CCIP-9952: Adding AllowAdditiveRemotePools variable to add additional… (#21636)

* CCIP-9952: Adding AllowAdditiveRemotePools variable to add additional remote pools for solana

* lint fix

* do add leftPadBytes

Author: b-gopalswami

deployment/ccip/changeset/v1_5_1/cs_configure_token_pools.go

@@ -262,6 +262,12 @@ type TokenPoolConfig struct {
 
 	// SkipOwnershipValidation, if true, skips validation of ownership on the token pool. Optional, defaults to false.
 	SkipOwnershipValidation bool `json:"skipOwnershipValidation,omitempty"`
+
+	// AllowAdditiveRemotePools, if true, allows adding additional remote pools to existing chain configurations
+	// without removing and re-adding the chain selector. When false (default), the behavior is to remove
+	// the chain selector and re-add it with the new pool configuration (spot replacement).
+	// This is particularly useful for Solana and other chains where multiple pools may need to coexist.
+	AllowAdditiveRemotePools bool `json:"allowAdditiveRemotePools,omitempty"`
 }
 
 func (c TokenPoolConfig) Validate(ctx context.Context, chain cldf_evm.Chain, ccipState stateview.CCIPOnChainState, useMcms bool, tokenSymbol shared.TokenSymbol) error {
@@ -482,13 +488,29 @@ func configureTokenPool(
 					break
 				}
 			}
-			if !bytes.Equal(remoteTokenAddress.Bytes(), remoteToken) || !isRemotePoolSupported {
-				// Remove & later re-add the chain if the remote token has changed OR the remote pool address is not supported
+
+			// Determine the action based on token and pool status
+			switch {
+			case !bytes.Equal(remoteTokenAddress.Bytes(), remoteToken):
+				// Remote token has changed - this always requires chain removal/re-addition
 				chainRemovals = append(chainRemovals, remoteChainSelector)
 				addChain = true
-			} else {
-				// Update the rate limits if the chain is already supported
-				// We dont need to add a new remote pool because solana only supports one remote pool per token
+			case !isRemotePoolSupported:
+				// Remote pool is not supported - behavior depends on AllowAdditiveRemotePools flag
+				if poolUpdate.AllowAdditiveRemotePools {
+					// Add the new remote pool without removing the chain
+					remotePoolAddressAdditions[remoteChainSelector] = common.LeftPadBytes(remotePoolAddress.Bytes(), 32)
+					// Also update rate limits
+					remoteChainSelectorsToUpdate = append(remoteChainSelectorsToUpdate, remoteChainSelector)
+					updatedOutboundConfigs = append(updatedOutboundConfigs, chainUpdate.RateLimiterConfig.Outbound)
+					updatedInboundConfigs = append(updatedInboundConfigs, chainUpdate.RateLimiterConfig.Inbound)
+				} else {
+					// Default behavior: Remove & later re-add the chain (spot replacement)
+					chainRemovals = append(chainRemovals, remoteChainSelector)
+					addChain = true
+				}
+			default:
+				// Remote pool is already supported, just update the rate limits
 				remoteChainSelectorsToUpdate = append(remoteChainSelectorsToUpdate, remoteChainSelector)
 				updatedOutboundConfigs = append(updatedOutboundConfigs, chainUpdate.RateLimiterConfig.Outbound)
 				updatedInboundConfigs = append(updatedInboundConfigs, chainUpdate.RateLimiterConfig.Inbound)
@@ -500,8 +522,8 @@ func configureTokenPool(
 				RemoteChainSelector:       remoteChainSelector,
 				InboundRateLimiterConfig:  chainUpdate.RateLimiterConfig.Inbound,
 				OutboundRateLimiterConfig: chainUpdate.RateLimiterConfig.Outbound,
-				RemoteTokenAddress:        remoteTokenAddress.Bytes(),
-				RemotePoolAddresses:       [][]byte{remotePoolAddress.Bytes()},
+				RemoteTokenAddress:        common.LeftPadBytes(remoteTokenAddress.Bytes(), 32),
+				RemotePoolAddresses:       [][]byte{common.LeftPadBytes(remotePoolAddress.Bytes(), 32)},
 			})
 		}
 	}
@@ -587,7 +609,9 @@ func configureTokenPool(
 				}
 			}
 			// Check if the remote pool to-be-set is non-empty and not already configured on the token pool
-			if len(remotePoolAddress) == 0 && !isRemotePoolSupported {
+			// For Sui, the default behavior has always been additive, so we maintain backward compatibility
+			// The AllowAdditiveRemotePools flag doesn't change Sui's existing behavior
+			if len(remotePoolAddress) > 0 && !isRemotePoolSupported {
 				remotePoolAddressAdditions[remoteChainSelector] = common.LeftPadBytes(remotePoolAddress, 32)
 			}
 		} else {