Lab2_web
/
webserverBlinky
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Dependencies: mbed
Fork of
webserverBlinky
by 
RealTimeCompLab2
Diff: main.cpp
- Revision:
- 87:9f5ac1fabd95
- Parent:
- 85:53e57ff1cf05
- Child:
- 88:b4a71242837c
diff -r 4186c46d968a -r 9f5ac1fabd95 main.cpp
--- a/main.cpp Thu Jul 20 01:03:13 2017 +0000
+++ b/main.cpp Fri Jul 21 00:35:24 2017 +0000
@@ -97,11 +97,11 @@
// a structure to keep all our ppp globals in
struct pppType {
int online; // we hunt for a PPP connection if this is zero
- int ident; // our IP ident value
+ unsigned int ident; // our IP ident value
unsigned int seq; // our TCP sequence number
int crc; // for calculating IP and TCP CRCs
int ledState; // state of LED1
- int httpFrame;
+ int httpFrameCount;
struct {
#define RXBUFLEN (1<<14)
char buf[RXBUFLEN]; // RXBUFLEN MUST be a power of two because we use & operator for fast wrap-around in ring buffer
@@ -139,7 +139,7 @@
ppp.ledState=0;
ppp.hdlc.frameFound=0;
ppp.hdlc.frameStartIndex=0;
- ppp.httpFrame=0;
+ ppp.httpFrameCount=0;
}
void led1Toggle()
@@ -551,7 +551,7 @@
int nHeader; // byte size of HTTP header
int contentLengthStart; // index where HTML starts
- ppp.httpFrame++; // increment count of response frames
+ ppp.httpFrameCount++; // increment the number of frames we have made
int rootFetch = strncmp(dataStart, "GET / HTTP/1.1", 14);
@@ -572,14 +572,14 @@
// this is where we insert our web page into the buffer
n=n+sprintf(n+dataStart,"%s", ourWebPage);
} else {
- // all other requests get 404 Not Found response a
- n=n+sprintf(n+dataStart,"<!DOCTYPE html>"); // html start
- n=n+sprintf(n+dataStart,"<title>%06d</title>",ppp.httpFrame); // shortest possible valid frame
+ // all other requests get 404 Not Found response with a http frame count - nice for debugging
+ n=n+sprintf(n+dataStart,"<!DOCTYPE html><title>ppp-blinky</title>"); // html start
+ n=n+sprintf(n+dataStart,"<body>%06d</body>",ppp.httpFrameCount); // body = the http frame count
}
- while( (n%4)!= 2)
- n=n+sprintf(n+dataStart," "); // insert spaces until n is exactly two away from a multiple of four
- n=n+sprintf(n+dataStart,"\r\n"); // add the last \r\n sequence - n is now an exact multiple of four
+ while( (n%4)!= 2) n=n+sprintf(n+dataStart," "); // insert spaces until n is exactly two away from a multiple of four
+ n=n+sprintf(n+dataStart,"\r\n"); // add the last two characters (\r\n) - n is now an exact multiple of four
+
#define CONTENTLENGTHSIZE 5
char contentLengthString[CONTENTLENGTHSIZE+1];
snprintf(contentLengthString,CONTENTLENGTHSIZE+1,"%*d",CONTENTLENGTHSIZE,n-nHeader); // print Content-Length with leading spaces and fixed width equal to csize
@@ -594,6 +594,8 @@
void tcpHandler()
{
+ // IP header
+
char * ipPkt = ppp.pkt.buf+4; // ip packet start
char * ihl = ipPkt; // bottom 4 bits
char * pktLen = ipPkt+2; // 2 bytes
@@ -605,30 +607,31 @@
int headerSizeIP = (ihl[0]&0xf)*4;
int packetLength = (pktLen[0]<<8)|pktLen[1]; // ip total packet length
- char * s = ppp.pkt.buf+4+headerSizeIP; // start of tcp packet
- char * srctcp = s + 0; // 2 bytes
- char * dsttcp = s + 2; // 2 bytes
- char * seqtcp = s + 4; // 4 bytes
- char * acktcp = s + 8; // 4 bytes
- char * offset = s + 12; // 4 bits
- char * flagbitstcp = s + 12; // 9 bits
- char * windowsizetcp = s + 14; // 2 bytes
- char * checksumtcp = s + 16; // 2 bytes
+ // TCP header
+
+ char * tcp = ppp.pkt.buf+4+headerSizeIP; // start of tcp packet
+ char * srctcp = tcp + 0; // 2 bytes
+ char * dsttcp = tcp + 2; // 2 bytes
+ char * seqtcp = tcp + 4; // 4 bytes
+ char * acktcp = tcp + 8; // 4 bytes
+ char * offset = tcp + 12; // 4 bits
+ char * flagbitstcp = tcp + 12; // 9 bits
+ char * windowsizetcp = tcp + 14; // 2 bytes
+ char * checksumtcp = tcp + 16; // 2 bytes
int tcpSize = packetLength - headerSizeIP;
int headerSizeTCP = ((offset[0]>>4)&0x0f)*4; // size of tcp header only
int protocolIP = protocol[0];
- int flagsTCP = ((flagbitstcp[0]&1)<<8)|flagbitstcp[1];
-
- char * dataStart = ppp.pkt.buf + 4 + headerSizeIP + headerSizeTCP; // start of data block after TCP header
+ char * tcpDataIn = tcp + headerSizeTCP; // start of data block after TCP header
int tcpDataSize = tcpSize - headerSizeTCP; // size of data block after TCP header
+ char * tcpDataOut = tcp + 20; // start of outgoing data
unsigned int seq_in = (seqtcp[0]<<24)|(seqtcp[1]<<16)|(seqtcp[2]<<8)|(seqtcp[3]);
unsigned int ack_in = (acktcp[0]<<24)|(acktcp[1]<<16)|(acktcp[2]<<8)|(acktcp[3]);
unsigned int ack_out = seq_in + tcpDataSize;
- unsigned int seq_out = ack_in; // ack_in is their calculation of our current sequence number
+ unsigned int seq_out = ack_in; // use their version of our current sequence number
#define TCP_FLAG_ACK (1<<4)
@@ -637,9 +640,19 @@
#define TCP_FLAG_RST (1<<2)
#define TCP_FLAG_FIN (1<<0)
+ // first we shorten the TCP response header to only 20 bytes.
+ // this means we ignore all TCP option requests
+
+ tcpSize = 20; // shorten total TCP packet size to 20 bytes (no data)
+ headerSizeTCP = 20; // shorten outgoing TCP header size 20 bytes
+ offset[0] = (headerSizeTCP/4)<<4; // shorten tcp header size to 20 bytes
+ packetLength = 40; // shorten total packet size to 40 bytes (20 ip + 20 tcp)
+ pktLen[1] = 40; // set total packet size to 40 bytes (20 ip + 20 tcp)
+ pktLen[0] = 0; // set total packet size to 40 bytes (20 ip + 20 tcp)
+
int dataLen = 0; // most of our responses will have zero TCP data, only a header
int flagsOut = TCP_FLAG_ACK; // the default case is an ACK packet
- int fastResponse = 0; // normally you wait 200ms before sending a packet but this can make it faster
+ int flagsTCP = ((flagbitstcp[0]&1)<<8)|flagbitstcp[1]; // the tcp flags we received
// A sparse TCP flag interpreter that implements simple TCP connections from a single source
// Clients are allowed ONE push packet, after which the link is closed with a FIN flag in the ACK packet
@@ -647,32 +660,18 @@
switch ( flagsTCP ) {
case TCP_FLAG_SYN:
+ flagsOut = TCP_FLAG_SYN | TCP_FLAG_ACK; // something wants to connect - acknowledge it
+ seq_out = seq_in+0x1000U; // create a new sequence number using their sequence as a base
ack_out++; // for SYN flag we have to increase the sequence by 1
- // ignore all TCP option requests by shortening the TCP header to 20 bytes
- headerSizeTCP = 20; // shorten TCP header size 20 bytes
- offset[0] = (headerSizeTCP/4)<<4; // shorten tcp header size to 20 bytes
- tcpSize = 20; // shorten total TCP packet size to 20 bytes (no data)
- packetLength = 40; // shorten total packet size to 40 bytes (20 ip + 20 tcp)
- pktLen[1] = 40; // shorten total packet size to 40 bytes (20 ip + 20 tcp)
- flagsOut = TCP_FLAG_SYN | TCP_FLAG_ACK; // something wants to connect - acknowledge it
- //ppp.seq = ppp.seq + 10000; // create a new sequence number (normally random)
- seq_out = 10+((seq_in+1)/10)*10; //ppp.seq; // create a new sequence number (normally random)
break;
case TCP_FLAG_ACK | TCP_FLAG_PSH:
flagsOut = TCP_FLAG_ACK | TCP_FLAG_FIN; // for every push we answer once AND close the link
- fastResponse = 1; // we can respond fast to a push
- if ( strncmp(dataStart, "GET ", 4) == 0) { // do we see an http GET command
- dataLen = httpResponse(dataStart); // send an http response
- while((dataLen %4 ) !=0) { // dataLen must be a multiple of four
- dataLen++; // must be a multiple of four
- dataStart[dataLen-1]=0; // clear the byte in the buffer
- ack_out++;
- }
+ if ( strncmp(tcpDataIn, "GET ", 4) == 0) { // check for an http GET command
+ dataLen = httpResponse(tcpDataOut); // send an http response
}
break;
case TCP_FLAG_FIN:
case TCP_FLAG_FIN | TCP_FLAG_ACK:
- case TCP_FLAG_FIN | TCP_FLAG_ACK | TCP_FLAG_PSH:
ack_out++; // for FIN flag we always have to increase sequence by 1
break;
default:
@@ -683,7 +682,7 @@
// The TCP flag handling is now done
// Now we have to recalculate all the header sizes, swap IP address/port source and destination, and do the IP and TCP checksums
- ppp.ident++; //
+ ppp.ident++; // get next ident number for our packet
ident[0] = ppp.ident>>8;
ident[1] = ppp.ident>>0; // insert OUR ident
@@ -696,7 +695,7 @@
memcpy(srctcp, dsttcp,2);
memcpy(dsttcp, tempHold,2); // swap ip port source/dest
- windowsizetcp[0]=2; // ignore window size negotiation
+ windowsizetcp[0]=4; // ignore window size negotiation
windowsizetcp[1]=0; // ignore winodw size negotiation
acktcp[0]=ack_out>>24;
@@ -726,7 +725,7 @@
// now we have to build the so-called 12-byte TCP "pseudo-header" in front of the TCP header (containing some IP header values) in order to correctly calculate the TCP checksum
// this header contains the most important parts of the IP header, i.e. source and destination address, protocol number and data length.
- char * pseudoHeader = s-12; // mark the start of the TCP pseudo-header
+ char * pseudoHeader = tcp-12; // mark the start of the TCP pseudo-header
memcpy(tempHold, pseudoHeader, 12); // preserve the 12 bytes of the IP header where the TCP pseudo-Header will be built
memcpy( pseudoHeader+0, srcAdr, 8); // IP source and destination addresses from IP header
memset( pseudoHeader+8, 0, 1); // reserved, set to zero
@@ -741,15 +740,8 @@
unsigned int pseudoHeaderSum=dataCheckSum((unsigned char *)pseudoHeader,tcpSize+12); // calculate the TCP checksum starting at the pseudo-header
checksumtcp[0]=pseudoHeaderSum>>8;
checksumtcp[1]=pseudoHeaderSum;
- memcpy( s-12, tempHold, 12); // restore the 12 bytes that the pseudo-header overwrote
+ memcpy( tcp-12, tempHold, 12); // restore the 12 bytes that the pseudo-header overwrote
- if (fastResponse==1) {
- fastResponse=0; // reset and skip 200 ms wait
- } else {
- // normally, you wait 200 ms before responding to a TCP packet
- // remove the wait to respond faster
- // wait(0.2);
- }
sendFrame(); // All preparation complete - send the TCP response
dumpHeaderIP();
dumpHeaderTCP();