add offset to CoinbaseOutputConstraints computation to account for solo mining outputs

Author: lucasbalieiro

stratum-apps/src/coinbase_output_constraints.rs

@@ -12,6 +12,14 @@ use stratum_core::{
 pub fn coinbase_output_constraints_message(
     coinbase_outputs: Vec<TxOut>,
 ) -> CoinbaseOutputConstraints {
+    // we are using this offset to compute the addional space required by the address that will be
+    // included in the coinbase output in case of solo mining. To see the rationale of this number
+    // see the test bellow test::test_coinbase_output_constraints_from_addresses.
+    // Since we will not dinamically adjust the CoinbaseOutputConstraint message to each address, we just got the max value
+    // for each address and added as offset.
+    const OFFSET_ADDITIONAL_SIZE: u32 = 86; // to account for p2tr
+    const OFFSET_MAX_SIGOPS: u16 = 8; // to account for p2pkh
+
     // calculate the max coinbase output size for CoinbaseOutputConstraints
     let max_size: u32 = coinbase_outputs.iter().map(|o| o.size() as u32).sum();
     tracing::debug!(
@@ -38,7 +46,72 @@ pub fn coinbase_output_constraints_message(
     tracing::debug!(max_sigops, "Calculated max sigops for coinbase");
 
     CoinbaseOutputConstraints {
-        coinbase_output_max_additional_size: max_size,
-        coinbase_output_max_additional_sigops: max_sigops,
+        coinbase_output_max_additional_size: max_size + OFFSET_ADDITIONAL_SIZE,
+        coinbase_output_max_additional_sigops: max_sigops + OFFSET_MAX_SIGOPS,
+    }
+}
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn test_coinbase_output_constraints_from_addresses() {
+        use std::str::FromStr;
+        use stratum_core::bitcoin::{Address, Amount, Network, TxOut};
+
+        let addresses = vec![
+            ("p2pkh", "19drg6CgjcvqFZSW5FLWdmqTBBeFLS5iC7"),
+            ("p2sh", "18tRWCdi2Fc9CM57fUfmFK3ZC6cpGQeBkV"),
+            ("p2wpkh", "bc1qwq787dzgj2w8hh58t4clr594y0cjgjashr0fz5"),
+            ("p2wsh", "bc1qn04san36d0j76j0xksz2tesmtww7uf24j2x6v3"),
+            (
+                "p2tr",
+                "bc1p8fltq0npm605tzl22gqewhy9dt5l25m7x67832vyhh9aem24rgdsgqwtpu",
+            ),
+        ];
+
+        let mut max_size = 0u32;
+        let mut max_sigops = 0u16;
+        let mut max_size_type = "";
+        let mut max_sigops_type = "";
+
+        for (name, addr_str) in addresses {
+            let addr = Address::from_str(addr_str)
+                .unwrap()
+                .require_network(Network::Bitcoin)
+                .unwrap();
+
+            let script = addr.script_pubkey();
+
+            let txout = TxOut {
+                value: Amount::from_sat(50_0000_0000),
+                script_pubkey: script.clone(),
+            };
+
+            let constraints = coinbase_output_constraints_message(vec![txout.clone()]);
+
+            println!("computing {constraints} for {name}");
+            let size = constraints.coinbase_output_max_additional_size;
+            let sigops = constraints.coinbase_output_max_additional_sigops;
+
+            if size > max_size {
+                max_size = size;
+                max_size_type = name;
+            }
+
+            if sigops > max_sigops {
+                max_sigops = sigops;
+                max_sigops_type = name;
+            }
+
+            println!("--- {}", name);
+            println!("address: {}", addr);
+            println!("script: {}", script.to_hex_string());
+            println!("txout_size: {}", txout.size());
+            println!("max_size={} max_sigops={}", size, sigops);
+        }
+
+        println!("\n=== worst case summary ===");
+        println!("largest output size: {} ({})", max_size, max_size_type);
+        println!("largest sigops: {} ({})", max_sigops, max_sigops_type);
     }
 }