da interface: add max blob size method

da.go

@@ -2,6 +2,9 @@ package da
 
 // DA defines very generic interface for interaction with Data Availability layers.
 type DA interface {
+	// Config returns the max blob size
+	Config() (uint64, error)
+
 	// Get returns Blob for each given ID, or an error.
 	//
 	// Error should be returned if ID is not formatted properly, there is no Blob for given ID or any other client-level

proto/da/da.proto

@@ -3,6 +3,9 @@ package da;
 
 // DAService is the protobuf service definition for interaction with Data Availability layers.
 service DAService {
+    // Config returns the maximum blob size
+    rpc Config(ConfigRequest) returns (ConfigResponse) {}
+
 	// Get returns Blob for each given ID, or an error.
 	rpc Get(GetRequest) returns (GetResponse) {}
 
@@ -39,6 +42,15 @@ message Proof {
 	bytes value = 1;
 }
 
+// ConfigRequest is the request type for the Config rpc method.
+message ConfigRequest {
+}
+
+// ConfigResponse is the response type for the Config rpc method.
+message ConfigResponse {
+    uint64 max_blob_size = 1;
+}
+
 // GetRequest is the request type for the Get rpc method.
 message GetRequest {
 	repeated ID ids = 1;
@@ -89,4 +101,4 @@ message ValidateRequest {
 // ValidateResponse is the response type for the Validate rpc method.
 message ValidateResponse {
 	repeated bool results = 1;
-}
+}

proxy/client.go

@@ -37,6 +37,16 @@ func (c *Client) Stop() error {
 	return c.conn.Close()
 }
 
+// Config returns the DA Config
+func (c *Client) Config() (uint64, error) {
+	req := &pbda.ConfigRequest{}
+	resp, err := c.client.Config(context.TODO(), req)
+	if err != nil {
+		return 0, err
+	}
+	return resp.MaxBlobSize, nil
+}
+
 // Get returns Blob for each given ID, or an error.
 func (c *Client) Get(ids []da.ID) ([]da.Blob, error) {
 	req := &pbda.GetRequest{

proxy/server.go

@@ -9,6 +9,35 @@ import (
 	pbda "github.com/rollkit/go-da/types/pb/da"
 )
 
+// The following consts are copied from appconsts to avoid dependency hell
+const (
+	// NamespaceVersionSize is the size of a namespace version in bytes.
+	NamespaceVersionSize = 1
+
+	// NamespaceIDSize is the size of a namespace ID in bytes.
+	NamespaceIDSize = 28
+
+	// NamespaceSize is the size of a namespace (version + ID) in bytes.
+	NamespaceSize = NamespaceVersionSize + NamespaceIDSize
+
+	// ShareSize is the size of a share in bytes.
+	ShareSize = 512
+
+	// ShareInfoBytes is the number of bytes reserved for information. The info
+	// byte contains the share version and a sequence start idicator.
+	ShareInfoBytes = 1
+
+	// ContinuationSparseShareContentSize is the number of bytes usable for data
+	// in a continuation sparse share of a sequence.
+	ContinuationSparseShareContentSize = ShareSize - NamespaceSize - ShareInfoBytes
+
+	// DefaultGovMaxSquareSize is the default value for the governance modifiable
+	// max square size.
+	DefaultGovMaxSquareSize = 64
+
+	DefaultMaxBytes = DefaultGovMaxSquareSize * DefaultGovMaxSquareSize * ContinuationSparseShareContentSize
+)
+
 // NewServer creates new gRPC Server configured to serve DA proxy.
 func NewServer(d da.DA, opts ...grpc.ServerOption) *grpc.Server {
 	srv := grpc.NewServer(opts...)
@@ -24,6 +53,10 @@ type proxySrv struct {
 	target da.DA
 }
 
+func (p *proxySrv) Config(ctx context.Context, request *pbda.ConfigRequest) (*pbda.ConfigResponse, error) {
+	return &pbda.ConfigResponse{MaxBlobSize: DefaultMaxBytes}, nil
+}
+
 func (p *proxySrv) Get(ctx context.Context, request *pbda.GetRequest) (*pbda.GetResponse, error) {
 	ids := idsPB2DA(request.Ids)
 	blobs, err := p.target.Get(ids)

test/dummy.go

@@ -40,6 +40,11 @@ func NewDummyDA() *DummyDA {
 
 var _ da.DA = &DummyDA{}
 
+// Config returns the max blob size in bytes.
+func (d *DummyDA) Config() (uint64, error) {
+	return 64 * 64 * 482, nil
+}
+
 // Get returns Blobs for given IDs.
 func (d *DummyDA) Get(ids []da.ID) ([]da.Blob, error) {
 	d.mu.Lock()