cjdns/interface/tuntap/windows/NDPServer.c

/* vim: set expandtab ts=4 sw=4: */
/*
 * You may redistribute this program and/or modify it under the terms of
 * the GNU General Public License as published by the Free Software Foundation,
 * either version 3 of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "interface/tuntap/windows/NDPServer.h"
#include "interface/InterfaceWrapper.h"
#include "util/Bits.h"
#include "util/Checksum.h"
#include "util/Identity.h"
#include "wire/Message.h"
#include "wire/Ethernet.h"
#include "wire/Headers.h"
#include "wire/NDPHeader.h"

struct NDPServer_pvt
{
    struct NDPServer pub;
    struct Interface* wrapped;
    Identity
};

#define MULTICAST_ADDR "\xff\x02\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\xff\x00\x00\x08"
//                        ff  02  00  00  00  00  00  00  00  00  00  01  ff  00  00  02 870099
#define UNICAST_ADDR   "\xfe\x80\0\0\0\0\0\0\0\0\0\0\0\0\0\x08"

#define ALL_ROUTERS    "\xff\x02\0\0\0\0\0\0\0\0\0\0\0\0\0\x02"


#include <stdio.h>
#include "util/Hex.h"


static int sendResponse(struct Message* msg,
                        struct Ethernet* eth,
                        struct Headers_IP6Header* ip6,
                        struct NDPServer_pvt* ns)
{
    Bits_memcpyConst(ip6->destinationAddr, ip6->sourceAddr, 16);
    Bits_memcpyConst(ip6->sourceAddr, UNICAST_ADDR, 16);
    ip6->hopLimit = 255;

    struct NDPHeader_RouterAdvert* adv = (struct NDPHeader_RouterAdvert*) msg->bytes;
    adv->checksum = Checksum_icmp6(ip6->sourceAddr, msg->bytes, msg->length);

    Message_push(msg, ip6, sizeof(struct Headers_IP6Header), NULL);

    // Eth
    Message_push(msg, eth, sizeof(struct Ethernet), NULL);
    struct Ethernet* ethP = (struct Ethernet*) msg->bytes;
    Bits_memcpyConst(ethP->destAddr, eth->srcAddr, 6);
    Bits_memcpyConst(ethP->srcAddr, eth->destAddr, 6);

printf("responding\n");
    Interface_sendMessage(ns->wrapped, msg);
    return 1;
}

static int tryRouterSolicitation(struct Message* msg,
                                 struct Ethernet* eth,
                                 struct Headers_IP6Header* ip6,
                                 struct NDPServer_pvt* ns)
{
    if (msg->length < NDPHeader_RouterSolicitation_SIZE) {
        return 0;
    }
    struct NDPHeader_RouterSolicitation* sol = (struct NDPHeader_RouterSolicitation*)msg->bytes;

    if (sol->oneThirtyThree != 133 || sol->zero != 0) {
printf("wrong type/code for router solicitation\n");
        return 0;
    }

    if (ns->pub.prefixLen < 1 || ns->pub.prefixLen > 128) {
printf("address prefix not set\n");
        return 0;
    }

    if (Bits_memcmp(ip6->destinationAddr, UNICAST_ADDR, 16)
        && Bits_memcmp(ip6->destinationAddr, ALL_ROUTERS, 16))
    {
printf("wrong address for router solicitation\n");
        return 0;
    }

    // now we're committed.
    Message_shift(msg, -msg->length, NULL);

    // Prefix option
    struct NDPHeader_RouterAdvert_PrefixOpt prefix = {
        .three = 3,
        .four = 4,
        .bits = 0,
        .validLifetimeSeconds_be = 0xffffffffu,
        .preferredLifetimeSeconds_be = 0xffffffffu,
        .reservedTwo = 0
    };
    Bits_memcpyConst(prefix.prefix, ns->pub.advertisePrefix, 16);
    prefix.prefixLen = ns->pub.prefixLen;
    Message_push(msg, &prefix, sizeof(struct NDPHeader_RouterAdvert_PrefixOpt), NULL);

    // NDP message
    struct NDPHeader_RouterAdvert adv = {
        .oneThirtyFour = 134,
        .zero = 0,
        .checksum = 0,
        .currentHopLimit = 0,
        .bits = 0,
        .routerLifetime_be = Endian_hostToBigEndian16(10),
        .reachableTime_be = 0,
        .retransTime_be = 0
    };
    Message_push(msg, &adv, sizeof(struct NDPHeader_RouterAdvert), NULL);

    sendResponse(msg, eth, ip6, ns);
    return 1;
}

static int tryNeighborSolicitation(struct Message* msg,
                                   struct Ethernet* eth,
                                   struct Headers_IP6Header* ip6,
                                   struct NDPServer_pvt* ns)
{
    if (msg->length < NDPHeader_RouterSolicitation_SIZE) {
        return 0;
    }
    struct NDPHeader_NeighborSolicitation* sol = (struct NDPHeader_NeighborSolicitation*)msg->bytes;

    if (sol->oneThirtyFive != 135 || sol->zero != 0) {
printf("wrong type/code for neighbor solicitation\n");
        return 0;
    }

    if (Bits_memcmp(ip6->destinationAddr, UNICAST_ADDR, 16)
        && Bits_memcmp(ip6->destinationAddr, MULTICAST_ADDR, 13))
    {
printf("wrong address for neighbor solicitation\n");
        return 0;
    }

    // now we're committed.
    Message_shift(msg, -msg->length, NULL);

    struct NDPHeader_NeighborAdvert_MacOpt macOpt = {
        .two = 2,
        .one = 1
    };
    Bits_memcpyConst(macOpt.mac, eth->destAddr, 6);
    Message_push(msg, &macOpt, sizeof(struct NDPHeader_NeighborAdvert_MacOpt), NULL);

    struct NDPHeader_NeighborAdvert na = {
        .oneThirtySix = 136,
        .zero = 0,
        .checksum = 0,
        .bits = NDPHeader_NeighborAdvert_bits_ROUTER
            | NDPHeader_NeighborAdvert_bits_SOLICITED
            | NDPHeader_NeighborAdvert_bits_OVERRIDE
    };
    Bits_memcpyConst(na.targetAddr, UNICAST_ADDR, 16);
    Message_push(msg, &na, sizeof(struct NDPHeader_NeighborAdvert), NULL);

    sendResponse(msg, eth, ip6, ns);
    return 1;
}

static uint8_t receiveMessage(struct Message* msg, struct Interface* iface)
{
    struct NDPServer_pvt* ns = Identity_check((struct NDPServer_pvt*)iface->receiverContext);

    if (msg->length < Ethernet_SIZE + Headers_IP6Header_SIZE) {
        return Interface_receiveMessage(&ns->pub.generic, msg);
    }

    struct Ethernet* eth = (struct Ethernet*) msg->bytes;
    struct Headers_IP6Header* ip6 = (struct Headers_IP6Header*) (&eth[1]);

    if (eth->ethertype != Ethernet_TYPE_IP6 || ip6->nextHeader != 58 /* ICMPv6 */) {
        return Interface_receiveMessage(&ns->pub.generic, msg);
    }

    // store the eth and ip6 headers so they don't get clobbered
    struct Ethernet storedEth;
    Message_pop(msg, &storedEth, sizeof(struct Ethernet), NULL);

    struct Headers_IP6Header storedIp6;
    Message_pop(msg, &storedIp6, sizeof(struct Headers_IP6Header), NULL);

    if (!tryNeighborSolicitation(msg, &storedEth, &storedIp6, ns)
        && !tryRouterSolicitation(msg, &storedEth, &storedIp6, ns))
    {
        Message_push(msg, &storedIp6, sizeof(struct Headers_IP6Header), NULL);
        Message_push(msg, &storedEth, sizeof(struct Ethernet), NULL);
        return Interface_receiveMessage(&ns->pub.generic, msg);
    }
    // responding happens in sendResponse..
    return 0;
}

static uint8_t sendMessage(struct Message* msg, struct Interface* iface)
{
    struct NDPServer_pvt* ns = Identity_check((struct NDPServer_pvt*)iface);
    return Interface_sendMessage(ns->wrapped, msg);
}

struct NDPServer* NDPServer_new(struct Interface* external, struct Allocator* alloc)
{
    struct NDPServer_pvt* out = Allocator_calloc(alloc, sizeof(struct NDPServer_pvt), 1);
    out->wrapped = external;
    Identity_set(out);
    InterfaceWrapper_wrap(external, sendMessage, receiveMessage, &out->pub.generic);
    return &out->pub;
}