[routeorch] Handle the empty "nexthop" field for backward compatibili…

…ty (sonic-net#1263)

* [routeorch] Handle the empty "nexthop" field for backward compatibility

orchagent/routeorch.cpp

@@ -466,6 +466,36 @@ void RouteOrch::doTask(Consumer& consumer)
             vector<string> ipv = tokenize(ips, ',');
             vector<string> alsv = tokenize(aliases, ',');
 
+            /*
+             * For backward compatibility, adjust ip string from old format to
+             * new format. Meanwhile it can deal with some abnormal cases.
+             */
+
+            /* Resize the ip vector to match ifname vector
+             * as tokenize(",", ',') will miss the last empty segment. */
+            if (alsv.size() == 0)
+            {
+                SWSS_LOG_WARN("Skip the route %s, for it has an empty ifname field.", key.c_str());
+                it = consumer.m_toSync.erase(it);
+                continue;
+            }
+            else if (alsv.size() != ipv.size())
+            {
+                SWSS_LOG_NOTICE("Route %s: resize ipv to match alsv, %zd -> %zd.", key.c_str(), ipv.size(), alsv.size());
+                ipv.resize(alsv.size());
+            }
+
+            /* Set the empty ip(s) to zero
+             * as IpAddress("") will construst a incorrect ip. */
+            for (auto &ip : ipv)
+            {
+                if (ip.empty())
+                {
+                    SWSS_LOG_NOTICE("Route %s: set the empty nexthop ip to zero.", key.c_str());
+                    ip = ip_prefix.isV4() ? "0.0.0.0" : "::";
+                }
+            }
+
             for (auto alias : alsv)
             {
                 if (alias == "eth0" || alias == "lo" || alias == "docker0")