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// Copyright 2019 The gVisor Authors.
//
// 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 (
"gvisor.dev/gvisor/pkg/tcpip"
"gvisor.dev/gvisor/pkg/tcpip/stack"
"gvisor.dev/gvisor/pkg/waiter"
)
// Forwarder is a session request forwarder, which allows clients to decide
// what to do with a session request, for example: ignore it, or process it.
//
// The canonical way of using it is to pass the Forwarder.HandlePacket function
// to stack.SetTransportProtocolHandler.
type Forwarder struct {
handler func(*ForwarderRequest)
stack *stack.Stack
}
// NewForwarder allocates and initializes a new forwarder.
func NewForwarder(s *stack.Stack, handler func(*ForwarderRequest)) *Forwarder {
return &Forwarder{
stack: s,
handler: handler,
}
}
// HandlePacket handles all packets.
//
// This function is expected to be passed as an argument to the
// stack.SetTransportProtocolHandler function.
func (f *Forwarder) HandlePacket(r *stack.Route, id stack.TransportEndpointID, pkt tcpip.PacketBuffer) bool {
f.handler(&ForwarderRequest{
stack: f.stack,
route: r,
id: id,
pkt: pkt,
})
return true
}
// ForwarderRequest represents a session request received by the forwarder and
// passed to the client. Clients may optionally create an endpoint to represent
// it via CreateEndpoint.
type ForwarderRequest struct {
stack *stack.Stack
route *stack.Route
id stack.TransportEndpointID
pkt tcpip.PacketBuffer
}
// ID returns the 4-tuple (src address, src port, dst address, dst port) that
// represents the session request.
func (r *ForwarderRequest) ID() stack.TransportEndpointID {
return r.id
}
// CreateEndpoint creates a connected UDP endpoint for the session request.
func (r *ForwarderRequest) CreateEndpoint(queue *waiter.Queue) (tcpip.Endpoint, *tcpip.Error) {
ep := newEndpoint(r.stack, r.route.NetProto, queue)
if err := r.stack.RegisterTransportEndpoint(r.route.NICID(), []tcpip.NetworkProtocolNumber{r.route.NetProto}, ProtocolNumber, r.id, ep, ep.reusePort, ep.bindToDevice); err != nil {
ep.Close()
return nil, err
}
ep.ID = r.id
ep.route = r.route.Clone()
ep.dstPort = r.id.RemotePort
ep.RegisterNICID = r.route.NICID()
ep.state = StateConnected
ep.rcvMu.Lock()
ep.rcvReady = true
ep.rcvMu.Unlock()
ep.HandlePacket(r.route, r.id, r.pkt)
return ep, nil
}
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