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portfwd: create separate gRPC streams for each UDP client #3724

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Merged
merged 1 commit into from
Jul 17, 2025
+18 −15
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portfwd: create separate gRPC streams for each UDP client #3724

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33 changes: 18 additions & 15 deletions pkg/portfwd/client.go
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,7 @@ import (
"context"
"fmt"
"net"
"sync/atomic"
"time"

"github.com/containers/gvisor-tap-vsock/pkg/services/forwarder"
Expand Down Expand Up @@ -40,33 +41,35 @@ func HandleTCPConnection(ctx context.Context, client *guestagentclient.GuestAgen
}

func HandleUDPConnection(ctx context.Context, client *guestagentclient.GuestAgentClient, conn net.PacketConn, guestAddr string) {
id := fmt.Sprintf("udp-%s", conn.LocalAddr().String())

stream, err := client.Tunnel(ctx)
if err != nil {
logrus.Errorf("could not open udp tunnel for id: %s error:%v", id, err)
return
}

// Handshake message to start tunnel
if err := stream.Send(&api.TunnelMessage{Id: id, Protocol: "udp", GuestAddr: guestAddr}); err != nil {
logrus.Errorf("could not start udp tunnel for id: %s error:%v", id, err)
return
}
var udpConnectionCounter atomic.Uint32
initialID := fmt.Sprintf("udp-%s", conn.LocalAddr().String())

// gvisor-tap-vsock's UDPProxy demultiplexes client connections internally based on their source address.
// It calls this dialer function only when it receives a datagram from a new, unrecognized client.
// For each new client, we must return a new net.Conn, which in our case is a new gRPC stream.
// The atomic counter ensures that each stream has a unique ID to distinguish them on the server side.
proxy, err := forwarder.NewUDPProxy(conn, func() (net.Conn, error) {
id := fmt.Sprintf("%s-%d", initialID, udpConnectionCounter.Add(1))
stream, err := client.Tunnel(ctx)
if err != nil {
return nil, fmt.Errorf("could not open udp tunnel for id: %s error:%w", id, err)
}
// Handshake message to start tunnel
if err := stream.Send(&api.TunnelMessage{Id: id, Protocol: "udp", GuestAddr: guestAddr}); err != nil {
return nil, fmt.Errorf("could not start udp tunnel for id: %s error:%w", id, err)
}
rw := &GrpcClientRW{stream: stream, id: id, addr: guestAddr, protocol: "udp"}
return rw, nil
})
if err != nil {
logrus.Errorf("error in udp tunnel proxy for id: %s error:%v", id, err)
logrus.Errorf("error in udp tunnel proxy for id: %s error:%v", initialID, err)
return
}

defer func() {
err := proxy.Close()
if err != nil {
logrus.Errorf("error in closing udp tunnel proxy for id: %s error:%v", id, err)
logrus.Errorf("error in closing udp tunnel proxy for id: %s error:%v", initialID, err)
}
}()
proxy.Run()
Expand Down
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