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icmp4.cpp
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icmp4.cpp
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// (C) 2020-2024 by folkert van heusden <[email protected]>, released under Apache License v2.0
#include <chrono>
#include <bsd/sys/time.h>
#include "icmp4.h"
#include "ipv4.h"
#include "log.h"
#include "time.h"
#include "utils.h"
icmp4::icmp4(stats *const s, const int n_threads) : icmp(s)
{
icmp_requests = s->register_stat("icmp_requests");
icmp_req_ping = s->register_stat("icmp_req_ping");
icmp_transmit = s->register_stat("icmp_transmit");
for(int i=0; i<n_threads; i++)
ths.push_back(new std::thread(std::ref(*this)));
}
icmp4::~icmp4()
{
pkts->interrupt();
for(auto & th : ths) {
th->join();
delete th;
}
}
void icmp4::operator()()
{
set_thread_name("myip-icmp4");
for(;;) {
auto po = pkts->get();
if (!po.has_value())
break;
const packet *pkt = po.value();
const uint8_t *const p = pkt->get_data();
const int size = pkt->get_size();
if (size < 8) {
DOLOG(ll_debug, "ICMP: not a valid packet (too small (%d bytes))\n", size);
delete pkt;
continue;
}
stats_inc_counter(icmp_requests);
const any_addr src_ip = pkt->get_src_addr();
DOLOG(ll_debug, "ICMP: request %d/%d by %s\n", p[0], p[1], src_ip.to_str().c_str());
uint8_t *reply = duplicate(p, size);
if (p[0] == 8) { // echo request
stats_inc_counter(icmp_req_ping);
reply[0] = 0; // echo reply
}
else if (p[0] == 13) { // timestamp request
if (size >= 20) {
reply[0] = 14; // timestamp reply
uint32_t reply_ts = ms_since_midnight();
reply[12] = reply[16] = reply_ts >> 24;
reply[13] = reply[17] = reply_ts >> 16;
reply[14] = reply[18] = reply_ts >> 8;
reply[15] = reply[19] = reply_ts;
}
else {
DOLOG(ll_debug, "ICMP: timestamp request has invalid size (%d)\n", size);
}
}
else {
DOLOG(ll_debug, "ICMP: dropping packet (type %d code %d)\n", p[0], p[1]);
delete pkt;
delete [] reply;
continue;
}
if (idev) {
auto header = pkt->get_header();
uint8_t *header_copy = duplicate(header.first, header.second);
uint16_t identification = ((header_copy[4] << 8) | header_copy[5]) + 1;
header_copy[4] = identification >> 8;
header_copy[5] = identification;
reply[2] = reply[3] = 0;
uint16_t checksum = ip_checksum(reinterpret_cast<const uint16_t *>(reply), size / 2);
reply[2] = checksum >> 8;
reply[3] = checksum;
timespec now_ts { 0, 0 };
if (clock_gettime(CLOCK_REALTIME, &now_ts) == -1)
DOLOG(ll_warning, "clock_gettime failed: %s", strerror(errno));
else {
timespec in_ts = pkt->get_recv_ts();
timespec diff { 0, 0 };
timespecsub(&now_ts, &in_ts, &diff);
int32_t tdiff = diff.tv_sec * 1000000 + diff.tv_nsec / 1000;
DOLOG(ll_debug, "ICMP: sending response after %dus\n", tdiff);
}
// this is the correct order! sending a reply!
idev->transmit_packet({ }, src_ip, pkt->get_dst_addr(), 0x01, reply, size, header_copy);
delete [] header_copy;
}
delete [] reply;
delete pkt;
}
}
void icmp4::send_packet(const any_addr & dst_ip, const any_addr & src_ip, const uint8_t type, const uint8_t code, const packet *const p) const
{
if (!idev)
return;
stats_inc_counter(icmp_transmit);
uint8_t *out = new uint8_t[576]();
out[0] = type;
out[1] = code;
out[2] = out[3] = 0; // checksum
out[4] = out[5] = 0; // unused
int mtu = idev->get_max_packet_size();
out[6] = mtu >> 8; // next hop MTU
out[7] = mtu & 255;
auto org_header = p->get_header();
auto org_payload = p->get_payload();
memcpy(&out[8], org_header.first, org_header.second);
int pl_size = std::min(8, org_payload.second);
memcpy(&out[8 + org_header.second], org_payload.first, pl_size);
int out_size = 8 + org_header.second + pl_size;
out_size += out_size & 1;
uint16_t checksum = ip_checksum((const uint16_t *)out, (out_size + 1) / 2);
out[2] = checksum >> 8;
out[3] = checksum;
idev->transmit_packet({ }, dst_ip, src_ip, 0x01, out, out_size, nullptr);
delete [] out;
}
void icmp4::send_destination_port_unreachable(const any_addr & dst_ip, const any_addr & src_ip, const packet *const p) const
{
send_packet(dst_ip, src_ip, 3, 3, p);
}
void icmp4::send_ttl_exceeded(const packet *const pkt) const
{
send_packet(pkt->get_src_addr(), pkt->get_dst_addr(), 11, 0, pkt);
}