Fix IP header checksum in handleSendSwitchCommand (#88)

Approach
What is the motivation for this PR?
Fix the IP header checksum error in the packet sent by handleSendSwitchCommand

Signed-off-by:
Longxiang Lyu [email protected]
Jing Zhang [email protected]

How did you do it?
Update IP header checksum after appending TlvCommand.

How did you verify/test it?

Author: zjswhhh

src/link_prober/LinkProber.cpp

@@ -261,25 +261,13 @@ void LinkProber::handleUpdateEthernetFrame()
 //
 void LinkProber::handleSendSwitchCommand()
 {
-    resetTxBufferTlv();
-    appendTlvCommand(Command::COMMAND_SWITCH_ACTIVE);
-    appendTlvSentinel();
-
-    size_t totalPayloadSize = mTxPacketSize - mPacketHeaderSize;
-    iphdr *ipHeader = reinterpret_cast<iphdr *> (mTxBuffer.data() + sizeof(ether_header));
-    icmphdr *icmpHeader = reinterpret_cast<icmphdr *> (mTxBuffer.data() + sizeof(ether_header) + sizeof(iphdr));
-    computeChecksum(icmpHeader, sizeof(icmphdr) + totalPayloadSize);
-    ipHeader->tot_len = htons(sizeof(iphdr) + sizeof(icmphdr) + totalPayloadSize);
+    initTxBufferTlvSendSwitch();
 
     sendHeartbeat();
 
-    resetTxBufferTlv();
-    appendTlvSentinel();
-    totalPayloadSize = mTxPacketSize - mPacketHeaderSize;
-    computeChecksum(icmpHeader, sizeof(icmphdr) + totalPayloadSize);
-    ipHeader->tot_len = htons(sizeof(iphdr) + sizeof(icmphdr) + totalPayloadSize);
+    initTxBufferTlvSentinel();
 
-    // inform the composite state machine about commend send completion
+    // inform the composite state machine about command send completion
     boost::asio::io_service::strand &strand = mLinkProberStateMachinePtr->getStrand();
     boost::asio::io_service &ioService = strand.context();
     ioService.post(strand.wrap(boost::bind(
@@ -754,6 +742,48 @@ size_t LinkProber::appendTlvDummy(size_t paddingSize, int seqNo)
     return tlvSize;
 }
 
+//
+// ---> initTxBufferTlvSendSwitch
+//
+// Initialize TX buffer TLVs to send switch command to peer
+//
+void LinkProber::initTxBufferTlvSendSwitch()
+{
+    resetTxBufferTlv();
+    appendTlvCommand(Command::COMMAND_SWITCH_ACTIVE);
+    appendTlvSentinel();
+
+    calculateTxPacketChecksum();
+}
+
+//
+// ---> initTxBufferTlvSentinel
+//
+// Initialize TX buffer to have only TLV sentinel
+//
+void LinkProber::initTxBufferTlvSentinel()
+{
+    resetTxBufferTlv();
+    appendTlvSentinel();
+
+    calculateTxPacketChecksum();
+}
+
+//
+// ---> calculateChecksum
+//
+// Calculate TX packet checksums in both IP header and ICMP header
+//
+void LinkProber::calculateTxPacketChecksum()
+{
+    size_t totalPayloadSize = mTxPacketSize - mPacketHeaderSize;
+    iphdr *ipHeader = reinterpret_cast<iphdr *> (mTxBuffer.data() + sizeof(ether_header));
+    icmphdr *icmpHeader = reinterpret_cast<icmphdr *> (mTxBuffer.data() + sizeof(ether_header) + sizeof(iphdr));
+    computeChecksum(icmpHeader, sizeof(icmphdr) + totalPayloadSize);
+    ipHeader->tot_len = htons(sizeof(iphdr) + sizeof(icmphdr) + totalPayloadSize);
+    computeChecksum(ipHeader, ipHeader->ihl << 2);
+}
+
 // 
 // ---> resetIcmpPacketCounts
 //

src/link_prober/LinkProber.h

@@ -450,7 +450,34 @@ class LinkProber
     *@return the appended TLV size
     */
     size_t appendTlvDummy(size_t paddingSize, int seqNo);
-    
+
+    /**
+     * @method initTlvSendSwitch
+     * 
+     * @brief initialize TX buffer TLVs to send switch command to peer
+     * 
+     * @return none
+     */
+    void initTxBufferTlvSendSwitch();
+
+    /**
+     * @method initTxBufferTlvSentinel
+     * 
+     * @brief initialize TX buffer to have only TLV sentinel
+     * 
+     * @return none
+     */
+    void initTxBufferTlvSentinel();
+
+    /**
+     * @method calculateChecksum
+     * 
+     * @brief calculate TX packet checksums in both IP header and ICMP header
+     * 
+     * @return none
+     */
+    inline void calculateTxPacketChecksum();
+
     /**
      * @method getProbingInterval
      * 

test/LinkProberTest.cpp

@@ -128,6 +128,26 @@ TEST_F(LinkProberTest, CalculateChecksum)
     EXPECT_TRUE(icmpHeader->checksum == 12100);
 }
 
+TEST_F(LinkProberTest, handleSendSwitchCommand)
+{
+    initializeSendBuffer();
+
+    iphdr *ipHeader = reinterpret_cast<iphdr *>(getTxBufferData() + sizeof(ether_header));
+    icmphdr *icmpHeader = reinterpret_cast<icmphdr *>(getTxBufferData() + sizeof(ether_header) + sizeof(iphdr));
+    ipHeader->id = static_cast<uint16_t> (17767);
+    initTxBufferSentinel();
+    EXPECT_TRUE(ipHeader->check == 62919);
+    EXPECT_TRUE(icmpHeader->checksum == 12100);
+
+    initTxBufferTlvSendSwitch();
+    EXPECT_TRUE(ipHeader->check == 61895);
+    EXPECT_TRUE(icmpHeader->checksum == 11838);
+
+    initTxBufferSentinel();
+    EXPECT_TRUE(ipHeader->check == 62919);
+    EXPECT_TRUE(icmpHeader->checksum == 12100);
+}
+
 TEST_F(LinkProberTest, UpdateEthernetFrame)
 {
     link_prober::IcmpPayload *icmpPayload = new (

test/LinkProberTest.h

@@ -57,6 +57,8 @@ class LinkProberTest: public ::testing::Test
     uint16_t getRxSelfSeqNo() {return mLinkProber.mRxSelfSeqNo;};
     uint16_t getRxPeerSeqNo() {return mLinkProber.mRxPeerSeqNo;};
     bool getSuspendTx() {return mLinkProber.mSuspendTx;};
+    void initTxBufferTlvSendSwitch() {mLinkProber.initTxBufferTlvSendSwitch();}
+    void initTxBufferSentinel() {mLinkProber.initTxBufferTlvSentinel();}
 
     boost::asio::io_service mIoService;
     common::MuxConfig mMuxConfig;