feat(pbs): dial builders outside the config for ePBS requests

config.example.toml

@@ -31,7 +31,7 @@ wait_all_registrations = true
 # this should be lower than that, leaving some margin for overhead
 # OPTIONAL, DEFAULT: 950
 timeout_get_header_ms = 950
-# (unreleased, from v0.12.0-rc1) ePBS bids only: ms kept back from the beacon node's X-Timeout-Ms deadline, must be under one slot, 12000 on mainnet (https://commit-boost.github.io/commit-boost-client/get_started/epbs#timing)
+# (unreleased, from v0.12.0-rc1) ePBS bids only: ms kept back from the beacon node's X-Timeout-Ms deadline, must be above 0 and under one slot, 12000 on mainnet (https://commit-boost.github.io/commit-boost-client/get_started/epbs#timing)
 # OPTIONAL, DEFAULT: 50
 # proposer_deadline_buffer_ms = 50
 # Timeout in milliseconds for the `submit_blinded_block` call to relays.

crates/common/src/config/pbs.rs

@@ -250,13 +250,12 @@ impl PbsConfig {
         );
         ensure!(self.late_in_slot_time_ms > 0, "late_in_slot_time_ms must be greater than 0");
 
-        // The buffer comes out of the proposer's deadline, which is clamped to
-        // one slot, so a buffer of a slot or more leaves no time for the bid
-        // request. 0 is allowed (no reserve).
+        // 0 leaves the bid no time to get back to the beacon node, and a slot or
+        // more leaves the builder none, as the proposer's deadline is clamped to a slot
         let slot_time_ms = chain.slot_time_sec().saturating_mul(1000);
         ensure!(
-            self.proposer_deadline_buffer_ms < slot_time_ms,
-            "proposer_deadline_buffer_ms must be less than one slot ({slot_time_ms} ms)"
+            (1..slot_time_ms).contains(&self.proposer_deadline_buffer_ms),
+            "proposer_deadline_buffer_ms must be greater than 0 and less than one slot ({slot_time_ms} ms)"
         );
 
         ensure!(
@@ -557,6 +556,42 @@ mod tests {
     use super::*;
     use crate::config::test_env::{RELAY_URL, with_env};
 
+    fn config_with_buffer(buffer: u64) -> String {
+        format!(
+            "chain = \"Holesky\"\n[pbs]\nproposer_deadline_buffer_ms = {buffer}\n\
+             [[relays]]\nurl = \"{RELAY_URL}\"\n"
+        )
+    }
+
+    #[tokio::test]
+    async fn test_deadline_buffer_range() {
+        for (buffer, accepted) in [(0, false), (1, true), (11999, true), (12000, false)] {
+            let config: CommitBoostConfig = toml::from_str(&config_with_buffer(buffer)).unwrap();
+            assert_eq!(config.validate().await.is_ok(), accepted, "{buffer}");
+        }
+    }
+
+    // The service and a custom PBS module load [pbs] through different functions
+    #[test]
+    fn test_loaders_reject_zero_deadline_buffer() {
+        #[derive(Deserialize)]
+        struct NoExtra {}
+        let dir = tempfile::tempdir().unwrap();
+        let path = dir.path().join("cb-config.toml");
+        std::fs::write(&path, config_with_buffer(0)).unwrap();
+        let runtime = tokio::runtime::Builder::new_current_thread().enable_all().build().unwrap();
+        let service = runtime.block_on(load_pbs_config(Some(path.clone()))).map(|_| ());
+        let custom = with_env(&[(CONFIG_ENV, path.to_str())], || {
+            runtime.block_on(load_pbs_custom_config::<NoExtra>()).map(|_| ())
+        });
+        for result in [service, custom] {
+            let err = result.expect_err("a zero deadline buffer loaded");
+            let expected =
+                "proposer_deadline_buffer_ms must be greater than 0 and less than one slot";
+            assert!(format!("{err:#}").contains(expected), "{err:#}");
+        }
+    }
+
     fn relay_with_headers(headers: &str) -> Result<RelayConfig, toml::de::Error> {
         toml::from_str(&format!("url = \"{RELAY_URL}\"\nheaders = {headers}\n"))
     }

crates/common/src/pbs/relay.rs

@@ -97,6 +97,14 @@ pub struct RelayClient {
 
 impl RelayClient {
     pub fn new(config: RelayConfig) -> eyre::Result<Self> {
+        Self::with_client_builder(config, reqwest::Client::builder())
+    }
+
+    /// [`Self::new`] on a client builder that already holds extra settings
+    pub fn with_client_builder(
+        config: RelayConfig,
+        builder: reqwest::ClientBuilder,
+    ) -> eyre::Result<Self> {
         let stream_url = match config.get_header {
             GetHeaderTransport::Http => None,
             GetHeaderTransport::Stream => Some(stream_url(&config.entry.url)?),
@@ -131,10 +139,8 @@ impl RelayClient {
             }
         }
 
-        let client = reqwest::Client::builder()
-            .default_headers(headers.clone())
-            .timeout(DEFAULT_REQUEST_TIMEOUT)
-            .build()?;
+        let client =
+            builder.default_headers(headers.clone()).timeout(DEFAULT_REQUEST_TIMEOUT).build()?;
 
         Ok(Self {
             id: Arc::new(config.id().to_owned()),
@@ -255,6 +261,13 @@ impl RelayClient {
     }
 }
 
+/// `address`, the auth data before any `?`, as a builder URL. Only `http` and
+/// `https` count, since `builder-a:prod` parses as a URL too.
+pub fn decode_auth_data_url(address: &[u8]) -> Option<Url> {
+    let url = Url::parse(std::str::from_utf8(address).ok()?).ok()?;
+    matches!(url.scheme(), "http" | "https").then_some(url)
+}
+
 /// First 4 bytes of the value's SHA-256: enough to see a rotation
 /// across reloads, too short to identify a value on its own
 fn value_fingerprint(value: &str) -> String {
@@ -268,12 +281,30 @@ mod tests {
 
     use alloy::primitives::B256;
 
-    use super::{GetHeaderRequest, RelayClient, RelayEntry, value_fingerprint};
+    use super::{
+        GetHeaderRequest, RelayClient, RelayEntry, decode_auth_data_url, value_fingerprint,
+    };
     use crate::{
         config::{GetHeaderTransport, RelayConfig, test_env::RELAY_URL},
         utils::bls_pubkey_from_hex_unchecked,
     };
 
+    #[test]
+    fn decode_auth_data_url_accepts_only_http_urls() {
+        let cases: [(&[u8], Option<&str>); 5] = [
+            (b"https://Builder-A.example.com:443/eth", Some("https://builder-a.example.com/eth")),
+            (b"http://10.0.0.1:18550", Some("http://10.0.0.1:18550/")),
+            // Opaque data and host:port parse as URLs with their own scheme
+            (b"builder-a:prod", None),
+            (b"localhost:18550", None),
+            (b"builder-a.example.com", None),
+        ];
+        for (data, expected) in cases {
+            let decoded = decode_auth_data_url(data).map(|url| url.to_string());
+            assert_eq!(decoded.as_deref(), expected, "{}", String::from_utf8_lossy(data));
+        }
+    }
+
     #[test]
     fn test_relay_entry() {
         let pubkey = bls_pubkey_from_hex_unchecked(

crates/pbs/Cargo.toml

@@ -5,6 +5,9 @@ publish = false
 rust-version.workspace = true
 version.workspace = true
 
+[features]
+testing-flags = []
+
 [dependencies]
 alloy.workspace = true
 async-trait.workspace = true
@@ -35,3 +38,6 @@ url.workspace = true
 uuid.workspace = true
 webpki-roots.workspace = true
 thiserror.workspace = true
+
+[dev-dependencies]
+tokio = { workspace = true, features = ["test-util"] }