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listener.go
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listener.go
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// Copyright (c) 2024 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
package muxlistener
import (
"context"
"crypto/tls"
"errors"
"fmt"
"io"
"net"
"sync"
"syscall"
"time"
"go.uber.org/net/metrics"
yarpctls "go.uber.org/yarpc/api/transport/tls"
tlsmetrics "go.uber.org/yarpc/transport/internal/tls/metrics"
"go.uber.org/zap"
)
var (
errListenerClosed = errors.New("listener closed")
// Connection has 15s to transmit first 5 bytes for sniffing.
_sniffReadTimeout = time.Second * 15
// Handshake timeout set to 120s, see gRPC-go:
// https://github.com/grpc/grpc-go/blob/fdc5d2f3da856f3cdd3483280ae33da5bee17a93/server.go#L467
_tlsHandshakeTimeout = time.Second * 120
)
// Config describes how listener should be configured.
type Config struct {
Listener net.Listener
TLSConfig *tls.Config
ServiceName string
TransportName string
Meter *metrics.Scope
Logger *zap.Logger
Mode yarpctls.Mode
}
// listener wraps original net listener and it accepts both TLS and non-TLS connections.
type listener struct {
net.Listener
tlsConfig *tls.Config
observer *tlsmetrics.Observer
logger *zap.Logger
mode yarpctls.Mode
closeOnce sync.Once
connChan chan net.Conn
stopChan chan struct{}
stoppedChan chan struct{}
}
// NewListener returns a multiplexed listener which accepts both TLS and
// plaintext connections.
func NewListener(c Config) net.Listener {
if c.Mode == yarpctls.Disabled {
return c.Listener
}
logger := c.Logger.With(zap.String("transportName", c.TransportName))
observer := tlsmetrics.NewObserver(tlsmetrics.Params{
Meter: c.Meter,
Logger: logger,
ServiceName: c.ServiceName,
TransportName: c.TransportName,
Mode: c.Mode,
Direction: "inbound",
})
lis := &listener{
Listener: c.Listener,
tlsConfig: c.TLSConfig,
observer: observer,
logger: logger,
connChan: make(chan net.Conn),
stoppedChan: make(chan struct{}),
stopChan: make(chan struct{}),
mode: c.Mode,
}
// Starts go routine for the connection server
go lis.serve()
return lis
}
// Accept returns multiplexed plaintext connetion.
// After close, returned error is errListenerClosed.
func (l *listener) Accept() (net.Conn, error) {
select {
case conn, ok := <-l.connChan:
if !ok {
return nil, errListenerClosed
}
return conn, nil
case <-l.stopChan:
return nil, errListenerClosed
}
}
// Close closes the listener and waits until the connection server drains
// accepted connections and stops the server.
func (l *listener) Close() error {
var err error
l.closeOnce.Do(func() {
err = l.Listener.Close()
close(l.stopChan)
<-l.stoppedChan
})
return err
}
// serve starts accepting the connection from the underlying listener and creates a new
// go routine for each connection for async muxing.
func (l *listener) serve() {
var wg sync.WaitGroup
ctx, cancel := context.WithCancel(context.Background())
defer func() {
cancel()
wg.Wait()
close(l.connChan)
close(l.stoppedChan)
}()
for {
conn, err := l.Listener.Accept()
if err != nil {
return
}
wg.Add(1)
go l.serveConnection(ctx, conn, &wg)
}
}
// serveConnection muxes the given connection and sends muxed connection to the
// connection channel.
func (l *listener) serveConnection(ctx context.Context, conn net.Conn, wg *sync.WaitGroup) {
defer wg.Done()
c, err := l.mux(ctx, conn)
if err != nil {
conn.Close()
logLevel := zap.ErrorLevel
if errors.Is(err, io.EOF) || errors.Is(err, syscall.ECONNRESET) {
// Log EOF and Connection Reset error at warn level as they mean that
// client has already closed connection and likely nothing is wrong with the server itself.
logLevel = zap.WarnLevel
}
// TODO: Replace with logger.Log once we upgrade to zap >=1.22
if ce := l.logger.Check(logLevel, "failed to serve connection"); ce != nil {
ce.Write(zap.Error(err))
}
return
}
select {
case l.connChan <- c:
case <-l.stopChan:
c.Close()
}
}
// mux accepts both plaintext and tls connection, and returns a plaintext
// connection.
func (l *listener) mux(ctx context.Context, conn net.Conn) (net.Conn, error) {
if l.mode == yarpctls.Enforced {
return l.handleTLSConn(ctx, conn)
}
c := newConnectionSniffer(conn)
isTLS, err := matchTLSConnection(c)
if err != nil {
return nil, fmt.Errorf("tls connection matcher failed: %w", err)
}
if isTLS {
return l.handleTLSConn(ctx, c)
}
return l.handlePlaintextConn(c)
}
// handleTLSConn completes the TLS handshake for the given connection and
// returns a TLS server wrapped plaintext connection.
func (l *listener) handleTLSConn(ctx context.Context, conn net.Conn) (net.Conn, error) {
ctx, cancel := context.WithTimeout(ctx, _tlsHandshakeTimeout)
defer cancel()
tlsConn := tls.Server(conn, l.tlsConfig)
if err := tlsConn.HandshakeContext(ctx); err != nil {
l.observer.IncTLSHandshakeFailures()
return nil, fmt.Errorf("tls handshake failed: %w", err)
}
l.observer.IncTLSConnections(tlsConn.ConnectionState().Version)
return tlsConn, nil
}
func (l *listener) handlePlaintextConn(conn net.Conn) (net.Conn, error) {
l.observer.IncPlaintextConnections()
return conn, nil
}
func matchTLSConnection(cs *connSniffer) (bool, error) {
if err := cs.SetReadDeadline(time.Now().Add(_sniffReadTimeout)); err != nil {
return false, err
}
// Reset read deadline after sniffing. See below:
// https://github.com/golang/go/blob/be0b2a393a5a7297a3c8f42ca7d5ad3e4b15dcbe/src/net/http/server.go#L1887
defer func() {
_ = cs.SetReadDeadline(time.Time{})
}()
isTLS, err := isTLSClientHelloRecord(cs)
if err != nil {
return false, err
}
cs.stopSniffing()
return isTLS, nil
}