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#include <assert.h>
#include <drivers/pit.h>
#include <kmalloc.h>
#include <network/arp.h>
#include <network/bytes.h>
#include <network/ethernet.h>
#include <network/ipv4.h>
#include <network/tcp.h>
#include <network/udp.h>
#include <string.h>
static u16 ip_checksum(const u16 *data, u16 length) {
// Initialise the accumulator.
u32 acc = 0xffff;
// Handle complete 16-bit blocks.
for (size_t i = 0; i < length / 2; i++) {
u16 word = *(data + i);
acc += ntohs(word);
if (acc > 0xffff) {
acc -= 0xffff;
}
}
// Return the checksum in network byte order.
return htons(~acc);
}
u8 ipv4_buffer[0x1000];
void send_ipv4_packet(ipv4_t ip, u8 protocol, const u8 *payload, u16 length) {
u16 header[10];
header[0] = (4 /*version*/ << 4) | (5 /*IHL*/);
header[1] = htons(length + 20);
header[2] = 0;
header[3] = 0;
header[4] = (protocol << 8) | 0xF8;
header[5] = 0;
header[6] = (ip_address.d >> 0) & 0xFFFF;
header[7] = (ip_address.d >> 16) & 0xFFFF;
header[8] = (ip.d >> 0) & 0xFFFF;
header[9] = (ip.d >> 16) & 0xFFFF;
header[5] = ip_checksum(header, 20);
u16 packet_length = length + 20;
assert(packet_length < sizeof(ipv4_buffer));
u8 *packet = ipv4_buffer;
memcpy(packet, header, 20);
memcpy(packet + 20, payload, length);
u8 mac[6];
for (; !get_mac_from_ip(ip, mac);)
;
send_ethernet_packet(mac, 0x0800, packet, packet_length);
}
void handle_ipv4(const u8 *payload, u32 packet_length) {
assert(packet_length > 4);
u16 saved_checksum = *(u16 *)(payload + 10);
*(u16 *)(payload + 10) = 0;
u16 calc_checksum = ip_checksum((const u16 *)payload, 20);
*(u16 *)(payload + 10) = saved_checksum;
if (calc_checksum != saved_checksum) {
klog(LOG_WARN, "Invalid ipv4 checksum");
return;
}
u8 version = (*payload & 0xF0) >> 4;
u8 IHL = (*payload & 0xF);
assert(4 == version);
assert(5 == IHL);
u16 ipv4_total_length = ntohs(*(u16 *)(payload + 2));
assert(ipv4_total_length >= 20);
// Make sure the ipv4 header is not trying to get uninitalized memory
assert(ipv4_total_length <= packet_length);
ipv4_t src_ip;
memcpy(&src_ip.d, payload + 12, sizeof(u8[4]));
ipv4_t dst_ip;
memcpy(&dst_ip.d, payload + 16, sizeof(u8[4]));
u8 protocol = *(payload + 9);
switch (protocol) {
case 0x6:
handle_tcp(src_ip, dst_ip, payload + 20, ipv4_total_length - 20);
break;
case 0x11:
handle_udp(src_ip, dst_ip, payload + 20, ipv4_total_length - 20);
break;
default:
kprintf("Protocol given in IPv4 header not handeld: %x\n", protocol);
break;
}
}
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