Static file range calculations panic with non-zero genesis blocks (L2 rollups)

[Vui-Chee]

Description

When running a reth node on snapshot data that begins with a custom (non-zero) genesis block number — common in L2 rollups — the node panics during static file initialization. The static file system expects files named with ranges starting from block 0 (e.g., multiples computed by find_fixed_range), but the actual files on disk start at the genesis block number.

Root Cause

The canonical file range computed by find_fixed_range always starts at 0, but when the genesis block is non-zero, the actual first static file starts at the genesis block number. This mismatch causes three distinct issues:

1. set_expected_block_start recomputes an incorrect end boundary — It uses find_fixed_range to derive the end block, which produces a wrong value when the range start has been adjusted for a non-zero genesis.
2. update_index attempts to load a non-existent file — It computes a fixed range starting below the genesis block, then tries to load a file with that range which doesn't exist on disk.
3. Static file writer looks up the wrong segment — The open() method uses an incorrect block number for segment lookup and creates new files with ranges that don't account for the genesis offset.

Impact

• Node panic on startup when using snapshot data with non-zero genesis blocks
• Affects L2 rollup deployments that use reth with custom genesis configurations
• Prevents proper static file initialization and indexing

Expected Behavior

Static file range calculations should account for non-zero genesis block numbers by:

• Preserving existing end boundaries in set_expected_block_start instead of recomputing them via find_fixed_range
• Clamping the fixed range start to the genesis block number in update_index
• Using the actual block number for segment lookup in the static file writer and creating new files with genesis-aware ranges

Affected Components

• crates/static-file/types/src/segment.rs — set_expected_block_start
• crates/storage/provider/src/providers/static_file/manager.rs — update_index
• crates/storage/provider/src/providers/static_file/writer.rs — open()