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lnwallet/size: correct commit to-local and 2nd stage script sizes

In this commit, we correct our size estimates for to-local scripts,
which are used on the commitment transaction and the htlc
success/timeout transactions. There have been observed cases of
transactions getting stuck because our estimates were too low, and cause
the transactions to not be relayed.

Our previous estimate for the commitment to-local script was derived
from an older version of the script. Though the estimate is greater than
the actual size, this has been updated with the current estimate of 79
bytes.

This estimates makes the assumption that CSV delays will be at most
4 bytes when serialized. Since this value is expressed in relative block
heights, this should be more than sufficient for our needs, even though
the maximum possible size for the little-endian int64 is 9 bytes (plus
an OP_DATA).

The other correction is to use the ToLocalScriptSize as our estimate for
htlc timeout/success scripts, as they are the same script. Previously,
our estimate was derived from the proper script, though we were 6 bytes
shy of the new to-local estimate, since we counted the csv_delay as 1
byte, and missed some other OP_DATAs.

All derived estimates have been updating depending on the new and
improved ToLocalScriptSize estimate, and fix some estimates that did not
include the witness length in the estimate.

Finally, we correct some weight miscalculations in:
 - AcceptedHtlcTimeoutWitnessSize: missing data push lengths
 - OfferedHtlcSuccessWitnessSize: extra 73 byte sig, missing data push lengths
 - OfferedHtlcPenaltyWitnessSize: missing 33 byte pubkey
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cfromknecht committed Jul 25, 2018
1 parent e0baa49 commit ee2f2573c1b1b33288d05ba59a1e8ef9e8fb621c
Showing with 72 additions and 96 deletions.
  1. +72 −96 lnwallet/size.go
@@ -143,8 +143,8 @@ const (
WitnessHeaderSize = 1 + 1

// BaseTxSize 8 bytes
// - Version: 4 bytes
// - LockTime: 4 bytes
// - Version: 4 bytes
// - LockTime: 4 bytes
BaseTxSize = 4 + 4

// BaseCommitmentTxSize 125 + 43 * num-htlc-outputs bytes
@@ -186,68 +186,39 @@ const (
// weight limits.
MaxHTLCNumber = 966

// ToLocalScriptSize 83 bytes
// ToLocalScriptSize 79 bytes
// - OP_IF: 1 byte
// - OP_DATA: 1 byte (revocationkey length)
// - revocationkey: 33 bytes
// - OP_CHECKSIG: 1 byte
// - OP_DATA: 1 byte
// - revoke_key: 33 bytes
// - OP_ELSE: 1 byte
// - OP_DATA: 1 byte (localkey length)
// - local_delay_key: 33 bytes
// - OP_CHECKSIG_VERIFY: 1 byte
// - OP_DATA: 1 byte (delay length)
// - delay: 8 bytes
// -OP_CHECKSEQUENCEVERIFY: 1 byte
// - OP_DATA: 1 byte
// - csv_delay: 4 bytes
// - OP_CHECKSEQUENCEVERIFY: 1 byte
// - OP_DROP: 1 byte
// - OP_DATA: 1 byte
// - delay_key: 33 bytes
// - OP_ENDIF: 1 byte
ToLocalScriptSize = 1 + 1 + 33 + 1 + 1 + 1 + 33 + 1 + 1 + 8 + 1 + 1

// ToLocalTimeoutWitnessSize x bytes
// - number_of_witness_elements: 1 byte
// - local_delay_sig_length: 1 byte
// - local_delay_sig: 73 bytes
// - zero_length: 1 byte
// - witness_script_length: 1 byte
// - witness_script (to_local_script)
// - OP_CHECKSIG: 1 byte
ToLocalScriptSize = 1 + 1 + 33 + 1 + 1 + 4 + 1 + 1 + 1 + 33 + 1 + 1

// ToLocalTimeoutWitnessSize 156 bytes
// - number_of_witness_elements: 1 byte
// - local_delay_sig_length: 1 byte
// - local_delay_sig: 73 bytes
// - zero_length: 1 byte
// - witness_script_length: 1 byte
// - witness_script (to_local_script)
ToLocalTimeoutWitnessSize = 1 + 1 + 73 + 1 + 1 + ToLocalScriptSize

// ToLocalPenaltyWitnessSize 160 bytes
// ToLocalPenaltyWitnessSize 156 bytes
// - number_of_witness_elements: 1 byte
// - revocation_sig_length: 1 byte
// - revocation_sig: 73 bytes
// - one_length: 1 byte
// - OP_TRUE: 1 byte
// - witness_script_length: 1 byte
// - witness_script (to_local_script)
ToLocalPenaltyWitnessSize = 1 + 1 + 73 + 1 + 1 + ToLocalScriptSize

// SecondLevelHtlcScriptSize 73 bytes
// - OP_IF: 1 byte
// - OP_DATA: 1 byte
// - revoke_key: 33 bytes
// - OP_ELSE: 1 byte
// - csv_delay: 1 byte
// - OP_CHECKSEQUENCEVERIFY: 1 byte
// - OP_DROP: 1 byte
// - delay_key: 33 bytes
// - OP_ENDIF: 1 byte
// - OP_CHECKSIG: 1 byte
SecondLevelHtlcScriptSize = 73

// SecondLevelHtlcPenaltyWitnessSize 149 bytes
// - number_of_witness_elements: 1 byte
// - revoke_sig_length: 1 byte
// - revoke_sig: 73 bytes
// - OP_TRUE: 1 byte
// - witness_script (second_level_script_size)
SecondLevelHtlcPenaltyWitnessSize = 1 + 1 + 73 + 1 + SecondLevelHtlcScriptSize

// SecondLevelHtlcSuccessWitnessSize 149 bytes
// - number_of_witness_elements: 1 byte
// - success_sig_length: 1 byte
// - success_sig: 73 bytes
// - nil_length: 1 byte
// - witness_script (second_level_script_size)
SecondLevelHtlcSuccessWitnessSize = 1 + 1 + 73 + 1 + SecondLevelHtlcScriptSize

// AcceptedHtlcScriptSize 139 bytes
// - OP_DUP: 1 byte
// - OP_HASH160: 1 byte
@@ -286,34 +257,36 @@ const (
AcceptedHtlcScriptSize = 3*1 + 20 + 5*1 + 33 + 7*1 + 20 + 4*1 +
33 + 5*1 + 4 + 5*1

// AcceptedHtlcTimeoutWitnessSize 214
// - number_of_witness_elements: 1 byte
// - sender_sig: 73 bytes
// - nil_length: 1 byte
// - witness_script: (accepted_htlc_script)
AcceptedHtlcTimeoutWitnessSize = 1 + 73 + 1 + AcceptedHtlcScriptSize

// AcceptedHtlcSuccessWitnessSize 325 bytes
// - number_of_witness_elements: 1 byte
// - nil_length: 1 byte
// - sig_alice_length: 1 byte
// - sig_alice: 73 bytes
// - sig_bob_length: 1 byte
// - sig_bob: 73 bytes
// - preimage_length: 1 byte
// - preimage: 32 bytes
// - witness_script_length: 1 byte
// - witness_script (accepted_htlc_script)
// AcceptedHtlcTimeoutWitnessSize 216
// - number_of_witness_elements: 1 byte
// - sender_sig_length: 1 byte
// - sender_sig: 73 bytes
// - nil_length: 1 byte
// - witness_script_length: 1 byte
// - witness_script: (accepted_htlc_script)
AcceptedHtlcTimeoutWitnessSize = 1 + 1 + 73 + 1 + 1 + AcceptedHtlcScriptSize

// AcceptedHtlcSuccessWitnessSize 322 bytes
// - number_of_witness_elements: 1 byte
// - nil_length: 1 byte
// - sig_alice_length: 1 byte
// - sig_alice: 73 bytes
// - sig_bob_length: 1 byte
// - sig_bob: 73 bytes
// - preimage_length: 1 byte
// - preimage: 32 bytes
// - witness_script_length: 1 byte
// - witness_script (accepted_htlc_script)
AcceptedHtlcSuccessWitnessSize = 1 + 1 + 73 + 1 + 73 + 1 + 32 + 1 + AcceptedHtlcScriptSize

// AcceptedHtlcPenaltyWitnessSize 249 bytes
// - number_of_witness_elements: 1 byte
// - revocation_sig_length: 1 byte
// - revocation_sig: 73 bytes
// - revocation_key_length: 1 byte
// - revocation_key: 33 bytes
// - witness_script_length: 1 byte
// - witness_script (accepted_htlc_script)
// - number_of_witness_elements: 1 byte
// - revocation_sig_length: 1 byte
// - revocation_sig: 73 bytes
// - revocation_key_length: 1 byte
// - revocation_key: 33 bytes
// - witness_script_length: 1 byte
// - witness_script (accepted_htlc_script)
AcceptedHtlcPenaltyWitnessSize = 1 + 1 + 73 + 1 + 33 + 1 + AcceptedHtlcScriptSize

// OfferedHtlcScriptSize 133 bytes
@@ -351,26 +324,29 @@ const (
OfferedHtlcScriptSize = 3*1 + 20 + 5*1 + 33 + 10*1 + 33 + 5*1 + 20 + 4*1

// OfferedHtlcTimeoutWitnessSize 285 bytes
// - number_of_witness_elements: 1 byte
// - nil_length: 1 byte
// - sig_alice_length: 1 byte
// - sig_alice: 73 bytes
// - sig_bob_length: 1 byte
// - sig_bob: 73 bytes
// - nil_length: 1 byte
// - witness_script_length: 1 byte
// - witness_script (offered_htlc_script)
// - number_of_witness_elements: 1 byte
// - nil_length: 1 byte
// - sig_alice_length: 1 byte
// - sig_alice: 73 bytes
// - sig_bob_length: 1 byte
// - sig_bob: 73 bytes
// - nil_length: 1 byte
// - witness_script_length: 1 byte
// - witness_script (offered_htlc_script)
OfferedHtlcTimeoutWitnessSize = 1 + 1 + 1 + 73 + 1 + 73 + 1 + 1 + OfferedHtlcScriptSize

// OfferedHtlcSuccessWitnessSize 283 bytes
// - number_of_witness_elements: 1 byte
// - nil_length: 1 byte
// - receiver_sig: 73 bytes
// - sender_sigs: 73 bytes
// - payment_preimage: 32 bytes
// - witness_script_length: 1 byte
// - witness_script (offered_htlc_script)
OfferedHtlcSuccessWitnessSize = 1 + 1 + 73 + 73 + 73 + 32 + 1 + OfferedHtlcScriptSize
// OfferedHtlcSuccessWitnessSize 317 bytes
// - number_of_witness_elements: 1 byte
// - nil_length: 1 byte
// - receiver_sig_length: 1 byte
// - receiver_sig: 73 bytes
// - sender_sig_length: 1 byte
// - sender_sig: 73 bytes
// - payment_preimage_length: 1 byte
// - payment_preimage: 32 bytes
// - witness_script_length: 1 byte
// - witness_script (offered_htlc_script)
OfferedHtlcSuccessWitnessSize = 1 + 1 + 1 + 73 + 1 + 73 + 1 + 32 + 1 + OfferedHtlcScriptSize

// OfferedHtlcPenaltyWitnessSize 243 bytes
// - number_of_witness_elements: 1 byte
@@ -380,7 +356,7 @@ const (
// - revocation_key: 33 bytes
// - witness_script_length: 1 byte
// - witness_script (offered_htlc_script)
OfferedHtlcPenaltyWitnessSize = 1 + 1 + 73 + 1 + 1 + OfferedHtlcScriptSize
OfferedHtlcPenaltyWitnessSize = 1 + 1 + 73 + 1 + 33 + 1 + OfferedHtlcScriptSize
)

// estimateCommitTxWeight estimate commitment transaction weight depending on

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