dekker.one
An Uppaal analysis of the connection setup of the TCP protocol.
Updated sequence number stuff
+25
-22
+25
-22
Model/model.xml
+25
-22
Model/model.xml
···
50
c:=0</label><nail x="-5440" y="-1408"/><nail x="-5440" y="-1664"/></transition></template><template><name>Host_Handshake</name><parameter>const int local, const int remote, const int network</parameter><declaration>clock c;
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meta int snd_una = 0;
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meta int snd_nxt = 0;
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-
meta int seg_ack = 0;
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-
meta int seg_len = 0;
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meta int rcv_nxt = 0;
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meta TCP_segment retrans;
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meta TCP_segment received;
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bool receive_packet(){
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-
received := from_network;
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-
snd_nxt = received.ackNr;
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-
seg_ack = (received.seqNr + 1 + len)%MAX_SEQ;
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-
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-
initialize(from_network);
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-
}
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-
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-
int update_win(){
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-
//TODO: do something usefull.
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-
return 0;
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-
}
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-
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void reset()
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-
{
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-
last_seq := 0;
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last_ack := 0;
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-
initialize(retrans);
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initialize(received);
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}
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void send(bool syn, bool ack) {
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target_address = remote;
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retrans.syn := syn;
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retrans.ack := ack;
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retrans.seqNr := snd_nxt;
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-
retrans.ackNr := seq_ack;
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-
retrans.win := update_win();
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to_network := retrans;
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}
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···
50
c:=0</label><nail x="-5440" y="-1408"/><nail x="-5440" y="-1664"/></transition></template><template><name>Host_Handshake</name><parameter>const int local, const int remote, const int network</parameter><declaration>clock c;
51
meta int snd_una = 0;
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meta int snd_nxt = 0;
53
+
meta int snd_ack = 0;
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meta int rcv_nxt = 0;
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+
const int seg_len = 0;
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+
const int window = 1;
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meta TCP_segment retrans;
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meta TCP_segment received;
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bool receive_packet(){
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+
if (from_network.syn) {
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+
rcv_nxt = from_network.seqNr;
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+
}
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+
if (rcv_nxt == from_network.seqNr) {
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+
if (received.ack && snd_una < from_network.ackNr) {
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+
snd_una = from_network.ackNr;
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+
}
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+
else if (received.ack) {
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+
return false;
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+
}
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+
received := from_network;
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+
snd_nxt = received.ackNr + 1;
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+
snd_ack = (received.seqNr + 1 + seg_len)%MAX_SEQ;
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+
initialize(from_network);
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+
return true;
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+
}
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+
return false;
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}
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void send(bool syn, bool ack) {
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+
if (syn) {
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+
snd_una := snd_nxt;
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+
}
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target_address = remote;
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retrans.syn := syn;
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retrans.ack := ack;
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retrans.seqNr := snd_nxt;
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+
retrans.ackNr := snd_ack;
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+
retrans.win := window;
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to_network := retrans;
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}
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