error_t ipv4FragmentDatagram(NetInterface *interface, Ipv4PseudoHeader *pseudoHeader,
uint16_t id, const ChunkedBuffer *payload, size_t payloadOffset, uint8_t timeToLive)
{
error_t error;
size_t offset;
size_t length;
size_t payloadLength;
size_t fragmentOffset;
ChunkedBuffer *fragment;
//Retrieve the length of the payload
payloadLength = chunkedBufferGetLength(payload) - payloadOffset;
//Allocate a memory buffer to hold IP fragments
fragment = ipAllocBuffer(0, &fragmentOffset);
//Failed to allocate memory?
if(!fragment)
return ERROR_OUT_OF_MEMORY;
//Split the payload into multiple IP fragments
for(offset = 0; offset < payloadLength; offset += length)
{
//Flush the contents of the fragment
error = chunkedBufferSetLength(fragment, fragmentOffset);
//Sanity check
if(error) break;
//Process the last fragment?
if((payloadLength - offset) <= IPV4_MAX_FRAG_SIZE)
{
//Size of the current fragment
length = payloadLength - offset;
//Copy fragment data
chunkedBufferConcat(fragment, payload, payloadOffset + offset, length);
//Do not set the MF flag for the last fragment
error = ipv4SendPacket(interface, pseudoHeader, id,
offset / 8, fragment, fragmentOffset, timeToLive);
}
else
{
//Size of the current fragment (must be a multiple of 8-byte blocks)
length = IPV4_MAX_FRAG_SIZE;
//Copy fragment data
chunkedBufferConcat(fragment, payload, payloadOffset + offset, length);
//Fragmented packets must have the MF flag set
error = ipv4SendPacket(interface, pseudoHeader, id,
IPV4_FLAG_MF | (offset / 8), fragment, fragmentOffset, timeToLive);
}
//Failed to send current IP packet?
if(error) break;
}
//Free previously allocated memory
chunkedBufferFree(fragment);
//Return status code
return error;
}
error_t ipv4SendDatagram(NetInterface *interface, Ipv4PseudoHeader *pseudoHeader,
NetBuffer *buffer, size_t offset, uint8_t ttl)
{
error_t error;
size_t length;
uint16_t id;
//Retrieve the length of payload
length = netBufferGetLength(buffer) - offset;
//Check whether the TTL value is zero
if(ttl == 0)
{
//Use default Time-To-Live value
ttl = IPV4_DEFAULT_TTL;
}
//Identification field is primarily used to identify
//fragments of an original IP datagram
id = osAtomicInc16(&interface->ipv4Identification);
//If the payload length is smaller than the network
//interface MTU then no fragmentation is needed
if((length + sizeof(Ipv4Header)) <= interface->ipv4Config.mtu)
{
//Send data as is
error = ipv4SendPacket(interface,
pseudoHeader, id, 0, buffer, offset, ttl);
}
//If the payload length exceeds the network interface MTU
//then the device must fragment the data
else
{
#if (IPV4_FRAG_SUPPORT == ENABLED)
//Fragment IP datagram into smaller packets
error = ipv4FragmentDatagram(interface,
pseudoHeader, id, buffer, offset, ttl);
#else
//Fragmentation is not supported
error = ERROR_MESSAGE_TOO_LONG;
#endif
}
//Return status code
return error;
}
error_t ipv4SendDatagram(NetInterface *interface, Ipv4PseudoHeader *pseudoHeader,
ChunkedBuffer *buffer, size_t offset, uint8_t timeToLive)
{
error_t error;
size_t length;
uint16_t id;
//Retrieve the length of payload
length = chunkedBufferGetLength(buffer) - offset;
//Identification field is primarily used to identify
//fragments of an original IP datagram
id = osAtomicInc16(&interface->ipv4Identification);
//If the payload length is smaller than the network
//interface MTU then no fragmentation is needed
if(length <= IPV4_MAX_PAYLOAD_SIZE)
{
//Send data as is
error = ipv4SendPacket(interface,
pseudoHeader, id, 0, buffer, offset, timeToLive);
}
//If the payload length exceeds the network interface MTU
//then the device must fragment the data
else
{
#if (IPV4_FRAG_SUPPORT == ENABLED)
//Fragment IP datagram into smaller packets
error = ipv4FragmentDatagram(interface,
pseudoHeader, id, buffer, offset, timeToLive);
#else
//Fragmentation is not supported
error = ERROR_MESSAGE_TOO_LONG;
#endif
}
//Return status code
return error;
}
