ir: Do not vote for the same validators list twice

Closes nspcc-dev#2365.

Signed-off-by: Pavel Karpy <carpawell@nspcc.ru>

CHANGELOG.md

@@ -11,6 +11,7 @@ Changelog for NeoFS Node
 ### Fixed
 - `neo-go` RPC connection loss handling (#1337)
 - Concurrent morph cache misses (#1248)
+- Double voting for validators on IR startup (#2365)
 
 ### Removed
 - Deprecated `morph.rpc_endpoint` SN and `morph.endpoint.client` IR config sections (#2400)

pkg/innerring/state.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"sort"
 
+	"github.com/nspcc-dev/neo-go/pkg/crypto/keys"
 	"github.com/nspcc-dev/neo-go/pkg/util"
 	"github.com/nspcc-dev/neofs-node/pkg/innerring/processors/governance"
 	auditClient "github.com/nspcc-dev/neofs-node/pkg/morph/client/audit"
@@ -108,13 +109,21 @@ func (s *Server) voteForSidechainValidator(prm governance.VoteValidatorPrm) erro
 		return nil
 	}
 
+	voted, err := s.alreadyVoted(validators)
+	if err != nil {
+		return fmt.Errorf("could not check validators state: %w", err)
+	}
+
+	if voted {
+		return nil
+	}
+
 	epoch := s.EpochCounter()
 
 	var (
 		nonce uint32 = 1
 		vub   uint32
 		vubP  *uint32
-		err   error
 	)
 
 	if prm.Hash != nil {
@@ -138,6 +147,30 @@ func (s *Server) voteForSidechainValidator(prm governance.VoteValidatorPrm) erro
 	return nil
 }
 
+func (s *Server) alreadyVoted(validatorsToVote keys.PublicKeys) (bool, error) {
+	currentValidators := make(map[keys.PublicKey]struct{}, len(s.contracts.alphabet))
+	for letter, contract := range s.contracts.alphabet {
+		validator, err := s.morphClient.VotesFor(contract)
+		if err != nil {
+			return false, fmt.Errorf("receiving %s's vote: %w", letter, err)
+		}
+
+		if validator == nil {
+			continue
+		}
+
+		currentValidators[*validator] = struct{}{}
+	}
+
+	for _, v := range validatorsToVote {
+		if _, voted := currentValidators[*v]; !voted {
+			return false, nil
+		}
+	}
+
+	return true, nil
+}
+
 // VoteForSidechainValidator calls vote method on alphabet contracts with
 // the provided list of keys.
 func (s *Server) VoteForSidechainValidator(prm governance.VoteValidatorPrm) error {

pkg/morph/client/client.go

@@ -430,7 +430,7 @@ func (c *Client) VotesFor(addr util.Uint160) (*keys.PublicKey, error) {
 		return nil, ErrConnectionLost
 	}
 
-	neoReader := neo.New(c.rpcActor)
+	neoReader := neo.NewReader(c.rpcActor)
 
 	state, err := neoReader.GetAccountState(addr)
 	if err != nil {