libp2p: warn/refuse bad prefer/ignore combos

1 files changed, 35 insertions, 2 deletions

diff --git a/src/transport/libp2p/config.rs b/src/transport/libp2p/config.rs
index 8b172ba..4db8444 100644
--- a/src/transport/libp2p/config.rs
+++ b/src/transport/libp2p/config.rs
@@ -59,8 +59,14 @@ pub(crate) fn check(settings: &crate::config::Settings) -> Result<()> {
     parse_addresses("libp2p-listen", &settings.libp2p_listen)?;
     parse_addresses("libp2p-announce", &settings.libp2p_announce)?;
     parse_addresses("libp2p-relays", &settings.libp2p_relays)?;
-    parse_ranges("libp2p-ignore", &settings.libp2p_ignore)?;
-    parse_ranges("libp2p-prefer", &settings.libp2p_prefer)?;
+    let ignore = parse_ranges("libp2p-ignore", &settings.libp2p_ignore)?;
+    let prefer = parse_ranges("libp2p-prefer", &settings.libp2p_prefer)?;
+    check_preferred(
+        &ignore,
+        &prefer,
+        &settings.libp2p_ignore,
+        &settings.libp2p_prefer,
+    )?;
     if settings.relay_only {
         if settings.libp2p_listen.is_empty() {
             bail!("relay-only needs libp2p-listen: where nodes reach the relay");
@@ -74,6 +80,33 @@ pub(crate) fn check(settings: &crate::config::Settings) -> Result<()> {
     Ok(())
 }
 
+/// A range both ignored and preferred: refused where all of the preferred one is
+/// ignored (it would name nothing usable), a warning where only part of it is (the
+/// ignored part stays left out). `ignore_given` and `prefer_given`: as written, for
+/// the messages. Ranges nest or are apart, so there's nothing in between.
+pub(super) fn check_preferred(
+    ignore: &[IpRange],
+    prefer: &[IpRange],
+    ignore_given: &[String],
+    prefer_given: &[String],
+) -> Result<()> {
+    for (preferred, preferred_given) in prefer.iter().zip(prefer_given) {
+        for (ignored, ignored_given) in ignore.iter().zip(ignore_given) {
+            if ignored.covers(preferred) {
+                bail!(
+                    "libp2p-prefer {preferred_given:?} is all in libp2p-ignore {ignored_given:?}: nothing there is used"
+                );
+            }
+            if preferred.covers(ignored) {
+                warn!(
+                    "libp2p-prefer {preferred_given:?} has libp2p-ignore {ignored_given:?} in it: addresses there stay left out"
+                );
+            }
+        }
+    }
+    Ok(())
+}
+
 impl Libp2pConfig {
     /// The configuration `settings` give; `relay_only`: a relay that is no node
     /// (`--relay-only`).