Incorporate low-R values into estimate signature size

diff --git a/lightning/src/chain/keysinterface.rs b/lightning/src/chain/keysinterface.rs
index b1290708b95f70a71ebf6193cceb1677aa3150bd..3ccab2ce9dabb0b36f9876210a1d39bd5faff98d 100644 (file)
--- a/lightning/src/chain/keysinterface.rs
+++ b/lightning/src/chain/keysinterface.rs
@@ -85,6 +85,8 @@ pub struct DelayedPaymentOutputDescriptor {
 }
 impl DelayedPaymentOutputDescriptor {
        /// The maximum length a well-formed witness spending one of these should have.
+       /// Note: If you have the grind_signatures feature enabled, this will be at least 1 byte
+       /// shorter.
        // Calculated as 1 byte length + 73 byte signature, 1 byte empty vec push, 1 byte length plus
        // redeemscript push length.
        pub const MAX_WITNESS_LENGTH: usize = 1 + 73 + 1 + chan_utils::REVOKEABLE_REDEEMSCRIPT_MAX_LENGTH + 1;
@@ -117,6 +119,8 @@ pub struct StaticPaymentOutputDescriptor {
 }
 impl StaticPaymentOutputDescriptor {
        /// The maximum length a well-formed witness spending one of these should have.
+       /// Note: If you have the grind_signatures feature enabled, this will be at least 1 byte
+       /// shorter.
        // Calculated as 1 byte legnth + 73 byte signature, 1 byte empty vec push, 1 byte length plus
        // redeemscript push length.
        pub const MAX_WITNESS_LENGTH: usize = 1 + 73 + 34;
@@ -1188,6 +1192,8 @@ impl KeysManager {
                                                witness: Witness::new(),
                                        });
                                        witness_weight += StaticPaymentOutputDescriptor::MAX_WITNESS_LENGTH;
+                                       #[cfg(feature = "grind_signatures")]
+                                       { witness_weight -= 1; } // Guarantees a low R signature
                                        input_value += descriptor.output.value;
                                        if !output_set.insert(descriptor.outpoint) { return Err(()); }
                                },
@@ -1199,6 +1205,8 @@ impl KeysManager {
                                                witness: Witness::new(),
                                        });
                                        witness_weight += DelayedPaymentOutputDescriptor::MAX_WITNESS_LENGTH;
+                                       #[cfg(feature = "grind_signatures")]
+                                       { witness_weight -= 1; } // Guarantees a low R signature
                                        input_value += descriptor.output.value;
                                        if !output_set.insert(descriptor.outpoint) { return Err(()); }
                                },
@@ -1210,6 +1218,8 @@ impl KeysManager {
                                                witness: Witness::new(),
                                        });
                                        witness_weight += 1 + 73 + 34;
+                                       #[cfg(feature = "grind_signatures")]
+                                       { witness_weight -= 1; } // Guarantees a low R signature
                                        input_value += output.value;
                                        if !output_set.insert(*outpoint) { return Err(()); }
                                }