Change TCP Window Size based on SrcPort, not DstPort.

When HTTPS fragment size was set, the program always used it for HTTP, even
if HTTP fragmentation was disabled. This is due to a bug which checked DstPort,
not SrcPort, and the packets passed DstPort != htons(80) HTTPS check.

README.md

@@ -65,6 +65,29 @@ And for x86_64:
 
 `make CPREFIX=x86_64-w64-mingw32 WINDIVERTHEADERS=/path/to/windivert/include WINDIVERTLIBS=/path/to/windivert/amd64`
 
+# How to install as Windows Service
+
+One way is using an [srvstart](http://www.rozanski.org.uk/software) program.  
+Unpack it to goodbyedpi directory and create 3 files:
+
+*goodbyedpi.ini*
+```INI
+[GoodByeDPI]
+startup=goodbyedpi.exe
+shutdown_method=winmessage
+auto_restart=n
+```
+*srvinstall.bat*
+```Batchfile
+srvstart install GoodByeDPI -c %CD%\goodbyedpi-svc.ini
+```
+*srvremove.bat*
+```Batchfile
+srvstart remove GoodByeDPI
+```
+Run these batch files as Administrator to install/remove service.  
+Open Windows Services panel to run service or make it start automaticaly.
+
 # Similar projects
 
 [zapret](https://github.com/bol-van/zapret) by @bol-van (for Linux).

goodbyedpi.c

@@ -355,11 +355,11 @@ int main(int argc, char *argv[]) {
                 if (addr.Direction == WINDIVERT_DIRECTION_INBOUND && 
                     ppTcpHdr->Syn == 1) {
                     //printf("Changing Window Size!\n");
-                    if (do_fragment_http && ppTcpHdr->DstPort == htons(80)) {
+                    if (do_fragment_http && ppTcpHdr->SrcPort == htons(80)) {
                         change_window_size(packet, http_fragment_size);
                         WinDivertHelperCalcChecksums(packet, packetLen, 0);
                     }
-                    else if (do_fragment_https && ppTcpHdr->DstPort != htons(80)) {
+                    else if (do_fragment_https && ppTcpHdr->SrcPort != htons(80)) {
                         change_window_size(packet, https_fragment_size);
                         WinDivertHelperCalcChecksums(packet, packetLen, 0);
                     }