This is a sub-milestone of %Etherlink: main launch, dedicated to implementing kernel changes required to be able to bridge FA assets between Etherlink and Tezos L1.

It mainly relies on two features: depositing and withdrawing. TODO for @naih: elaborate just a bit so that readers understand the global architecture and flow of assets behind with these two operations (with pointers to https://github.com/baking-bad/etherlink-bridge and TZIP-029). Also expose why it's important to have that (for tokens like tzBTC, USDT, etc.)

Work break down

Headless bridge

Permissionless ticket transport, w/o full indexing support.

Preliminaries

• !11840 (merged): Kernel/EVM: FA bridge module
• !13618 (merged): Kernel/EVM: Moving ticketer to the world state
• !12072 (merged): EVM: Add ticket table to account for FA deposits
• !13535 (merged): Etherlink: FA Bridge feature flag in kernel

FA deposits

• !13532 (merged): EVM: add support for FA deposits to the sequencer
• !13720 (merged): EVM: add FA deposit structure and helper methods
• !13773 (merged): EVM: add methods for FA deposit execution.
• !13835 (merged): EVM: integrate FA deposit application behind the feature flag.

FA withdrawals

• !13751 (merged): EVM: refactor xtz native withdrawals.
• !13843 (merged): EVM: add FA withdrawal struct and helper methods.
• !13941 (merged): EVM: add FA bridge precompile and FA withdrawal execution.
• !13958 (merged): EVM: enable FA withdrawals behind the feature flag.

Merged bridge

Full indexing support, including native bridge.

Track XTZ deposits and withdrawals on L2

• !14012 (merged): EVM: add event logs for native token deposits
• !14014 (merged): EVM: emit event log when native token withdrawal is applied.
• !14260 (merged) EVM: L1 proxy address added to the FA withdrawal event

Track XTZ and FA withdrawals on L1*

The resolution is that we can do matching without tracking transactions (and dummy contract on L1).

• !13925 (merged): Kernel SDK: allow to enqueue heterogeneous batches of messages to outbox.
• !14059 (closed) TODO: To index withdrawals, we need to include an additional "tracking" transaction to the outbox message batch.

Fixups

• !14389 (merged): EVM/Kernel: make withdrawal counter revertible

Enable bridge

• !14342 (merged) EVM/Kernel: Enable FA bridge in Ghostnet
• Test Ghostnet upgrade that enables FA bridge

Follow up

Adjusting tick model and addressing issues discovered during the audit.

Tick & gas model

• !14475 (merged): EVM/Kernel: benchmark FA deposits and withdrawals
• !14481 (merged): EVM/Kernel: rewrite delayed outbox queue resilience tezt scenario
• !14016 (merged): EVM/Kernel: tune FA bridge tick & gas model

Reentrancy fixups

• !14545 (merged): EVM/Kernel: ensure FA deposit cannot invoke XTZ/FA withdrawal precompiles
• !14390 (merged): EVM/Kernel: prevent circular calls of impure precompiles

Misc

• !14639 (closed): EVM/Kernel: FA bridge whitelisted code hashes