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TCP retransmission fixes and fuzz failure fixes (#59)

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* fix for #58

* add fixes for both retransmit and fuzz failure found

* fix infinite challenge ack due to RST+SYN+FIN corrupt packet in SYNRCV state

* fuzz: previous recovery ack path led to infinite transmit

* fuzz: calculate CRCs when fuzzing to reduce search space to non-CRC error cases

* add local fuzz corpus to tests

* add more cases to fuzz corpus
This commit is contained in:
Pat Whittingslow
2026-03-20 14:25:31 +01:00
committed by GitHub
parent 493446244f
commit faae7ab076
216 changed files with 1299 additions and 35 deletions
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ipv4/frame.go
+13 -1
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@@ -127,7 +127,13 @@ func (ifrm Frame) SetCRC(cs uint16) {
binary.BigEndian.PutUint16(ifrm.buf[10:12], cs)
}
// CalculateHeaderCRC calculates the CRC for this IPv4 frame.
// CalculateHeaderCRC calculates the CRC for this IPv4 frame including CRC field.
// If the result of this function is 0 then the CRC is valid for the frame.
// To calculate the CRC for a frame set the CRC field to zero and then call this function:
//
// ifrm.SetCRC(0)
// crcValue := ifrm.CalculateHeaderCRC()
// ifrm.SetCRC(crcValue)
func (ifrm Frame) CalculateHeaderCRC() uint16 {
var crc lneto.CRC791
ifrm.CRCWriteHeader(&crc)
@@ -138,6 +144,12 @@ func (ifrm Frame) CRCWriteHeader(crc *lneto.CRC791) {
crc.WriteEven(ifrm.buf[:20])
}
// CRCWriteTCPPseudo is used to calculate the TCP checksum for IPv4 framed packets.
// To calculate the CRC of a TCP frame:
//
// ifrm.CRCWriteTCPPseudo(&crc)
// // tfrm.SetCRC(0) // Zero if calculating frame for sending out.
// crcValue := crc.PayloadSum16(ifrm.Payload()) // If validating a received frame crcValue should be zero here.
func (ifrm Frame) CRCWriteTCPPseudo(crc *lneto.CRC791) {
crc.WriteEven(ifrm.sourceAndDestinationAddr())
crc.AddUint16(ifrm.TotalLength() - uint16(ifrm.HeaderLength()))