Diff: PPP-Blinky/ppp-blinky.cpp

Revision:

149:969d98f6fb88

Parent:

148:4225c3608b80

Child:

150:3366bf3d294e

--- a/PPP-Blinky/ppp-blinky.cpp	Wed Aug 30 15:18:56 2017 +0000
+++ b/PPP-Blinky/ppp-blinky.cpp	Wed Aug 30 16:13:34 2017 +0000
@@ -211,7 +211,6 @@
 {
     led1 = (ppp.ledState >> 1) & 1; // use second bit, in other words toggle LED only every second packet
     ppp.ledState++;
-
 }
 
 /// returns 1 after a connect messasge, 0 at startup or after a disconnect message
@@ -529,6 +528,18 @@
     memcpy(ppp.pkt.buf+20, tempHold,4); // dest <- tempHold
 }
 
+/// swap the IP source and destination ports
+void swapIpPorts()
+{
+    int headerSizeIP    = 4*(ppp.pkt.buf[4]&0xf); // calculate size of IP header
+    char * ipSrcPort = 4 + ppp.pkt.buf + headerSizeIP + 0; // ip source port location
+    char * ipDstPort = 4 + ppp.pkt.buf + headerSizeIP + 2; // ip destin port location
+    char tempHold[2];
+    memcpy(tempHold, ipSrcPort,2); // tempHold <- source
+    memcpy(ipSrcPort,ipDstPort,2); // source <- dest
+    memcpy(ipDstPort,tempHold, 2); // dest <- tempHold
+}
+
 /// Process an incoming UDP packet.
 /// If the packet starts with the string "echo " or "test" we echo back a special packet
 void UDPpacket()
@@ -537,8 +548,6 @@
     char * ipSizeBuf    = ipHeader+2; // size of IP packet
     int headerSizeIP    = 4*(ipHeader[0]&0xf); // size of IP header
     char * udpHeader    = ipHeader + headerSizeIP; // udp info start
-    char * udpSrcPort   = udpHeader+0; // source port
-    char * udpDstPort   = udpHeader+2; // destination port
     char * udpLen       = udpHeader+4; // udp data length
     char * udpCheckSum  = udpHeader+6; // udp checksum
     char * udpData = udpHeader+8; // start of UDP data
@@ -548,6 +557,8 @@
 #ifdef SERIAL_PORT_MONITOR_YES
     char * srcIP        = ipHeader+12; // IP source
     char * dstIP        = ipHeader+16; // IP destination
+    char * udpSrcPort   = udpHeader+0; // source port
+    char * udpDstPort   = udpHeader+2; // destination port
     int udpSrc = (udpSrcPort[0]<<8)|udpSrcPort[1]; // integer of UDP source port
     int udpDst = (udpDstPort[0]<<8)|udpDstPort[1]; // integer of UDP dest port
     if(v0) debugPrintf("UDP %d.%d.%d.%d:%d ", srcIP[0],srcIP[1],srcIP[2],srcIP[3],udpSrc);
@@ -571,10 +582,7 @@
     int testFound = !strncmp(udpData,"test" ,4); // true if UDP message starts with "test"
     if ( (echoFound) || (testFound)) { // if the UDP message starts with "echo " or "test" we answer back
         swapIpAddresses(); // swap IP source and destination
-        char tempHold[4];
-        memcpy(tempHold, udpSrcPort,2);
-        memcpy(udpSrcPort, udpDstPort,2);
-        memcpy(udpDstPort, tempHold,2); // swap udp port source/dest
+        swapIpPorts(); // swap IP source and destination ports
         if (echoFound) {
             memcpy(udpData,"Got{",4); // in the UDP data modify "echo" to "Got:"
             char endString[] = "} UDP Server: PPP-Blinky\n"; // an appendix
@@ -931,16 +939,16 @@
     char * pktLen =     ipPkt+2;  // 2 bytes
     char * ident =      ipPkt+4;  // 2 bytes
     char * protocol =   ipPkt+9;  // 1 byte
-//    char * headercheck= ipPkt+10; // 2 bytes
+    //char * headercheck= ipPkt+10; // 2 bytes
     char * srcAdr =     ipPkt+12; // 4 bytes
-//    char * dstAdr =     ipPkt+16; // 4 bytes = total of 20 bytes
+    //char * dstAdr =     ipPkt+16; // 4 bytes = total of 20 bytes
     int headerSizeIP = (ihl[0]&0xf)*4;
     int packetLength = (pktLen[0]<<8)|pktLen[1]; // ip total packet length
 
     // 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 * 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
@@ -963,6 +971,7 @@
     // 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
+    ipPkt[0] = 0x45; // short IP packet size to 45
     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)
@@ -1004,11 +1013,8 @@
 
     // The TCP flag handling is now done
     // first we swap source and destination TCP addresses and insert the new ack and seq numbers
-    char tempHold[12]; // it's 12 long because we later reuse it when building the TCP pseudo-header
     swapIpAddresses(); // swap IP source and destination addresses
-    memcpy(tempHold,srctcp,2);
-    memcpy(srctcp, dsttcp,2);
-    memcpy(dsttcp, tempHold,2); // swap ip port source/dest
+    swapIpPorts(); // swap IP  source and destination ports
 
     acktcp[0]=ack_out>>24;
     acktcp[1]=ack_out>>16;
@@ -1036,6 +1042,7 @@
 
     // 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 tempHold[12]; // it's 12 long because we later reuse it when building 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