filters.go

// Copyright 2019-2020 Authors of Hubble
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package filters

import (
	"context"

	flowpb "github.com/cilium/cilium/api/v1/flow"
	v1 "github.com/cilium/cilium/pkg/hubble/api/v1"
)

// FilterFunc is the function will be used to filter the given data.
// Should return true if the filter is hit, false otherwise.
type FilterFunc func(ev *v1.Event) bool

// FilterFuncs is a combination of multiple filters, typically applied together.
type FilterFuncs []FilterFunc

// Apply filters the flow with the given white- and blacklist. Returns true
// if the flow should be included in the result.
func Apply(whitelist, blacklist FilterFuncs, ev *v1.Event) bool {
	return whitelist.MatchOne(ev) && blacklist.MatchNone(ev)
}

// MatchAll returns true if all the filters match the provided data, i.e. AND.
func (fs FilterFuncs) MatchAll(ev *v1.Event) bool {
	for _, f := range fs {
		if !f(ev) {
			return false
		}
	}
	return true
}

// MatchOne returns true if at least one of the filters match the provided data or
// if no filters are specified, i.e. OR.
func (fs FilterFuncs) MatchOne(ev *v1.Event) bool {
	if len(fs) == 0 {
		return true
	}

	for _, f := range fs {
		if f(ev) {
			return true
		}
	}
	return false
}

// MatchNone returns true if none of the filters match the provided data or
// if no filters are specified, i.e. NOR
func (fs FilterFuncs) MatchNone(ev *v1.Event) bool {
	if len(fs) == 0 {
		return true
	}

	for _, f := range fs {
		if f(ev) {
			return false
		}
	}
	return true
}

// OnBuildFilter is invoked while building a flow filter
type OnBuildFilter interface {
	OnBuildFilter(context.Context, *flowpb.FlowFilter) ([]FilterFunc, error)
}

// OnBuildFilterFunc implements OnBuildFilter for a single function
type OnBuildFilterFunc func(context.Context, *flowpb.FlowFilter) ([]FilterFunc, error)

// OnBuildFilter is invoked while building a flow filter
func (f OnBuildFilterFunc) OnBuildFilter(ctx context.Context, flow *flowpb.FlowFilter) ([]FilterFunc, error) {
	return f(ctx, flow)
}

// BuildFilter builds a filter based on a FlowFilter. It returns:
// - the FilterFunc to be used to filter packets based on the requested
//   FlowFilter;
// - an error in case something went wrong.
func BuildFilter(ctx context.Context, ff *flowpb.FlowFilter, auxFilters []OnBuildFilter) (FilterFuncs, error) {
	var fs []FilterFunc

	for _, f := range auxFilters {
		fl, err := f.OnBuildFilter(ctx, ff)
		if err != nil {
			return nil, err
		}
		if fl != nil {
			fs = append(fs, fl...)
		}
	}

	return fs, nil
}

// BuildFilterList constructs a list of filter functions representing the list
// of FlowFilter. It returns:
// - the FilterFunc to be used to filter packets based on the requested
//   FlowFilter;
// - an error in case something went wrong.
func BuildFilterList(ctx context.Context, ff []*flowpb.FlowFilter, auxFilters []OnBuildFilter) (FilterFuncs, error) {
	filterList := make([]FilterFunc, 0, len(ff))

	for _, flowFilter := range ff {
		// Build filter matching on all requirements of the FlowFilter
		tf, err := BuildFilter(ctx, flowFilter, auxFilters)
		if err != nil {
			return nil, err
		}

		// All filters representing a FlowFilter must match
		filterFunc := func(ev *v1.Event) bool {
			return tf.MatchAll(ev)
		}

		filterList = append(filterList, filterFunc)
	}

	return filterList, nil
}

// DefaultFilters is the list of default filters
var DefaultFilters = []OnBuildFilter{
	&EventTypeFilter{},
	&VerdictFilter{},
	&ReplyFilter{},
	&IdentityFilter{},
	&ProtocolFilter{},
	&IPFilter{},
	&PodFilter{},
	&ServiceFilter{},
	&FQDNFilter{},
	&LabelsFilter{},
	&PortFilter{},
	&HTTPFilter{},
}