Improve short_channel_id utils

Modifies scid_from_parts to use u64 inputs allowing untruncated
validation. Adds public constants for limits.

diff --git a/lightning/src/routing/network_graph.rs b/lightning/src/routing/network_graph.rs
index 34859cf07c462311ee1623bae195e7527ddb4205..b8655fb0abd3d59bed177456d572dc2529733b1d 100644 (file)
--- a/lightning/src/routing/network_graph.rs
+++ b/lightning/src/routing/network_graph.rs
@@ -30,7 +30,7 @@ use ln::msgs;
 use util::ser::{Writeable, Readable, Writer};
 use util::logger::Logger;
 use util::events::{MessageSendEvent, MessageSendEventsProvider};
-use util::scid_utils::{block_from_scid, scid_from_parts};
+use util::scid_utils::{block_from_scid, scid_from_parts, MAX_SCID_BLOCK};
 
 use std::{cmp, fmt};
 use std::sync::{RwLock, RwLockReadGuard};
@@ -329,11 +329,11 @@ impl<C: Deref + Sync + Send, L: Deref + Sync + Send> RoutingMessageHandler for N
 
                let network_graph = self.network_graph.read().unwrap();
 
-               let start_scid = scid_from_parts(msg.first_blocknum, 0, 0);
+               let start_scid = scid_from_parts(msg.first_blocknum as u64, 0, 0);
 
                // We receive valid queries with end_blocknum that would overflow SCID conversion.
                // Manually cap the ending block to avoid this overflow.
-               let exclusive_end_scid = scid_from_parts(cmp::min(msg.end_blocknum(), 0xffffff), 0, 0);
+               let exclusive_end_scid = scid_from_parts(cmp::min(msg.end_blocknum() as u64, MAX_SCID_BLOCK), 0, 0);
 
                // Per spec, we must reply to a query. Send an empty message when things are invalid.
                if msg.chain_hash != network_graph.genesis_hash || start_scid.is_err() || exclusive_end_scid.is_err() {

diff --git a/lightning/src/util/scid_utils.rs b/lightning/src/util/scid_utils.rs
index 2b9e6fed2be8db8b21554ba64e9541d75c076c10..7902a5271a6bcab604627fcd454634fd479ec2a9 100644 (file)
--- a/lightning/src/util/scid_utils.rs
+++ b/lightning/src/util/scid_utils.rs
@@ -7,32 +7,47 @@
 // You may not use this file except in accordance with one or both of these
 // licenses.
 
+/// Maximum block height that can be used in a `short_channel_id`. This
+/// value is based on the 3-bytes available for block height.
+pub const MAX_SCID_BLOCK: u64 = 0x00ffffff;
+
+/// Maximum transaction index that can be used in a `short_channel_id`.
+/// This value is based on the 3-bytes available for tx index.
+pub const MAX_SCID_TX_INDEX: u64 = 0x00ffffff;
+
+/// Maximum vout index that can be used in a `short_channel_id`. This
+/// value is based on the 2-bytes available for the vout index.
+pub const MAX_SCID_VOUT_INDEX: u64 = 0xffff;
+
 /// A `short_channel_id` construction error
 #[derive(Debug, PartialEq)]
 pub enum ShortChannelIdError {
        BlockOverflow,
        TxIndexOverflow,
+       VoutIndexOverflow,
 }
 
 /// Extracts the block height (most significant 3-bytes) from the `short_channel_id`
-#[allow(dead_code)]
 pub fn block_from_scid(short_channel_id: &u64) -> u32 {
        return (short_channel_id >> 40) as u32;
 }
 
 /// Constructs a `short_channel_id` using the components pieces. Results in an error
-/// if the block height or tx index overflow the 3-bytes for each component.
-#[allow(dead_code)]
-pub fn scid_from_parts(block: u32, tx_index: u32, vout_index: u16) -> Result<u64, ShortChannelIdError> {
-       if block > 0x00ffffff {
+/// if the block height, tx index, or vout index overflow the maximum sizes.
+pub fn scid_from_parts(block: u64, tx_index: u64, vout_index: u64) -> Result<u64, ShortChannelIdError> {
+       if block > MAX_SCID_BLOCK {
                return Err(ShortChannelIdError::BlockOverflow);
        }
 
-       if      tx_index > 0x00ffffff {
+       if tx_index > MAX_SCID_TX_INDEX {
                return Err(ShortChannelIdError::TxIndexOverflow);
        }
 
-       Ok(((block as u64) << 40) | ((tx_index as u64) << 16) | (vout_index as u64))
+       if vout_index > MAX_SCID_VOUT_INDEX {
+               return Err(ShortChannelIdError::VoutIndexOverflow);
+       }
+
+       Ok((block << 40) | (tx_index << 16) | vout_index)
 }
 
 #[cfg(test)]
@@ -56,5 +71,6 @@ mod tests {
                assert_eq!(scid_from_parts(0x00ffffff, 0x00ffffff, 0xffff).unwrap(), 0xffffff_ffffff_ffff);
                assert_eq!(scid_from_parts(0x01ffffff, 0x00000000, 0x0000).err().unwrap(), ShortChannelIdError::BlockOverflow);
                assert_eq!(scid_from_parts(0x00000000, 0x01ffffff, 0x0000).err().unwrap(), ShortChannelIdError::TxIndexOverflow);
+               assert_eq!(scid_from_parts(0x00000000, 0x00000000, 0x010000).err().unwrap(), ShortChannelIdError::VoutIndexOverflow);
        }
 }