[202012] fix dual-tor relay-reply handing issue (sonic-net#40)

* 202012 dhcpv6 relay dual tor issue fix

.azure-pipelines/build.yml

@@ -30,6 +30,8 @@ jobs:
         sudo apt-get install -y dotnet-sdk-6.0
       displayName: install .Net
   - script: |
+      set -ex
+      sudo apt-get update
       sudo apt-get install -y \
           libboost-system1.71-dev \
           libboost-thread1.71-dev \

src/configInterface.cpp

@@ -9,6 +9,8 @@ bool pollSwssNotifcation = true;
 std::shared_ptr<boost::thread> mSwssThreadPtr;
 swss::Select swssSelect;
 
+extern bool dual_tor_sock;
+
 /**
  * @code                void initialize_swss()
  * 
@@ -116,15 +118,21 @@ void handleRelayNotification(swss::SubscriberStateTable &ipHelpersTable, std::un
 void processRelayNotification(std::deque<swss::KeyOpFieldsValuesTuple> &entries, std::unordered_map<std::string, relay_config> &vlans)
 {
     std::vector<std::string> servers;
+    bool option_79_default = true;
+    bool interface_id_default = false;
+
+    if (dual_tor_sock) {
+        interface_id_default = true;
+    }
 
     for (auto &entry: entries) {
         std::string vlan = kfvKey(entry);
         std::string operation = kfvOp(entry);
         std::vector<swss::FieldValueTuple> fieldValues = kfvFieldsValues(entry);
 
         relay_config intf;
-        intf.is_option_79 = true;
-        intf.is_interface_id = false;
+        intf.is_option_79 = option_79_default;
+        intf.is_interface_id = interface_id_default;
         intf.interface = vlan;
         intf.mux_key = "";
         intf.state_db = nullptr;

src/configInterface.h

@@ -11,6 +11,7 @@ struct swssNotification {
     std::unordered_map<std::string, relay_config> vlans;
     swss::SubscriberStateTable *ipHelpersTable;
 };
+
 /**
  * @code                void initialize_swss()
  * 

src/main.cpp

@@ -4,23 +4,32 @@
 #include "configInterface.h"
 
 bool dual_tor_sock = false;
+char loopback[IF_NAMESIZE] = "Loopback0";
 
 static void usage()
 {
-    printf("Usage: ./dhcp6relay {-d}\n");
-    printf("\t-d: enable dual tor option\n");
+    printf("Usage: ./dhcp6relay [-u <loopback interface>]\n");
+    printf("\tloopback interface: is the loopback interface for dual tor setup\n");
 }
 
 int main(int argc, char *argv[]) {
-    if (argc > 1) {
+    if (argc > 2) {
         switch (argv[1][1])
         {
-            case 'd':
+            case 'u':
+                if (strlen(argv[2]) != 0 && strlen(argv[2]) < IF_NAMESIZE) {
+                    std::memset(loopback, 0, IF_NAMESIZE);
+                    std::memcpy(loopback, argv[2], strlen(argv[2]));
+                } else {
+                    syslog(LOG_ERR, "loopback interface name over length %d.\n", IF_NAMESIZE);
+                    return 1;
+                }
                 dual_tor_sock = true;
                 break;
             default:
                 fprintf(stderr, "%s: Unknown option\n", basename(argv[0]));
                 usage();
+                return 0;
         }
     }
     try {