open-consul/tools/internal-grpc-proxy/main.go

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// Copyright (c) HashiCorp, Inc.
// SPDX-License-Identifier: MPL-2.0
package main
import (
"fmt"
"io"
"net"
"os"
)
// gRPC byte prefix (see RPCGRPC in agent/pool/conn.go).
const bytePrefix byte = 8
func main() {
if len(os.Args) != 2 {
log("usage: %s host:port", os.Args[0])
os.Exit(1)
}
serverAddr := os.Args[1]
lis, err := net.Listen("tcp", "127.0.0.1:0")
if err != nil {
log("failed to start listener: %v", err)
os.Exit(1)
}
defer lis.Close()
fmt.Println("Proxying connections to Consul's internal gRPC server")
fmt.Printf("Use this address: %s\n", lis.Addr())
for {
conn, err := lis.Accept()
if err != nil {
log("failed to accept connection: %v", err)
continue
}
go func(conn net.Conn) {
if err := handleClient(serverAddr, conn); err != nil {
log(err.Error())
}
}(conn)
}
}
func handleClient(serverAddr string, clientConn net.Conn) error {
defer clientConn.Close()
serverConn, err := net.Dial("tcp", serverAddr)
if err != nil {
return fmt.Errorf("failed to dial server connection: %w", err)
}
defer serverConn.Close()
if _, err := serverConn.Write([]byte{bytePrefix}); err != nil {
return fmt.Errorf("failed to write byte prefix: %v", err)
}
errCh := make(chan error, 1)
go func() {
_, err := io.Copy(serverConn, clientConn)
errCh <- err
}()
go func() {
_, err := io.Copy(clientConn, serverConn)
errCh <- err
}()
return <-errCh
}
func log(message string, args ...interface{}) {
fmt.Fprintf(os.Stderr, message+"\n", args...)
}