ws: allow filtering notification by parameters

[carpawell]

Closes #3624.

[carpawell]

Some questions:

1. Is there any full test for client-to-server communication to check that filtering works? Not just unmarshalling but also creating notifications and receiving only the important ones. Have not found it.
2. Are type limitations correct?
3. What limit should be used for parameter filters? Why should we have it (the issue says)? Just not to have some OOMs on a server side or it is possible to abuse a node somehow?

[codecov]

Codecov Report

Attention: Patch coverage is 60.37736% with 21 lines in your changes missing coverage. Please review.

Project coverage is 83.01%. Comparing base (ff15e39) to head (97bd73b).
Report is 10 commits behind head on master.

Files with missing lines	Patch %	Lines
pkg/neorpc/filters.go	50.00%	13 Missing and 5 partials ⚠️
pkg/neorpc/rpcevent/filter.go	82.35%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3689      +/-   ##
==========================================
- Coverage   83.04%   83.01%   -0.04%     
==========================================
  Files         335      335              
  Lines       46719    46782      +63     
==========================================
+ Hits        38800    38834      +34     
- Misses       6327     6350      +23     
- Partials     1592     1598       +6     

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[AnnaShaleva]

1. Is there any full test for client-to-server communication to check that filtering works?

Use and extend the following tests:

neo-go/pkg/services/rpcsrv/subscription_test.go

Line 130 in 990634a

func TestSubscriptions(t *testing.T) {

neo-go/pkg/services/rpcsrv/client_test.go

Line 2131 in 990634a

func TestWSClient_SubscriptionsCompat(t *testing.T) {

That's the way how we test subscriptions. If it's not enough, then create your own test based on

neo-go/pkg/services/rpcsrv/client_test.go

Line 1895 in 990634a

func TestSubClientWait(t *testing.T) {

2. Are type limitations correct?

Will be answered in review.

3. What limit should be used for parameter filters?

Let's limit the number of parameters to 16 for now, it's pretty enough for notifications used by NeoFS and at the same time it won't allow to DoS the node with useless filtering process for large notifications/filters. Also, parameter types should be limited by non-compound types (simple Integer, String, Hash160 and etc.; excluding Arrays, Structs and Maps), we don't need compounds for now and NeoFS contracts don't use them in notifications; in future the set of supported types may be extended.

Why should we have it (the issue says)?

Avoid filters misuse and unwanted load for RPC server. This extension will be available on public RPC nodes.

it is possible to abuse a node somehow?

Deploy contract that emits thousands of notifications (it's possible, hi, #3490), then subscribe to RPC server with matching filters.

[carpawell]

@AnnaShaleva thanks for the review! It was kinda draft with the main questions but tried to answer and fix all the threads you left, check one more time, please.

[AnnaShaleva]

Tests are not yet checked, will review them after PR finalisation.

[AnnaShaleva]

@carpawell tests are failing.

[AnnaShaleva]

Some of previous conversations are unresolved.

[carpawell]

Some of previous conversations are unresolved.

Can you point me, please? As I see it: it is either fixed or I asked some questions that have not been answered or something is not relevant already.