raw-sockets

I am studying raw sockets. I used the IP_HDRINCL option to build my own IP headers. After the IP header, I am building a UDP header. Then I am sending the packet to my system's loopback address. I have another program running which will catch the UDP packets as they come. To check whether the packets are being correctly formed and received, I have another process running which is reading raw IP datagrams. My problem is that although the second process(reading raw datagrams) is working well(all the IP and UDP fields seem to be okay), but the first process(receiving UDP) is not receiving any of

I'm trying to write a program that receives DHCP discoveries (UDP) and forwards them on to a given IP address using a different source IP address depending on the content of a specific field (GIADDR) in the DHCP packet. I could get working the receiving and sending bit but I'm having an issue with using as IP source address anything that is not a configured IP address on the local machine. I believe that this can only be done using Raw sockets; is that true ? Are there any examples out there on how to do that in Go ? I've spent a couple of days looking around but could not find much. Cheers,

I'm trying to get accurate timestamps for outgoing packets (sent using raw sockets). According to Linux/Documentation/networking/timestamping.txt , "For send time stamps the outgoing packet is looped back to the socket's error queue with the send time stamp(s) attached. It can be received with recvmsg(flags=MSG_ERRQUEUE).". Unfortunately, recvmsg is always returning -1 when called on a raw socket (created with socket(PF_INET, SOCK_RAW, IPPROTO_RAW) and with SO_TIMESTAMP set to 1 with setsockopt ). What am I doing wrong? Is there a better way of getting an accurate timestamp for an outgoing

Please any one could help on this issue. Please In the below sample code,we had bind raw sock with eth0. but while running the program the recvfrom of raw sock is receiving packets from eth0 & eth1 on same machine(xx_86). It is not clear to me why,could help one on this issue. I hope the setsockopt is not working properly OS: Fedora core 6(2.6.18-1.2798.fc6) Sampe code: #include <stdio.h> #include <stdlib.h> #include <errno.h> #include <unistd.h> #include <sys/socket.h> #include <netinet/in.h> #include <linux/if_ether.h> #include <net/if.h> #include <linux/filter.h> #include <sys/ioctl.h>

I have been having trouble doing the checksum for TCP for several days now. I have looked at many sources on the Internet but none of the examples that I have seen show you how to do the TCP checksum. I have also looked at the RFC document and still I am having trouble: Below is the code I am using to generate the checksum: unsigned short checksum(unsigned short * buffer, int bytes) { unsigned long sum = 0; unsigned short answer = 0; int i = bytes; while(i>0) { sum+=*buffer; buffer+=1; i-=2; } sum = (sum >> 16) + (sum & htonl(0x0000ffff)); sum += (sum >> 16); return ~sum; } This function works

My application is running on CentOS 5.5. I'm using raw socket to send data: sd = socket(AF_INET, SOCK_RAW, IPPROTO_RAW); if (sd < 0) { // Error } const int opt_on = 1; rc = setsockopt(m_SocketDescriptor, IPPROTO_IP, IP_HDRINCL, &opt_on, sizeof(opt_on)); if (rc < 0) { close(sd); // Error } struct sockaddr_in sin; memset(&sin, 0, sizeof(sin)); sin.sin_family = AF_INET; sin.sin_addr.s_addr = my_ip_address; if (sendto(m_SocketDescriptor, DataBuffer, (size_t)TotalSize, 0, (struct sockaddr *)&sin, sizeof(struct sockaddr)) < 0) { close(sd); // Error } How can I bind this socket to specific network