icmp.c

Go to the documentation of this file.

#include "icmp.h"
#include "libk/serial.h"
#include <str.h>
#include "net/ethernet.h"
#include "net/ip_type.h"
#include "net/ipv4.h"
#include "net/netbuff.h"
#include "net/socket.h"
#include "netutils.h"
 
void handle_icmp(netdev_t* dev, struct ipv4_header* ip, uint8_t mac_dst[6]) {
 
    uint8_t ihl = ip->version_ihl & 0x0F;
    uint16_t ip_hdr_len = ihl * 4;
 
    uint16_t total_len = vxNtohs(ip->total_length);
    if (total_len < ip_hdr_len + 8)
        return; // minimal ICMP
 
    struct icmp_header* icmp =
        (struct icmp_header*) ((uint8_t*) ip + ip_hdr_len);
 
    uint16_t icmp_len = total_len - ip_hdr_len;
 
    // echo request
    char ip_buf[16];
    vxInetNtoa(ip->src_ip, ip_buf);
 
    uint16_t frag_field = vxNtohs(ip->flags_fragment);
 
    // 1. Cek bit "More Fragments" (MF)
    // Bit ini ada di posisi 0x2000
    bool has_more_fragments = (frag_field & 0x2000);
 
    // 2. Cek "Fragment Offset"
    // Offset ada di 13 bit bawah (0x1FFF)
    uint16_t fragment_offset = (frag_field & 0x1FFF);
 
    if (has_more_fragments || fragment_offset > 0) {
        LOG2_WARN("ICMP", "packet ini terfragmentasi");
        // TODO: handle reassembly untuk packet besar
        return;
    }
 
    if (icmp->type == 8) {
        auto nb = create_netbuff();
 
        // Alokasi space untuk ICMP payload + header
        struct icmp_echo* icmp_reply =
            (struct icmp_echo*) netbuff_put(nb, icmp_len);
 
        // Copy data dari ICMP request
        memcopy(icmp_reply, icmp, icmp_len);
 
        // Ubah jadi Echo Reply
        icmp_reply->type = 0;
        icmp_reply->checksum = 0;
        icmp_reply->checksum = checksum16_adc(
            (uint16_t*) (void*) icmp_reply, icmp_len);
 
        // Kirim ke layer IP
        ipv4_send(dev, nb, ip->src_ip, 1,
              mac_dst); // 1 adalah protokol ICMP
 
        free_netbuff(nb);
    }
}