solana: populate an address lookup table to reduce tx size

ci_tests/src/index.ts

@@ -330,6 +330,15 @@ async function initSolana(
   });
   console.log("Initialized ntt at", manager.program.programId.toString());
 
+  // NOTE: this is a hack. The next instruction will fail if we don't wait
+  // here, because the address lookup table is not yet available, despite
+  // the transaction having been confirmed.
+  // Looks like a bug, but I haven't investigated further. In practice, this
+  // won't be an issue, becase the address lookup table will have been
+  // created well before anyone is trying to use it, but we might want to be
+  // mindful in the deploy script too.
+  await new Promise((resolve) => setTimeout(resolve, 400));
+
   await manager.registerTransceiver({
     payer: SOL_PRIVATE_KEY,
     owner: SOL_PRIVATE_KEY,

solana/Cargo.toml

@@ -47,6 +47,7 @@ anchor-spl = "0.29.0"
 solana-program = "=1.18.10"
 solana-program-runtime = "=1.18.10"
 solana-program-test = "=1.18.10"
+solana-address-lookup-table-program = "=1.18.10"
 spl-token = "4.0.0"
 spl-token-2022 = "3.0.2"
 

solana/programs/example-native-token-transfers/Cargo.toml

@@ -38,6 +38,7 @@ bitmaps = "3.2.1"
 hex.workspace = true
 cfg-if.workspace = true
 solana-program.workspace = true
+solana-address-lookup-table-program.workspace = true
 spl-token-2022 = { workspace = true, features = ["no-entrypoint"] }
 wormhole-anchor-sdk.workspace = true
 wormhole-io.workspace = true

solana/programs/example-native-token-transfers/src/instructions/luts.rs

@@ -0,0 +1,172 @@
+//! This instructions manages a canonical address lookup table (or LUT) for the
+//! NTT program.
+//! LUTs in general can be created permissionlessly, so support from the
+//! program's side is not strictly necessary. When submitting a transaction, the
+//! client could just manage its own ad-hoc lookup table.
+//! Nevertheless, we provide this instruction to make it easier for the client
+//! to query the lookup table from a deterministic address, and for integrators
+//! to be able to fetch the accounts from the LUT in a standardised way.
+//!
+//! This way, the client sdk can abstract away the lookup table logic in a
+//! maintanable way.
+//!
+//! The [`initialize_lut`] instruction can be called multiple times, each time
+//! it will create a new lookup table, with the accounts defined in the
+//! [`Entries`] struct.
+//! An alternative would be to keep extending the existing lookup table, but
+//! ensuring the instruction is idempotent (which requires ensuring no duplicate
+//! entries) has O(n^2) complexity (since LUTs are append only, we can't keep it
+//! sorted), and in the worst case would require ~16k checks. So we keep things
+//! simple, and just create a new LUT each time. This operation won't be called
+//! often, so the extra allocation is justifiable.
+//!
+//! Because of all the above, this instruction can be called permissionlessly.
+
+use anchor_lang::prelude::*;
+use solana_address_lookup_table_program;
+use solana_program::program::{invoke, invoke_signed};
+
+use crate::{config::Config, queue::outbox::OutboxRateLimit, transceivers::wormhole::accounts::*};
+
+#[account]
+#[derive(InitSpace)]
+pub struct LUT {
+    pub bump: u8,
+    pub address: Pubkey,
+}
+
+#[derive(Accounts)]
+#[instruction(recent_slot: u64)]
+pub struct InitializeLUT<'info> {
+    #[account(mut)]
+    pub payer: Signer<'info>,
+
+    #[account(
+        seeds = [b"lut_authority"],
+        bump
+    )]
+    pub authority: AccountInfo<'info>,
+
+    #[account(
+        mut,
+        seeds = [authority.key().as_ref(), &recent_slot.to_le_bytes()],
+        seeds::program = solana_address_lookup_table_program::id(),
+        bump
+    )]
+    pub lut_address: AccountInfo<'info>,
+
+    #[account(
+        init_if_needed,
+        payer = payer,
+        space = 8 + LUT::INIT_SPACE,
+        seeds = [b"lut"],
+        bump
+    )]
+    pub lut: Account<'info, LUT>,
+
+    /// CHECK: address lookup table program (checked by instruction)
+    #[account(executable)]
+    pub lut_program: AccountInfo<'info>,
+
+    pub system_program: Program<'info, System>,
+
+    /// These are the entries that will populate the LUT.
+    pub entries: Entries<'info>,
+}
+
+#[derive(Accounts)]
+pub struct Entries<'info> {
+    pub config: Account<'info, Config>,
+
+    #[account(
+        constraint = custody.key() == config.custody,
+    )]
+    pub custody: AccountInfo<'info>,
+
+    #[account(
+        constraint = token_program.key() == config.token_program,
+    )]
+    pub token_program: AccountInfo<'info>,
+
+    #[account(
+        constraint = mint.key() == config.mint,
+    )]
+    pub mint: AccountInfo<'info>,
+
+    #[account(
+        seeds = [crate::TOKEN_AUTHORITY_SEED],
+        bump,
+    )]
+    pub token_authority: AccountInfo<'info>,
+
+    pub outbox_rate_limit: Account<'info, OutboxRateLimit>,
+
+    // NOTE: this includes the system program so we don't need to add it in the outer context
+    pub wormhole: WormholeAccounts<'info>,
+}
+
+pub fn initialize_lut(ctx: Context<InitializeLUT>, recent_slot: u64) -> Result<()> {
+    let (ix, lut_address) = solana_address_lookup_table_program::instruction::create_lookup_table(
+        ctx.accounts.authority.key(),
+        ctx.accounts.payer.key(),
+        recent_slot,
+    );
+
+    // just a sanity check, should never be hit, so we don't provide a custom
+    // error message
+    assert_eq!(lut_address, ctx.accounts.lut_address.key());
+
+    // the LUT might already exist, in which case the new one will simply
+    // override it. Since we don't delete the old LUTs, this is safe -- clients
+    // holding references to old LUTs will still be able to use them.
+    ctx.accounts.lut.set_inner(LUT {
+        bump: ctx.bumps.lut,
+        address: lut_address,
+    });
+
+    // NOTE: LUTs can be permissionlessly created (i.e. the authority does
+    // not need to sign the transaction). This means that the LUT might
+    // already exist (if someone frontran us). However, it's not a problem:
+    // AddressLookupTable::create_lookup_table checks if the LUT already
+    // exists and does nothing if it does.
+    //
+    // LUTs can only be created permissionlessly, but only the authority is
+    // authorised to actually populate the fields, so we don't have to worry
+    // about the frontrunner populating it with junk. The only risk of that would
+    // be the LUT being filled to capacity (256 addresses), with no
+    // possibility for us to add our own accounts -- no other security impact.
+    invoke(
+        &ix,
+        &[
+            ctx.accounts.lut_address.to_account_info(),
+            ctx.accounts.authority.to_account_info(),
+            ctx.accounts.payer.to_account_info(),
+            ctx.accounts.system_program.to_account_info(),
+        ],
+    )?;
+
+    let entries_infos = ctx.accounts.entries.to_account_infos();
+    let mut entries = Vec::with_capacity(1 + entries_infos.len());
+    entries.push(crate::ID);
+    entries.extend(entries_infos.into_iter().map(|x| x.key));
+
+    let ix = solana_address_lookup_table_program::instruction::extend_lookup_table(
+        ctx.accounts.lut_address.key(),
+        ctx.accounts.authority.key(),
+        Some(ctx.accounts.payer.key()),
+        entries,
+    );
+
+    invoke_signed(
+        &ix,
+        &[
+            ctx.accounts.lut_address.to_account_info(),
+            ctx.accounts.authority.to_account_info(),
+            ctx.accounts.payer.to_account_info(),
+            ctx.accounts.system_program.to_account_info(),
+        ],
+        &[&[b"lut_authority", &[ctx.bumps.authority]]],
+    )?;
+
+    Ok(())
+}

solana/programs/example-native-token-transfers/src/instructions/mod.rs

@@ -1,11 +1,13 @@
 pub mod admin;
 pub mod initialize;
+pub mod luts;
 pub mod redeem;
 pub mod release_inbound;
 pub mod transfer;
 
 pub use admin::*;
 pub use initialize::*;
+pub use luts::*;
 pub use redeem::*;
 pub use release_inbound::*;
 pub use transfer::*;

solana/programs/example-native-token-transfers/src/lib.rs

@@ -73,6 +73,10 @@ pub mod example_native_token_transfers {
         instructions::initialize(ctx, args)
     }
 
+    pub fn initialize_lut(ctx: Context<InitializeLUT>, recent_slot: u64) -> Result<()> {
+        instructions::initialize_lut(ctx, recent_slot)
+    }
+
     pub fn version(_ctx: Context<Version>) -> Result<String> {
         Ok(VERSION.to_string())
     }

solana/tests/example-native-token-transfer.ts

@@ -176,6 +176,15 @@ describe("example-native-token-transfers", () => {
         mode: "burning",
       });
 
+      // NOTE: this is a hack. The next instruction will fail if we don't wait
+      // here, because the address lookup table is not yet available, despite
+      // the transaction having been confirmed.
+      // Looks like a bug, but I haven't investigated further. In practice, this
+      // won't be an issue, becase the address lookup table will have been
+      // created well before anyone is trying to use it, but we might want to be
+      // mindful in the deploy script too.
+      await new Promise((resolve) => setTimeout(resolve, 200));
+
       await ntt.registerTransceiver({
         payer,
         owner: payer,