We can't reliably distinguish HTTP data from other data on port 80 when fragmentation is used.
HTTP method code has a special case which tries to find HTTP method when fragmentation = 1 or 2 is used,
but not for other values.
Some servers set "don't fragment" flag and never increase TCP ID
field. If they send HTTP redirection to another website, it would
be blocked by the program.
This is a hack to block redirects only with "Connection: close"
header as presumably legal redirects are most likely would
use keep-alive.
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.
Old code used to reduce packet size by one byte to remove space in
HTTP Host header. This introduces one unACKed byte which OS later
tried to send to the host. This byte was \n (the last byte in original
packet) which broke POST requests.
New code in this commit moves "stolen" space in the end of User-Agent
header value and do not reduce packet size anymore.
User-Agent value is used because not all web servers are compatible
with additional space in the end of Host value.
Fix#3
ValdikSS
beatcracker
Pavel Rubin