/*
 * ZMap Copyright 2013 Regents of the University of Michigan
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy
 * of the License at http://www.apache.org/licenses/LICENSE-2.0
 */

// probe module for performing ICMP echo request (ping) scans that allows calculation
// of RTT

#include <stdlib.h>
#include <stdio.h>
#include <stdint.h>
#include <time.h>
#include <unistd.h>
#include <string.h>
#include <sys/time.h>

#include "../../lib/includes.h"
#include "probe_modules.h"
#include "../fieldset.h"
#include "packet.h"
#include "validate.h"

#define ICMP_SMALLEST_SIZE 5
#define ICMP_TIMXCEED_UNREACH_HEADER_SIZE 8

probe_module_t module_icmp_echo_time;

struct icmp_payload_for_rtt {
  uint32_t sent_tv_sec;
  uint32_t sent_tv_usec;
  ipaddr_n_t dst;
};

static int icmp_echo_init_perthread(void* buf, macaddr_t *src,
        macaddr_t *gw, __attribute__((unused)) port_h_t dst_port,
        __attribute__((unused)) void **arg_ptr)
{
    memset(buf, 0, MAX_PACKET_SIZE);

    struct ether_header *eth_header = (struct ether_header *) buf;
    make_eth_header(eth_header, src, gw);

    struct ip *ip_header = (struct ip *) (&eth_header[1]);
    uint16_t len = htons(sizeof(struct ip) + sizeof(struct icmp) - 8);
    make_ip_header(ip_header, IPPROTO_ICMP, len);

    struct icmp *icmp_header = (struct icmp*)(&ip_header[1]);
    make_icmp_header(icmp_header);

    return EXIT_SUCCESS;
}

static int icmp_echo_make_packet(void *buf, ipaddr_n_t src_ip, ipaddr_n_t dst_ip,
                uint32_t *validation, __attribute__((unused)) int probe_num,
                __attribute__((unused)) void *arg)
{
    struct ether_header *eth_header = (struct ether_header *) buf;
    struct ip *ip_header = (struct ip *)(&eth_header[1]);
    struct icmp *icmp_header = (struct icmp*)(&ip_header[1]);
    struct icmp_payload_for_rtt *payload = (struct icmp_payload_for_rtt*)(((char *)icmp_header) + 8);
    uint16_t icmp_idnum = validation[2] & 0xFFFF;
    struct timeval tv;

    ip_header->ip_src.s_addr = src_ip;
    ip_header->ip_dst.s_addr = dst_ip;

    icmp_header->icmp_id = icmp_idnum;

    gettimeofday(&tv, NULL);
    payload->sent_tv_sec = tv.tv_sec;
    payload->sent_tv_usec = tv.tv_usec;
    payload->dst = dst_ip;

    icmp_header->icmp_cksum = 0;
    icmp_header->icmp_cksum = icmp_checksum((unsigned short *) icmp_header);

    ip_header->ip_sum = 0;
    ip_header->ip_sum = zmap_ip_checksum((unsigned short *) ip_header);

    return EXIT_SUCCESS;
}

static void icmp_echo_print_packet(FILE *fp, void* packet)
{
    struct ether_header *ethh = (struct ether_header *) packet;
    struct ip *iph = (struct ip *) &ethh[1];
    struct icmp *icmp_header = (struct icmp*) (&iph[1]);

    fprintf(fp, "icmp { type: %u | code: %u "
            "| checksum: %#04X | id: %u | seq: %u }\n",
            icmp_header->icmp_type,
            icmp_header->icmp_code,
            ntohs(icmp_header->icmp_cksum),
            ntohs(icmp_header->icmp_id),
            ntohs(icmp_header->icmp_seq));
    fprintf_ip_header(fp, iph);
    fprintf_eth_header(fp, ethh);
    fprintf(fp, "------------------------------------------------------\n");
}

static int icmp_validate_packet(const struct ip *ip_hdr,
        uint32_t len, uint32_t *src_ip, uint32_t *validation)
{
    if (ip_hdr->ip_p != IPPROTO_ICMP) {
        return 0;
    }

    if (((uint32_t) 4 * ip_hdr->ip_hl + ICMP_SMALLEST_SIZE) > len) {
        // buffer not large enough to contain expected icmp header
        return 0;
    }

    struct icmp *icmp_h = (struct icmp *) ((char *) ip_hdr + 4*ip_hdr->ip_hl);
    uint16_t icmp_idnum = icmp_h->icmp_id;

    // ICMP validation is tricky: for some packet types, we must look inside
    // the payload
    if (icmp_h->icmp_type == ICMP_TIMXCEED || icmp_h->icmp_type == ICMP_UNREACH) {

        // Should have 16B TimeExceeded/Dest_Unreachable header + original IP header
        // + 1st 8B of original ICMP frame
        if ((4*ip_hdr->ip_hl + ICMP_TIMXCEED_UNREACH_HEADER_SIZE +
            sizeof(struct ip)) > len) {
            return 0;
        }

        struct ip *ip_inner = (struct ip *)(icmp_h + 1);
        if (((uint32_t) 4 * ip_hdr->ip_hl + ICMP_TIMXCEED_UNREACH_HEADER_SIZE +
                4*ip_inner->ip_hl + 8 /*1st 8 bytes of original*/ ) > len) {
            return 0;
        }

        struct icmp *icmp_inner = (struct icmp *)((char *) ip_inner + 4*ip_hdr->ip_hl);

        // Regenerate validation and icmp id based off inner payload
        icmp_idnum = icmp_inner->icmp_id;
        *src_ip = ip_inner->ip_dst.s_addr;
        validate_gen(ip_hdr->ip_dst.s_addr, ip_inner->ip_dst.s_addr,
                 (uint8_t *) validation);
    }

    return 1;
}

static void icmp_echo_process_packet(const u_char *packet,
        __attribute__((unused)) uint32_t len, fieldset_t *fs)
{
    struct ip *ip_hdr = (struct ip *) &packet[sizeof(struct ether_header)];
    struct icmp *icmp_hdr = (struct icmp *) ((char *) ip_hdr + 4*ip_hdr->ip_hl);
    fs_add_uint64(fs, "type", icmp_hdr->icmp_type);
    fs_add_uint64(fs, "code", icmp_hdr->icmp_code);
    fs_add_uint64(fs, "icmp-id", ntohs(icmp_hdr->icmp_id));
    fs_add_uint64(fs, "seq", ntohs(icmp_hdr->icmp_seq));
    struct icmp_payload_for_rtt *payload = (struct icmp_payload_for_rtt *)(((char *)icmp_hdr) + 8);
    fs_add_uint64(fs, "sent-timestamp-ts", (uint64_t)payload->sent_tv_sec);
    fs_add_uint64(fs, "sent-timestamp-us", (uint64_t)payload->sent_tv_usec);
    fs_add_uint64(fs, "dst-raw", (uint64_t)payload->dst);

    switch (icmp_hdr->icmp_type) {
        case ICMP_ECHOREPLY:
            fs_add_string(fs, "classification", (char*) "echoreply", 0);
            fs_add_uint64(fs, "success", 1);
            break;
        case ICMP_UNREACH:
            fs_add_string(fs, "classification", (char*) "unreach", 0);
            fs_add_uint64(fs, "success", 0);
            break;
        case ICMP_SOURCEQUENCH:
            fs_add_string(fs, "classification", (char*) "sourcequench", 0);
            fs_add_uint64(fs, "success", 0);
            break;
        case ICMP_REDIRECT:
            fs_add_string(fs, "classification", (char*) "redirect", 0);
            fs_add_uint64(fs, "success", 0);
            break;
        case ICMP_TIMXCEED:
            fs_add_string(fs, "classification", (char*) "timxceed", 0);
            fs_add_uint64(fs, "success", 0);
            break;
        default:
            fs_add_string(fs, "classification", (char*) "other", 0);
            fs_add_uint64(fs, "success", 0);
            break;
    }
}

static fielddef_t fields[] = {
    {.name="type", .type="int", .desc="icmp message type"},
    {.name="code", .type="int", .desc="icmp message sub type code"},
    {.name="icmp-id", .type="int", .desc="icmp id number"},
    {.name="seq", .type="int", .desc="icmp sequence number"},
    {.name="sent-timestamp-ts", .type="int", .desc="timestamp of sent probe in seconds since Epoch"},
    {.name="sent-timestamp-us", .type="int", .desc="microsecond part of sent timestamp"},
    {.name="dst-raw", .type="int", .desc="raw destination IP address of sent probe"},
    {.name="classification", .type="string", .desc="probe module classification"},
    {.name="success", .type="int", .desc="did probe module classify response as success"}
};


probe_module_t module_icmp_echo_time = {
    .name = "icmp_echo_time",
    .packet_length = 62,
    .pcap_filter = "icmp and icmp[0]!=8",
    .pcap_snaplen = 96,
    .port_args = 0,
    .thread_initialize = &icmp_echo_init_perthread,
    .make_packet = &icmp_echo_make_packet,
    .print_packet = &icmp_echo_print_packet,
    .process_packet = &icmp_echo_process_packet,
    .validate_packet = &icmp_validate_packet,
    .close = NULL,
    .fields = fields,
    .numfields = 9};
