/* Check for consistent ACK and SEQ number */
int check_tcp_consistency(socket_t *current_tcp_socket, tcp_hdr_t *tcp_header)
{
if (IS_TCP_ACK(tcp_header->reserved_flags)) {
if (tcp_header->ack_nr > (current_tcp_socket->tcp_control.send_nxt)) {
/* ACK of not yet sent byte, discard */
return ACK_NO_TOO_BIG;
}
else if (tcp_header->ack_nr <= (current_tcp_socket->tcp_control.send_una)) {
/* ACK of previous segments, maybe dropped? */
return ACK_NO_TOO_SMALL;
}
}
else if ((current_tcp_socket->tcp_control.rcv_nxt > 0) && (tcp_header->seq_nr < current_tcp_socket->tcp_control.rcv_nxt)) {
/* segment repetition, maybe ACK got lost? */
return SEQ_NO_TOO_SMALL;
}
return PACKET_OK;
}
uint16_t compress_tcp_packet(socket_internal_t *current_socket,
uint8_t *current_tcp_packet,
ipv6_hdr_t *temp_ipv6_header,
uint8_t flags,
uint8_t payload_length)
{
socket_t *current_tcp_socket = ¤t_socket->socket_values;
tcp_hc_context_t *tcp_context = ¤t_tcp_socket->tcp_control.tcp_context;
tcp_cb_t *tcp_cb = ¤t_tcp_socket->tcp_control;
tcp_hdr_t full_tcp_header;
uint16_t packet_size = 0;
/* Connection establisment phase, use FULL_HEADER TCP */
if (tcp_context->hc_type == FULL_HEADER) {
/* draft-aayadi-6lowpan-tcphc-01: 5.1 Full header TCP segment.
* Establishing Connection */
/* Move tcp packet 3 bytes to add padding and Context ID */
memmove(current_tcp_packet + 3, current_tcp_packet,
((((tcp_hdr_t *)current_tcp_packet)->data_offset) * 4) +
payload_length);
/* 1 padding byte with value 0x01 to introduce full header TCP_HC
* segment */
memset(current_tcp_packet, 0x01, 1);
/* Adding Context ID */
uint16_t current_context = HTONS(tcp_context->context_id);
memcpy(current_tcp_packet + 1, ¤t_context, 2);
/* Return correct header length (+3) */
packet_size = ((((tcp_hdr_t *)(current_tcp_packet + 3))->data_offset) * 4) + 3 +
payload_length;
/* Update the tcp context fields */
update_tcp_hc_context(false, current_socket, (tcp_hdr_t *)(current_tcp_packet + 3));
/* Convert TCP packet to network byte order */
switch_tcp_packet_byte_order((tcp_hdr_t *)(current_tcp_packet + 3));
return packet_size;
}
/* Check for header compression type: COMPRESSED_HEADER */
else if (tcp_context->hc_type == COMPRESSED_HEADER) {
/* draft-aayadi-6lowpan-tcphc-01: 5.1 Compressed header TCP segment. */
/* Temporary variable for TCP_HC_Header Bytes */
uint16_t tcp_hc_header = 0x0000;
/* Save TCP_Header to refresh TCP Context values after compressing the
* packet */
memcpy(&full_tcp_header, current_tcp_packet, TCP_HDR_LEN);
/* Temporary variable for storing TCP header beginning */
uint8_t *tcp_packet_begin = current_tcp_packet;
/* Position for first TCP header value, TCP_HC_Header and Context ID */
current_tcp_packet += 4;
/* Packet size value */
packet_size += 4;
/* 5.2. LOWPAN_TCPHC Format */
/* First 3 bits of TCP_HC_Header are not exactly specified. In this
* implementation they are (1|1|0) * for compressed headers and the
* CID is always 16 bits (1) */
/* (1|1|0|1) = D */
tcp_hc_header |= 0xD000;
/*----------------------------------*/
/*| Sequence number handling |*/
/*----------------------------------*/
if (full_tcp_header.seq_nr == tcp_context->seq_snd) {
/* Nothing to do, Seq = (0|0) */
}
/* If the 24 most significant bits haven't changed from previous
* packet, don't transmit them */
else if ((full_tcp_header.seq_nr & 0xFFFFFF00) == (tcp_context->seq_snd &
0xFFFFFF00)) {
/* Seq = (0|1) */
tcp_hc_header |= 0x0400;
/* Copy first 8 less significant bits of sequence number into
* buffer */
*current_tcp_packet = (uint8_t)(full_tcp_header.seq_nr & 0x000000FF);
current_tcp_packet += 1;
packet_size += 1;
}
/* If the 16 most significant bits haven't changed from previous packet,
* don't transmit them */
else if ((full_tcp_header.seq_nr & 0xFFFF0000) == (tcp_context->seq_snd & 0xFFFF0000)) {
/* Seq = (1|0) */
tcp_hc_header |= 0x0800;
/* Copy first 16 less significant bits of sequence number into buffer */
*((uint16_t *)current_tcp_packet) =
HTONS((uint16_t)(full_tcp_header.seq_nr & 0x0000FFFF));
current_tcp_packet += 2;
packet_size += 2;
}
/* Sending uncompressed sequence number */
else {
/* Seq = (1|1) */
tcp_hc_header |= 0x0C00;
/* Copy all bits of sequence number into buffer */
uint32_t cur_seq_no = HTONL(full_tcp_header.seq_nr);
memcpy(current_tcp_packet, &cur_seq_no, 4);
current_tcp_packet += 4;
packet_size += 4;
}
/*----------------------------------*/
/*| Acknowledgment number handling |*/
/*----------------------------------*/
if ((IS_TCP_ACK(full_tcp_header.reserved_flags) &&
(tcp_cb->tcp_context.ack_snd == full_tcp_header.ack_nr))) {
tcp_context->ack_snd = tcp_context->seq_rcv;
}
if (full_tcp_header.ack_nr == tcp_context->ack_snd) {
/* Nothing to do, Ack = (0|0) */
}
/* If the 24 most significant bits haven't changed from previous packet,
* don't transmit them */
else if ((full_tcp_header.ack_nr & 0xFFFFFF00) == (tcp_context->ack_snd &
0xFFFFFF00)) {
/* Ack = (0|1) */
tcp_hc_header |= 0x0100;
/* Copy first 8 less significant bits of acknowledgment number into
* buffer */
*current_tcp_packet = (uint8_t)(full_tcp_header.ack_nr & 0x000000FF);
current_tcp_packet += 1;
packet_size += 1;
}
/* If the 16 most significant bits haven't changed from previous packet,
* don't transmit them */
else if ((full_tcp_header.ack_nr & 0xFFFF0000) == (tcp_context->ack_snd &
0xFFFF0000)) {
/* Ack = (1|0) */
tcp_hc_header |= 0x0200;
/* Copy first 16 less significant bits of acknowledgment number
* into buffer */
*((uint16_t *)current_tcp_packet) =
HTONS((uint16_t)(full_tcp_header.ack_nr & 0x0000FFFF));
current_tcp_packet += 2;
packet_size += 2;
}
/* Sending uncompressed acknowledgment number */
else {
/* Ack = (1|1) */
tcp_hc_header |= 0x0300;
/* Copy all bits of acknowledgment number into buffer */
uint32_t cur_ack_nr = HTONL(full_tcp_header.ack_nr);
memcpy(current_tcp_packet, &cur_ack_nr, 4);
current_tcp_packet += 4;
packet_size += 4;
}
/*----------------------------------*/
/*| Window handling |*/
/*----------------------------------*/
if (full_tcp_header.window == tcp_context->wnd_snd) {
/* Nothing to do, Wnd = (0|0) */
}
/* If the 8 most significant bits haven't changed from previous packet,
* don't transmit them */
else if ((full_tcp_header.window & 0xFF00) == (tcp_context->wnd_snd & 0xFF00)) {
/* Wnd = (0|1) */
tcp_hc_header |= 0x0040;
/* Copy first 8 less significant bits of window size into buffer */
*current_tcp_packet = (uint8_t)(full_tcp_header.window & 0x00FF);
current_tcp_packet += 1;
packet_size += 1;
}
/* If the 8 less significant bits haven't changed from previous packet,
* don't transmit them */
else if ((full_tcp_header.window & 0x00FF) == (tcp_context->wnd_snd &
0x00FF)) {
/* Wnd = (1|0) */
tcp_hc_header |= 0x0080;
/* Copy first 8 most significant bits of window size into buffer */
*current_tcp_packet = (uint8_t)(full_tcp_header.window & 0xFF00);
current_tcp_packet += 1;
packet_size += 1;
}
/* Sending uncompressed window */
else {
/* Wnd = (1|1) */
tcp_hc_header |= 0x00C0;
/* Copy all bits of window size into buffer */
uint16_t cur_window = HTONS(full_tcp_header.window);
memcpy(current_tcp_packet, &cur_window, 2);
current_tcp_packet += 2;
packet_size += 2;
}
/* FIN flag */
if (IS_TCP_FIN(full_tcp_header.reserved_flags)) {
/* F = (1) */
tcp_hc_header |= 0x0008;
}
/* Copy checksum into buffer */
uint16_t cur_chk_sum = HTONS(full_tcp_header.checksum);
memcpy(current_tcp_packet, &cur_chk_sum, 2);
current_tcp_packet += 2;
packet_size += 2;
/* Copy TCP_HC Bytes into buffer */
uint16_t cur_tcp_hc_header = HTONS(tcp_hc_header);
memcpy(tcp_packet_begin, &cur_tcp_hc_header, 2);
/* Copy TCP_HC Context ID into buffer */
uint16_t cur_context_id = HTONS(tcp_context->context_id);
memcpy(tcp_packet_begin + 2, &cur_context_id, 2);
/* Move payload to end of tcp header */
memmove(current_tcp_packet, tcp_packet_begin + TCP_HDR_LEN,
payload_length);
/* Adding TCP payload length to TCP_HC header length */
packet_size += payload_length;
update_tcp_hc_context(false, current_socket, &full_tcp_header);
return packet_size;
}
/* Check for header compression type: MOSTLY_COMPRESSED_HEADER */
else if (tcp_context->hc_type == MOSTLY_COMPRESSED_HEADER) {
/* draft-aayadi-6lowpan-tcphc-01: 5.1 Compressed header TCP segment. */
/* Temporary variable for TCP_HC_Header Bytes */
uint16_t tcp_hc_header = 0x0000;
/* Save TCP_Header to refresh TCP Context values after compressing the
* packet */
memcpy(&full_tcp_header, current_tcp_packet, TCP_HDR_LEN);
/* Temporary variable for storing TCP header beginning */
uint8_t *tcp_packet_begin = current_tcp_packet;
/* Position for first TCP header value, TCP_HC_Header and Context ID */
current_tcp_packet += 4;
/* Packet size value */
packet_size += 4;
/* 5.2. LOWPAN_TCPHC Format */
/* First 3 bits of TCP_HC_Header are not exactly specified. In this
* implementation they are (1|0|0) for mostly compressed headers and
* the CID is always 16 bits (1) */
/* (1|0|0|1) = 9 */
tcp_hc_header |= 0x9000;
/*----------------------------------*/
/*| Sequence number handling |*/
/*----------------------------------*/
/* Sending uncompressed sequence number */
/* Seq = (1|1) */
tcp_hc_header |= 0x0C00;
/* Copy all bits of sequence number into buffer */
uint32_t cur_seq_no = HTONL(full_tcp_header.seq_nr);
memcpy(current_tcp_packet, &cur_seq_no, 4);
current_tcp_packet += 4;
packet_size += 4;
/*----------------------------------*/
/*| Acknowledgment number handling |*/
/*----------------------------------*/
/* Ack = (1|1) */
tcp_hc_header |= 0x0300;
/* Copy all bits of acknowledgment number into buffer */
uint32_t cur_ack_nr = HTONL(full_tcp_header.ack_nr);
memcpy(current_tcp_packet, &cur_ack_nr, 4);
current_tcp_packet += 4;
packet_size += 4;
/*----------------------------------*/
/*| Window handling |*/
/*----------------------------------*/
/* Wnd = (1|1) */
tcp_hc_header |= 0x00C0;
/* Copy all bits of window size into buffer */
uint16_t cur_window = HTONS(full_tcp_header.window);
memcpy(current_tcp_packet, &cur_window, 2);
current_tcp_packet += 2;
packet_size += 2;
/* FIN flag */
if (IS_TCP_FIN(full_tcp_header.reserved_flags)) {
/* F = (1) */
tcp_hc_header |= 0x0008;
}
/* Copy checksum into buffer */
uint16_t cur_chk_sum = HTONS(full_tcp_header.checksum);
memcpy(current_tcp_packet, &cur_chk_sum, 2);
current_tcp_packet += 2;
packet_size += 2;
/* Copy TCP_HC Bytes into buffer */
uint16_t cur_tcp_hc_header = HTONS(tcp_hc_header);
memcpy(tcp_packet_begin, &cur_tcp_hc_header, 2);
/* Copy TCP_HC Context ID into buffer */
uint16_t cur_context_id = HTONS(tcp_context->context_id);
memcpy(tcp_packet_begin + 2, &cur_context_id, 2);
/* Move payload to end of tcp header */
memmove(current_tcp_packet, tcp_packet_begin + TCP_HDR_LEN,
payload_length);
/* Adding TCP payload length to TCP_HC header length */
packet_size += payload_length;
update_tcp_hc_context(false, current_socket, &full_tcp_header);
return packet_size;
}
return 0;
}
socket_internal_t *decompress_tcp_packet(ipv6_hdr_t *temp_ipv6_header)
{
uint8_t *packet_buffer = ((uint8_t *)temp_ipv6_header) + IPV6_HDR_LEN;
uint16_t tcp_hc_header;
socket_internal_t *current_socket = NULL;
uint16_t packet_size = 0;
/* Full header TCP segment */
if (*(((uint8_t *)temp_ipv6_header) + IPV6_HDR_LEN) == 0x01) {
switch_tcp_packet_byte_order(((tcp_hdr_t *)(((uint8_t *)temp_ipv6_header) +
IPV6_HDR_LEN + 3)));
current_socket = get_tcp_socket(temp_ipv6_header,
((tcp_hdr_t *)(((uint8_t *)temp_ipv6_header) +
IPV6_HDR_LEN + 3)));
if (current_socket != NULL) {
if (current_socket->socket_values.tcp_control.state == LISTEN) {
memcpy(¤t_socket->socket_values.tcp_control.tcp_context.context_id,
((uint8_t *)temp_ipv6_header) + IPV6_HDR_LEN + 1, 2);
current_socket->socket_values.tcp_control.tcp_context.context_id =
NTOHS(current_socket->socket_values.tcp_control.tcp_context.context_id);
}
memmove(((uint8_t *)temp_ipv6_header) + IPV6_HDR_LEN,
(((uint8_t *)temp_ipv6_header) + IPV6_HDR_LEN + 3),
temp_ipv6_header->length - 3);
temp_ipv6_header->length -= 3;
return current_socket;
}
else {
printf("Socket Null!\n");
/* Found no matching socket for this packet -> Drop it */
return NULL;
}
}
/* Compressed header TCP segment */
else {
/* Temporary TCP Header */
tcp_hdr_t full_tcp_header;
memset(&full_tcp_header, 0, sizeof(tcp_hdr_t));
/* Current context ID */
uint16_t current_context;
memcpy(¤t_context, (packet_buffer + 2), 2);
current_context = NTOHS(current_context);
/* Copy TCP_HC header into local variable
* (1,0,0,1|SEQ,SEQ,0)(1,0,0,1|0,0,0,0) */
memcpy(&tcp_hc_header, packet_buffer, 2);
tcp_hc_header = NTOHS(tcp_hc_header);
uint8_t header_type = UNDEFINED;
if (BITSET(tcp_hc_header, 15) && !BITSET(tcp_hc_header, 14) &&
!BITSET(tcp_hc_header, 13)) {
header_type = MOSTLY_COMPRESSED_HEADER;
}
else if (BITSET(tcp_hc_header, 15) && BITSET(tcp_hc_header, 14) &&
!BITSET(tcp_hc_header, 13)) {
header_type = COMPRESSED_HEADER;
}
/* Setting pointer to first tcp_hc field */
packet_buffer += 4;
packet_size += 4;
/* Current socket */
socket_internal_t *current_socket =
get_tcp_socket_by_context(temp_ipv6_header, current_context);
if (current_socket == NULL) {
printf("Current Socket == NULL!\n");
return NULL;
}
/* Current TCP Context values */
tcp_hc_context_t *current_tcp_context =
¤t_socket->socket_values.tcp_control.tcp_context;
/*----------------------------------*/
/*| Sequence number handling |*/
/*----------------------------------*/
if (!BITSET(tcp_hc_header, 11) && !BITSET(tcp_hc_header, 10)) {
/* Seq = (0|0), sequence number didn't change, copy old value */
memcpy(&full_tcp_header.seq_nr, ¤t_tcp_context->seq_rcv, 4);
}
/* The 24 most significant bits haven't changed from previous packet */
else if (!BITSET(tcp_hc_header, 11) && BITSET(tcp_hc_header, 10)) {
/* Seq = (0|1), copy 1 byte of tcp_hc packet and 3 bytes from
* previous packet */
full_tcp_header.seq_nr |= *packet_buffer;
full_tcp_header.seq_nr |= ((current_tcp_context->seq_rcv) &
0xFFFFFF00);
packet_buffer += 1;
packet_size += 1;
}
/* If the 16 most significant bits haven't changed from previous packet */
else if (BITSET(tcp_hc_header, 11) && !BITSET(tcp_hc_header, 10)) {
/* Seq = (1|0), copy 2 bytes of tcp_hc packet and 2 bytes from
* previous packet */
full_tcp_header.seq_nr |= NTOHS(*((uint16_t *)packet_buffer));
full_tcp_header.seq_nr |= ((current_tcp_context->seq_rcv) & 0xFFFF0000);
packet_buffer += 2;
packet_size += 2;
}
/* Sending uncompressed sequence number */
else {
/* Seq = (1|1), copy 4 bytes of tcp_hc packet */
memcpy(&full_tcp_header.seq_nr, packet_buffer, 4);
full_tcp_header.seq_nr = NTOHL(full_tcp_header.seq_nr);
packet_buffer += 4;
packet_size += 4;
}
/*----------------------------------*/
/*| Acknowledgment number handling |*/
/*----------------------------------*/
if (!BITSET(tcp_hc_header, 9) && !BITSET(tcp_hc_header, 8)) {
/* Ack = (0|0), acknowledgment number didn't change, copy old value */
memcpy(&full_tcp_header.ack_nr, ¤t_tcp_context->ack_rcv, 4);
}
/* The 24 most significant bits haven't changed from previous packet */
else if (!BITSET(tcp_hc_header, 9) && BITSET(tcp_hc_header, 8)) {
/* Ack = (0|1), copy 1 byte of tcp_hc packet and 3 bytes from
* previous packet */
full_tcp_header.ack_nr |= *packet_buffer;
full_tcp_header.ack_nr |= ((current_tcp_context->ack_rcv) & 0xFFFFFF00);
packet_buffer += 1;
packet_size += 1;
SET_TCP_ACK(full_tcp_header.reserved_flags);
}
/* If the 16 most significant bits haven't changed from previous packet */
else if (BITSET(tcp_hc_header, 9) && !BITSET(tcp_hc_header, 8)) {
/* Ack = (1|0), copy 2 bytes of tcp_hc packet and 2 bytes from
* previous packet */
full_tcp_header.ack_nr |= NTOHS(*((uint16_t *)packet_buffer));
full_tcp_header.ack_nr |= ((current_tcp_context->ack_rcv) & 0xFFFF0000);
packet_buffer += 2;
packet_size += 2;
SET_TCP_ACK(full_tcp_header.reserved_flags);
}
/* Sending uncompressed acknowledgment number */
else {
/* Ack = (1|1), copy 4 bytes of tcp_hc packet */
memcpy(&full_tcp_header.ack_nr, packet_buffer, 4);
full_tcp_header.ack_nr = NTOHL(full_tcp_header.ack_nr);
packet_buffer += 4;
packet_size += 4;
if (header_type == COMPRESSED_HEADER) {
SET_TCP_ACK(full_tcp_header.reserved_flags);
}
}
/*----------------------------------*/
/*| Window handling |*/
/*----------------------------------*/
if (!BITSET(tcp_hc_header, 7) && !BITSET(tcp_hc_header, 6)) {
/* Wnd = (0|0), copy old value */
memcpy(&full_tcp_header.window, ¤t_tcp_context->wnd_rcv, 2);
}
/* The 8 most significant bits haven't changed from previous packet */
else if (!BITSET(tcp_hc_header, 7) && BITSET(tcp_hc_header, 6)) {
/* Wnd = (0|1), copy 1 byte of tcp_hc packet and 1 byte from
* previous packet */
full_tcp_header.window |= *packet_buffer;
full_tcp_header.window |= ((current_tcp_context->wnd_rcv) & 0xFF00);
packet_buffer += 1;
packet_size += 1;
}
/* If the 8 less significant bits haven't changed from previous packet */
else if (BITSET(tcp_hc_header, 7) && !BITSET(tcp_hc_header, 6)) {
/* Wnd = (1|0), copy 1 byte of tcp_hc packet and 1 byte from previous packet */
full_tcp_header.window |= ((*((uint16_t *)packet_buffer)) & 0xFF00);
full_tcp_header.window |= ((current_tcp_context->wnd_rcv) & 0x00FF);
packet_buffer += 1;
packet_size += 1;
}
/* Sending uncompressed window size */
else {
/* Wnd = (1|1), copy 2 bytes of tcp_hc packet */
memcpy(&full_tcp_header.window, packet_buffer, 2);
full_tcp_header.window = NTOHS(full_tcp_header.window);
packet_buffer += 2;
packet_size += 2;
}
/* FIN flag */
if (BITSET(tcp_hc_header, 3)) {
/* F = (1) */
if (IS_TCP_ACK(full_tcp_header.reserved_flags)) {
SET_TCP_FIN_ACK(full_tcp_header.reserved_flags);
}
else {
SET_TCP_FIN(full_tcp_header.reserved_flags);
}
}
/* Copy checksum into into tcp header */
memcpy(&full_tcp_header.checksum, packet_buffer, 2);
full_tcp_header.checksum = NTOHS(full_tcp_header.checksum);
packet_buffer += 2;
packet_size += 2;
/* Copy dest. and src. port into tcp header */
memcpy(&full_tcp_header.dst_port,
¤t_socket->socket_values.local_address.sin6_port, 2);
memcpy(&full_tcp_header.src_port,
¤t_socket->socket_values.foreign_address.sin6_port, 2);
/* Ordinary TCP header length */
full_tcp_header.data_offset = TCP_HDR_LEN / 4;
/* Move payload to end of tcp header */
memmove(((uint8_t *)temp_ipv6_header) + IPV6_HDR_LEN + TCP_HDR_LEN,
packet_buffer, temp_ipv6_header->length - packet_size);
/* Copy TCP uncompressed header in front of payload */
memcpy(((uint8_t *)temp_ipv6_header) + IPV6_HDR_LEN, &full_tcp_header,
TCP_HDR_LEN);
/* Set IPV6 header length */
temp_ipv6_header->length = temp_ipv6_header->length - packet_size +
TCP_HDR_LEN;
return current_socket;
}
}
