/*      $NetBSD: ip4_frag_1.c,v 1.2 2010/10/03 19:41:25 rmind Exp $     */

/*-
 * Copyright (c) 2010 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software developed for The NetBSD Foundation
 * by Mindaugas Rasiukevicius <rmind at NetBSD org>.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * Test various cases of IPv4 reassembly.
 */

#include <sys/cdefs.h>

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stddef.h>
#include <unistd.h>
#include <netdb.h>
#include <assert.h>
#include <err.h>

#include <sys/socket.h>
#include <netinet/in_systm.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/udp.h>
#include <netinet/ip_icmp.h>
#include <arpa/inet.h>

#define IP_SIZE                 sizeof(struct ip)
#define ICMP_SIZE               offsetof(struct icmp, icmp_ip)

static void *
xalloc(size_t sz)
{
        void *ptr = calloc(1, sz);

        if (ptr == NULL) {
                err(EXIT_FAILURE, "calloc");
        }
        return ptr;
}

static int
create_socket(void)
{
        int s, val = 1;

        s = socket(AF_INET, SOCK_RAW, IPPROTO_RAW);
        if (s == -1) {
                err(EXIT_FAILURE, "socket");
        }
        if (setsockopt(s, IPPROTO_IP, IP_HDRINCL, &val, sizeof(val)) == -1) {
                err(EXIT_FAILURE, "setsockopt");
        }
        return s;
}

void *
create_ip_packet(in_addr_t target, int foff, size_t addlen)
{
        struct ip *ip;
        unsigned int n;
        uint8_t *data;
        int first;

        /* Header at zero offset - first fragment. */
        first = ((foff & IP_MF) == 0);
        if (first) {
                assert(addlen >= ICMP_SIZE);
                addlen -= ICMP_SIZE;
        }
        ip = xalloc(IP_SIZE + addlen);

        /*
         * IP header.
         * Note: ip_len and ip_off shall be in host byte order.
         */
        ip->ip_v = IPVERSION;
        ip->ip_hl = 5;
        ip->ip_tos = 0;
        ip->ip_len = (5 << 2) + addlen;
        ip->ip_id = htons(1);
        ip->ip_off = foff;
        ip->ip_ttl = 64;
        ip->ip_p = IPPROTO_ICMP;
        ip->ip_sum = 0;

        ip->ip_src.s_addr = INADDR_ANY;
        ip->ip_dst.s_addr = target;

        /* Fill in some data. */
        data = (void *)(ip + 1);
        if (first) {
                struct icmp *icmp = (void *)data;
                icmp->icmp_type = ICMP_ECHO;
                icmp->icmp_code = 0;
                icmp->icmp_cksum = 0;
                n = ICMP_SIZE;
        } else {
                n = 0;
        }
        for (data += n; n < addlen; n++) {
                *data = (0xf & n);
                data++;
        }
        return (void *)ip;
}

void
send_packet(int s, void *p, in_addr_t target)
{
        struct ip *ip = (struct ip *)p;
        struct sockaddr_in addr;
        ssize_t ret;

        memset(&addr, 0, sizeof(addr));
        addr.sin_family = AF_INET;
        addr.sin_addr.s_addr = target;

        /* Note: total length was set host byte-order. */
        ret = sendto(s, p, ip->ip_len, 0,
            (struct sockaddr *)&addr, sizeof(struct sockaddr_in));
        if (ret == -1) {
                err(EXIT_FAILURE, "sendto");
        }
        free(p);
}

void
test_case_0(int sock, in_addr_t target)
{
        void *p;

        /*
         * Case 0: normal reassembly.
         * => IP_STAT_FRAGMENTS
         */

        p = create_ip_packet(target, 0 | IP_MF, 1480);
        send_packet(sock, p, target);

        p = create_ip_packet(target, 185, 1480);
        send_packet(sock, p, target);
}

void
test_case_1(int sock, in_addr_t target)
{
        void *p;

        /*
         * Case 1: ip_len of the first fragment and ip_off + hlen of other
         * fragments should be at least 68 (IP_MINFRAGSIZE - 1) bytes.
         * => IP_STAT_BADFRAGS (malformed)
         */

        /* 20 + 48 == 68, OK */
        p = create_ip_packet(target, 0 | IP_MF, 48);
        send_packet(sock, p, target);

        /* 20 + (5 * 8) = 60 < 68, ERR */
        p = create_ip_packet(target, 6 - 1, 8);
        send_packet(sock, p, target);
}

void
test_case_2(int sock, in_addr_t target)
{
        void *p;
        struct ip *ip;

        /*
         * Case 2: mismatch of TOS.
         * => IP_STAT_BADFRAGS (malformed)
         */

        p = create_ip_packet(target, 0 | IP_MF, 48);
        ip = (struct ip *)p;
        ip->ip_tos = 123;
        send_packet(sock, p, target);

        p = create_ip_packet(target, 6, 48);
        send_packet(sock, p, target);
}

void
test_case_3(int sock, in_addr_t target)
{
        void *p;

        /*
         * Case 3: data length is not multiple of 8 bytes.
         * => IP_STAT_BADFRAGS (malformed)
         */

        p = create_ip_packet(target, 0 | IP_MF, 48);
        send_packet(sock, p, target);

        /* (48 + 1) & 0x7 != 0, ERR */
        p = create_ip_packet(target, 6, 48 + 1);
        send_packet(sock, p, target);
}

void
test_case_4(int sock, in_addr_t target)
{
        void *p;

        /*
         * Case 4: fragment covering previous (duplicate).
         * => IP_STAT_FRAGDROPPED (dup, out of space)
         */

        p = create_ip_packet(target, 0 | IP_MF, 48);
        send_packet(sock, p, target);

        p = create_ip_packet(target, 6 | IP_MF, 96);
        send_packet(sock, p, target);

        p = create_ip_packet(target, 6, 48);
        send_packet(sock, p, target);
}

void
test_case_5(int sock, in_addr_t target)
{
        void *p;
        int cnt, left, off;

        /*
         * Case 5: construct packet larger than IP_MAXPACKET.
         * => IP_STAT_TOOLONG (with length > max ip packet size)
         */

        /*
         * Assumptions:
         * - 1500 MTU.  Minus IP header - 1480.
         * - Bytes left: 65535 - (1480 * 44) = 415.
         */
        cnt = IP_MAXPACKET / 1480;
        left = IP_MAXPACKET - (1480 * cnt);
        left = (left / 8) * 8;

        for (off = 0; cnt != 0; cnt--) {
                p = create_ip_packet(target, off | IP_MF, 1480);
                send_packet(sock, p, target);
                off += (1480 >> 3);
        }
        /* Add 8 bytes and thus cross IP_MAXPACKET limit. */
        p = create_ip_packet(target, off, left + 8);
        send_packet(sock, p, target);
}

void
test_case_6(int sock, in_addr_t target)
{
        struct ip *ip;
        void *p;

        /*
         * Case 6: cause a fragment timeout.
         * => IP_STAT_FRAGTIMEOUT (fragments dropped after timeout)
         */

        p = create_ip_packet(target, 0 | IP_MF, 48);
        ip = (struct ip *)p;
        ip->ip_id = htons(321);
        send_packet(sock, p, target);
        /*
         * Missing non-MF packet - timeout.
         */
}

int
main(int argc, char **argv)
{
        struct hostent *he;
        in_addr_t target;
        int sock;

        if (argc < 2) {
                printf("%s: <target host>\n", argv[0]);
                exit(EXIT_SUCCESS);
        }

        he = gethostbyname(argv[1]);
        if (he == NULL) {
                err(EXIT_FAILURE, "gethostbyname");
        }
        memcpy(&target, he->h_addr, sizeof(target));

        sock = create_socket();

        test_case_0(sock, target);
        test_case_1(sock, target);
        test_case_2(sock, target);
        test_case_3(sock, target);
        test_case_4(sock, target);
        test_case_5(sock, target);
        test_case_6(sock, target);

        close(sock);

        return 0;
}