Feature (contd.): Device Emulation - Test case and code to support sending ping echo reply in response to received ping echo request

server/device.cpp

@@ -197,6 +197,9 @@ void Device::receivePacket(PacketBuffer *pktBuf)
         break;
 
     case 0x0800: // IPv4
+        receiveIp4(pktBuf);
+        break;
+
     case 0x86dd: // IPv6
     default:
         break;
@@ -481,6 +484,113 @@ void Device::sendArpRequest(PacketBuffer *pktBuf)
             qPrintable(QHostAddress(tgtIp).toString()));
 }
 
+void Device::receiveIp4(PacketBuffer *pktBuf)
+{
+    uchar *pktData = pktBuf->data();
+    uchar ipProto;
+    quint32 dstIp;
+
+    if (pktData[0] != 0x45) {
+        qDebug("%s: Unsupported IP version or options (%02x) ", __FUNCTION__,
+                pktData[0]);
+        goto _invalid_exit;
+    }
+
+    if (pktBuf->length() < 20) {
+        qDebug("incomplete IPv4 header: expected 20, actual %d",
+                pktBuf->length());
+        goto _invalid_exit;
+    }
+
+    // XXX: We don't verify IP Header checksum
+
+    dstIp = qFromBigEndian<quint32>(pktData + 16);
+    if (dstIp != ip4_) {
+        qDebug("%s: dstIp %x is not me (%x)", __FUNCTION__, dstIp, ip4_);
+        goto _invalid_exit;
+    }
+
+    ipProto = pktData[9];
+    switch (ipProto) {
+    case 1: // ICMP
+        pktBuf->pull(20);
+        receiveIcmp4(pktBuf);
+        break;
+    default:
+        break;
+    }
+
+_invalid_exit:
+    return;
+}
+
+// This function assumes we are replying back to the same IP
+// that originally sent us the packet and therefore we can reuse the
+// ingress packet for egress; in other words, it assumes the
+// original IP header is intact and will just reuse it after
+// minimal modifications
+void Device::sendIp4Reply(PacketBuffer *pktBuf)
+{
+    uchar *pktData = pktBuf->push(20);
+    uchar origTtl = pktData[8];
+    uchar ipProto = pktData[9];
+    quint32 srcIp, dstIp;
+    quint32 sum;
+
+    // Swap src/dst IP addresses
+    dstIp = qFromBigEndian<quint32>(pktData + 12); // srcIp in original pkt
+    srcIp = qFromBigEndian<quint32>(pktData + 16); // dstIp in original pkt
+
+    if (!arpTable.contains(dstIp))
+        return;
+
+    *(quint32*)(pktData + 12) = qToBigEndian(srcIp);
+    *(quint32*)(pktData + 16) = qToBigEndian(dstIp);
+
+    // Reset TTL
+    pktData[8] = 64;
+
+    // Incremental checksum update (RFC 1624 [Eqn.3])
+    // HC' = ~(~HC + ~m + m')
+    sum =  quint16(~qFromBigEndian<quint16>(pktData + 10)); // old cksum
+    sum += quint16(~quint16(origTtl << 8 | ipProto)); // old value
+    sum += quint16(pktData[8] << 8 | ipProto); // new value
+    while(sum >> 16)
+        sum = (sum & 0xFFFF) + (sum >> 16);
+    *(quint16*)(pktData + 10) = qToBigEndian(quint16(~sum));
+
+    encap(pktBuf, arpTable.value(dstIp), 0x0800);
+    transmitPacket(pktBuf);
+}
+
+void Device::receiveIcmp4(PacketBuffer *pktBuf)
+{
+    uchar *pktData = pktBuf->data();
+    quint32 sum;
+
+    // XXX: We don't verify icmp checksum
+
+    // We handle only ping request
+    if (pktData[0] != 8) { // Echo Request
+        qDebug("%s: Ignoring non echo request (%d)", __FUNCTION__, pktData[0]);
+        return;
+    }
+
+    pktData[0] = 0; // Echo Reply
+
+    // Incremental checksum update (RFC 1624 [Eqn.3])
+    // HC' = ~(~HC + ~m + m')
+    sum =  quint16(~qFromBigEndian<quint16>(pktData + 2)); // old cksum
+    sum += quint16(~quint16(8 << 8 | pktData[1])); // old value
+    sum += quint16(0 << 8 | pktData[1]); // new value
+    while(sum >> 16)
+        sum = (sum & 0xFFFF) + (sum >> 16);
+    *(quint16*)(pktData + 2) = qToBigEndian(quint16(~sum));
+
+    sendIp4Reply(pktBuf);
+    qDebug("Sent ICMP Echo Reply");
+}
+
 bool operator<(const DeviceKey &a1, const DeviceKey &a2)
 {
     int i = 0;

server/device.h

@@ -68,6 +68,11 @@ private: // methods
     void receiveArp(PacketBuffer *pktBuf);
     void sendArpRequest(PacketBuffer *pktBuf);
 
+    void receiveIp4(PacketBuffer *pktBuf);
+    void sendIp4Reply(PacketBuffer *pktBuf);
+
+    void receiveIcmp4(PacketBuffer *pktBuf);
+
 private: // data
     static const int kMaxVlan = 4;
 

server/pcapport.cpp

@@ -966,18 +966,18 @@ void PcapPort::EmulationTransceiver::run()
     libpcap changes their implementation, this will need to change as well.
 */
     const char *capture_filter =
-        "arp or "
+        "arp or icmp or "
-        "(vlan and arp) or "
+        "(vlan and (arp or icmp)) or "
-        "(vlan and vlan and arp) or "
+        "(vlan and vlan and (arp or icmp)) or "
-        "(vlan and vlan and vlan and arp) or "
+        "(vlan and vlan and vlan and (arp or icmp)) or "
-        "(vlan and vlan and vlan and vlan and arp)";
+        "(vlan and vlan and vlan and vlan and (arp or icmp))";
 #else
     const char *capture_filter =
-        "arp or "
+        "arp or icmp or "
-        "(vlan and arp) or "
+        "(vlan and (arp or icmp)) or "
-        "(vlan and arp) or "
+        "(vlan and (arp or icmp)) or "
-        "(vlan and arp) or "
+        "(vlan and (arp or icmp)) or "
-        "(vlan and arp)";
+        "(vlan and (arp or icmp))";
 #endif
 
     const int optimize = 1;

test/emultest.py

@@ -219,6 +219,16 @@ def stream_id(request, drone, ports):
 
     return stream_id
 
+@pytest.fixture
+def dut_ip(request, dut_ports):
+    sudo('ip address add 10.10.1.1/24 dev ' + dut_ports.rx)
+    sudo('ip address add 10.10.2.1/24 dev ' + dut_ports.tx)
+
+    def fin():
+        sudo('ip address delete 10.10.1.1/24 dev ' + dut_ports.rx)
+        sudo('ip address delete 10.10.2.1/24 dev ' + dut_ports.tx)
+    request.addfinalizer(fin)
+
 @pytest.fixture
 def dut_vlans(request, dut_ports):
     class Devices(object):
@@ -326,8 +336,8 @@ def dut_vlans(request, dut_ports):
     {'mac_step': 1, 'ip_step': 1},
     {'mac_step': 2, 'ip_step': 5},
 ])
-def test_multiEmulDevNoVlan(drone, ports, dut, dut_ports, stream_id,
+def test_multiEmulDevNoVlan(drone, ports, dut, dut_ports, dut_ip,
-        emul_ports, dgid_list, dev_cfg):
+        stream_id, emul_ports, dgid_list, dev_cfg):
     # ----------------------------------------------------------------- #
     # TESTCASE: Emulate multiple IPv4 devices (no vlans)
     #          DUT
@@ -343,10 +353,6 @@ def test_multiEmulDevNoVlan(drone, ports, dut, dut_ports, stream_id,
     mac_step = dev_cfg['mac_step']
     ip_step = dev_cfg['ip_step']
 
-    # configure the DUT
-    sudo('ip address add 10.10.1.1/24 dev ' + dut_ports.rx)
-    sudo('ip address add 10.10.2.1/24 dev ' + dut_ports.tx)
-
     # configure the tx device(s)
     devgrp_cfg = ost_pb.DeviceGroupConfigList()
     devgrp_cfg.port_id.CopyFrom(ports.tx.port_id[0])
@@ -520,6 +526,16 @@ def test_multiEmulDevNoVlan(drone, ports, dut, dut_ports, stream_id,
             print('%08x: %08x %012x' %
                     (dev_cfg.ip4, arp.ip4, arp.mac))
 
+    # ping the tx devices from the DUT
+    for i in range(num_devs):
+        out = run('ping -c3 10.10.1.'+str(101+i*ip_step), warn_only=True)
+        assert '100% packet loss' not in out
+
+    # ping the tx devices from the DUT
+    for i in range(num_devs):
+        out = run('ping -c3 10.10.2.'+str(101+i*ip_step), warn_only=True)
+        assert '100% packet loss' not in out
+
     # We are all set now - so transmit the stream now
     drone.startCapture(ports.rx)
     drone.startTransmit(ports.tx)
@@ -547,10 +563,6 @@ def test_multiEmulDevNoVlan(drone, ports, dut, dut_ports, stream_id,
     drone.stopTransmit(ports.tx)
     run('ip neigh show')
 
-    # unconfigure DUT
-    sudo('ip address delete 10.10.1.1/24 dev ' + dut_ports.rx)
-    sudo('ip address delete 10.10.2.1/24 dev ' + dut_ports.tx)
-
 @pytest.mark.parametrize('vlan_cfg', [
     [{'base': 11, 'count': 5}],
 
@@ -814,6 +826,23 @@ def test_multiEmulDevPerVlan(request, drone, ports, dut, dut_ports, stream_id,
             print('v%d|%08x: %08x %012x' %
                     (dev_cfg.vlan[0] & 0xffff, dev_cfg.ip4, arp.ip4, arp.mac))
 
+    # ping the tx devices from the DUT
+    for i in range(num_vlans):
+        vrf = 'vrf' + str(i+1)
+        for j in range(num_devs_per_vlan):
+            out = sudo('ip netns exec ' + vrf
+                            + ' ping -c3 10.1.1.'+str(101+j), warn_only=True)
+            assert '100% packet loss' not in out
+
+    # ping the tx devices from the DUT
+    for i in range(num_vlans):
+        vrf = 'vrf' + str(i+1)
+        for j in range(num_devs_per_vlan):
+            out = sudo('ip netns exec ' + vrf
+                            + ' ping -c3 10.1.2.'+str(101+j), warn_only=True)
+            assert '100% packet loss' not in out
+
+    # we are all set - send data stream(s)
     drone.startCapture(ports.rx)
     drone.startTransmit(ports.tx)
     log.info('waiting for transmit to finish ...')
@@ -857,4 +886,6 @@ def test_multiEmulDevPerVlan(request, drone, ports, dut, dut_ports, stream_id,
 #           vlanMode: no-repeat; ip4Mode: no-repeat
 # ----------------------------------------------------------------- #
 
+import pytest
+pytest.main(__file__)