Linux C raw socket 发送ipv4下的简单udp数据包

问题描述：

在linux下使用C语言和raw socket来简单实现ipv4下的udp数据包的发送

参考资源：

http://www.pdbuchan.com/rawsock/rawsock.html

解决方案：

下面的代码拷贝于"参考资源"中的udp4.c文件。

#include <stdio.h>#include <stdlib.h>#include <unistd.h>           // close()#include <string.h>           // strcpy, memset(), and memcpy()#include <netdb.h>            // struct addrinfo#include <sys/types.h>        // needed for socket(), uint8_t, uint16_t, uint32_t#include <sys/socket.h>       // needed for socket()#include <netinet/in.h>       // IPPROTO_RAW, IPPROTO_IP, IPPROTO_UDP, INET_ADDRSTRLEN#include <netinet/ip.h>       // struct ip and IP_MAXPACKET (which is 65535)#include <netinet/udp.h>      // struct udphdr#include <arpa/inet.h>        // inet_pton() and inet_ntop()#include <sys/ioctl.h>        // macro ioctl is defined#include <bits/ioctls.h>      // defines values for argument "request" of ioctl.#include <net/if.h>           // struct ifreq#include <errno.h>            // errno, perror()// Define some constants.#define IP4_HDRLEN 20         // IPv4 header length#define UDP_HDRLEN  8         // UDP header length, excludes data// Function prototypesuint16_t checksum (uint16_t *, int);uint16_t udp4_checksum (struct ip, struct udphdr, uint8_t *, int);char *allocate_strmem (int);uint8_t *allocate_ustrmem (int);int *allocate_intmem (int);intmain (int argc, char **argv){  int status, datalen, sd, *ip_flags;  const int on = 1;  char *interface, *target, *src_ip, *dst_ip;  struct ip iphdr;  struct udphdr udphdr;  uint8_t *data, *packet;  struct addrinfo hints, *res;  struct sockaddr_in *ipv4, sin;  struct ifreq ifr;  void *tmp;  // Allocate memory for various arrays.  data = allocate_ustrmem (IP_MAXPACKET);  packet = allocate_ustrmem (IP_MAXPACKET);  interface = allocate_strmem (40);  target = allocate_strmem (40);  src_ip = allocate_strmem (INET_ADDRSTRLEN);  dst_ip = allocate_strmem (INET_ADDRSTRLEN);  ip_flags = allocate_intmem (4);  // Interface to send packet through.  //-指定需要发送数据的网卡接口  strcpy (interface, "eth0");  // Submit request for a socket descriptor to look up interface.  if ((sd = socket (AF_INET, SOCK_RAW, IPPROTO_RAW)) < 0) {    perror ("socket() failed to get socket descriptor for using ioctl() ");    exit (EXIT_FAILURE);  }  // Use ioctl() to look up interface index which we will use to  // bind socket descriptor sd to specified interface with setsockopt() since  // none of the other arguments of sendto() specify which interface to use.  memset (&ifr, 0, sizeof (ifr));  snprintf (ifr.ifr_name, sizeof (ifr.ifr_name), "%s", interface);  if (ioctl (sd, SIOCGIFINDEX, &ifr) < 0) {    perror ("ioctl() failed to find interface ");    return (EXIT_FAILURE);  }  close (sd);  printf ("Index for interface %s is %i\n", interface, ifr.ifr_ifindex);  // Source IPv4 address: you need to fill this out  //-指定IP的源地址  strcpy (src_ip, "192.168.1.132");  // Destination URL or IPv4 address: you need to fill this out  //-指定IP的目的地址  strcpy (target, "www.google.com");  // Fill out hints for getaddrinfo().  memset (&hints, 0, sizeof (struct addrinfo));  hints.ai_family = AF_INET;  hints.ai_socktype = SOCK_STREAM;  hints.ai_flags = hints.ai_flags | AI_CANONNAME;  // Resolve target using getaddrinfo().  if ((status = getaddrinfo (target, NULL, &hints, &res)) != 0) {    fprintf (stderr, "getaddrinfo() failed: %s\n", gai_strerror (status));    exit (EXIT_FAILURE);  }    ipv4 = (struct sockaddr_in *) res->ai_addr;  tmp = &(ipv4->sin_addr);  if (inet_ntop (AF_INET, tmp, dst_ip, INET_ADDRSTRLEN) == NULL) {    status = errno;    fprintf (stderr, "inet_ntop() failed.\nError message: %s", strerror (status));    exit (EXIT_FAILURE);  }  freeaddrinfo (res);  // UDP data  // 构造UDP的数据  datalen = 4;  data[0] = 'T';  data[1] = 'e';  data[2] = 's';  data[3] = 't';  // IPv4 header  // 构造ip报文  // IPv4 header length (4 bits): Number of 32-bit words in header = 5  iphdr.ip_hl = IP4_HDRLEN / sizeof (uint32_t);  // Internet Protocol version (4 bits): IPv4  iphdr.ip_v = 4;  // Type of service (8 bits)  iphdr.ip_tos = 0;  // Total length of datagram (16 bits): IP header + UDP header + datalen  iphdr.ip_len = htons (IP4_HDRLEN + UDP_HDRLEN + datalen);  // ID sequence number (16 bits): unused, since single datagram  iphdr.ip_id = htons (0);  // Flags, and Fragmentation offset (3, 13 bits): 0 since single datagram  // Zero (1 bit)  ip_flags[0] = 0;  // Do not fragment flag (1 bit)  ip_flags[1] = 0;  // More fragments following flag (1 bit)  ip_flags[2] = 0;  // Fragmentation offset (13 bits)  ip_flags[3] = 0;  iphdr.ip_off = htons ((ip_flags[0] << 15)                      + (ip_flags[1] << 14)                      + (ip_flags[2] << 13)                      +  ip_flags[3]);  // Time-to-Live (8 bits): default to maximum value  iphdr.ip_ttl = 255;  // Transport layer protocol (8 bits): 17 for UDP  iphdr.ip_p = IPPROTO_UDP;  // Source IPv4 address (32 bits)  if ((status = inet_pton (AF_INET, src_ip, &(iphdr.ip_src))) != 1) {    fprintf (stderr, "inet_pton() failed.\nError message: %s", strerror (status));    exit (EXIT_FAILURE);  }  // Destination IPv4 address (32 bits)  if ((status = inet_pton (AF_INET, dst_ip, &(iphdr.ip_dst))) != 1) {    fprintf (stderr, "inet_pton() failed.\nError message: %s", strerror (status));    exit (EXIT_FAILURE);  }  // IPv4 header checksum (16 bits): set to 0 when calculating checksum  iphdr.ip_sum = 0;  iphdr.ip_sum = checksum ((uint16_t *) &iphdr, IP4_HDRLEN);  // UDP header  // Source port number (16 bits): pick a number  //指定UDP报文源端口  udphdr.source = htons (4950);  // Destination port number (16 bits): pick a number  //指定UDP报文的目的端口  udphdr.dest = htons (4950);  // Length of UDP datagram (16 bits): UDP header + UDP data  udphdr.len = htons (UDP_HDRLEN + datalen);  // UDP checksum (16 bits)  udphdr.check = udp4_checksum (iphdr, udphdr, data, datalen);  // Prepare packet.  // First part is an IPv4 header.  memcpy (packet, &iphdr, IP4_HDRLEN * sizeof (uint8_t));  // Next part of packet is upper layer protocol header.  memcpy ((packet + IP4_HDRLEN), &udphdr, UDP_HDRLEN * sizeof (uint8_t));  // Finally, add the UDP data.  memcpy (packet + IP4_HDRLEN + UDP_HDRLEN, data, datalen * sizeof (uint8_t));  // The kernel is going to prepare layer 2 information (ethernet frame header) for us.  // For that, we need to specify a destination for the kernel in order for it  // to decide where to send the raw datagram. We fill in a struct in_addr with  // the desired destination IP address, and pass this structure to the sendto() function.  memset (&sin, 0, sizeof (struct sockaddr_in));  sin.sin_family = AF_INET;  sin.sin_addr.s_addr = iphdr.ip_dst.s_addr;  // Submit request for a raw socket descriptor.  if ((sd = socket (AF_INET, SOCK_RAW, IPPROTO_RAW)) < 0) {    perror ("socket() failed ");    exit (EXIT_FAILURE);  }  // Set flag so socket expects us to provide IPv4 header.  if (setsockopt (sd, IPPROTO_IP, IP_HDRINCL, &on, sizeof (on)) < 0) {    perror ("setsockopt() failed to set IP_HDRINCL ");    exit (EXIT_FAILURE);  }  // Bind socket to interface index.  if (setsockopt (sd, SOL_SOCKET, SO_BINDTODEVICE, &ifr, sizeof (ifr)) < 0) {    perror ("setsockopt() failed to bind to interface ");    exit (EXIT_FAILURE);  }  // Send packet.  if (sendto (sd, packet, IP4_HDRLEN + UDP_HDRLEN + datalen, 0, (struct sockaddr *) &sin, sizeof (struct sockaddr)) < 0)  {    perror ("sendto() failed ");    exit (EXIT_FAILURE);  }  // Close socket descriptor.  close (sd);  // Free allocated memory.  free (data);  free (packet);  free (interface);  free (target);  free (src_ip);  free (dst_ip);  free (ip_flags);  return (EXIT_SUCCESS);}// Checksum functionuint16_tchecksum (uint16_t *addr, int len){  int nleft = len;  int sum = 0;  uint16_t *w = addr;  uint16_t answer = 0;  while (nleft > 1) {    sum += *w++;    nleft -= sizeof (uint16_t);  }  if (nleft == 1) {    *(uint8_t *) (&answer) = *(uint8_t *) w;    sum += answer;  }  sum = (sum >> 16) + (sum & 0xFFFF);  sum += (sum >> 16);  answer = ~sum;  return (answer);}// Build IPv4 UDP pseudo-header and call checksum function.uint16_tudp4_checksum (struct ip iphdr, struct udphdr udphdr, uint8_t *payload, int payloadlen){  char buf[IP_MAXPACKET];  char *ptr;  int chksumlen = 0;  int i;  ptr = &buf[0];  // ptr points to beginning of buffer buf  // Copy source IP address into buf (32 bits)  memcpy (ptr, &iphdr.ip_src.s_addr, sizeof (iphdr.ip_src.s_addr));  ptr += sizeof (iphdr.ip_src.s_addr);  chksumlen += sizeof (iphdr.ip_src.s_addr);  // Copy destination IP address into buf (32 bits)  memcpy (ptr, &iphdr.ip_dst.s_addr, sizeof (iphdr.ip_dst.s_addr));  ptr += sizeof (iphdr.ip_dst.s_addr);  chksumlen += sizeof (iphdr.ip_dst.s_addr);  // Copy zero field to buf (8 bits)  *ptr = 0; ptr++;  chksumlen += 1;  // Copy transport layer protocol to buf (8 bits)  memcpy (ptr, &iphdr.ip_p, sizeof (iphdr.ip_p));  ptr += sizeof (iphdr.ip_p);  chksumlen += sizeof (iphdr.ip_p);  // Copy UDP length to buf (16 bits)  memcpy (ptr, &udphdr.len, sizeof (udphdr.len));  ptr += sizeof (udphdr.len);  chksumlen += sizeof (udphdr.len);  // Copy UDP source port to buf (16 bits)  memcpy (ptr, &udphdr.source, sizeof (udphdr.source));  ptr += sizeof (udphdr.source);  chksumlen += sizeof (udphdr.source);  // Copy UDP destination port to buf (16 bits)  memcpy (ptr, &udphdr.dest, sizeof (udphdr.dest));  ptr += sizeof (udphdr.dest);  chksumlen += sizeof (udphdr.dest);  // Copy UDP length again to buf (16 bits)  memcpy (ptr, &udphdr.len, sizeof (udphdr.len));  ptr += sizeof (udphdr.len);  chksumlen += sizeof (udphdr.len);  // Copy UDP checksum to buf (16 bits)  // Zero, since we don't know it yet  *ptr = 0; ptr++;  *ptr = 0; ptr++;  chksumlen += 2;  // Copy payload to buf  memcpy (ptr, payload, payloadlen);  ptr += payloadlen;  chksumlen += payloadlen;  // Pad to the next 16-bit boundary  for (i=0; i<payloadlen%2; i++, ptr++) {    *ptr = 0;    ptr++;    chksumlen++;  }  return checksum ((uint16_t *) buf, chksumlen);}// Allocate memory for an array of chars.char *allocate_strmem (int len){  void *tmp;  if (len <= 0) {    fprintf (stderr, "ERROR: Cannot allocate memory because len = %i in allocate_strmem().\n", len);    exit (EXIT_FAILURE);  }  tmp = (char *) malloc (len * sizeof (char));  if (tmp != NULL) {    memset (tmp, 0, len * sizeof (char));    return (tmp);  } else {    fprintf (stderr, "ERROR: Cannot allocate memory for array allocate_strmem().\n");    exit (EXIT_FAILURE);  }}// Allocate memory for an array of unsigned chars.uint8_t *allocate_ustrmem (int len){  void *tmp;  if (len <= 0) {    fprintf (stderr, "ERROR: Cannot allocate memory because len = %i in allocate_ustrmem().\n", len);    exit (EXIT_FAILURE);  }  tmp = (uint8_t *) malloc (len * sizeof (uint8_t));  if (tmp != NULL) {    memset (tmp, 0, len * sizeof (uint8_t));    return (tmp);  } else {    fprintf (stderr, "ERROR: Cannot allocate memory for array allocate_ustrmem().\n");    exit (EXIT_FAILURE);  }}// Allocate memory for an array of ints.int *allocate_intmem (int len){  void *tmp;  if (len <= 0) {    fprintf (stderr, "ERROR: Cannot allocate memory because len = %i in allocate_intmem().\n", len);    exit (EXIT_FAILURE);  }  tmp = (int *) malloc (len * sizeof (int));  if (tmp != NULL) {    memset (tmp, 0, len * sizeof (int));    return (tmp);  } else {    fprintf (stderr, "ERROR: Cannot allocate memory for array allocate_intmem().\n");    exit (EXIT_FAILURE);  }}

补充：

在"参考资源"中有很多raw socket相关的例子(tcp,ipv6,udp6,tcp6...)