iscsi-scst: Add link_local parameter

Add a link_local parameter to control whether an IPv6 SendTargets
response includes link local addresses.  The default is to preserve
the existing behavior and include them.

iscsi-scst/README

@@ -200,6 +200,9 @@ is /sys/kernel/scst_tgt/targets/iscsi. It has the following entries:
    iSCSI-SCST attributes before it starts accepting new connections. 0
    by default.
 
+ - link_local - if set, makes the response to an IPv6 SendTargets include
+   any link local addresses. Default is set.
+
  - open_state - read-only attribute, which allows to see if the user
    space part of iSCSI-SCST connected to the kernel part.
 
@@ -663,6 +666,7 @@ both iSCSI-SCST targets will look like:
 |       |   |       |-- reinstating
 |       |   |       `-- sid
 |       |   `-- tid
+|       |-- link_local
 |       |-- mgmt
 |       |-- open_state
 |       |-- trace_level

iscsi-scst/usr/event.c

@@ -644,6 +644,16 @@ static int handle_e_get_attr_value(int fd, const struct iscsi_kern_event *event)
 			goto out_free;
 		}
 		snprintf(res_str, sizeof(res_str), "%s", isns_entity_target_name);
+	} else if (strcasecmp(ISCSI_LINK_LOCAL_ATTR_NAME, pp) == 0)	{
+		if (target != NULL) {
+			log_error("Not NULL target %s for global attribute %s",
+				target->name, pp);
+			res = -EINVAL;
+			goto out_free;
+		}
+		snprintf(res_str, sizeof(res_str), "%d\n", send_targets_link_local);
+		if (send_targets_link_local != DEFAULT_SEND_TARGETS_LINK_LOCAL)
+			add_key_mark(res_str, sizeof(res_str), 0);
 	} else	{
 		log_error("Unknown attribute %s", pp);
 		res = -EINVAL;
@@ -1067,6 +1077,23 @@ static int handle_e_set_attr_value(int fd, const struct iscsi_kern_event *event)
 	} else if (strcasecmp(ISCSI_ISNS_ENTITY_ATTR_NAME, pp) == 0) {
 		pp = config_sep_string(&p);
 		strlcpy(isns_entity_target_name, pp, sizeof(isns_entity_target_name));
+	} else if (strcasecmp(ISCSI_LINK_LOCAL_ATTR_NAME, pp) == 0) {
+		if (target != NULL) {
+			log_error("Not NULL target %s for global attribute %s",
+				target->name, pp);
+			res = -EINVAL;
+			goto out_free;
+		}
+		pp = config_sep_string(&p);
+		if (strcmp(pp, "1") == 0)
+			send_targets_link_local = 1;
+		else if (strcmp(pp, "0") == 0)
+			send_targets_link_local = 0;
+		else {
+			log_error("Unknown value %s", pp);
+			res = -EINVAL;
+			goto out_free;
+		}
 	} else	{
 		log_error("Unknown attribute %s", pp);
 		res = -EINVAL;

iscsi-scst/usr/iscsi_scstd.c

@@ -961,6 +961,9 @@ int main(int argc, char **argv)
 			S_IRUSR|S_IRGRP|S_IROTH|S_IWUSR, 0);
 	if (err != 0)
 		exit(err);
+	err = kernel_attr_add(NULL, ISCSI_LINK_LOCAL_ATTR_NAME, 0644, 0);
+	if (err != 0)
+		exit(err);
 
 	if ((ipc_fd = iscsi_adm_request_listen()) < 0) {
 		perror("Opening AF_LOCAL socket failed");

iscsi-scst/usr/iscsid.h

@@ -307,6 +307,8 @@ extern void session_free(struct session *session);
 extern struct connection *conn_find(struct session *session, u16 cid);
 
 /* target.c */
+#define DEFAULT_SEND_TARGETS_LINK_LOCAL 1
+extern int send_targets_link_local;
 extern struct __qelem targets_list;
 extern int target_create(const char *name, struct target **out_target);
 extern void target_free(struct target *target);

iscsi-scst/usr/param.h

@@ -26,6 +26,7 @@
 #define ISCSI_TARGET_REDIRECTION_VALUE_TEMP	"temp"
 #define ISCSI_TARGET_REDIRECTION_VALUE_PERM	"perm"
 #define ISCSI_TARGET_ALIAS_ATTR_NAME		"alias"
+#define ISCSI_LINK_LOCAL_ATTR_NAME		"link_local"
 
 struct iscsi_key;
 

iscsi-scst/usr/target.c

@@ -33,6 +33,8 @@
 
 struct __qelem targets_list = LIST_HEAD_INIT(targets_list);
 
+int send_targets_link_local = DEFAULT_SEND_TARGETS_LINK_LOCAL;
+
 const char *iscsi_make_full_initiator_name(int per_portal_acl,
 	const char *initiator_name, const char *target_portal,
 	char *buf, int size)
@@ -204,6 +206,10 @@ static void target_print_addr(struct connection *conn, char *addr, int family)
 {
 	char taddr[NI_MAXHOST + NI_MAXSERV + 5];
 
+	/* Maybe skip IPv6 link local addresses */
+	if (family == AF_INET6 && !send_targets_link_local && (strncasecmp(addr, "fe80:", 5) == 0))
+		return;
+
 	snprintf(taddr, sizeof(taddr),
 		(family == AF_INET) ? "%s:%d,1" : "[%s]:%d,1",
 							addr, server_port);