Glad to help. Windows and Linux are very different and usually you need to use different implementations libraries creating 2 versions of your code or 1 version with macros to compile 1 part or another.
Show 2 more comments. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password.
Post as a guest Name. Email Required, but never shown. The Overflow Blog. Podcast Helping communities build their own LTE networks. Podcast Making Agile work for data science.
The field type then decides on the rest of the extra fields. The value of 8 denotes an Echo message and a value of 0 an echo reply. The code field is always 0. The checksum field is the normal internet checksum and its value should be zero before calculating the checksum.
The next two fields id and sequence number share the same role. On sending an echo message, an echo reply is received.
However to match the echo reply message with the echo message, the id and sequence number fields are used which together become a unique id for the packet. The echo reply message copies the values of these fields plus more and then returns the packet. The id field is set to the process id thus making it absolutely unique. However, if more than one echo request packet is sent, the sequence field is changed to a different value each time.
In the echo reply, all these extra bytes are returned back without any change. This helps in validating the packet for any data corruption. Not really needed. The timestamp field is set to the current time and it factors the time taken for the packet to reach and return back. Not part of the protocol. Once the packet is ready, the sendto function is used to send this packet over. The first parameter to this function is the raw socket handle and the second is the bytes to be sent across.
The third is for the number of bytes, whereas the fourth is for options if any. The fifth is the IP address of the site to be visited. The sendto function returns the number of bytes sent. First comes the recvfrom function to accept this message. The recvfrom function returns the number of bytes it has received, which is Thus with raw sockets we can manually look at the IP bytes received. The parameters for the recvfrom and sendto functions are similar.
After the transport layer header, there is data payload remaining. For this, we will move the pointer to the data, and then print. To send a packet, we first have to know the source and destination IP addresses as well as the MAC address. The second way is more efficient and will make your program machine-independent, which means you should not enter ifconfig in each machine.
Linux supports some standard ioctls to configure network devices. They pass an ifreq structure, which means that if you want to know some information about the network, like the interface index or interface name, you can use ioctl and it will fill the value of the ifreq structure passed as a third argument.
In short, the ifreq structure is a way to get and set the network configuration. It is defined in the if. There may be various interfaces in your machine like loopback, wired interface and wireless interface. So you have to decide the interface through which we can send our packet. After deciding on the interface, you have to get the index of that interface.
First, take a buffer in which you will place all information like the Ethernet header, IP header, UDP header and data. That buffer will be your packet.
To construct the IP header, increment sendbuff by the size of the Ethernet header and fill each field of the iphdr structure. Data after the IP header is called the payload for the IP header and, in the same way, data after the Ethernet header is called the payload for the Ethernet header. So, some field of the iphdr structure will get the value after filling the UDP header field. Assign values to the fields of the udphdr structure. For this, increment the sendbuff pointer by the size of the Ethernet and the IP headers.
So, first, you have to know the UDP payload, which is the actual data that will be sent. There is one more field remaining in the IP header check, which is used to have a checksum. A checksum is used for error checking of the header.
When the packet arrives at the router, it calculates the checksum, and if the calculated checksum does not match with the checksum field of the header, the router will drop the packet; and if it matches, the router will decrement the time to the live field by one, and forward it.
To calculate the checksum, sum up all the bit words of the IP header and if there is any carry, add it again to get a bit word. To check whether our checksum is correct, use the above algorithm. NET Framework 4. RawCap cannot capture packets from IPv6 interfaces. This also include the localhost IPv6 interface associated with address Unfortunately the name "localhost" often resolves to rather than Therefore, when trying to capture application traffic on localhost, make sure the monitored application is connecting to " To create an exception, simply follow these steps: Run WF.
0コメント