3 files changed, 34 insertions, 18 deletions

diff --git a/src/model/k2v/causality.rs b/src/model/k2v/causality.rs
index 665b02b2..b1ec8035 100644
--- a/src/model/k2v/causality.rs
+++ b/src/model/k2v/causality.rs
@@ -15,6 +15,8 @@ use serde::{Deserialize, Serialize};
 
 use garage_util::data::*;
 
+use crate::helper::error::{Error as HelperError, OkOrBadRequest};
+
 /// Node IDs used in K2V are u64 integers that are the abbreviation
 /// of full Garage node IDs which are 256-bit UUIDs.
 pub type K2VNodeId = u64;
@@ -50,6 +52,7 @@ impl CausalContext {
 	pub fn new() -> Self {
 		Self::default()
 	}
+
 	/// Make binary representation and encode in base64
 	pub fn serialize(&self) -> String {
 		let mut ints = Vec::with_capacity(2 * self.vector_clock.len());
@@ -66,12 +69,13 @@ impl CausalContext {
 
 		base64::encode_config(bytes, base64::URL_SAFE_NO_PAD)
 	}
-	/// Parse from base64-encoded binary representation
-	pub fn parse(s: &str) -> Result<Self, String> {
-		let bytes = base64::decode_config(s, base64::URL_SAFE_NO_PAD)
-			.map_err(|e| format!("bad causality token base64: {}", e))?;
+
+	/// Parse from base64-encoded binary representation.
+	/// Returns None on error.
+	pub fn parse(s: &str) -> Option<Self> {
+		let bytes = base64::decode_config(s, base64::URL_SAFE_NO_PAD).ok()?;
 		if bytes.len() % 16 != 8 || bytes.len() < 8 {
-			return Err("bad causality token length".into());
+			return None;
 		}
 
 		let checksum = u64::from_be_bytes(bytes[..8].try_into().unwrap());
@@ -88,11 +92,16 @@ impl CausalContext {
 		let check = ret.vector_clock.iter().fold(0, |acc, (n, t)| acc ^ *n ^ *t);
 
 		if check != checksum {
-			return Err("bad causality token checksum".into());
+			return None;
 		}
 
-		Ok(ret)
+		Some(ret)
 	}
+
+	pub fn parse_helper(s: &str) -> Result<Self, HelperError> {
+		Self::parse(s).ok_or_bad_request("Invalid causality token")
+	}
+
 	/// Check if this causal context contains newer items than another one
 	pub fn is_newer_than(&self, other: &Self) -> bool {
 		vclock_gt(&self.vector_clock, &other.vector_clock)
diff --git a/src/model/k2v/rpc.rs b/src/model/k2v/rpc.rs
index 04801ebf..3b4d7465 100644
--- a/src/model/k2v/rpc.rs
+++ b/src/model/k2v/rpc.rs
@@ -29,6 +29,7 @@ use garage_rpc::*;
 use garage_table::replication::{TableReplication, TableShardedReplication};
 use garage_table::{PartitionKey, Table};
 
+use crate::helper::error::Error as HelperError;
 use crate::k2v::causality::*;
 use crate::k2v::item_table::*;
 use crate::k2v::seen::*;
@@ -212,7 +213,7 @@ impl K2VRpcHandler {
 		sort_key: String,
 		causal_context: CausalContext,
 		timeout_msec: u64,
-	) -> Result<Option<K2VItem>, Error> {
+	) -> Result<Option<K2VItem>, HelperError> {
 		let poll_key = PollKey {
 			partition: K2VItemPartition {
 				bucket_id,
@@ -255,7 +256,7 @@ impl K2VRpcHandler {
 					}
 				}
 				K2VRpc::PollItemResponse(None) => (),
-				v => return Err(Error::unexpected_rpc_message(v)),
+				v => return Err(Error::unexpected_rpc_message(v).into()),
 			}
 		}
 
@@ -267,12 +268,12 @@ impl K2VRpcHandler {
 		range: PollRange,
 		seen_str: Option<String>,
 		timeout_msec: u64,
-	) -> Result<Option<(BTreeMap<String, K2VItem>, String)>, Error> {
+	) -> Result<Option<(BTreeMap<String, K2VItem>, String)>, HelperError> {
 		let has_seen_marker = seen_str.is_some();
 
 		let mut seen = seen_str
 			.as_deref()
-			.map(RangeSeenMarker::decode)
+			.map(RangeSeenMarker::decode_helper)
 			.transpose()?
 			.unwrap_or_default();
 		seen.restrict(&range);
@@ -316,7 +317,7 @@ impl K2VRpcHandler {
 					}
 				}
 			} else {
-				return Err(Error::unexpected_rpc_message(v));
+				return Err(Error::unexpected_rpc_message(v).into());
 			}
 		}
 
@@ -435,7 +436,7 @@ impl K2VRpcHandler {
 		seen_str: &Option<String>,
 	) -> Result<Vec<K2VItem>, Error> {
 		if let Some(seen_str) = seen_str {
-			let seen = RangeSeenMarker::decode(seen_str)?;
+			let seen = RangeSeenMarker::decode(seen_str).ok_or_message("Invalid seenMarker")?;
 
 			// Subscribe now to all changes on that partition,
 			// so that new items that are inserted while we are reading the range
diff --git a/src/model/k2v/seen.rs b/src/model/k2v/seen.rs
index d2cd54c7..314d0f9e 100644
--- a/src/model/k2v/seen.rs
+++ b/src/model/k2v/seen.rs
@@ -13,8 +13,9 @@ use serde::{Deserialize, Serialize};
 
 use garage_util::data::Uuid;
 use garage_util::encode::{nonversioned_decode, nonversioned_encode};
-use garage_util::error::{Error, OkOrMessage};
+use garage_util::error::Error;
 
+use crate::helper::error::{Error as HelperError, OkOrBadRequest};
 use crate::k2v::causality::*;
 use crate::k2v::item_table::*;
 use crate::k2v::sub::*;
@@ -80,10 +81,15 @@ impl RangeSeenMarker {
 		Ok(base64::encode(&bytes))
 	}
 
-	pub fn decode(s: &str) -> Result<Self, Error> {
-		let bytes = base64::decode(&s).ok_or_message("invalid base64")?;
-		let bytes = zstd::stream::decode_all(&mut &bytes[..])?;
-		Ok(nonversioned_decode(&bytes)?)
+	/// Decode from msgpack+zstd+b64 representation, returns None on error.
+	pub fn decode(s: &str) -> Option<Self> {
+		let bytes = base64::decode(&s).ok()?;
+		let bytes = zstd::stream::decode_all(&mut &bytes[..]).ok()?;
+		nonversioned_decode(&bytes).ok()
+	}
+
+	pub fn decode_helper(s: &str) -> Result<Self, HelperError> {
+		Self::decode(s).ok_or_bad_request("Invalid causality token")
 	}
 
 	pub fn is_new_item(&self, item: &K2VItem) -> bool {