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ICMP6Generator.c
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ICMP6Generator.c
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/* 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/ICMP6Generator_pvt.h"
#include "util/Checksum.h"
#include "util/Bits.h"
#include "util/log/Log.h"
#include "wire/Headers.h"
#include "wire/Error.h"
#include <stddef.h>
/** MTU at switch layer, not including switch header overhead. */
#define EXPECTED_MTU \
(1492 /* PPPoE */ \
- Headers_IP4Header_SIZE \
- Headers_UDPHeader_SIZE \
- 20 /* CryptoAuth in ESTABLISHED state. */ )
#define CJDNS_OVERHEAD \
(Headers_SwitchHeader_SIZE \
+ 4 /* handle */ \
+ Headers_CryptoAuth_SIZE \
/* IPv6 header goes here but operating system subtracts it. */ \
+ Headers_CryptoAuth_SIZE)
static inline uint8_t numForType(enum ICMP6Generator_Type type)
{
switch (type) {
case ICMP6Generator_Type_NO_ROUTE_TO_HOST: return 1; /* ICMPV6_DEST_UNREACH */
case ICMP6Generator_Type_PACKET_TOO_BIG: return 2; /* ICMPV6_PKT_TOOBIG */
default: return 0;
}
}
/**
* Generate an ICMPv6 message.
* The message parameter must contain all content which will be beneath the ICMPv6 header
* including the MTU in the case of a "packet too big" message.
*
* @param message a message containing the content. This message must have enough padding
* to contain an additional ICMP header and IPv6 header totaling 44 bytes.
* @param sourceAddr the IPv6 address which this ICMP message will be said to have come from.
* @param destAddr the IPv6 address which this ICMP message will be directed to.
* @param type the ICMP message type/code for this message.
* @param mtu the MTU value for this message.
*/
void ICMP6Generator_generate(struct Message* msg,
const uint8_t* restrict sourceAddr,
const uint8_t* restrict destAddr,
enum ICMP6Generator_Type type,
uint32_t mtu)
{
Message_shift(msg, Headers_ICMP6Header_SIZE);
struct Headers_ICMP6Header* icmp6 = (struct Headers_ICMP6Header*) msg->bytes;
Message_shift(msg, Headers_IP6Header_SIZE);
struct Headers_IP6Header* ip6 = (struct Headers_IP6Header*) msg->bytes;
if (ICMP6Generator_MIN_IPV6_MTU < msg->length) {
msg->length = ICMP6Generator_MIN_IPV6_MTU;
}
uint16_t contentLen = msg->length - Headers_IP6Header_SIZE;
icmp6->type = numForType(type);
icmp6->code = 0;
icmp6->checksum = 0;
icmp6->additional = Endian_hostToBigEndian32(mtu);
ip6->versionClassAndFlowLabel = 0;
Headers_setIpVersion(ip6);
ip6->flowLabelLow_be = 0;
ip6->payloadLength_be = Endian_hostToBigEndian16(contentLen);
ip6->nextHeader = 58; /* IPPROTO_ICMPV6 */
ip6->hopLimit = 64;
Bits_memcpyConst(ip6->sourceAddr, sourceAddr, 16);
Bits_memcpyConst(ip6->destinationAddr, destAddr, 16);
icmp6->checksum = Checksum_icmp6(ip6->sourceAddr, (uint8_t*)icmp6, contentLen);
}
static uint8_t sendFragmented(struct ICMP6Generator_pvt* ctx,
struct Message* msg,
uint32_t mtu,
int offsetBytes)
{
uint64_t msgHeader[(Headers_IP6Header_SIZE + Headers_IP6Fragment_SIZE) / 8];
Assert_true(msg->length > (int)sizeof(msgHeader));
Bits_memcpyConst(msgHeader, msg->bytes, sizeof(msgHeader));
const int headersSize = (Headers_IP6Header_SIZE + Headers_IP6Fragment_SIZE);
struct Headers_IP6Header* ip6 = (struct Headers_IP6Header*) msg->bytes;
struct Headers_IP6Fragment* frag = (struct Headers_IP6Fragment*) (&ip6[1]);
Message_shift(msg, -headersSize);
// prepare next message.
struct Message* nextMessage = &(struct Message) {
.bytes = msg->bytes,
.length = msg->length,
.padding = msg->padding
};
int nextMessageOffsetBytes = offsetBytes + (((mtu - headersSize) / 8) * 8);
Message_shift(nextMessage, -(nextMessageOffsetBytes - offsetBytes));
msg->length -= nextMessage->length;
ip6->payloadLength_be = Endian_hostToBigEndian16(msg->length + Headers_IP6Fragment_SIZE);
Message_shift(msg, headersSize);
// sanity check
Assert_true(!Bits_memcmp(&msg->bytes[msg->length], nextMessage->bytes, 8));
uint64_t msgNextPartFirstLong = ((uint64_t*)nextMessage->bytes)[0];
// Set the required fields.
// RFC-2460 includes the fragment header in the offset so we have to add another 8 bytes.
Headers_IP6Fragment_setOffset(frag, offsetBytes / 8);
Headers_IP6Fragment_setMoreFragments(frag, true);
Interface_receiveMessage(&ctx->pub.internal, msg);
// sanity check
Assert_true(!Bits_memcmp(&msgNextPartFirstLong, nextMessage->bytes, 8));
Message_shift(nextMessage, sizeof(msgHeader));
Bits_memcpyConst(nextMessage->bytes, msgHeader, sizeof(msgHeader));
if (nextMessage->length > (int)mtu) {
return sendFragmented(ctx, nextMessage, mtu, nextMessageOffsetBytes);
}
// Set the required fields for the last fragment.
ip6 = (struct Headers_IP6Header*) nextMessage->bytes;
frag = (struct Headers_IP6Fragment*) (nextMessage->bytes + Headers_IP6Header_SIZE);
Headers_IP6Fragment_setOffset(frag, nextMessageOffsetBytes / 8);
// If the kernel did some fragmentation of it's own, we don't want to set the "last fragment"
// flag so we'll leave it as it is.
//Headers_IP6Fragment_setMoreFragments(frag, false);
ip6->payloadLength_be = Endian_hostToBigEndian16(nextMessage->length - Headers_IP6Header_SIZE);
return Interface_receiveMessage(&ctx->pub.internal, nextMessage);
}
/** Message from the external (TUN facing) interface. */
static uint8_t incoming(struct Message* msg, struct Interface* iface)
{
struct ICMP6Generator_pvt* ctx =
Identity_cast((struct ICMP6Generator_pvt*)
(((uint8_t*)iface) - offsetof(struct ICMP6Generator, external)));
// TODO calculate this on a per-node basis.
int mtu = ctx->mtu;
// source address for packets coming from the router.
const uint8_t magicAddr[] = { 0xfc,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1 };
struct Headers_IP6Header* header = (struct Headers_IP6Header*) msg->bytes;
if (msg->length >= Headers_IP6Header_SIZE
&& Headers_getIpVersion(header) == 6
&& msg->length > mtu)
{
if (header->nextHeader == Headers_IP6Fragment_TYPE) {
return sendFragmented(ctx, msg, mtu, 0);
}
uint8_t destAddr[16];
Bits_memcpyConst(destAddr, header->sourceAddr, 16);
ICMP6Generator_generate(msg,
magicAddr,
destAddr,
ICMP6Generator_Type_PACKET_TOO_BIG,
mtu);
Interface_receiveMessage(&ctx->pub.external, msg);
return Error_NONE;
}
return Interface_receiveMessage(&ctx->pub.internal, msg);
}
/** Message from the internal (Ducttape facing) interface. */
static uint8_t outgoing(struct Message* msg, struct Interface* iface)
{
struct ICMP6Generator_pvt* ctx =
Identity_cast((struct ICMP6Generator_pvt*)
(((uint8_t*)iface) - offsetof(struct ICMP6Generator, internal)));
return Interface_receiveMessage(&ctx->pub.external, msg);
}
struct ICMP6Generator* ICMP6Generator_new(struct Allocator* alloc)
{
struct ICMP6Generator_pvt* out = Allocator_clone(alloc, (&(struct ICMP6Generator_pvt) {
.pub = {
.external = {
.sendMessage = incoming
},
.internal = {
.sendMessage = outgoing
}
},
.mtu = EXPECTED_MTU - CJDNS_OVERHEAD
}));
Identity_set(out);
return &out->pub;
}