[#SignalsOptInRBF]
= SignalsOptInRBF
:mrdocs:

Check whether the sequence numbers on this transaction are signaling opt‐in to replace‐by‐fee, according to BIP 125. Allow opt‐out of transaction replacement by setting nSequence > MAX_BIP125_RBF_SEQUENCE (SEQUENCE_FINAL‐2) on all inputs.

== Synopsis

Declared in `<util/rbf.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
bool
SignalsOptInRBF(xref:CTransaction.adoc[CTransaction] const& tx);
----

== Description

SEQUENCE_FINAL‐1 is picked to still allow use of nLockTime by non‐replaceable transactions. All inputs rather than just one is for the sake of multi‐party protocols, where we don't want a single party to be able to disable replacement by opting out in their own input.

== Return Value

true if any input signals opt‐in replaceability under BIP 125.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *tx*
| The transaction whose input sequence numbers are inspected.
|===


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