tcp lab almost finished and mitnick lab initialized

Tcp/Labsetup/volumes/sniffer.c

@@ -0,0 +1,52 @@
+#include <pcap.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <arpa/inet.h>
+
+struct ipheader {
+  unsigned char      iph_ihl:4, iph_ver:4;
+  unsigned char      iph_tos;
+  unsigned short int iph_len;
+  unsigned short int iph_ident;
+  unsigned short int iph_flag:3, iph_offset:13;
+  unsigned char      iph_ttl;
+  unsigned char      iph_protocol;
+  unsigned short int iph_chksum;
+  struct  in_addr    iph_sourceip;
+  struct  in_addr    iph_destip;
+};
+
+void got_packet(u_char *args, const struct pcap_pkthdr *header, const u_char *packet)
+{
+  struct ipheader *ip = (struct ipheader *)(packet + 14); // Skip ethernet header
+  printf("Got a packet\n");
+  printf("   From: %s\n", inet_ntoa(ip->iph_sourceip));
+  printf("     To: %s\n", inet_ntoa(ip->iph_destip));
+  fflush(stdout);
+}
+
+int main()
+{
+  pcap_t *handle;
+  char errbuf[PCAP_ERRBUF_SIZE];
+  struct bpf_program fp;
+  char filter_exp[] = "icmp";
+  bpf_u_int32 net;
+
+  // Change interface name to the correct one
+  handle = pcap_open_live("br-603d3788c443", BUFSIZ, 1, 1000, errbuf);
+  if (handle == NULL) {
+      fprintf(stderr, "Couldn't open device: %s\n", errbuf);
+      return 2;
+  }
+
+  pcap_compile(handle, &fp, filter_exp, 0, net);
+  if (pcap_setfilter(handle, &fp) != 0) {
+      pcap_perror(handle, "Error:");
+      exit(EXIT_FAILURE);
+  }
+
+  pcap_loop(handle, -1, got_packet, NULL);
+  pcap_close(handle);
+  return 0;
+}