void tcp_droppedPacket(TCP* tcp, Packet* packet) {
MAGIC_ASSERT(tcp);
PacketTCPHeader header;
packet_getTCPHeader(packet, &header);
/* if we run a server, the packet could be for an existing child */
tcp = _tcp_getSourceTCP(tcp, header.destinationIP, header.destinationPort);
/* if we are closed, we don't care */
if(tcp->state == TCPS_CLOSED) {
return;
}
/* the packet was "dropped" - this is basically a negative ack.
* handle congestion control.
* TCP-Reno-like fast retransmit, i.e. multiplicative decrease. */
tcp->congestion.window /= 2;
if(tcp->congestion.window < 1) {
tcp->congestion.window = 1;
}
if(tcp->isSlowStart && tcp->congestion.threshold == 0) {
tcp->congestion.threshold = (guint32) tcp->congestion.window;
}
debug("%s <-> %s: retransmitting packet# %u", tcp->super.boundString, tcp->super.peerString, header.sequence);
/* buffer and send as appropriate */
_tcp_removeRetransmit(tcp, header.sequence);
_tcp_bufferPacketOut(tcp, packet);
_tcp_flush(tcp);
}
void pcapwriter_writePacket(PCapWriter* pcap, Packet* packet) {
if(!pcap || !pcap->pcapFile || !packet) {
return;
}
guint32 ts_sec; /* timestamp seconds */
guint32 ts_usec; /* timestamp microseconds */
guint32 incl_len; /* number of octets of packet saved in file */
guint32 orig_len; /* actual length of packet */
/* get the current time that the packet is being sent/received */
SimulationTime now = worker_getCurrentTime();
ts_sec = now / SIMTIME_ONE_SECOND;
ts_usec = (now % SIMTIME_ONE_SECOND) / SIMTIME_ONE_MICROSECOND;
/* get the header and payload lengths */
guint headerSize = packet_getHeaderSize(packet);
guint payloadLength = packet_getPayloadLength(packet);
incl_len = headerSize + payloadLength;
orig_len = headerSize + payloadLength;
/* get the TCP header and the payload */
PacketTCPHeader tcpHeader;
guchar *payload = g_new0(guchar, payloadLength);
packet_getTCPHeader(packet, &tcpHeader);
packet_copyPayload(packet, 0, payload, payloadLength);
/* write the PCAP packet header to the pcap file */
fwrite(&ts_sec, sizeof(ts_sec), 1, pcap->pcapFile);
fwrite(&ts_usec, sizeof(ts_usec), 1, pcap->pcapFile);
fwrite(&incl_len, sizeof(incl_len), 1, pcap->pcapFile);
fwrite(&orig_len, sizeof(orig_len), 1, pcap->pcapFile);
/* write the ethernet header */
guint8 destinationMAC[6] = {0x01, 0x23, 0x45, 0x67, 0x89, 0xAB};
guint8 sourceMAC[6] = {0xA1, 0xB2, 0xC3, 0xD4, 0xE5, 0xF6};
guint16 type = htons(0x0800);
fwrite(destinationMAC, 1, sizeof(destinationMAC), pcap->pcapFile);
fwrite(sourceMAC, 1, sizeof(sourceMAC), pcap->pcapFile);
fwrite(&type, 1, sizeof(type), pcap->pcapFile);
/* write the IP header */
guint8 versionAndHeaderLength = 0x45;
guint8 fields = 0x00;
guint16 totalLength = htons(orig_len - 14);
guint16 identification = 0x0000;
guint16 flagsAndFragment = 0x0040;
guint8 timeToLive = 64;
guint8 protocol = 6; /* TCP */
guint16 headerChecksum = 0x0000;
guint32 sourceIP = tcpHeader.sourceIP;
guint32 destinationIP = tcpHeader.destinationIP;
fwrite(&versionAndHeaderLength, 1, sizeof(versionAndHeaderLength), pcap->pcapFile);
fwrite(&fields, 1, sizeof(fields), pcap->pcapFile);
fwrite(&totalLength, 1, sizeof(totalLength), pcap->pcapFile);
fwrite(&identification, 1, sizeof(identification), pcap->pcapFile);
fwrite(&flagsAndFragment, 1, sizeof(flagsAndFragment), pcap->pcapFile);
fwrite(&timeToLive, 1, sizeof(timeToLive), pcap->pcapFile);
fwrite(&protocol, 1, sizeof(protocol), pcap->pcapFile);
fwrite(&headerChecksum, 1, sizeof(headerChecksum), pcap->pcapFile);
fwrite(&sourceIP, 1, sizeof(sourceIP), pcap->pcapFile);
fwrite(&destinationIP, 1, sizeof(destinationIP), pcap->pcapFile);
/* write the TCP header */
guint16 sourcePort = tcpHeader.sourcePort;
guint16 destinationPort = tcpHeader.destinationPort;
guint32 sequence = tcpHeader.sequence;
guint32 acknowledgement = 0;
if(tcpHeader.flags & PTCP_ACK) {
acknowledgement = htonl(tcpHeader.acknowledgment);
}
guint8 headerLength = 0x80;
guint8 tcpFlags = 0;
if(tcpHeader.flags & PTCP_RST) tcpFlags |= 0x04;
if(tcpHeader.flags & PTCP_SYN) tcpFlags |= 0x02;
if(tcpHeader.flags & PTCP_ACK) tcpFlags |= 0x10;
if(tcpHeader.flags & PTCP_FIN) tcpFlags |= 0x01;
guint16 window = tcpHeader.window;
guint16 tcpChecksum = 0x0000;
guint8 options[14] = {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
fwrite(&sourcePort, 1, sizeof(sourcePort), pcap->pcapFile);
fwrite(&destinationPort, 1, sizeof(destinationPort), pcap->pcapFile);
fwrite(&sequence, 1, sizeof(sequence), pcap->pcapFile);
fwrite(&acknowledgement, 1, sizeof(acknowledgement), pcap->pcapFile);
fwrite(&headerLength, 1, sizeof(headerLength), pcap->pcapFile);
fwrite(&tcpFlags, 1, sizeof(tcpFlags), pcap->pcapFile);
fwrite(&window, 1, sizeof(window), pcap->pcapFile);
fwrite(&tcpChecksum, 1, sizeof(tcpChecksum), pcap->pcapFile);
fwrite(options, 1, sizeof(options), pcap->pcapFile);
/* write payload data */
if(payloadLength > 0) {
fwrite(payload, 1, payloadLength, pcap->pcapFile);
}
g_free(payload);
}
/* return TRUE if the packet should be retransmitted */
gboolean tcp_processPacket(TCP* tcp, Packet* packet) {
MAGIC_ASSERT(tcp);
/* fetch the TCP info from the packet */
PacketTCPHeader header;
packet_getTCPHeader(packet, &header);
guint packetLength = packet_getPayloadLength(packet);
/* if we run a server, the packet could be for an existing child */
tcp = _tcp_getSourceTCP(tcp, header.sourceIP, header.sourcePort);
/* now we have the true TCP for the packet */
MAGIC_ASSERT(tcp);
/* print packet info for debugging */
debug("%s <-> %s: processing packet# %u length %u",
tcp->super.boundString, tcp->super.peerString, header.sequence, packetLength);
/* if packet is reset, don't process */
if(header.flags & PTCP_RST) {
/* @todo: not sure if this is handled correctly */
debug("received RESET packet");
if(!(tcp->state & TCPS_LISTEN) && !(tcp->error & TCPE_CONNECTION_RESET)) {
tcp->error |= TCPE_CONNECTION_RESET;
tcp->flags |= TCPF_REMOTE_CLOSED;
_tcp_setState(tcp, TCPS_TIMEWAIT);
/* it will send no more user data after what we have now */
tcp->receive.end = tcp->receive.next;
}
packet_unref(packet);
return FALSE;
}
/* if we are a server, we have to remember who we got this from so we can
* respond back to them. this is because we could be bound to several
* interfaces and otherwise cant decide which to send on.
*/
if(tcp->server) {
tcp->server->lastPeerIP = header.sourceIP;
tcp->server->lastPeerPort = header.sourcePort;
tcp->server->lastIP = header.destinationIP;
}
/* go through the state machine, tracking processing and response */
gboolean wasProcessed = FALSE;
enum ProtocolTCPFlags responseFlags = PTCP_NONE;
switch(tcp->state) {
case TCPS_LISTEN: {
/* receive SYN, send SYNACK, move to SYNRECEIVED */
if(header.flags & PTCP_SYN) {
MAGIC_ASSERT(tcp->server);
wasProcessed = TRUE;
/* we need to multiplex a new child */
Node* node = worker_getPrivate()->cached_node;
gint multiplexedHandle = node_createDescriptor(node, DT_TCPSOCKET);
TCP* multiplexed = (TCP*) node_lookupDescriptor(node, multiplexedHandle);
multiplexed->child = _tcpchild_new(multiplexed, tcp, header.sourceIP, header.sourcePort);
g_assert(g_hash_table_lookup(tcp->server->children, &(multiplexed->child->key)) == NULL);
g_hash_table_replace(tcp->server->children, &(multiplexed->child->key), multiplexed->child);
multiplexed->receive.start = header.sequence;
multiplexed->receive.next = multiplexed->receive.start + 1;
debug("%s <-> %s: server multiplexed child socket %s <-> %s",
tcp->super.boundString, tcp->super.peerString,
multiplexed->super.boundString, multiplexed->super.peerString);
_tcp_setState(multiplexed, TCPS_SYNRECEIVED);
/* parent will send response */
responseFlags = PTCP_SYN|PTCP_ACK;
}
break;
}
case TCPS_SYNSENT: {
/* receive SYNACK, send ACK, move to ESTABLISHED */
if((header.flags & PTCP_SYN) && (header.flags & PTCP_ACK)) {
wasProcessed = TRUE;
tcp->receive.start = header.sequence;
tcp->receive.next = tcp->receive.start + 1;
responseFlags |= PTCP_ACK;
_tcp_setState(tcp, TCPS_ESTABLISHED);
}
/* receive SYN, send ACK, move to SYNRECEIVED (simultaneous open) */
else if(header.flags & PTCP_SYN) {
wasProcessed = TRUE;
tcp->receive.start = header.sequence;
tcp->receive.next = tcp->receive.start + 1;
responseFlags |= PTCP_ACK;
_tcp_setState(tcp, TCPS_SYNRECEIVED);
}
break;
}
case TCPS_SYNRECEIVED: {
/* receive ACK, move to ESTABLISHED */
if(header.flags & PTCP_ACK) {
wasProcessed = TRUE;
_tcp_setState(tcp, TCPS_ESTABLISHED);
/* if this is a child, mark it accordingly */
if(tcp->child) {
tcp->child->state = TCPCS_PENDING;
g_queue_push_tail(tcp->child->parent->server->pending, tcp->child);
/* user should accept new child from parent */
descriptor_adjustStatus(&(tcp->child->parent->super.super.super), DS_READABLE, TRUE);
}
}
break;
}
case TCPS_ESTABLISHED: {
/* receive FIN, send FINACK, move to CLOSEWAIT */
if(header.flags & PTCP_FIN) {
wasProcessed = TRUE;
/* other side of connections closed */
tcp->flags |= TCPF_REMOTE_CLOSED;
responseFlags |= (PTCP_FIN|PTCP_ACK);
_tcp_setState(tcp, TCPS_CLOSEWAIT);
/* remote will send us no more user data after this sequence */
tcp->receive.end = header.sequence;
}
break;
}
case TCPS_FINWAIT1: {
/* receive FINACK, move to FINWAIT2 */
if((header.flags & PTCP_FIN) && (header.flags & PTCP_ACK)) {
wasProcessed = TRUE;
_tcp_setState(tcp, TCPS_FINWAIT2);
}
/* receive FIN, send FINACK, move to CLOSING (simultaneous close) */
else if(header.flags & PTCP_FIN) {
wasProcessed = TRUE;
responseFlags |= (PTCP_FIN|PTCP_ACK);
tcp->flags |= TCPF_REMOTE_CLOSED;
_tcp_setState(tcp, TCPS_CLOSING);
/* it will send no more user data after this sequence */
tcp->receive.end = header.sequence;
}
break;
}
case TCPS_FINWAIT2: {
/* receive FIN, send FINACK, move to TIMEWAIT */
if(header.flags & PTCP_FIN) {
wasProcessed = TRUE;
responseFlags |= (PTCP_FIN|PTCP_ACK);
tcp->flags |= TCPF_REMOTE_CLOSED;
_tcp_setState(tcp, TCPS_TIMEWAIT);
/* it will send no more user data after this sequence */
tcp->receive.end = header.sequence;
}
break;
}
case TCPS_CLOSING: {
/* receive FINACK, move to TIMEWAIT */
if((header.flags & PTCP_FIN) && (header.flags & PTCP_ACK)) {
wasProcessed = TRUE;
_tcp_setState(tcp, TCPS_TIMEWAIT);
}
break;
}
case TCPS_TIMEWAIT: {
break;
}
case TCPS_CLOSEWAIT: {
break;
}
case TCPS_LASTACK: {
/* receive FINACK, move to CLOSED */
if((header.flags & PTCP_FIN) && (header.flags & PTCP_ACK)) {
wasProcessed = TRUE;
_tcp_setState(tcp, TCPS_CLOSED);
/* we closed, cant use tcp anymore, no retransmit */
packet_unref(packet);
return FALSE;
}
break;
}
case TCPS_CLOSED: {
/* stray packet, drop without retransmit */
packet_unref(packet);
return FALSE;
break;
}
default: {
break;
}
}
gint nPacketsAcked = 0;
/* check if we can update some TCP control info */
if(header.flags & PTCP_ACK) {
wasProcessed = TRUE;
if((header.acknowledgement > tcp->send.unacked) && (header.acknowledgement <= tcp->send.next)) {
/* some data we sent got acknowledged */
nPacketsAcked = header.acknowledgement - tcp->send.unacked;
/* the packets just acked are 'released' from retransmit queue */
for(guint i = tcp->send.unacked; i < header.acknowledgement; i++) {
_tcp_removeRetransmit(tcp, i);
}
tcp->send.unacked = header.acknowledgement;
/* update congestion window and keep track of when it was updated */
tcp->congestion.lastWindow = header.window;
tcp->congestion.lastSequence = header.sequence;
tcp->congestion.lastAcknowledgement = header.acknowledgement;
}
}
gboolean doRetransmitData = FALSE;
/* check if the packet carries user data for us */
if(packetLength > 0) {
/* it has data, check if its in the correct range */
if(header.sequence >= (tcp->receive.next + tcp->receive.window)) {
/* its too far ahead to accept now, but they should re-send it */
wasProcessed = TRUE;
doRetransmitData = TRUE;
} else if(header.sequence >= tcp->receive.next) {
/* its in our window, so we can accept the data */
wasProcessed = TRUE;
/*
* if this is THE next packet, we MUST accept it to avoid
* deadlocks (unless we are blocked b/c user should read)
*/
gboolean isNextPacket = (header.sequence == tcp->receive.next) ? TRUE : FALSE;
gboolean waitingUserRead = (socket_getInputBufferSpace(&(tcp->super)) > 0) ? TRUE : FALSE;
gboolean packetFits = (packetLength <= _tcp_getBufferSpaceIn(tcp)) ? TRUE : FALSE;
if((isNextPacket && !waitingUserRead) || (packetFits)) {
/* make sure its in order */
_tcp_bufferPacketIn(tcp, packet);
} else {
debug("no space for packet even though its in our window");
doRetransmitData = TRUE;
}
}
}
/* if it is a spurious packet, send a reset */
if(!wasProcessed) {
g_assert(responseFlags == PTCP_NONE);
responseFlags = PTCP_RST;
}
/* try to update congestion window based on potentially new info */
_tcp_updateCongestionWindow(tcp, nPacketsAcked);
/* now flush as many packets as we can to socket */
_tcp_flush(tcp);
/* send ack if they need updates but we didn't send any yet (selective acks) */
if((tcp->receive.next > tcp->send.lastAcknowledgement) ||
(tcp->receive.window != tcp->send.lastWindow))
{
responseFlags |= PTCP_ACK;
}
/* send control packet if we have one */
if(responseFlags != PTCP_NONE) {
debug("%s <-> %s: sending response control packet",
tcp->super.boundString, tcp->super.peerString);
Packet* response = _tcp_createPacket(tcp, responseFlags, NULL, 0);
_tcp_bufferPacketOut(tcp, response);
_tcp_flush(tcp);
}
/* we should free packets that are done but were not buffered */
if(!doRetransmitData && packetLength <= 0) {
packet_unref(packet);
}
return doRetransmitData;
}
static void _tcp_flush(TCP* tcp) {
MAGIC_ASSERT(tcp);
/* make sure our information is up to date */
_tcp_updateReceiveWindow(tcp);
_tcp_updateSendWindow(tcp);
/* flush packets that can now be sent to socket */
while(g_queue_get_length(tcp->throttledOutput) > 0) {
/* get the next throttled packet, in sequence order */
Packet* packet = g_queue_pop_head(tcp->throttledOutput);
/* break out if we have no packets left */
if(!packet) {
break;
}
guint length = packet_getPayloadLength(packet);
if(length > 0) {
PacketTCPHeader header;
packet_getTCPHeader(packet, &header);
/* we cant send it if our window is too small */
gboolean fitsInWindow = (header.sequence < (tcp->send.unacked + tcp->send.window)) ? TRUE : FALSE;
/* we cant send it if we dont have enough space */
gboolean fitsInBuffer = (length <= socket_getOutputBufferSpace(&(tcp->super))) ? TRUE : FALSE;
if(!fitsInBuffer || !fitsInWindow) {
/* we cant send the packet yet */
g_queue_push_head(tcp->throttledOutput, packet);
break;
} else {
/* we will send: store length in virtual retransmission buffer
* so we can reduce buffer space consumed when we receive the ack */
_tcp_addRetransmit(tcp, header.sequence, length);
}
}
/* packet is sendable, we removed it from out buffer */
tcp->throttledOutputLength -= length;
/* update TCP header to our current advertised window and acknowledgement */
packet_updateTCP(packet, tcp->receive.next, tcp->receive.window);
/* keep track of the last things we sent them */
tcp->send.lastAcknowledgement = tcp->receive.next;
tcp->send.lastWindow = tcp->receive.window;
/* socket will queue it ASAP */
gboolean success = socket_addToOutputBuffer(&(tcp->super), packet);
/* we already checked for space, so this should always succeed */
g_assert(success);
}
/* any packets now in order can be pushed to our user input buffer */
while(g_queue_get_length(tcp->unorderedInput) > 0) {
Packet* packet = g_queue_pop_head(tcp->unorderedInput);
PacketTCPHeader header;
packet_getTCPHeader(packet, &header);
if(header.sequence == tcp->receive.next) {
/* move from the unordered buffer to user input buffer */
gboolean fitInBuffer = socket_addToInputBuffer(&(tcp->super), packet);
if(fitInBuffer) {
tcp->unorderedInputLength -= packet_getPayloadLength(packet);
(tcp->receive.next)++;
continue;
}
}
/* we could not buffer it because its out of order or we have no space */
g_queue_push_head(tcp->unorderedInput, packet);
break;
}
/* check if user needs an EOF signal */
gboolean wantsEOF = ((tcp->flags & TCPF_LOCAL_CLOSED) || (tcp->flags & TCPF_REMOTE_CLOSED)) ? TRUE : FALSE;
if(wantsEOF) {
/* if anyone closed, can't send anymore */
tcp->error |= TCPE_SEND_EOF;
if((tcp->receive.next >= tcp->receive.end) && !(tcp->flags & TCPF_EOF_SIGNALED)) {
/* user needs to read a 0 so it knows we closed */
tcp->error |= TCPE_RECEIVE_EOF;
descriptor_adjustStatus((Descriptor*)tcp, DS_READABLE, TRUE);
}
}
}
