gprs_ns2: implement a simple load sharing for UDP
Implement the load sharing based on modulo of the LSP. As long the gprs_ns2 doesn't
support the resource distribution function (48.016 ยง 4.4a) this simple
approach is good enought.
Fixes: OS#4836
Change-Id: I8c2fe5d647694886ac600470fca6ea5d5d210a85
diff --git a/src/gb/gprs_ns2.c b/src/gb/gprs_ns2.c
index bc4db53..e290734 100644
--- a/src/gb/gprs_ns2.c
+++ b/src/gb/gprs_ns2.c
@@ -384,6 +384,45 @@
return NULL;
}
+/* 4.4.2 Load Sharing function for the IP Sub-Network
+ *
+ * Implement a simple approach for UDP load sharing of data weight based on the modulo of the lsp.
+ *
+ * E.g. 3 NSVC: 1st weight 5, 2nd weight 3, 3rd weight 1, lsp = 3.
+ * sum all weights = 9
+ * target_weight = lsp % sum = 3
+ *
+ * 1st NSVC will be the target for 0-4
+ * 2nd NSVC will be the target for 5-7
+ * 3rd NSVC will be the target for 8
+ *
+ * The 1st NSVC will be used.
+ * E.g. lsp = 7. The 2nd NSVC will used.
+ */
+static struct gprs_ns2_vc *ns2_load_sharing_weight_modulo(
+ struct gprs_ns2_nse *nse,
+ uint16_t bvci,
+ uint32_t load_selector)
+{
+ struct gprs_ns2_vc *tmp;
+ uint32_t mod;
+ uint32_t i = 0;
+
+ if (nse->nsvc_count == 0)
+ return NULL;
+
+ mod = (bvci + load_selector) % nse->sum_data_weight;
+ llist_for_each_entry(tmp, &nse->nsvc, list) {
+ if (!ns2_vc_is_unblocked(tmp))
+ continue;
+ if (i == mod || mod < i + tmp->data_weight)
+ return tmp;
+ i += tmp->data_weight;
+ }
+
+ return NULL;
+}
+
/* pick the first available data NSVC - no load sharing */
struct gprs_ns2_vc *ns2_load_sharing_first(struct gprs_ns2_nse *nse)
{
@@ -421,7 +460,7 @@
nsvc = ns2_load_sharing_signal(nse);
} else {
/* data with load sharing parameter */
- nsvc = ns2_load_sharing_first(nse);
+ nsvc = ns2_load_sharing_weight_modulo(nse, bvci, link_selector);
}
break;
}