chore: render contextual information more Sentry-friendly (#10386)

Sentry can group issues together that have unique identifiers in their
message. Unfortunately, it does that only well for integers and UUIDs
and not so much for hex-values. To avoid alert fatigue, we render the
public key as a u256 which hopefully allows Sentry to group these
together.

rust/Cargo.lock

@@ -943,6 +943,12 @@ dependencies = [
  "piper",
 ]
 
+[[package]]
+name = "bnum"
+version = "0.13.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "119771309b95163ec7aaf79810da82f7cd0599c19722d48b9c03894dca833966"
+
 [[package]]
 name = "boringtun"
 version = "0.6.1"
@@ -6907,6 +6913,7 @@ name = "snownet"
 version = "0.1.0"
 dependencies = [
  "anyhow",
+ "bnum",
  "boringtun",
  "bufferpool",
  "bytecodec",

rust/Cargo.toml

@@ -56,6 +56,7 @@ aya-log-ebpf = { git = "https://github.com/aya-rs/aya" }
 backoff = { version = "0.4", features = ["tokio"] }
 base64 = { version = "0.22.1", default-features = false }
 bimap = "0.6"
+bnum = "0.13.0"
 boringtun = { version = "0.6", default-features = false }
 bufferpool = { path = "connlib/bufferpool" }
 bytecodec = "0.5.0"

rust/connlib/snownet/Cargo.toml

@@ -6,6 +6,7 @@ license = { workspace = true }
 
 [dependencies]
 anyhow = { workspace = true }
+bnum = { workspace = true }
 boringtun = { workspace = true }
 bufferpool = { workspace = true }
 bytecodec = { workspace = true }

rust/connlib/snownet/src/node.rs

@@ -1465,7 +1465,7 @@ where
         let id = self
             .established_by_wireguard_session_index
             .get(&index.global())
-            .with_context(|| format!("No connection for with index {index}"))?;
+            .with_context(|| format!("No connection for index {}", index.global()))?;
         let connection = self
             .established
             .get_mut(id)
@@ -1482,7 +1482,7 @@ where
             .established
             .iter_mut()
             .find(|(_, c)| c.tunnel.remote_static_public().as_bytes() == &key)
-            .with_context(|| format!("No connection with public key {}", hex::encode(key)))?;
+            .with_context(|| format!("No connection for public key {}", into_u256(key)))?;
 
         Ok((*id, conn))
     }
@@ -1529,6 +1529,12 @@ where
     }
 }
 
+fn into_u256(key: [u8; 32]) -> bnum::BUint<4> {
+    // Note: `parse_str_radix` panics when the number is too big.
+    // We are passing 32 u8's though which fits exactly into a u256.
+    bnum::types::U256::parse_str_radix(&hex::encode(key), 16)
+}
+
 fn add_local_candidate<TId>(
     id: TId,
     agent: &mut IceAgent,
@@ -2753,4 +2759,20 @@ mod tests {
         assert!(agent.remote_candidates().contains(&expected_candidate2));
         assert!(!agent.remote_candidates().contains(&unexpected_candidate3));
     }
+
+    #[test]
+    fn can_make_u256_out_of_byte_array() {
+        let bytes = random();
+        let _num = into_u256(bytes);
+    }
+
+    #[test]
+    fn u256_renders_as_int() {
+        let num = into_u256([1; 32]);
+
+        assert_eq!(
+            num.to_string(),
+            "454086624460063511464984254936031011189294057512315937409637584344757371137"
+        );
+    }
 }