfgstruct cfg;
@@ -81,6 +82,7 @@ MOD_TEST()
 	EfunctionAdd(modinfo->handle, EFUNC_CHECK_DENY_VERSION, _check_deny_version);
 	EfunctionAddVoid(modinfo->handle, EFUNC_BROADCAST_SINFO, _broadcast_sinfo);
 	EfunctionAddVoid(modinfo->handle, EFUNC_CONNECT_SERVER, _connect_server);
+	EfunctionAdd(modinfo->handle, EFUNC_IS_SERVICES_BUT_NOT_ULINED, _is_services_but_not_ulined);
 	HookAdd(modinfo->handle, HOOKTYPE_CONFIGTEST, 0, server_config_test);
 	return MOD_SUCCESS;
 }
@@ -1979,3 +1981,25 @@ static int connect_server_helper(ConfigItem_link *aconf, Client *client)
 	return 1;
 }
 
+int _is_services_but_not_ulined(Client *client)
+{
+	if (!client->server || !client->server->features.software || !*client->name)
+		return 0; /* cannot detect software version or name not available yet */
+
+	if (our_strcasestr(client->server->features.software, "anope") ||
+	    our_strcasestr(client->server->features.software, "atheme"))
+	{
+		if (!find_uline(client->name))
+		{
+			unreal_log(ULOG_ERROR, "link", "LINK_NO_ULINES", client,
+			           "Server $client is a services server ($software). "
+			           "However, server $me does not have $client in the ulines { } block, "
+			           "which is required for services servers. "
+			           "See https://www.unrealircd.org/docs/Ulines_block",
+			           log_data_client("me", &me),
+			           log_data_string("software", client->server->features.software));
+			return 1; /* Is services AND no ulines { } entry */
+		}
+	}
+	return 0;
+}

src/modules/sinfo.c

@@ -104,6 +104,14 @@ CMD_FUNC(sinfo_server)
 	else
 		safe_strdup(client->server->features.software, parv[parc-1]);
 
+	if (is_services_but_not_ulined(client))
+	{
+		char buf[512];
+		snprintf(buf, sizeof(buf), "Services detected but no ulines { } for server name %s", client->name);
+		exit_client_ex(client, &me, NULL, buf);
+		return;
+	}
+
 	/* Broadcast to 'the other side' of the net */
 	concat_params(buf, sizeof(buf), parc, parv);
 	sendto_server(client, 0, 0, NULL, ":%s SINFO %s", client->id, buf);