I am trying to understand how recvfrom() works in linux.
I opened a raw socket and read ICMP packets on an interface.
What I thought was recvfrom() copies a packet from Kernel to the application.
I tried to read ICMP request packet and clear the buffer and expect I cannot receive ICMP reply.

But it seems I still receive ICMP reply.
Am I misunderstanding the network operation or there is something wrong in the code?
The default ICMP packet size was 98.
So, I have just used the packet length to check whether the packet read is ICMP or not.

What I want to do is receive an ICMP packet from an interface and clear or drop the packet buffer.
And that can actually break ICMP packet exchange or not.

I ran this program on the PC2 from the diagram below.
And send a ICMP packet from PC1 to PC3.

    +-------+       +-------+       +-------+                
    |       |       |       |       |       |
    | PC 1  | ----- | PC 2  | ----- | PC 3  |
    |       |       |       |       |       |  
    +-------+       +-------+       +-------+

int main(int argc, char *argv[])
{
   int32_t sock;
   int8_t buf[1522];
   int32_t ifindex;
   int32_t ret;
   int32_t bytes;
   struct sockaddr_ll sll;
   struct ifreq ifr;
   time_t rawtime;
   struct tm *info;

   time(&rawtime);
   info = localtime(&rawtime);

   sock = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL));
   if (sock == -1)
   {
      printf("socket open failedn");
      return 1;
   }

   strncpy(ifr.ifr_name, "eth1", sizeof(ifr.ifr_name));
   ret = ioctl(sock, SIOCGIFINDEX, &ifr);
   if (ret < 0)
   {
      printf("failed to get indexn");
      return -1;
   }

   sll.sll_family    = AF_PACKET;
   sll.sll_ifindex   = ifr.ifr_ifindex;
   sll.sll_protocol  = htons(ETH_P_ALL);

   ret = bind(sock, (struct sockaddr *)&sll, sizeof(struct sockaddr_ll));
   if (ret < 0)
   {
      close(sock);
      printf("interface binding errorn");
      return 1;
   }

   while(1)
   {
      bytes = recvfrom(sock, buf, 1522, 0, NULL, NULL);
      if (bytes < 0)
      {
         printf("error in recvfromn");
         exit;
      }
      if (bytes == 98)
      {
         memset(buf, 0x0, 1522);
      }
      printf("%s : received bytes = %dn", bytes);
   }

   close(sock);
   return 0;
}