 | RockSaw Frequently Asked Questions |
RockSaw FAQ- 1. Why do I get an “invalid argument”
error when I try to write to a TCP raw socket?
- 2. Why can't I send TCP packets on Windows XP?
- 3. Why can't I establish a TCP connection?
- 4. Why can I get replies to ICMPv6 echo requests on POSIX
systems but not on Microsoft Windows?
- 5. Where's the name come from?
1. | Why do I get an “invalid argument”
error when I try to write to a TCP raw socket? |
|
java.io.IOException: An invalid argument was supplied.
at org.savarese.rocksaw.net.RawSocket.__throwIOException(RawSocket.java:)
at org.savarese.rocksaw.net.RawSocket.write(RawSocket.java:) This problem occurs only under the Windows family of
operating systems. It occurs when you open a raw socket in
the TCP protocol family (IPPROTO_TCP) and
then try to write to it. Windows does not support writing to
IPPROTO_TCP raw sockets even though it allows
you to create one. It does, however, support
IPPROTO_UDP. In order to write TCP packets via a raw socket on
Windows, you have to open the socket with either
IPPROTO_IP or IPPROTO_RAW.
Then you have to set the IP_HDRINCL socket
option and populate both the IP and TCP headers of each
packet. What this means in terms of RockSaw is that on
Windows you have to use
RawSocket.getProtocolByName("ip") and
setIPHeaderInclude(true). |
2. | Why can't I send TCP packets on Windows XP? |
| New restrictions on raw socket functionality were
imposed in Windows XP SP2. If you're running Windows XP SP2,
you cannot send TCP packets (but you can still receive them),
nor can you spoof the source address of IP packets. The
source address must exist on a local network interface. |
3. | Why can't I establish a TCP connection? |
| Even though you can send TCP packets with a raw
socket, the operating system's TCP/IP stack will process
incoming TCP and UDP packets. When you send a TCP SYN
packet with a raw socket, the destination's response will be
rejected by the operating system because it is unaware of
the SYN you sent. Therefore, you cannot complete a
three-way handshake. |
4. | Why can I get replies to ICMPv6 echo requests on POSIX
systems but not on Microsoft Windows? |
| The Microsoft Windows family of operating systems does
not calculate the ICMPv6 checksum for outgoing ICMPv6 packets.
Therefore, you have to calculate the checksum yourself. This
can be tricky because you have to determine the address of the
outgoing network interface, which can vary on multi-interface
systems depending on the available routes. See the
example.Ping source code to see how to compute the required
checksum and send an ICMPv6 echo request on Windows. |
5. | Where's the name come from? |
| ($rocksaw="SOCK_RAW\n")=~s/(.)([^_]+)_(.)(.+)/$3\L$2\E$1\L$4\E/&&print$rocksaw |
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