Merge pull request 'pusher: optional IPv6 preference for welist reports + log report failures' (#1) from SAFE21.io/bal-server:fix/pusher-welist-ipv6-preference into main

Reviewed-on: #1

docs/07_deployment_and_ops.md

@@ -45,6 +45,7 @@ WELIST_URL=https://welist.example.com/api/stats
 - `BAL_SSL_KEY_PATH`: The path to the Ed25519 private key (`private_key.pem`) used to sign the statistics payload before sending it to the `welist` server. This is a critical secret.
 - `SEND_STATS`: A boolean flag to enable the reporting of statistics to the remote `welist` server.
 - `WELIST_URL`: The URL to which the statistics are sent. If `SEND_STATS` is `true`, this URL must be reachable. If the server is unreachable, the pusher will log an error but might not crash (see `08_security_audit.md` for DoS analysis).
+- `BAL_PUSHER_PREFER_IPV6`: Optional boolean flag (default `false`). When set to `true`, the pusher resolves the `welist` host itself and pins the HTTP connection to its first IPv6 (AAAA) address, still using the hostname for the `Host` header and TLS SNI. This works around networks where the IPv4 route to the `welist` host is broken while IPv6 works — the default connector may otherwise pick the unreachable family and the request would stall. Leave unset unless you hit this specific connectivity problem.
 
 ---
 

src/bin/bal-pusher.rs

@@ -29,7 +29,9 @@ use openssl::sign::Signer;
 use openssl::sign::Verifier;
 use reqwest::Client as rClient;
 use std::fs;
+use std::net::SocketAddr;
 use std::time::Instant;
+use url::Url;
 
 const LOCKTIME_THRESHOLD: i64 = 5000000;
 const VERSION: &str = "0.0.2";
@@ -331,8 +333,14 @@ async fn main_result(cfg: &MyConfig, network_params: &NetworkParams) -> Result<(
                 stmt.bind((2, Value::String(txid.clone()))).unwrap();
                 let _ = stmt.next();
             }
-            let _ = send_stats_report(cfg, bcinfo).await;
-            let _ = calculate_stats(&db, network_params.db_field.clone()).await;
+            if let Err(e) = send_stats_report(cfg, bcinfo).await {
+                // Never discard silently: a failing report is otherwise
+                // invisible in the logs and can go unnoticed for a long time.
+                warn!("send_stats_report failed: {e}");
+            }
+            if let Err(e) = calculate_stats(&db, network_params.db_field.clone()).await {
+                warn!("calculate_stats failed: {e}");
+            }
         }
         Err(erx) => {
             error!("impossible to get client: {}, retrying on next block", erx);
@@ -422,6 +430,76 @@ ON CONFLICT(chain) DO UPDATE SET
     }
     Ok(())
 }
+/// Parse the `(host, port)` pair from a base URL like `https://host[:port]`.
+///
+/// Falls back to the scheme's well-known default port (443 for `https`,
+/// 80 for plain `http`), or to 443 when the scheme is unknown.
+fn parse_host_port(base_url: &str) -> Option<(String, u16)> {
+    let url = Url::parse(base_url).ok()?;
+    let host = url
+        .host_str()?
+        .trim_start_matches('[')
+        .trim_end_matches(']')
+        .to_string();
+    let port = url.port_or_known_default().unwrap_or(443);
+    Some((host, port))
+}
+
+/// Resolve `host:port` and return the first IPv6 (AAAA) address, if any.
+///
+/// Returns `None` when the host has no IPv6 address.
+async fn resolve_first_ipv6(host: &str, port: u16) -> Option<SocketAddr> {
+    use std::net::ToSocketAddrs;
+    let host = host.to_string();
+    tokio::task::spawn_blocking(move || {
+        format!("{}:{}", host, port)
+            .to_socket_addrs()
+            .ok()
+            .and_then(|mut addrs| addrs.find(|a| a.is_ipv6()))
+    })
+    .await
+    .ok()
+    .flatten()
+}
+
+/// Build the HTTP client used for welist reports.
+///
+/// When `BAL_PUSHER_PREFER_IPV6` is truthy, the welist host is resolved and
+/// the client is pinned to its first IPv6 address (the original hostname is
+/// still used for the `Host` header and TLS SNI). This works around networks
+/// where the IPv4 route to the welist host is broken while IPv6 works: the
+/// default connector may otherwise pick the broken family and the request
+/// stalls. When the variable is unset (the default), behavior is unchanged.
+async fn welist_http_client(welist_url: &str) -> rClient {
+    let prefer_ipv6 = env::var("BAL_PUSHER_PREFER_IPV6")
+        .unwrap_or("false".to_string())
+        .parse::<bool>()
+        .unwrap_or(false);
+    if !prefer_ipv6 {
+        return rClient::new();
+    }
+    let (host, port) = match parse_host_port(welist_url) {
+        Some(hp) => hp,
+        None => {
+            warn!("BAL_PUSHER_PREFER_IPV6: cannot parse '{welist_url}', using default resolver");
+            return rClient::new();
+        }
+    };
+    match resolve_first_ipv6(&host, port).await {
+        Some(addr) => {
+            debug!("BAL_PUSHER_PREFER_IPV6: pinning {host} to {addr}");
+            rClient::builder()
+                .resolve(&host, addr)
+                .build()
+                .unwrap_or_else(|_| rClient::new())
+        }
+        None => {
+            debug!("BAL_PUSHER_PREFER_IPV6: no IPv6 address for {host}, using default resolver");
+            rClient::new()
+        }
+    }
+}
+
 async fn send_stats_report(
     cfg: &MyConfig,
     bcinfo: GetBlockchainInfoResult,
@@ -437,7 +515,7 @@ async fn send_stats_report(
             );
             return Ok(());
         }
-        let client = rClient::new();
+        let client = welist_http_client(&welist_url).await;
         let url = format!("{}/ping", welist_url);
         debug!("welist url: {}", url);
         let chain = bcinfo.chain.to_string().to_lowercase();
@@ -724,3 +802,45 @@ fn seq_to_str(seq: &Vec<u8>) -> String {
     }
     "Unknown".to_string()
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn parse_host_port_https_default_port() {
+        assert_eq!(
+            parse_host_port("https://welist.bitcoin-after.life"),
+            Some(("welist.bitcoin-after.life".to_string(), 443))
+        );
+    }
+
+    #[test]
+    fn parse_host_port_explicit_port_and_path() {
+        assert_eq!(
+            parse_host_port("https://example.com:8443/ping"),
+            Some(("example.com".to_string(), 8443))
+        );
+    }
+
+    #[test]
+    fn parse_host_port_http_default_port() {
+        assert_eq!(
+            parse_host_port("http://example.com"),
+            Some(("example.com".to_string(), 80))
+        );
+    }
+
+    #[test]
+    fn parse_host_port_ipv6_literal_brackets_stripped() {
+        assert_eq!(
+            parse_host_port("https://[2a13:2c0::1]:443"),
+            Some(("2a13:2c0::1".to_string(), 443))
+        );
+    }
+
+    #[test]
+    fn parse_host_port_invalid_url() {
+        assert_eq!(parse_host_port("not a url"), None);
+    }
+}