swapserver: bump fee of refund tx if needed

electrum/submarine_swaps.py

@@ -299,6 +299,7 @@ class SwapManager(Logger):
             self._add_or_reindex_swap(swap)  # to update _swaps_by_funding_outpoint
             funding_height = self.lnwatcher.adb.get_tx_height(txin.prevout.txid.hex())
             spent_height = txin.spent_height
+            should_bump_fee = False
             if spent_height is not None:
                 swap.spending_txid = txin.spent_txid
                 if spent_height > 0:
@@ -326,18 +327,27 @@ class SwapManager(Logger):
             if not swap.is_reverse:
                 if swap.preimage is None and spent_height is not None:
                     # extract the preimage, add it to lnwatcher
-                    tx = self.lnwatcher.adb.get_transaction(txin.spent_txid)
-                    preimage = tx.inputs()[0].witness_elements()[1]
+                    claim_tx = self.lnwatcher.adb.get_transaction(txin.spent_txid)
+                    preimage = claim_tx.inputs()[0].witness_elements()[1]
                     if sha256(preimage) == swap.payment_hash:
                         swap.preimage = preimage
                         self.logger.info(f'found preimage: {preimage.hex()}')
                         self.lnworker.preimages[swap.payment_hash.hex()] = preimage.hex()
                         # note: we must check the payment secret before we broadcast the funding tx
                     else:
-                        # refund tx
+                        # this is our refund tx
                         if spent_height > 0:
+                            self.logger.info(f'refund tx confirmed: {txin.spent_txid} {spent_height}')
                             self._fail_swap(swap, 'refund tx confirmed')
                             return
+                        else:
+                            claim_tx.add_info_from_wallet(self.wallet)
+                            claim_tx_fee = claim_tx.get_fee()
+                            recommended_fee = self.get_claim_fee()
+                            if claim_tx_fee * 1.1 < recommended_fee:
+                                should_bump_fee = True
+                                self.logger.info(f'claim tx fee too low {claim_tx_fee} < {recommended_fee}. we will bump the fee')
+
                 if remaining_time > 0:
                     # too early for refund
                     return
@@ -362,7 +372,7 @@ class SwapManager(Logger):
                     # for testing: do not create claim tx
                     return
 
-            if spent_height is not None:
+            if spent_height is not None and not should_bump_fee:
                 return
             try:
                 tx = self._create_and_sign_claim_tx(txin=txin, swap=swap, config=self.wallet.config)