Diff: tcp/tcp.cpp

Revision:

10:f0854784e960

Child:

21:02c82594c8c0

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/tcp/tcp.cpp	Sun Apr 16 14:21:55 2017 +0000
@@ -0,0 +1,336 @@
+#include "mbed.h"
+#include  "log.h"
+#include  "net.h"
+#include  "tcp.h"
+#include  "tcb.h"
+#include "http.h"
+#include  "ip4.h"
+#include "dhcp.h"
+
+#define MAX_MSS 536 //This is 576 - 20 - 20
+
+__packed struct header
+{
+    uint16_t srcPort;
+    uint16_t dstPort;
+    uint32_t seqnum;
+    uint32_t acknum;
+    uint8_t  dataOffset;
+    uint8_t  flags;
+    uint16_t window; 
+    uint16_t checksum;
+    uint16_t urgent;
+};
+
+uint32_t now = 0;
+static void ticked()
+{
+    now++;
+    TcbReap(now);
+}
+static Ticker ticker;
+
+void TcpInit()
+{
+    ticker.attach(&ticked, 1);
+    TcbInit();
+}
+
+//Header variables
+    
+static    uint16_t    srcPort;
+static    uint16_t    dstPort;
+static    uint32_t     seqnum;
+static    uint32_t     acknum;
+static    int      headersize;
+static    uint8_t       flags;
+static    bool            URG; //indicates that the Urgent pointer field is significant
+static    bool            ACK; //indicates that the Acknowledgment field is significant. All packets after the initial SYN packet sent by the client should have this flag set.
+static    bool            PSH; //Push function. Asks to push the buffered data to the receiving application.
+static    bool            RST; //Reset the connection
+static    bool            SYN; //Synchronize sequence numbers. Only the first packet sent from each end should have this flag set. Some other flags and fields change meaning based on this flag, and some are only valid for when it is set, and others when it is clear.
+static    bool            FIN; //No more data from sender
+
+static    uint16_t     window;
+static    uint16_t   checksum;
+static    uint16_t     urgent;
+static    int    optionLength;
+    
+static    char*    pOptions;
+static    void*    pData;
+static    int      dataLength;
+static    uint16_t mss;
+
+void TcpLogHeader(char* title, void* pPacket, uint16_t calculatedChecksum)
+{    
+    LogTimeF("TCP %s\r\n", title);
+    LogF("  Source port      %hu\r\n",   srcPort);
+    LogF("  Destination port %hu\r\n",   dstPort);
+    LogF("  Sequence number  %u\r\n",    seqnum);
+    LogF("  Ack number       %u\r\n",    acknum);
+    LogF("  Header size      %u\r\n",    headersize);
+    LogF("  Flags            %02X",      flags);
+    if (URG) LogF("    URG");
+    if (ACK) LogF("    ACK");
+    if (PSH) LogF("    PSH");
+    if (RST) LogF("    RST");
+    if (SYN) LogF("    SYN");
+    if (FIN) LogF("    FIN");
+    LogF("\r\n");
+    LogF("  Window           %hu\r\n",   window);
+    LogF("  Checksum (hex)   %04hX\r\n", checksum);
+    LogF("  Calculated (hex) %04hX\r\n", calculatedChecksum);
+    LogF("  Urgent pointer   %hu\r\n",   urgent);
+    LogF("  Option length    %d\r\n",    optionLength);
+    LogF("  Data length      %d\r\n",    dataLength);
+}
+void TcpAddChecksum(void* pPacket, uint16_t checksum)
+{
+    struct header* pHeader = (header*)pPacket;
+    pHeader->checksum    = checksum;
+}
+static void readOptions()
+{
+    mss = 536; //default MSS for IPv4 [576 - 20(TCP) - 20(IP)];
+    for (char* p = pOptions; p < pOptions + optionLength; p++)
+    {
+        switch (*p)
+        {
+            case 0: break; //End of options - used to pad to 32 bit boundary
+            case 1: break; //NOP, padding - optional
+            case 2:
+                p++;
+                if (*p != 4) LogTimeF("MSS option width %d when expected 4\r\n", *p);
+                p++;
+                mss = ((uint16_t)*p) << 8;
+                p++;
+                mss += *p;
+                return;
+            default: LogTimeF("Unrecognised TCP option %d\r\n", *p);
+        }
+    }
+    if (mss > MAX_MSS) mss = MAX_MSS;
+}
+static void writeOptions()
+{
+    pOptions[0]  = 2;
+    pOptions[1]  = 4;
+    pOptions[2]  = mss >> 8;
+    pOptions[3]  = mss & 0xFF;
+    optionLength = 4;
+}
+
+void TcpReadHeader(void* pPacket, uint16_t size)
+{
+    struct header* pHeader = (header*)pPacket;
+                        
+            srcPort = NetToHost16(pHeader->srcPort);
+            dstPort = NetToHost16(pHeader->dstPort);
+             seqnum = NetToHost32(pHeader->seqnum);
+             acknum = NetToHost32(pHeader->acknum);
+         headersize =            (pHeader->dataOffset >> 2) & 0xFC; //Same as right shifting by 4 bits and multiplying by 4
+              flags =             pHeader->flags;
+                URG = flags & 0x20; //indicates that the Urgent pointer field is significant
+                ACK = flags & 0x10; //indicates that the Acknowledgment field is significant. All packets after the initial SYN packet sent by the client should have this flag set.
+                PSH = flags & 0x08; //Push function. Asks to push the buffered data to the receiving application.
+                RST = flags & 0x04; //Reset the connection
+                SYN = flags & 0x02; //Synchronize sequence numbers. Only the first packet sent from each end should have this flag set. Some other flags and fields change meaning based on this flag, and some are only valid for when it is set, and others when it is clear.
+                FIN = flags & 0x01; //No more data from sender
+    
+             window = NetToHost16(pHeader->window);
+           checksum = NetToHost16(pHeader->checksum);
+             urgent = NetToHost16(pHeader->urgent);
+           pOptions = (char*)pPacket + 20;
+       optionLength = headersize - 20;
+
+                  pData = (char*)pPacket + headersize;
+             dataLength =           size - headersize;
+}
+
+void TcpMakeHeader(int size, void* pPacket)
+{
+    struct header* pHeader = (header*)pPacket;
+    
+    pHeader->dstPort    = NetToHost16(dstPort);
+    pHeader->srcPort    = NetToHost16(srcPort);
+    pHeader->seqnum     = NetToHost32(seqnum); //This is the sequence number of the first byte of this message
+    pHeader->acknum     = NetToHost32(acknum); //This is the sequence number we expect in the next message
+    pHeader->dataOffset = headersize << 2;     //Same as dividing by 4 to get bytes and left shifting by 4 bits
+    flags = 0;
+    if(URG) flags |= 0x20; //indicates that the Urgent pointer field is significant
+    if(ACK) flags |= 0x10; //indicates that the Acknowledgment field is significant. All packets after the initial SYN packet sent by the client should have this flag set.
+    if(PSH) flags |= 0x08; //Push function. Asks to push the buffered data to the receiving application.
+    if(RST) flags |= 0x04; //Reset the connection
+    if(SYN) flags |= 0x02; //Synchronize sequence numbers. Only the first packet sent from each end should have this flag set. Some other flags and fields change meaning based on this flag, and some are only valid for when it is set, and others when it is clear.
+    if(FIN) flags |= 0x01; //No more data from sender
+    pHeader->flags      = flags;
+    pHeader->window     = NetToHost16(window);
+    pHeader->urgent     = NetToHost16(urgent);
+    
+    pHeader->checksum   = 0;
+}
+static int stateClosed(struct tcb* pTcb)
+{
+    if (!SYN)    //Reset if anything other than a request to establish conection from client
+    {
+        dataLength = 0;
+        headersize = 20;
+        seqnum = acknum;
+        acknum = 0;
+        ACK = false;                    //Send RST
+        PSH = false;
+        RST = true;
+        SYN = false;
+        FIN = false;
+        return 1;        
+    }
+    
+    readOptions();                 //Get the MSS
+    pTcb->mss    = mss;
+    
+    pTcb->state  = TCB_SYN_RECEIVED;
+    pTcb->timer  = now;
+    pTcb->port   = srcPort;
+    pTcb->locIsn = TcbGetIsn();
+    pTcb->locSeq = pTcb->locIsn;  
+    pTcb->remIsn = seqnum;
+    pTcb->remSeq = pTcb->remIsn;
+    
+    pTcb->remSeq += 1;             //Add one to acknowledge the SYN
+    acknum = pTcb->remSeq;
+    
+    seqnum = pTcb->locSeq;         //Set the sequence number to the first byte of this message
+    pTcb->locSeq += 1;             //Add one to the next sequence number as we are sending a SYN
+    
+    dataLength = 0;
+    
+    mss = MAX_MSS;                 //Ethernet 1500 - 20 - 20; or, in our case 768 - 20 - 20
+    writeOptions();
+    headersize = 24;               //20 header plus 4 option
+   
+    ACK = true;                    //Send ACK and SYN
+    PSH = false;
+    RST = false;
+    SYN = true;
+    FIN = false;
+    
+    return 1;
+}
+static int stateSynReceived(struct tcb* pTcb)
+{
+    if (dataLength) LogTimeF("%d bytes data received before TCB established\r\n", dataLength);
+    if (ACK)
+    {
+        pTcb->state = TCB_ESTABLISHED;
+        pTcb->timer = now;
+        pTcb->tag = 0;
+    }
+    return 0;
+}
+static int stateEstablished(struct tcb* pTcb)
+{
+    if (!ACK) return 0;              //Ignore any packets which don't contain an ACK
+    
+    //Handle reception of data
+    if (dataLength)
+    {
+        pTcb->tag = HttpRequest(seqnum - pTcb->remIsn - 1, dataLength, (char*)pData);
+        pTcb->remSeq = seqnum + dataLength;
+    }
+    acknum = pTcb->remSeq;      //Set the ack num to the next byte expected from the client
+    
+    
+    //Rearrange the buffers
+    headersize = 20;
+    pData = pOptions;
+   
+    //Handle sending of any data
+    dataLength = HttpResponse(pTcb->locSeq - pTcb->locIsn - 1, mss, (char*)pData, pTcb->tag);
+    
+    seqnum = pTcb->locSeq;      //Set the sequence number to the first byte of this message
+    
+
+    ACK = true;                 //Send ACK
+    RST = false;
+    SYN = false;
+    
+    if (dataLength)
+    {
+        pTcb->locSeq += dataLength; //Record the next sequence number
+        PSH = false;
+        FIN = false;
+    }
+    else
+    {
+        pTcb->locSeq += 1; //Record the FIN
+        PSH = true;
+        FIN = true;
+        pTcb->state = TCB_CLOSING;  //Start closing
+    }
+    pTcb->timer = now;
+    return 1;
+}
+static int stateClosing(struct tcb* pTcb)
+{
+    if (!FIN) return 0;       //Ignore any packets which don't contain a FIN
+    
+    pTcb->remSeq += 1;        //Add one to acknowledge the FIN
+    acknum = pTcb->remSeq;
+    
+    seqnum = pTcb->locSeq;    //Set the sequence number to the first byte of this message
+                              //but don't change it for the next
+    
+    ACK = true;               //Send ACK
+    PSH = false;
+    RST = false;
+    SYN = false;
+    FIN = false;
+    
+    headersize = 20;
+    dataLength = 0;
+    
+    pTcb->state  = TCB_CLOSED;
+    
+    return 1;
+}
+
+int TcpHandleReceivedPacket(int* pSize, void* pPacket)
+{
+    struct tcb* pTcb = TcbGetExisting(srcPort);
+    if (!pTcb)  pTcb = TcbGetEmpty();
+    if (!pTcb) return DO_NOTHING; //Bomb out if no more tcbs are available
+
+    if (RST)
+    {
+        pTcb->state  = TCB_CLOSED; //Reset connection
+        return DO_NOTHING;         //Bomb out
+    }
+
+    switch (dstPort)
+    {
+        case 80: break;
+        default: return DO_NOTHING; //This needs to become a reset
+    }
+    
+    //Drop duplicate packets
+    //if (!TCB_CLOSED && (int32_t)(seqnum - pTcb->remSeq) < 0)
+    //{
+    //    LogTimeF("Dropped duplicate seq num=%d expected=%d packet length %d from port %u\r\n", seqnum, pTcb->remSeq, size, srcPort);
+    //    return IP4_DO_NOTHING;
+    //}
+
+    switch (pTcb->state)
+    {
+        case TCB_CLOSED:       if (stateClosed     (pTcb)) break; return DO_NOTHING;
+        case TCB_SYN_RECEIVED: if (stateSynReceived(pTcb)) break; return DO_NOTHING;
+        case TCB_ESTABLISHED:  if (stateEstablished(pTcb)) break; return DO_NOTHING;
+        case TCB_CLOSING:      if (stateClosing    (pTcb)) break; return DO_NOTHING;
+    }
+    
+    srcPort = dstPort;
+    dstPort = pTcb->port;
+    
+    *pSize = dataLength + headersize;
+    return UNICAST;
+
+}