This EIP adds a new field to transactions,
valid_until_block. Transactions containing this field may only be included in blocks with numbers less than or equal to the value in this field.
Presently, transaction eviction is a significant problem for nodes; if a node’s transaction pool fills up, resulting in the eviction of a transaction, it may receive the same transaction from another node immediately afterwards. Without tracking evicted transactions, nodes cannot determine that they’ve seen the transaction before, and if they do track evicted transactions, an attacker can compel them to waste space keeping track of them. The result of this is that even legitimate transactions may stick around in a busy pool indefinitely, while an attacker can deliberately seek to bloat the network’s transaction pools.
Further, in cases where the network is busy, or a transaction is published with a low gas price, or with a nonce gap or other problem that prevents it from being mined immediately, the transaction may be executed at any time in the future. This can cause trouble for users, where an effect can take place much later than intended, with no clean way to cancel it.
This proposal addresses both of these issues by allowing nodes to place a hard limit on how long they will retain and propagate transactions, limiting the impact of transaction pool bloat and allowing smarter eviction strategies, while also providing users with a way to submit transactions that self-destruct if not mined within a fixed time period.