rtes_messenger/src/client.c

/*!
 * \file client.c
 *
 * \author Christos Choutouridis AEM:8997 <cchoutou@ece.auth.gr>
 */

#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/ip_icmp.h>
#include <sys/time.h>
#include <unistd.h>
#include <string.h>
#include <stdio.h>

#include "client.h"


// Calculating the Check Sum
static unsigned short _checksum(void *b, int len) {
   unsigned short *buf = b;
   unsigned int sum=0;
   unsigned short result;

   for ( sum = 0; len > 1; len -= 2 )
      sum += *buf++;
   if ( len == 1 )
      sum += *(unsigned char*)buf;
   sum = (sum >> 16) + (sum & 0xFFFF);
   sum += (sum >> 16);
   result = ~sum;
   return result;
}

static void _mk_ping_pkt (ping_pkt_t* pkt) {
   memset ((void*)&pkt->hdr, 0, sizeof(pkt->hdr));
   //memset ((void*)&pkt->msg, '0', sizeof(pkt->msg));
   pkt->msg[PING_MSG_S -1] = 0;

   pkt->hdr.type = ICMP_ECHO;
   pkt->hdr.un.echo.id = getpid();
   pkt->hdr.un.echo.sequence = 0;
   pkt->hdr.checksum = _checksum (&pkt, sizeof(pkt));
}

bool ping (device_t* dev) {
   static int sockfd =-1;
   int ttl_val =64;
   struct timeval tv_out = { 1, 0 };


   if (sockfd == -1 && dev) {
      // create socket  and set options at ip to TTL and value to 64 and timeout of recv
      if ((sockfd = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP)) == -1) {
         log_error ("Error: Can not create raw socket for icmp\n");
         return false;
      }
      #ifndef NO_DEBUG
         log_debug("Debug: Raw socket for icmp created\n");
      #endif
      int ret  = setsockopt(sockfd, SOL_IP, IP_TTL, &ttl_val, sizeof(ttl_val));
          ret |= setsockopt(sockfd, SOL_SOCKET, SO_RCVTIMEO, (const char*)&tv_out, sizeof(tv_out));
      if (ret == -1) {
         log_error ("Error: Can not set options to socket\n");
         close (sockfd);
         sockfd =-1;
         return false;
      }
      #ifndef NO_DEBUG
         log_debug("Debug: Raw socket options set\n");
      #endif
   }

   if (!dev) {
      // Close socket
      close (sockfd);
      sockfd =-1;
      #ifndef NO_DEBUG
         log_debug ("Debug: Raw socket closed\n");
      #endif
      return true;
   }
   else {
      // ping packet structure
      ping_pkt_t pkt;
      _mk_ping_pkt (&pkt);
      int st;

      //send packet
      struct sockaddr_in ping_addr = {
         .sin_family = AF_INET,
         .sin_addr = { htonl (device2addr (dev)) }
      };
      if ((st=sendto (sockfd, &pkt, sizeof(pkt), 0, (struct sockaddr*)&ping_addr, sizeof(ping_addr))) <= 0)
          return false;
      #ifndef NO_DEBUG
         log_debug ("Debug: Echo send to %s\n", inet_ntoa(ping_addr.sin_addr));
      #endif
      //receive packet
      struct sockaddr_in r_addr;
      socklen_t addr_len =sizeof(r_addr);
      if ((st=recvfrom (sockfd, &pkt, sizeof(pkt), 0, (struct sockaddr*)&r_addr, &addr_len)) <= 0)
          return false;
      #ifndef NO_DEBUG
         log_debug ("Debug: Echo received from %s\n", inet_ntoa(ping_addr.sin_addr));
      #endif
      return (pkt.hdr.type == 69 && pkt.hdr.code == 0) ? true: false;
   }
   return false;
}