pmlag

commit 120ec87fd77624a5c99f6318ac2599dbf0b91261
parent 8f59fc8fe4f7d7cac898f1c1698ce6216f9bc192
Author: Robin Bron <robin@finwo.nl>
Date:   Wed, 27 Apr 2022 20:52:50 +0200

Debug listening on named interface

Diffstat:
M
src/main.c
 | 
103
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

1 file changed, 103 insertions(+), 0 deletions(-)
diff --git a/src/main.c b/src/main.c
@@ -1,3 +1,106 @@
+#include <arpa/inet.h>
+#include <net/ethernet.h>
+#include <net/if.h>
+#include <netinet/ip.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <sys/socket.h>
+
+#include <linux/if_packet.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define INTERFACE "wlp2s0"
+#define ERR_NAME "pmlag"
+
 int main(int argc, char **argv) {
+
+  // Open socket
+  int sockfd = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_ALL));
+  if (sockfd < 0) {
+    perror(ERR_NAME ": socket");
+    exit(EXIT_FAILURE);
+  }
+
+  struct sockaddr_ll sll;
+  struct ifreq ifr;
+  bzero(&sll, sizeof(sll));
+  bzero(&ifr, sizeof(ifr));
+
+  // Get interface index
+  strncpy((char *)ifr.ifr_name, INTERFACE, IFNAMSIZ);
+  if ((ioctl(sockfd, SIOCGIFINDEX, &ifr)) == -1) {
+    perror(ERR_NAME ": Error getting interface index");
+    exit(EXIT_FAILURE);
+  }
+
+  // Bind socket to interface
+  sll.sll_family   = AF_PACKET;
+  sll.sll_ifindex  = ifr.ifr_ifindex;
+  sll.sll_protocol = htons(ETH_P_ALL);
+  if((bind(sockfd, (struct sockaddr *)&sll, sizeof(sll))) == -1) {
+    perror(ERR_NAME ": Error binding raw socket to interface");
+    exit(EXIT_FAILURE);
+  }
+
+  // Prepare ingress buffer
+  int buflen;
+  unsigned char *buffer = (unsigned char *) malloc(65536);
+  memset(buffer, 0, 65536);
+  struct sockaddr saddr;
+  int saddr_len  = sizeof(saddr);
+
+  // Fetch a packet
+  buflen = recvfrom(sockfd, buffer, 65536, 0, &saddr, (socklen_t *)&saddr_len);
+  if (buflen < 0) {
+    perror(ERR_NAME ": recvfrom");
+    exit(EXIT_FAILURE);
+  }
+
+  printf("\n");
+  printf("Got packet: %d bytes\n", buflen);
+  printf("\n");
+
+  struct ethhdr *eth = (struct ethhdr *)(buffer);
+  printf("Ethernet header\n");
+  printf("\t|- DST    %.2X-%.2X-%.2X-%.2X-%.2X-%.2X\n",eth->h_dest[0],eth->h_dest[1],eth->h_dest[2],eth->h_dest[3],eth->h_dest[4],eth->h_dest[5]);
+  printf("\t|- SRC    %.2X-%.2X-%.2X-%.2X-%.2X-%.2X\n",eth->h_source[0],eth->h_source[1],eth->h_source[2],eth->h_source[3],eth->h_source[4],eth->h_source[5]);
+  printf("\t|- PROTO  %d\n",eth->h_proto);
+
+  printf("\n");
+
+  struct sockaddr_in source;
+  struct sockaddr_in dest;
+  if (eth->h_proto == 8) {
+    unsigned short iphdrlen;
+    struct iphdr *ip = (struct iphdr*)(buffer + sizeof(struct ethhdr));
+    memset(&source, 0, sizeof(source));
+    source.sin_addr.s_addr = ip->saddr;
+    memset(&dest, 0, sizeof(dest));
+    dest.sin_addr.s_addr = ip->daddr;
+
+    printf("IP header\n");
+    printf("\t|- Version          %d\n",(unsigned int)ip->version);
+    printf("\t|- Internet hlen    %d DWORDS or %d Bytes\n",(unsigned int)ip->ihl,((unsigned int)(ip->ihl))*4);
+    printf("\t|- Type Of Service  %d\n",(unsigned int)ip->tos);
+    printf("\t|- Total Length     %d Bytes\n",ntohs(ip->tot_len));
+    printf("\t|- Identification   %d\n",ntohs(ip->id));
+    printf("\t|- Time To Live     %d\n",(unsigned int)ip->ttl);
+    printf("\t|- Protocol         %d\n",(unsigned int)ip->protocol);
+    printf("\t|- Header Checksum  %d\n",ntohs(ip->check));
+    printf("\t|- Source IP        %s\n", inet_ntoa(source.sin_addr));
+    printf("\t|- Destination IP   %s\n",inet_ntoa(dest.sin_addr));
+
+    printf("\n");
+  }
+
   return 42;
 }
+
+#ifdef __cplusplus
+} // extern "C"
+#endif