feat: added basic tcp, udp and icmp handling

.vscode/settings.json

@@ -0,0 +1,13 @@
+{
+    "files.associations": {
+        "ip_icmp.h": "c",
+        "tcp.h": "c",
+        "features-time64.h": "c",
+        "packet.h": "c",
+        "types.h": "c",
+        "socket.h": "c",
+        "stdint.h": "c",
+        "cstdint": "c",
+        "stdio.h": "c"
+    }
+}

npcap.c

@@ -1,11 +1,13 @@
 //
 // Created by ako on 8/22/25.
 //
+#define _GNU_SOURCE
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
 #include <sys/socket.h>
+#include <netinet/in.h>
 #include <arpa/inet.h>
 #include <netinet/ip.h>
 #include <netinet/if_ether.h>
@@ -15,7 +17,10 @@
 #include "nethdr.h"
 #include "npcap_handle.h"
 #include <netpacket/packet.h>
-#include <net/if.h> // if_nametoindex()
+#include <net/if.h>
+#include <netinet/ip_icmp.h>
+#include <netinet/tcp.h>
+#include <netinet/udp.h>
 
 void cleanup(int socket, unsigned char* buffer) {
     close(socket);
@@ -103,13 +108,16 @@ int main()
 
                 switch (ip->protocol) {
                     case 0x01:
-                        handle_icmp();
+                        struct icmphdr *icmp = (struct icmphdr *) (buffer + sizeof(struct ethhdr) + ip->ihl * 4);
+                        handle_icmp(icmp);
                         break;
                     case 0x06:
-                        handle_tcp();
+                        struct tcphdr *tcp = (struct tcphdr *) (buffer + sizeof(struct ethhdr) + ip->ihl * 4);
+                        handle_tcp(tcp);
                         break;
                     case 0x11:
-                        handle_udp();
+                        struct udphdr *udp = (struct udphdr *) (buffer + sizeof(struct ethhdr) + ip->ihl * 4);
+                        handle_udp(udp);
                         break;
                     default:
                         break;

npcap_handle.c

@@ -67,3 +67,41 @@ int handle_ip(struct iphdr* ip) {
     return 0;
 
 }
+
+int handle_icmp(struct icmphdr* icmp) {
+    printf("\n\t\tICMP:\n");
+    printf("\t\t\tType       : %d\n", icmp->type);
+    printf("\t\t\tCode       : %d\n", icmp->code);
+    printf("\t\t\tChecksum   : %d\n", icmp->checksum);
+    return 0;
+}
+
+int handle_tcp(struct tcphdr* tcp) {
+    printf("\n\t\tTCP:\n");
+    printf("\t\t\tPort Source      : %d\n", ntohs(tcp->source));
+    printf("\t\t\tPort Destination : %d\n", ntohs(tcp->dest));
+    printf("\t\t\tSeq Number       : %u\n", ntohl(tcp->seq));
+    printf("\t\t\tAck Number       : %u\n", ntohl(tcp->ack_seq));
+    printf("\t\t\tData Offset      : %d\n", tcp->doff);
+    printf("\t\t\tFlags            : ");
+    if (tcp->urg) printf("URG ");
+    if (tcp->ack) printf("ACK ");
+    if (tcp->psh) printf("PSH ");
+    if (tcp->rst) printf("RST ");
+    if (tcp->syn) printf("SYN ");
+    if (tcp->fin) printf("FIN ");
+    printf("\n");
+    printf("\t\t\tWindow Size      : %d\n", ntohs(tcp->window));
+    printf("\t\t\tChecksum         : %d\n", ntohs(tcp->check));
+    printf("\t\t\tUrgent Pointer   : %d\n", tcp->urg_ptr);
+    return 0;
+}
+
+int handle_udp(struct udphdr* udp) {
+    printf("\n\t\tUDP:\n");
+    printf("\t\t\tPort Source      : %d\n", ntohs(udp->source));
+    printf("\t\t\tPort Destination : %d\n", ntohs(udp->dest));
+    printf("\t\t\tLength           : %d\n", ntohs(udp->len));
+    printf("\t\t\tChecksum         : %d\n", ntohs(udp->check));
+    return 0;
+}

npcap_handle.h

@@ -4,10 +4,17 @@
 #include "nethdr.h"
 #include <stdio.h>
 #include <arpa/inet.h>
+#include <netinet/in.h>
 #include <netinet/ip.h>
+#include <netinet/ip_icmp.h>
+#include <netinet/tcp.h>
+#include <netinet/udp.h>
 
 int handle_eth(struct ethhdr* eth);
 int handle_arp(struct arphdr_c* arp);
 int handle_ip(struct iphdr* ip);
+int handle_icmp(struct icmphdr* icmp);
+int handle_tcp(struct tcphdr* tcp);
+int handle_udp(struct udphdr* udp);
 
 #endif