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firewall.go
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firewall.go
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// Copyright © 2019 The Things Network Foundation, The Things Industries B.V.
//
// 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 udp
import (
"bytes"
"context"
"net"
"sync"
"time"
"go.thethings.network/lorawan-stack/pkg/errors"
encoding "go.thethings.network/lorawan-stack/pkg/ttnpb/udp"
)
// Firewall filters packets by tracking addresses and time.
type Firewall interface {
Filter(packet encoding.Packet) error
}
type addrTime struct {
net.IP
lastSeen time.Time
}
type memoryFirewall struct {
m sync.Map
addrChangeBlock time.Duration
}
// NewMemoryFirewall returns an in-memory Firewall.
func NewMemoryFirewall(ctx context.Context, addrChangeBlock time.Duration) Firewall {
f := &memoryFirewall{
addrChangeBlock: addrChangeBlock,
}
go func() {
ticker := time.NewTicker(addrChangeBlock)
for {
select {
case <-ctx.Done():
ticker.Stop()
return
case <-ticker.C:
f.gc()
}
}
}()
return f
}
var (
errNoEUI = errors.DefineInvalidArgument("no_eui", "packet has no gateway EUI")
errNoAddress = errors.DefineInvalidArgument("no_address", "packet has no gateway address")
errAlreadyConnected = errors.DefineFailedPrecondition("already_connected", "gateway is already connected")
)
func (f *memoryFirewall) Filter(packet encoding.Packet) error {
if packet.GatewayEUI == nil {
return errNoEUI.New()
}
if packet.GatewayAddr == nil {
return errNoAddress.New()
}
now := time.Now().UTC()
eui := *packet.GatewayEUI
val, ok := f.m.Load(eui)
if ok {
a := val.(addrTime)
if !bytes.Equal(a.IP, packet.GatewayAddr.IP) && a.lastSeen.Add(f.addrChangeBlock).After(now) {
return errAlreadyConnected.WithAttributes(
"connected_ip", a.IP.String(),
"connecting_ip", packet.GatewayAddr.IP.String(),
)
}
}
f.m.Store(eui, addrTime{
IP: packet.GatewayAddr.IP,
lastSeen: now,
})
return nil
}
func (f *memoryFirewall) gc() {
now := time.Now().UTC()
f.m.Range(func(k, val interface{}) bool {
a := val.(addrTime)
if a.lastSeen.Add(f.addrChangeBlock).Before(now) {
f.m.Delete(k)
}
return true
})
}