In case of ECMP calculation, update the ECMP index in the forwaring

metadata

ECMP index in the forwarding metadata is used by datapath to derive
various information at various stages of the path. If vRouter was
computing the ECMP index, it was not updating the ECMP index in the
forwarding metadata, leading to problems such as wrong/invalid label
in the packet.

Change-Id: Ic86b15c3d6c8f83af11caf74ea1d69cc8ce841ea
Closes-BUG: #1603963

dp-core/vr_nexthop.c

@@ -612,14 +612,13 @@ static struct vr_nexthop *
 nh_composite_ecmp_select_nh(struct vr_packet *pkt, struct vr_nexthop *nh,
         struct vr_forwarding_md *fmd)
 {
-    int ret;
+    int ret, ecmp_index;
     unsigned int hash, hash_ecmp, count;
 
     struct vr_flow flow;
     struct vr_ip6 *ip6;
     struct vr_nexthop *cnh = NULL;
     struct vr_component_nh *cnhp = nh->nh_component_nh;
-    struct vr_component_nh *cnhp_ecmp = nh->nh_component_ecmp;
 
     if (!(count = nh->nh_component_cnt))
         return NULL;
@@ -640,12 +639,20 @@ nh_composite_ecmp_select_nh(struct vr_packet *pkt, struct vr_nexthop *nh,
 
     hash = hash_ecmp = vr_hash(&flow, flow.flow_key_len, 0);
     hash %= count;
+    ecmp_index = cnhp[hash].cnh_ecmp_index;
     cnh = cnhp[hash].cnh;
-    if (!cnh && nh->nh_component_ecmp_cnt) {
-        hash_ecmp %= nh->nh_component_ecmp_cnt;
-        cnh = cnhp_ecmp[hash_ecmp].cnh;
+    if (!cnh) {
+        if (nh->nh_component_ecmp_cnt) {
+            cnhp = nh->nh_component_ecmp;
+            hash_ecmp %= nh->nh_component_ecmp_cnt;
+            ecmp_index = cnhp[hash_ecmp].cnh_ecmp_index;
+            cnh = cnhp[hash_ecmp].cnh;
+        }
     }
 
+    if (cnh)
+        fmd->fmd_ecmp_nh_index = ecmp_index;
+
     return cnh;
 }
 
@@ -2300,7 +2307,14 @@ nh_composite_add(struct vr_nexthop *nh, vr_nexthop_req *req)
         nh->nh_component_nh[i].cnh_label = req->nhr_label_list[i];
         if (nh->nh_component_nh[i].cnh)
             active++;
+
+        if (req->nhr_flags & NH_FLAG_COMPOSITE_ECMP) {
+            nh->nh_component_nh[i].cnh_ecmp_index = i;
+        } else {
+            nh->nh_component_nh[i].cnh_ecmp_index = -1;
+        }
     }
+
     nh->nh_component_cnt = req->nhr_nh_list_size;
 
     if (nh_composite_mcast_validate(nh, req))
@@ -2324,6 +2338,8 @@ nh_composite_add(struct vr_nexthop *nh, vr_nexthop_req *req)
                 if (nh->nh_component_nh[i].cnh) {
                     memcpy(&nh->nh_component_ecmp[j++], &nh->nh_component_nh[i],
                             sizeof(struct vr_component_nh));
+                    /* this happens implicitly */
+                    /* nh->nh_component_ecmp[j++].cnh_ecmp_index = i */
                 }
             }
             nh->nh_component_ecmp_cnt = j;

include/vr_nexthop.h

@@ -70,6 +70,7 @@ struct vr_forwarding_md;
 
 struct vr_component_nh {
     int cnh_label;
+    int cnh_ecmp_index;
     struct vr_nexthop *cnh;
 };