[#142] Support resolving container nicename

Signed-off-by: Denis Kirillov <denis@nspcc.ru>

resolver/neofs.go

@@ -0,0 +1,46 @@
+package resolver
+
+import (
+	"context"
+	"errors"
+	"fmt"
+
+	"github.com/nspcc-dev/neofs-sdk-go/netmap"
+	"github.com/nspcc-dev/neofs-sdk-go/pool"
+)
+
+// NeoFSResolver represents virtual connection to the NeoFS network.
+// It implements resolver.NeoFS.
+type NeoFSResolver struct {
+	pool *pool.Pool
+}
+
+// NewNeoFSResolver creates new NeoFSResolver using provided pool.Pool.
+func NewNeoFSResolver(p *pool.Pool) *NeoFSResolver {
+	return &NeoFSResolver{pool: p}
+}
+
+// SystemDNS implements resolver.NeoFS interface method.
+func (x *NeoFSResolver) SystemDNS(ctx context.Context) (string, error) {
+	networkInfo, err := x.pool.NetworkInfo(ctx)
+	if err != nil {
+		return "", fmt.Errorf("read network info via client: %w", err)
+	}
+
+	var domain string
+
+	networkInfo.NetworkConfig().IterateParameters(func(parameter *netmap.NetworkParameter) bool {
+		if string(parameter.Key()) == "SystemDNS" {
+			domain = string(parameter.Value())
+			return true
+		}
+
+		return false
+	})
+
+	if domain == "" {
+		return "", errors.New("system DNS parameter not found or empty")
+	}
+
+	return domain, nil
+}