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vlan and qinq handling, protocol printout

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This commit is contained in:
Matthias Cramer
2025-03-30 15:15:24 +02:00
parent 99fbd6f600
commit a128da1328
1 changed files with 61 additions and 7 deletions
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68
main.c
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@@ -75,6 +75,43 @@ void list_interfaces() {
pcap_freealldevs(alldevs);
}
// Function to lookup protocol name or return protocol number as a string
const char *lookup_protocol_name(int protocol) {
static char buf[5]; // Buffer to hold protocol number as a string
switch (protocol) {
case 1:
return "ICMP";
case 2:
return "IGMP";
case 6:
return "TCP";
case 17:
return "UDP";
case 41:
return "IPv6";
case 47:
return "GRE";
case 50:
return "ESP";
case 51:
return "AH";
case 58:
return "ICMPv6";
case 89:
return "OSPF";
case 112:
return "VRRP";
case 124:
return "ISIS";
case 132:
return "SCTP";
default:
snprintf(buf, sizeof(buf), "%d", protocol); // Convert protocol number to string
return buf;
}
}
void print_usage(const char *program_name) {
printf("Usage: %s [options]\n", program_name);
printf("Options:\n");
@@ -302,30 +339,47 @@ int main(int argc, char *argv[]) {
// Check EtherType
uint16_t ether_type = ntohs(eth_header->ether_type);
int vlan_offset = 0; // Offset for VLAN-tagged packets
// Check for VLAN tags (including Q-in-Q)
while (ether_type == 0x8100 || ether_type == 0x88A8) {
// VLAN tag is present
vlan_offset += 4; // Each VLAN tag adds 4 bytes
uint16_t vlan_tag = ntohs(*(uint16_t *)(packet + ETHERNET_HEADER_LENGTH + vlan_offset - 4));
uint16_t vlan_id = vlan_tag & 0x0FFF; // Extract VLAN ID (12 bits)
uint8_t vlan_pcp = (vlan_tag >> 13) & 0x07; // Extract Priority Code Point (3 bits)
uint8_t vlan_dei = (vlan_tag >> 12) & 0x01; // Extract Drop Eligible Indicator (1 bit)
printf("VLAN Tag: VLAN ID=%d, PCP=%d, DEI=%d\n", vlan_id, vlan_pcp, vlan_dei);
// Update EtherType to the next protocol
ether_type = ntohs(*(uint16_t *)(packet + ETHERNET_HEADER_LENGTH + vlan_offset - 2));
}
if (ether_type == ETHERTYPE_IP) {
// Handle IPv4 traffic
ip_header = (struct ip *)(packet + ETHERNET_HEADER_LENGTH);
ip_header = (struct ip *)(packet + ETHERNET_HEADER_LENGTH + vlan_offset);
ip_protocol = ip_header->ip_v & 0x0F; // Get IP version
if (ip_protocol == 4) {
inet_ntop(AF_INET, &(ip_header->ip_src.s_addr), source_ip_str, INET6_ADDRSTRLEN);
inet_ntop(AF_INET, &(ip_header->ip_dst.s_addr), dest_ip_str, INET6_ADDRSTRLEN);
printf("IPv4 Packet: %s -> %s, IP Protocol: %d\n",
source_ip_str, dest_ip_str, ip_header->ip_p);
printf("IPv4 Packet: %s -> %s, IP Protocol: %s\n",
source_ip_str, dest_ip_str, lookup_protocol_name(ip_header->ip_p));
}
} else if (ether_type == ETHERTYPE_IPV6) {
// Handle IPv6 traffic
ip6_header = (struct ip6_hdr *)(packet + ETHERNET_HEADER_LENGTH);
ip6_header = (struct ip6_hdr *)(packet + ETHERNET_HEADER_LENGTH + vlan_offset);
inet_ntop(AF_INET6, &(ip6_header->ip6_src), source_ip_str, INET6_ADDRSTRLEN);
inet_ntop(AF_INET6, &(ip6_header->ip6_dst), dest_ip_str, INET6_ADDRSTRLEN);
printf("IPv6 Packet: %s -> %s, Next Header: %d\n",
source_ip_str, dest_ip_str, ip6_header->ip6_nxt);
printf("IPv6 Packet: %s -> %s, Next Header: %s\n",
source_ip_str, dest_ip_str, lookup_protocol_name(ip6_header->ip6_nxt));
} else if (ether_type == ETHERTYPE_ARP) {
// Handle ARP traffic
struct arp_header *arp = (struct arp_header *)(packet + ETHERNET_HEADER_LENGTH);
struct arp_header *arp = (struct arp_header *)(packet + ETHERNET_HEADER_LENGTH + vlan_offset);
printf("ARP Packet: Operation: %s\n",
(ntohs(arp->oper) == 1) ? "Request" : "Reply");