dcb: Add dcb_ieee_getapp_mask() for drivers to query APP settings

With multiple APP entries per selector and protocol drivers
or stacks may want to pick a specific value or stripe traffic
across many priorities. Also if an APP entry in use is
deleted the stack/driver may want to choose from the existing
APP entries.

To facilitate this and avoid having duplicate code to walk
the APP ring provide a routine dcb_ieee_getapp_mask() to
return a u8 bitmask of all priorities set for the specified
selector and protocol. This routine and bitmask is a helper
for DCB kernel users.

Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 26 insertions, 0 deletions

diff --git a/net/dcb/dcbnl.c b/net/dcb/dcbnl.c
index 196084f310d2..b7d0be01dcc4 100644
--- a/net/dcb/dcbnl.c
+++ b/net/dcb/dcbnl.c
@@ -1929,6 +1929,32 @@ out:
 EXPORT_SYMBOL(dcb_setapp);
 
 /**
+ * dcb_ieee_getapp_mask - retrieve the IEEE DCB application priority
+ *
+ * Helper routine which on success returns a non-zero 802.1Qaz user
+ * priority bitmap otherwise returns 0 to indicate the dcb_app was
+ * not found in APP list.
+ */
+u8 dcb_ieee_getapp_mask(struct net_device *dev, struct dcb_app *app)
+{
+        struct dcb_app_type *itr;
+        u8 prio = 0;
+
+        spin_lock(&dcb_lock);
+        list_for_each_entry(itr, &dcb_app_list, list) {
+                if (itr->app.selector == app->selector &&
+                    itr->app.protocol == app->protocol &&
+                    (strncmp(itr->name, dev->name, IFNAMSIZ) == 0)) {
+                        prio |= 1 << itr->app.priority;
+                }
+        }
+        spin_unlock(&dcb_lock);
+
+        return prio;
+}
+EXPORT_SYMBOL(dcb_ieee_getapp_mask);
+
+/**
  * dcb_ieee_setapp - add IEEE dcb application data to app list
  *
  * This adds Application data to the list. Multiple application