tipc: Allow run-time alteration of default link settings

Permits run-time alteration of default link settings on a per-media
and per-bearer basis, in addition to the existing per-link basis.
The following syntax can now be used:

    tipc-config -lt=<link-name|bearer-name|media-name>/<tolerance>
    tipc-config -lp=<link-name|bearer-name|media-name>/<priority>
    tipc-config -lw=<link-name|bearer-name|media-name>/<window>

Note that changes to the default settings for a given media type has
no effect on the default settings used by existing bearers. Similarly,
changes to default bearer settings has no effect on existing link
endpoints that utilize that interface.

Thanks to Florian Westphal <fw@strlen.de> for his contributions to
the development of this enhancement.

Signed-off-by: Allan Stephens <allan.stephens@windriver.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

1 files changed, 109 insertions, 41 deletions

diff --git a/net/tipc/link.c b/net/tipc/link.c
index ae98a72da11a..332915e43043 100644
--- a/net/tipc/link.c
+++ b/net/tipc/link.c
@@ -343,7 +343,7 @@ struct link *tipc_link_create(struct tipc_node *n_ptr,
 	l_ptr->checkpoint = 1;
 	l_ptr->peer_session = INVALID_SESSION;
 	l_ptr->b_ptr = b_ptr;
-	link_set_supervision_props(l_ptr, b_ptr->media->tolerance);
+	link_set_supervision_props(l_ptr, b_ptr->tolerance);
 	l_ptr->state = RESET_UNKNOWN;
 
 	l_ptr->pmsg = (struct tipc_msg *)&l_ptr->proto_msg;
@@ -355,7 +355,7 @@ struct link *tipc_link_create(struct tipc_node *n_ptr,
 	strcpy((char *)msg_data(msg), if_name);
 
 	l_ptr->priority = b_ptr->priority;
-	tipc_link_set_queue_limits(l_ptr, b_ptr->media->window);
+	tipc_link_set_queue_limits(l_ptr, b_ptr->window);
 
 	link_init_max_pkt(l_ptr);
 
@@ -2754,13 +2754,113 @@ static struct link *link_find_link(const char *name, struct tipc_node **node)
 	return l_ptr;
 }
 
+/**
+ * link_value_is_valid -- validate proposed link tolerance/priority/window
+ *
+ * @cmd - value type (TIPC_CMD_SET_LINK_*)
+ * @new_value - the new value
+ *
+ * Returns 1 if value is within range, 0 if not.
+ */
+
+static int link_value_is_valid(u16 cmd, u32 new_value)
+{
+	switch (cmd) {
+	case TIPC_CMD_SET_LINK_TOL:
+		return (new_value >= TIPC_MIN_LINK_TOL) &&
+			(new_value <= TIPC_MAX_LINK_TOL);
+	case TIPC_CMD_SET_LINK_PRI:
+		return (new_value <= TIPC_MAX_LINK_PRI);
+	case TIPC_CMD_SET_LINK_WINDOW:
+		return (new_value >= TIPC_MIN_LINK_WIN) &&
+			(new_value <= TIPC_MAX_LINK_WIN);
+	}
+	return 0;
+}
+
+
+/**
+ * link_cmd_set_value - change priority/tolerance/window for link/bearer/media
+ * @name - ptr to link, bearer, or media name
+ * @new_value - new value of link, bearer, or media setting
+ * @cmd - which link, bearer, or media attribute to set (TIPC_CMD_SET_LINK_*)
+ *
+ * Caller must hold 'tipc_net_lock' to ensure link/bearer/media is not deleted.
+ *
+ * Returns 0 if value updated and negative value on error.
+ */
+
+static int link_cmd_set_value(const char *name, u32 new_value, u16 cmd)
+{
+	struct tipc_node *node;
+	struct link *l_ptr;
+	struct tipc_bearer *b_ptr;
+	struct media *m_ptr;
+
+	l_ptr = link_find_link(name, &node);
+	if (l_ptr) {
+		/*
+		 * acquire node lock for tipc_link_send_proto_msg().
+		 * see "TIPC locking policy" in net.c.
+		 */
+		tipc_node_lock(node);
+		switch (cmd) {
+		case TIPC_CMD_SET_LINK_TOL:
+			link_set_supervision_props(l_ptr, new_value);
+			tipc_link_send_proto_msg(l_ptr,
+				STATE_MSG, 0, 0, new_value, 0, 0);
+			break;
+		case TIPC_CMD_SET_LINK_PRI:
+			l_ptr->priority = new_value;
+			tipc_link_send_proto_msg(l_ptr,
+				STATE_MSG, 0, 0, 0, new_value, 0);
+			break;
+		case TIPC_CMD_SET_LINK_WINDOW:
+			tipc_link_set_queue_limits(l_ptr, new_value);
+			break;
+		}
+		tipc_node_unlock(node);
+		return 0;
+	}
+
+	b_ptr = tipc_bearer_find(name);
+	if (b_ptr) {
+		switch (cmd) {
+		case TIPC_CMD_SET_LINK_TOL:
+			b_ptr->tolerance = new_value;
+			return 0;
+		case TIPC_CMD_SET_LINK_PRI:
+			b_ptr->priority = new_value;
+			return 0;
+		case TIPC_CMD_SET_LINK_WINDOW:
+			b_ptr->window = new_value;
+			return 0;
+		}
+		return -EINVAL;
+	}
+
+	m_ptr = tipc_media_find(name);
+	if (!m_ptr)
+		return -ENODEV;
+	switch (cmd) {
+	case TIPC_CMD_SET_LINK_TOL:
+		m_ptr->tolerance = new_value;
+		return 0;
+	case TIPC_CMD_SET_LINK_PRI:
+		m_ptr->priority = new_value;
+		return 0;
+	case TIPC_CMD_SET_LINK_WINDOW:
+		m_ptr->window = new_value;
+		return 0;
+	}
+	return -EINVAL;
+}
+
 struct sk_buff *tipc_link_cmd_config(const void *req_tlv_area, int req_tlv_space,
 				     u16 cmd)
 {
 	struct tipc_link_config *args;
 	u32 new_value;
-	struct link *l_ptr;
-	struct tipc_node *node;
 	int res;
 
 	if (!TLV_CHECK(req_tlv_area, req_tlv_space, TIPC_TLV_LINK_CONFIG))
@@ -2769,6 +2869,10 @@ struct sk_buff *tipc_link_cmd_config(const void *req_tlv_area, int req_tlv_space
 	args = (struct tipc_link_config *)TLV_DATA(req_tlv_area);
 	new_value = ntohl(args->value);
 
+	if (!link_value_is_valid(cmd, new_value))
+		return tipc_cfg_reply_error_string(
+			"cannot change, value invalid");
+
 	if (!strcmp(args->name, tipc_bclink_name)) {
 		if ((cmd == TIPC_CMD_SET_LINK_WINDOW) &&
 		    (tipc_bclink_set_queue_limits(new_value) == 0))
@@ -2778,43 +2882,7 @@ struct sk_buff *tipc_link_cmd_config(const void *req_tlv_area, int req_tlv_space
 	}
 
 	read_lock_bh(&tipc_net_lock);
-	l_ptr = link_find_link(args->name, &node);
-	if (!l_ptr) {
-		read_unlock_bh(&tipc_net_lock);
-		return tipc_cfg_reply_error_string("link not found");
-	}
-
-	tipc_node_lock(node);
-	res = -EINVAL;
-	switch (cmd) {
-	case TIPC_CMD_SET_LINK_TOL:
-		if ((new_value >= TIPC_MIN_LINK_TOL) &&
-		    (new_value <= TIPC_MAX_LINK_TOL)) {
-			link_set_supervision_props(l_ptr, new_value);
-			tipc_link_send_proto_msg(l_ptr, STATE_MSG,
-						 0, 0, new_value, 0, 0);
-			res = 0;
-		}
-		break;
-	case TIPC_CMD_SET_LINK_PRI:
-		if ((new_value >= TIPC_MIN_LINK_PRI) &&
-		    (new_value <= TIPC_MAX_LINK_PRI)) {
-			l_ptr->priority = new_value;
-			tipc_link_send_proto_msg(l_ptr, STATE_MSG,
-						 0, 0, 0, new_value, 0);
-			res = 0;
-		}
-		break;
-	case TIPC_CMD_SET_LINK_WINDOW:
-		if ((new_value >= TIPC_MIN_LINK_WIN) &&
-		    (new_value <= TIPC_MAX_LINK_WIN)) {
-			tipc_link_set_queue_limits(l_ptr, new_value);
-			res = 0;
-		}
-		break;
-	}
-	tipc_node_unlock(node);
-
+	res = link_cmd_set_value(args->name, new_value, cmd);
 	read_unlock_bh(&tipc_net_lock);
 	if (res)
 		return tipc_cfg_reply_error_string("cannot change link setting");