solana: Add set_threshold ix (#589)

This PR adds:
* `set_threshold` ix to update the threshold (`0 < threshold <= # of enabled transceivers`)
* `deregister_transceiver` ix to deregister (disable transceiver in enabled transceiver bitmap):
   * Also decrements threshold (down to minimum 1) if # of enabled transceivers < threshold 
* Update `register_transceiver` ix to also act as re-enable:
   * If `RegisteredTransceiver` account is init for the first time, assign new id
   * Otherwise, reuse old id
* Rust tests to verify edge cases
* `createSetThresholdInstruction` and `createDeregisterTransceiverIx` TS helpers as a part of NTT namespace and `SolanaNtt` class respectively
* Update IDL

Author: nvsriram

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

@@ -48,8 +48,11 @@ impl Bitmap {
             .expect("Bitmap length must not exceed the bounds of u8")
     }
 
-    pub fn len(self) -> usize {
-        BM::<128>::from_value(self.map).len()
+    pub fn len(self) -> u8 {
+        BM::<128>::from_value(self.map)
+            .len()
+            .try_into()
+            .expect("Bitmap length must not exceed the bounds of u8")
     }
 
     pub fn is_empty(self) -> bool {

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

@@ -61,6 +61,10 @@ pub enum NTTError {
     IncorrectRentPayer,
     #[msg("InvalidMultisig")]
     InvalidMultisig,
+    #[msg("ThresholdTooHigh")]
+    ThresholdTooHigh,
+    #[msg("InvalidTransceiverProgram")]
+    InvalidTransceiverProgram,
 }
 
 impl From<ScalingError> for NTTError {

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

@@ -3,6 +3,7 @@ use ntt_messages::chain_id::ChainId;
 
 use crate::{
     config::Config,
+    error::NTTError,
     peer::NttManagerPeer,
     queue::{inbox::InboxRateLimit, outbox::OutboxRateLimit, rate_limit::RateLimitState},
     registered_transceiver::RegisteredTransceiver,
@@ -76,7 +77,7 @@ pub fn set_peer(ctx: Context<SetPeer>, args: SetPeerArgs) -> Result<()> {
     Ok(())
 }
 
-// * Register transceivers
+// * Transceiver registration
 
 #[derive(Accounts)]
 pub struct RegisterTransceiver<'info> {
@@ -91,13 +92,16 @@ pub struct RegisterTransceiver<'info> {
     #[account(mut)]
     pub payer: Signer<'info>,
 
-    #[account(executable)]
+    #[account(
+        executable,
+        constraint = transceiver.key() != Pubkey::default() @ NTTError::InvalidTransceiverProgram
+    )]
     /// CHECK: transceiver is meant to be a transceiver program. Arguably a `Program` constraint could be
     /// used here that wraps the Transceiver account type.
     pub transceiver: UncheckedAccount<'info>,
 
     #[account(
-        init,
+        init_if_needed,
         space = 8 + RegisteredTransceiver::INIT_SPACE,
         payer = payer,
         seeds = [RegisteredTransceiver::SEED_PREFIX, transceiver.key().as_ref()],
@@ -109,17 +113,62 @@ pub struct RegisterTransceiver<'info> {
 }
 
 pub fn register_transceiver(ctx: Context<RegisterTransceiver>) -> Result<()> {
-    let id = ctx.accounts.config.next_transceiver_id;
-    ctx.accounts.config.next_transceiver_id += 1;
+    // initialize registered transceiver with new id on init
+    if ctx.accounts.registered_transceiver.transceiver_address == Pubkey::default() {
+        let id = ctx.accounts.config.next_transceiver_id;
+        ctx.accounts.config.next_transceiver_id += 1;
+        ctx.accounts
+            .registered_transceiver
+            .set_inner(RegisteredTransceiver {
+                bump: ctx.bumps.registered_transceiver,
+                id,
+                transceiver_address: ctx.accounts.transceiver.key(),
+            });
+    }
+
     ctx.accounts
-        .registered_transceiver
-        .set_inner(RegisteredTransceiver {
-            bump: ctx.bumps.registered_transceiver,
-            id,
-            transceiver_address: ctx.accounts.transceiver.key(),
-        });
-
-    ctx.accounts.config.enabled_transceivers.set(id, true)?;
+        .config
+        .enabled_transceivers
+        .set(ctx.accounts.registered_transceiver.id, true)?;
+    Ok(())
+}
+
+#[derive(Accounts)]
+pub struct DeregisterTransceiver<'info> {
+    #[account(
+        mut,
+        has_one = owner,
+    )]
+    pub config: Account<'info, Config>,
+
+    #[account(mut)]
+    pub owner: Signer<'info>,
+
+    #[account(executable)]
+    /// CHECK: transceiver is meant to be a transceiver program. Arguably a `Program` constraint could be
+    /// used here that wraps the Transceiver account type.
+    pub transceiver: UncheckedAccount<'info>,
+
+    #[account(
+        seeds = [RegisteredTransceiver::SEED_PREFIX, transceiver.key().as_ref()],
+        bump,
+        constraint = config.enabled_transceivers.get(registered_transceiver.id)? @ NTTError::DisabledTransceiver,
+    )]
+    pub registered_transceiver: Account<'info, RegisteredTransceiver>,
+}
+
+pub fn deregister_transceiver(ctx: Context<DeregisterTransceiver>) -> Result<()> {
+    ctx.accounts
+        .config
+        .enabled_transceivers
+        .set(ctx.accounts.registered_transceiver.id, false)?;
+
+    // decrement threshold if too high
+    let num_enabled_transceivers = ctx.accounts.config.enabled_transceivers.len();
+    if num_enabled_transceivers < ctx.accounts.config.threshold {
+        // threshold should be at least 1
+        ctx.accounts.config.threshold = num_enabled_transceivers.max(1);
+    }
     Ok(())
 }
 
@@ -200,3 +249,26 @@ pub fn set_paused(ctx: Context<SetPaused>, paused: bool) -> Result<()> {
     ctx.accounts.config.paused = paused;
     Ok(())
 }
+
+// * Set Threshold
+
+#[derive(Accounts)]
+#[instruction(threshold: u8)]
+pub struct SetThreshold<'info> {
+    pub owner: Signer<'info>,
+
+    #[account(
+        mut,
+        has_one = owner,
+        constraint = threshold <= config.enabled_transceivers.len() @ NTTError::ThresholdTooHigh
+    )]
+    pub config: Account<'info, Config>,
+}
+
+pub fn set_threshold(ctx: Context<SetThreshold>, threshold: u8) -> Result<()> {
+    if threshold == 0 {
+        return Err(NTTError::ZeroThreshold.into());
+    }
+    ctx.accounts.config.threshold = threshold;
+    Ok(())
+}

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

@@ -155,7 +155,7 @@ fn initialize_config_and_rate_limit(
         pending_owner: None,
         paused: false,
         next_transceiver_id: 0,
-        // NOTE: can't be changed for now
+        // NOTE: can be changed via `set_threshold` ix
         threshold: 1,
         enabled_transceivers: Bitmap::new(),
         custody: common.custody.key(),

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

@@ -188,6 +188,10 @@ pub mod example_native_token_transfers {
         instructions::register_transceiver(ctx)
     }
 
+    pub fn deregister_transceiver(ctx: Context<DeregisterTransceiver>) -> Result<()> {
+        instructions::deregister_transceiver(ctx)
+    }
+
     pub fn set_outbound_limit(
         ctx: Context<SetOutboundLimit>,
         args: SetOutboundLimitArgs,
@@ -206,6 +210,10 @@ pub mod example_native_token_transfers {
         instructions::mark_outbox_item_as_released(ctx)
     }
 
+    pub fn set_threshold(ctx: Context<SetThreshold>, threshold: u8) -> Result<()> {
+        instructions::set_threshold(ctx, threshold)
+    }
+
     // standalone transceiver stuff
 
     pub fn set_wormhole_peer(