Feature (contd.): Device Emulation - fixed problems in code and in test case for multi-tagged vlans

server/devicemanager.cpp

@@ -324,22 +324,62 @@ void DeviceManager::enumerateDevices(
     OstEmul::VlanEmulation pbVlan = deviceGroup->GetExtension(OstEmul::encap)
                                         .vlan();
     int numTags = pbVlan.stack_size();
-    int vlanCount = 1;
+    int n = 1;
+    QList<int> vlanCount;
 
     OstEmul::MacEmulation mac = deviceGroup->GetExtension(OstEmul::mac);
     OstEmul::Ip4Emulation ip4 = deviceGroup->GetExtension(OstEmul::ip4);
 
-    for (int i = 0; i < numTags; i++)
+    /*
-        vlanCount *= pbVlan.stack(i).count();
+     * vlanCount[] stores the number of unique vlans at each tag level
+     * e.g. for a 3-tag config with 2, 3, 4 vlans at each level respectively
+     * vlanCount = [24, 12, 4]
+     *      0 - 0, 0, 0
+     *      1 - 0, 0, 1
+     *      2 - 0, 0, 2
+     *      3 - 0, 0, 3
+     *      4 - 0, 1, 0
+     *      5 - 0, 1, 1
+     *      6 - 0, 1, 2
+     *      7 - 0, 1, 3
+     *      8 - 0, 2, 0
+     *      9 - 0, 2, 1
+     *     10 - 0, 2, 2
+     *     11 - 0, 2, 3
+     *     12 - 1, 0, 0
+     *     13 - 1, 0, 1
+     *     14 - 1, 0, 2
+     *     15 - 1, 0, 3
+     *     16 - 1, 1, 0
+     *     17 - 1, 1, 1
+     *     18 - 1, 1, 2
+     *     19 - 1, 1, 3
+     *     21 - 1, 2, 0
+     *     21 - 1, 2, 1
+     *     22 - 1, 2, 2
+     *     23 - 1, 2, 3
+     *
+     * Note that vlanCount[0] repesents total-number-of-vlans
+     *
+     * Another way to think about this is that at a particular vlan tag
+     * level, we need to repeat a particular vlan-id as many times as the
+     * next level's count before we can increment the vlan-id at that level
+     *
+     * We use this list to calculate the vlan ids for each tag level for
+     * all the vlans.
+     *
+     * For implementation convenience we append a '1' as the last element
+     */
+    vlanCount.append(n);
+    for (int i = numTags - 1; i >= 0 ; i--) {
+        n *= pbVlan.stack(i).count();
+        vlanCount.prepend(n);
+    }
 
-    // If we have no vlans, we still have the non-vlan-segmented LAN
+    for (int i = 0; i < vlanCount.at(0); i++) {
-    if (vlanCount == 0)
-        vlanCount = 1;
-
-    for (int i = 0; i < vlanCount; i++) {
         for (int j = 0; j < numTags; j++) {
             OstEmul::VlanEmulation::Vlan vlan = pbVlan.stack(j);
-            quint16 vlanAdd = i*vlan.step();
+            quint16 vlanAdd = (i/vlanCount.at(j+1) % vlan.count())*vlan.step();
 
             dk.setVlan(j, vlan.vlan_tag() + vlanAdd);
         }

server/pcapport.cpp

@@ -946,7 +946,40 @@ void PcapPort::EmulationTransceiver::run()
     int flags = PCAP_OPENFLAG_PROMISCUOUS;
     char errbuf[PCAP_ERRBUF_SIZE] = "";
     struct bpf_program bpf;
-    const char *capture_filter = "arp or (vlan and arp)";
+#if 0
+/*
+    Ideally we should use the below filter, but the 'vlan' capture filter
+    in libpcap is implemented as a kludge. From the pcap-filter man page -
+
+    vlan [vlan_id]
+       Note that the first vlan keyword encountered in expression changes
+       the decoding offsets for the remainder of expression on the
+       assumption that the packet is a VLAN packet.
+
+       The  vlan [vlan_id] expression may be used more than once, to filter on
+       VLAN hierarchies. Each use of that expression increments the filter
+       offsets by 4.
+
+    See https://ask.wireshark.org/questions/31953/unusual-behavior-with-stacked-vlan-tags-and-capture-filter
+
+    So we use the modified filter expression that works as we intend. If ever
+    libpcap changes their implementation, this will need to change as well.
+*/
+    const char *capture_filter =
+        "arp or "
+        "(vlan and arp) or "
+        "(vlan and vlan and arp) or "
+        "(vlan and vlan and vlan and arp) or "
+        "(vlan and vlan and vlan and vlan and arp)";
+#else
+    const char *capture_filter =
+        "arp or "
+        "(vlan and arp) or "
+        "(vlan and arp) or "
+        "(vlan and arp) or "
+        "(vlan and arp)";
+#endif
+
     const int optimize = 1;
 
     qDebug("In %s", __PRETTY_FUNCTION__);

test/emultest.py

@@ -624,6 +624,7 @@ def test_multiEmulDevPerVlan(request, drone, ports, dut, dut_ports, stream_id,
     for i in range(num_vlans):
         s = stream_cfg.stream.add()
         s.stream_id.id = stream_id.stream_id[i].id
+        s.core.name = 'stream ' + str(s.stream_id.id)
         s.core.is_enabled = True
         s.core.ordinal = i
         s.control.packets_per_sec = 100
@@ -635,10 +636,11 @@ def test_multiEmulDevPerVlan(request, drone, ports, dut, dut_ports, stream_id,
         p.Extensions[mac].dst_mac_mode = Mac.e_mm_resolve
         p.Extensions[mac].src_mac_mode = Mac.e_mm_resolve
 
-        for vcfg in vlan_cfg:
+        ids = dut_vlans.vlans[i].split('.')
+        for id in ids:
             p = s.protocol.add()
             p.protocol_id.id = ost_pb.Protocol.kVlanFieldNumber
-            p.Extensions[vlan].vlan_tag = vcfg['base']+(i % vcfg['count'])
+            p.Extensions[vlan].vlan_tag = int(id)
 
         p = s.protocol.add()
         p.protocol_id.id = ost_pb.Protocol.kEth2FieldNumber
@@ -658,7 +660,7 @@ def test_multiEmulDevPerVlan(request, drone, ports, dut, dut_ports, stream_id,
         p = s.protocol.add()
         p.protocol_id.id = ost_pb.Protocol.kPayloadFieldNumber
 
-        log.info('configuring tx_stream %d' % stream_id.stream_id[0].id)
+        log.info('configuring tx_stream %d' % stream_id.stream_id[i].id)
 
     drone.modifyStream(stream_cfg)
 
@@ -708,7 +710,7 @@ def test_multiEmulDevPerVlan(request, drone, ports, dut, dut_ports, stream_id,
     log.info('dumping Rx capture buffer (all)')
     cap_pkts = subprocess.check_output([tshark, '-nr', 'capture.pcap'])
     print(cap_pkts)
-    log.info('dumping Tx capture buffer (all pkts - vlans only)')
+    log.info('dumping Rx capture buffer (all pkts - vlans only)')
     cap_pkts = subprocess.check_output([tshark, '-nr', 'capture.pcap',
                         '-Tfields', '-eframe.number', '-evlan.id'])
     print(cap_pkts)
@@ -734,6 +736,7 @@ def test_multiEmulDevPerVlan(request, drone, ports, dut, dut_ports, stream_id,
     for dev_cfg, device in zip(device_config, devices):
         resolved = False
         for arp in device.arp:
+            # TODO: print all configured vlans, not just the first
             # TODO: pretty print ip and mac
             print('v%d|%08x: %08x %012x' %
                     (dev_cfg.vlan[0] & 0xffff, dev_cfg.ip4, arp.ip4, arp.mac))