Andrew Boyson / net

A stack which works with or without an Mbed os library. Provides IPv4 or IPv6 with a full 1500 byte buffer.

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tcp/tcp.txt@72:19457bba58d0, 2018-10-22 (annotated)

Committer:
andrewboyson
Date:
Mon Oct 22 10:24:58 2018 +0000
Revision:
72:19457bba58d0
Parent:
71:736a5747ade1
Child:
75:603b10404183
Removed positioninquery and positioninreply variables. Working.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
andrewboyson 71:736a5747ade1 1 Names
andrewboyson 71:736a5747ade1 2 =====
andrewboyson 71:736a5747ade1 3 ISN == Initial Sequence Number
andrewboyson 71:736a5747ade1 4 SEQ num == Sequence Number is the sequence of the first byte of the sent data packet - unless a SYN in which case it is the ISN
andrewboyson 71:736a5747ade1 5 ACK num == Acknowledge Number is the next sequence number that the sender of the ACK is expecting
andrewboyson 71:736a5747ade1 6 TCB == Transmission Control Block
andrewboyson 71:736a5747ade1 7 RTO == Retransmission Time Out
andrewboyson 71:736a5747ade1 8
andrewboyson 71:736a5747ade1 9 Protocol
andrewboyson 71:736a5747ade1 10 ========
andrewboyson 71:736a5747ade1 11 Goes:
andrewboyson 71:736a5747ade1 12 0 SYN
andrewboyson 71:736a5747ade1 13 1 Data (length == MSS)
andrewboyson 71:736a5747ade1 14 1+ MSS Data (length == MSS)
andrewboyson 71:736a5747ade1 15 1+2xMSS Data (length < MSS) + FIN
andrewboyson 71:736a5747ade1 16
andrewboyson 71:736a5747ade1 17 TcpHandleReceivedPacket
andrewboyson 71:736a5747ade1 18 =======================
andrewboyson 71:736a5747ade1 19 Called from the network stack
andrewboyson 71:736a5747ade1 20 Reads the header to get: the src and dst ports; the ACK and SEQ numbers; SYN, ACK, PSH, RST and FIN flags
andrewboyson 71:736a5747ade1 21 Only handles dst port 80 (HTTP)
andrewboyson 71:736a5747ade1 22 Retrieves the TCB for the src port
andrewboyson 71:736a5747ade1 23 Handles RST or SYN requests
andrewboyson 71:736a5747ade1 24 Subtract the initial sequence numbers to get the position in the query from the SEQ num and the position in the reply from the ACK num.
andrewboyson 71:736a5747ade1 25 If the position in the query is not the same as the TCB recd bytes then adjust the TCB recd bytes
andrewboyson 71:736a5747ade1 26 If the position in the reply is not the same as the TCB sent bytes then adjust the TCB sent bytes
andrewboyson 71:736a5747ade1 27 Increment the TCB recd bytes by the received datalength and by 1 for a SYN or FIN
andrewboyson 71:736a5747ade1 28 Handle the packet according to the TCB state, for established connections pass the position in the query and the position in the reply
andrewboyson 71:736a5747ade1 29 Set the ACK number to the TCB recd bytes plus the ISN
andrewboyson 71:736a5747ade1 30 Set the SEQ number to the TCB sent bytes plus the ISN
andrewboyson 71:736a5747ade1 31 Increment the TCB sent bytes by the sent datalength and by 1 for a SYN or FIN
andrewboyson 71:736a5747ade1 32 Swap the ports
andrewboyson 71:736a5747ade1 33 Return to the network stack for unicast transmission
andrewboyson 71:736a5747ade1 34
andrewboyson 71:736a5747ade1 35 Todo
andrewboyson 71:736a5747ade1 36 ====
andrewboyson 71:736a5747ade1 37 Separate the work into TcpHandleReceivedPacket and TcpPollForPacketToSend: this would allow RTO to be implemented.
andrewboyson 71:736a5747ade1 38 Need to add the IP to the TCB
andrewboyson 71:736a5747ade1 39 Change TCB_ACK_WAIT and TCB_FIN_WAIT to TCB_CLOSE_ACK_WAIT and TCB_CLOSE_FIN_WAIT
andrewboyson 71:736a5747ade1 40 Add state TCB_SEND_ACK_WAIT
andrewboyson 71:736a5747ade1 41 Add ackdBytes to TCB so that can tell if sentBytes has been acked or not; if so then send the next; if not and within timeout then wait; if not and RTO then send again
andrewboyson 71:736a5747ade1 42
andrewboyson 71:736a5747ade1 43 State
andrewboyson 71:736a5747ade1 44 =====
andrewboyson 72:19457bba58d0 45 State Received Do New state
andrewboyson 72:19457bba58d0 46 TCB_EMPTY SYN record ISN TCB_SYN_RECEIVED
andrewboyson 72:19457bba58d0 47 TCB_SYN_RECEIVED ACK TCB_ESTABLISHED
andrewboyson 72:19457bba58d0 48 TCB_ESTABLISHED
andrewboyson 72:19457bba58d0 49 TCB_ACK_WAIT
andrewboyson 72:19457bba58d0 50 TCB_FIN_WAIT
andrewboyson 72:19457bba58d0 51
andrewboyson 72:19457bba58d0 52 State
andrewboyson 71:736a5747ade1 53 TCB_EMPTY do nothing
andrewboyson 71:736a5747ade1 54 TCB_SYN_RECEIVED if (TCB.sent == 0) or (TCB.sent == 1 and TCB.ackd == 0 and RTO) then send SYN ACK and ISN.
andrewboyson 71:736a5747ade1 55 TCB_ESTABLISHED if (!TCB.finished) then send from TCB.sent. if RTO and TCB.ackd < TCB.sent then resend TCB.ackd
andrewboyson 72:19457bba58d0 56 TCB_ACK_WAIT
andrewboyson 71:736a5747ade1 57 TCB_FIN_WAIT