150 lines
4.6 KiB
Go
150 lines
4.6 KiB
Go
package pubsub
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import (
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"errors"
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"regexp"
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pb "github.com/status-im/go-wakurelay-pubsub/pb"
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"github.com/libp2p/go-libp2p-core/peer"
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)
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// ErrTooManySubscriptions may be returned by a SubscriptionFilter to signal that there are too many
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// subscriptions to process.
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var ErrTooManySubscriptions = errors.New("too many subscriptions")
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// SubscriptionFilter is a function that tells us whether we are interested in allowing and tracking
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// subscriptions for a given topic.
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//
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// The filter is consulted whenever a subscription notification is received by another peer; if the
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// filter returns false, then the notification is ignored.
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//
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// The filter is also consulted when joining topics; if the filter returns false, then the Join
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// operation will result in an error.
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type SubscriptionFilter interface {
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// CanSubscribe returns true if the topic is of interest and we can subscribe to it
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CanSubscribe(topic string) bool
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// FilterIncomingSubscriptions is invoked for all RPCs containing subscription notifications.
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// It should filter only the subscriptions of interest and my return an error if (for instance)
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// there are too many subscriptions.
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FilterIncomingSubscriptions(peer.ID, []*pb.RPC_SubOpts) ([]*pb.RPC_SubOpts, error)
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}
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// WithSubscriptionFilter is a pubsub option that specifies a filter for subscriptions
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// in topics of interest.
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func WithSubscriptionFilter(subFilter SubscriptionFilter) Option {
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return func(ps *PubSub) error {
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ps.subFilter = subFilter
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return nil
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}
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}
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// NewAllowlistSubscriptionFilter creates a subscription filter that only allows explicitly
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// specified topics for local subscriptions and incoming peer subscriptions.
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func NewAllowlistSubscriptionFilter(topics ...string) SubscriptionFilter {
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allow := make(map[string]struct{})
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for _, topic := range topics {
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allow[topic] = struct{}{}
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}
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return &allowlistSubscriptionFilter{allow: allow}
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}
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type allowlistSubscriptionFilter struct {
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allow map[string]struct{}
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}
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var _ SubscriptionFilter = (*allowlistSubscriptionFilter)(nil)
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func (f *allowlistSubscriptionFilter) CanSubscribe(topic string) bool {
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_, ok := f.allow[topic]
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return ok
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}
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func (f *allowlistSubscriptionFilter) FilterIncomingSubscriptions(from peer.ID, subs []*pb.RPC_SubOpts) ([]*pb.RPC_SubOpts, error) {
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return FilterSubscriptions(subs, f.CanSubscribe), nil
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}
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// NewRegexpSubscriptionFilter creates a subscription filter that only allows topics that
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// match a regular expression for local subscriptions and incoming peer subscriptions.
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//
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// Warning: the user should take care to match start/end of string in the supplied regular
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// expression, otherwise the filter might match unwanted topics unexpectedly.
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func NewRegexpSubscriptionFilter(rx *regexp.Regexp) SubscriptionFilter {
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return &rxSubscriptionFilter{allow: rx}
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}
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type rxSubscriptionFilter struct {
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allow *regexp.Regexp
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}
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var _ SubscriptionFilter = (*rxSubscriptionFilter)(nil)
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func (f *rxSubscriptionFilter) CanSubscribe(topic string) bool {
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return f.allow.MatchString(topic)
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}
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func (f *rxSubscriptionFilter) FilterIncomingSubscriptions(from peer.ID, subs []*pb.RPC_SubOpts) ([]*pb.RPC_SubOpts, error) {
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return FilterSubscriptions(subs, f.CanSubscribe), nil
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}
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// FilterSubscriptions filters (and deduplicates) a list of subscriptions.
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// filter should return true if a topic is of interest.
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func FilterSubscriptions(subs []*pb.RPC_SubOpts, filter func(string) bool) []*pb.RPC_SubOpts {
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accept := make(map[string]*pb.RPC_SubOpts)
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for _, sub := range subs {
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topic := sub.GetTopicid()
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if !filter(topic) {
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continue
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}
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otherSub, ok := accept[topic]
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if ok {
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if sub.GetSubscribe() != otherSub.GetSubscribe() {
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delete(accept, topic)
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}
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} else {
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accept[topic] = sub
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}
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}
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if len(accept) == 0 {
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return nil
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}
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result := make([]*pb.RPC_SubOpts, 0, len(accept))
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for _, sub := range accept {
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result = append(result, sub)
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}
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return result
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}
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// WrapLimitSubscriptionFilter wraps a subscription filter with a hard limit in the number of
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// subscriptions allowed in an RPC message.
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func WrapLimitSubscriptionFilter(filter SubscriptionFilter, limit int) SubscriptionFilter {
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return &limitSubscriptionFilter{filter: filter, limit: limit}
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}
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type limitSubscriptionFilter struct {
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filter SubscriptionFilter
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limit int
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}
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var _ SubscriptionFilter = (*limitSubscriptionFilter)(nil)
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func (f *limitSubscriptionFilter) CanSubscribe(topic string) bool {
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return f.filter.CanSubscribe(topic)
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}
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func (f *limitSubscriptionFilter) FilterIncomingSubscriptions(from peer.ID, subs []*pb.RPC_SubOpts) ([]*pb.RPC_SubOpts, error) {
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if len(subs) > f.limit {
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return nil, ErrTooManySubscriptions
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}
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return f.filter.FilterIncomingSubscriptions(from, subs)
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}
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