I am trying to learn something about sockets in Linux. I have small development board something like raspberry Pi with Linux running inside. Unfortunatly it doesn't have ethernet or usb port.I have created a dummy network interface and used it like default gateway. I have written a small program using raw sockets listening on dummy interface (then sends all packets over serial line to computer where is program which send this packets to the internet and recieves answers a sends them back).My problem is when i am trying to ping some public IP address i can see in tcpdump the ICMP requests and responses in both computer and development board. But the ping looks like it does recieve nothing.I have tryed to use loopback interface instead of dummy interface, but in this case the pings gets looped and the device becomes unresponsible in a while:). But the ping did recieve ICMP response, and TCP connection didn't work.I also have tryed to use 2 dummy interfaces and create bridge.I would be very grateful for any advices.
Raw sockets allow new IPv4 protocols to be implemented in user space. A raw socket receives or sends the raw datagram not including link level headers. RAW-sockets are an additional type of Internet socket available in. This also chooses the Transport Layer Protocol that is being used (UDP.
TCP/IP Raw Sockets. 9 minutes to read.In this articleA raw socket is a type of socket that allows access to the underlying transport provider. This topic focuses only on raw sockets and the IPv4 and IPv6 protocols. This is because most other protocols with the exception of ATM do not support raw sockets. To use raw sockets, an application needs to have detailed information on the underlying protocol being used.Winsock service providers for the IP protocol may support a socket type of SOCKRAW. The Windows Sockets 2 provider for TCP/IP included on Windows supports this SOCKRAW socket type.There are two basic types of such raw sockets:. The first type uses a known protocol type written in the IP header that is recognized by a Winsock service provider.
An example of the first type of socket is a socket for the ICMP protocol (IP protocol type = 1) or the ICMPv6 protocol (IP procotol type = 58). The second type allows any protocol type to be specified. NoteAn application may not specify zero (0) as the protocol parameter for the, and functions if the type parameter is set to SOCKRAW.Raw sockets offer the capability to manipulate the underlying transport, so they can be used for malicious purposes that pose a security threat.
Therefore, only members of the Administrators group can create sockets of type SOCKRAW on Windows 2000 and later. Send and Receive OperationsOnce an application creates a socket of type SOCKRAW, this socket may be used to send and receive data. All packets sent or received on a socket of type SOCKRAW are treated as datagrams on an unconnected socket.The following rules apply to the operations over SOCKRAW sockets:.The or function is normally used to send data on a socket of type SOCKRAW.
The destination address can be any valid address in the socket's address family, including a broadcast or multicast address. To send to a broadcast address, an application must have used with SOBROADCAST enabled. Otherwise, sendto or WSASendTo will fail with the error code. For IP, an application can send to any multicast address (without becoming a group member).When sending IPv4 data, an application has a choice on whether to specify the IPv4 header at the front of the outgoing datagram for the packet.
If the IPHDRINCL socket option is set to true for an IPv4 socket (address family of AFINET), the application must supply the IPv4 header in the outgoing data for send operations. If this socket option is false (the default setting), then the IPv4 header should not be in included the outgoing data for send operations.When sending IPv6 data, an application has a choice on whether to specify the IPv6 header at the front of the outgoing datagram for the packet. If the IPV6HDRINCL socket option is set to true for an IPv6 socket (address family of AFINET6), the application must supply the IPv6 header in the outgoing data for send operations. The default setting for this option is false. If this socket option is false (the default setting), then the IPv6 header should not be included in the outgoing data for send operations. For IPv6, there should be no need to include the IPv6 header. If information is available using socket functions, then the IPv6 header should not be included to avoid compatibility problems in the future.
These issues are discussed in RFC 3542 published by the IETF. Using the IPV6HDRINCL socket option is not recommended and may be deprecated in future.The or function is normally used to receive data on a socket of type SOCKRAW. Both of these functions have an option to return the source IP address where the packet was sent from. The received data is a datagram from an unconnected socket.For IPv4 (address family of AFINET), an application receives the IP header at the front of each received datagram regardless of the IPHDRINCL socket option.For IPv6 (address family of AFINET6), an application receives everything after the last IPv6 header in each received datagram regardless of the IPV6HDRINCL socket option. The application does not receive any IPv6 headers using a raw socket.Received datagrams are copied into all SOCKRAW sockets that satisfy the following conditions:. The protocol number specified in the protocol parameter when the socket was created should match the protocol number in the IP header of the received datagram. If a local IP address is defined for the socket, it should correspond to the destination address as specified in the IP header of the received datagram.
An application may specify the local IP address by calling the function. If no local IP address is specified for the socket, the datagrams are copied into the socket regardless of the destination IP address in the IP header of the received datagram. If a foreign address is defined for the socket, it should correspond to the source address as specified in the IP header of the received datagram. An application may specify the foreign IP address by calling the or function.
If no foreign IP address is specified for the socket, the datagrams are copied into the socket regardless of the source IP address in the IP header of the received datagram.It is important to understand that some sockets of type SOCKRAW may receive many unexpected datagrams. For example, a PING program may create a socket of type SOCKRAW to send ICMP echo requests and receive responses. While the application is expecting ICMP echo responses, all other ICMP messages (such as ICMP HOSTUNREACHABLE) may also be delivered to this application. Moreover, if several SOCKRAW sockets are open on a computer at the same time, the same datagrams may be delivered to all the open sockets. An application must have a mechanism to recognize the datagrams of interest and to ignore all others. For a PING program, such a mechanism might include inspecting the received IP header for unique identifiers in the ICMP header (the application's process ID, for example).
NoteTo use a socket of type SOCKRAW requires administrative privileges. Users running Winsock applications that use raw sockets must be a member of the Administrators group on the local computer, otherwise raw socket calls will fail with an error code of. On Windows Vista and later, access for raw sockets is enforced at socket creation.
In earlier versions of Windows, access for raw sockets is enforced during other socket operations.Common Uses of Raw SocketsOne common use of raw sockets are troubleshooting applications that need to examine IP packets and headers in detail. For example, a raw socket can be used with the SIORCVALL IOCTL to enable a socket to receive all IPv4 or IPv6 packets passing through a network interface.
![]()
For more information, see the reference. Limitations on Raw SocketsOn Windows 7, Windows Vista, Windows XP with Service Pack 2 (SP2), and Windows XP with Service Pack 3 (SP3), the ability to send traffic over raw sockets has been restricted in several ways:.TCP data cannot be sent over raw sockets.UDP datagrams with an invalid source address cannot be sent over raw sockets. The IP source address for any outgoing UDP datagram must exist on a network interface or the datagram is dropped. This change was made to limit the ability of malicious code to create distributed denial-of-service attacks and limits the ability to send spoofed packets (TCP/IP packets with a forged source IP address).A call to the function with a raw socket for the IPPROTOTCP protocol is not allowed. NoteThe Microsoft implementation of TCP/IP on Windows is capable of opening a raw UDP or TCP socket based on the above restrictions. Other Winsock providers may not support the use of raw sockets.There are further limitations for applications that use a socket of type SOCKRAW.
For example, all applications listening for a specific protocol will receive all packets received for this protocol. This may not be what is desired for multiple applications using a protocol. This is also not suitable for high-performance applications. To get around these issues, it may be required to write a Windows network protocol driver (device driver) for the specific network protocol. On Windows Vista and later, Winsock Kernel (WSK), a new transport-independent kernel mode Network Programming Interface can be used to write a network protocol driver.
On Windows Server 2003 and earlier, a Transport Driver Interface (TDI) provider and a Winsock helper DLL can be written to support the network protocol. The network protocol would then be added to the Winsock catalog as a supported protocol. This allows multiple applications to open sockets for this specific protocol and the device driver can keep track of which socket receives specific packets and errors. For information on writing a network protocol provider, see the sections on WSK and TDI in the Windows Driver Kit (WDK).Applications also need to be aware of the impact that firewall settings may have on sending and receiving packets using raw sockets.
Comments are closed.
|
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |