Merge pull request #307 from wneessen/feature/269_goroutineconcurrenc…

…y-safety

go-mail goroutine-/thread-safety

client.go

@@ -12,6 +12,7 @@ import (
  "net"
  "os"
  "strings"
+ "sync"
  "time"
 
  "github.com/wneessen/go-mail/log"
@@ -87,12 +88,12 @@ type DialContextFunc func(ctx context.Context, network, address string) (net.Con
 
 // Client is the SMTP client struct
 type Client struct {
- // connection is the net.Conn that the smtp.Client is based on
- connection net.Conn
-
  // Timeout for the SMTP server connection
  connTimeout time.Duration
 
+ // dialContextFunc is a custom DialContext function to dial target SMTP server
+ dialContextFunc DialContextFunc
+
  // dsn indicates that we want to use DSN for the Client
  dsn bool
 
@@ -102,24 +103,34 @@ type Client struct {
  // dsnrntype defines the DSNRcptNotifyOption in case DSN is enabled
  dsnrntype []string
 
- // isEncrypted indicates if a Client connection is encrypted or not
- isEncrypted bool
-
- // noNoop indicates the Noop is to be skipped
- noNoop bool
+ // fallbackPort is used as an alternative port number in case the primary port is unavailable or
+ // fails to bind.
+ fallbackPort int
 
  // HELO/EHLO string for the greeting the target SMTP server
  helo string
 
  // Hostname of the target SMTP server to connect to
  host string
 
+ // isEncrypted indicates if a Client connection is encrypted or not
+ isEncrypted bool
+
+ // logger is a logger that implements the log.Logger interface
+ logger log.Logger
+
+ // mutex is used to synchronize access to shared resources, ensuring that only one goroutine can
+ // modify them at a time.
+ mutex sync.RWMutex
+
+ // noNoop indicates the Noop is to be skipped
+ noNoop bool
+
  // pass is the corresponding SMTP AUTH password
  pass string
 
- // Port of the SMTP server to connect to
- port int
- fallbackPort int
+ // port specifies the network port number on which the server listens for incoming connections.
+ port int
 
  // smtpAuth is a pointer to smtp.Auth
  smtpAuth smtp.Auth
@@ -130,26 +141,20 @@ type Client struct {
  // smtpClient is the smtp.Client that is set up when using the Dial*() methods
  smtpClient *smtp.Client
 
- // Use SSL for the connection
- useSSL bool
-
  // tlspolicy sets the client to use the provided TLSPolicy for the STARTTLS protocol
  tlspolicy TLSPolicy
 
  // tlsconfig represents the tls.Config setting for the STARTTLS connection
  tlsconfig *tls.Config
 
- // user is the SMTP AUTH username
- user string
-
  // useDebugLog enables the debug logging on the SMTP client
  useDebugLog bool
 
- // logger is a logger that implements the log.Logger interface
- logger log.Logger
+ // user is the SMTP AUTH username
+ user string
 
- // dialContextFunc is a custom DialContext function to dial target SMTP server
- dialContextFunc DialContextFunc
+ // Use SSL for the connection
+ useSSL bool
 }
 
 // Option returns a function that can be used for grouping Client options
@@ -550,6 +555,9 @@ func (c *Client) SetLogger(logger log.Logger) {
 
 // SetTLSConfig overrides the current *tls.Config with the given *tls.Config value
 func (c *Client) SetTLSConfig(tlsconfig *tls.Config) error {
+ c.mutex.Lock()
+ defer c.mutex.Unlock()
+
  if tlsconfig == nil {
  return ErrInvalidTLSConfig
  }
@@ -589,6 +597,9 @@ func (c *Client) setDefaultHelo() error {
 
 // DialWithContext establishes a connection to the SMTP server with a given context.Context
 func (c *Client) DialWithContext(dialCtx context.Context) error {
+ c.mutex.Lock()
+ defer c.mutex.Unlock()
+
  ctx, cancel := context.WithDeadline(dialCtx, time.Now().Add(c.connTimeout))
  defer cancel()
 
@@ -602,17 +613,16 @@ func (c *Client) DialWithContext(dialCtx context.Context) error {
  c.dialContextFunc = tlsDialer.DialContext
  }
  }
- var err error
- c.connection, err = c.dialContextFunc(ctx, "tcp", c.ServerAddr())
+ connection, err := c.dialContextFunc(ctx, "tcp", c.ServerAddr())
  if err != nil && c.fallbackPort != 0 {
  // TODO: should we somehow log or append the previous error?
- c.connection, err = c.dialContextFunc(ctx, "tcp", c.serverFallbackAddr())
+ connection, err = c.dialContextFunc(ctx, "tcp", c.serverFallbackAddr())
  }
  if err != nil {
  return err
  }
 
- client, err := smtp.NewClient(c.connection, c.host)
+ client, err := smtp.NewClient(connection, c.host)
  if err != nil {
  return err
  }
@@ -691,7 +701,7 @@ func (c *Client) DialAndSendWithContext(ctx context.Context, messages ...*Msg) e
 // checkConn makes sure that a required server connection is available and extends the
 // connection deadline
 func (c *Client) checkConn() error {
- if c.connection == nil {
+ if !c.smtpClient.HasConnection() {
  return ErrNoActiveConnection
  }
 
@@ -701,7 +711,7 @@ func (c *Client) checkConn() error {
  }
  }
 
- if err := c.connection.SetDeadline(time.Now().Add(c.connTimeout)); err != nil {
+ if err := c.smtpClient.UpdateDeadline(c.connTimeout); err != nil {
  return ErrDeadlineExtendFailed
  }
  return nil
@@ -715,7 +725,7 @@ func (c *Client) serverFallbackAddr() string {
 
 // tls tries to make sure that the STARTTLS requirements are satisfied
 func (c *Client) tls() error {
- if c.connection == nil {
+ if !c.smtpClient.HasConnection() {
  return ErrNoActiveConnection
  }
  if !c.useSSL && c.tlspolicy != NoTLS {
@@ -791,6 +801,9 @@ func (c *Client) auth() error {
 // sendSingleMsg sends out a single message and returns an error if the transmission/delivery fails.
 // It is invoked by the public Send methods
 func (c *Client) sendSingleMsg(message *Msg) error {
+ c.mutex.Lock()
+ defer c.mutex.Unlock()
+
  if message.encoding == NoEncoding {
  if ok, _ := c.smtpClient.Extension("8BITMIME"); !ok {
  return &SendError{Reason: ErrNoUnencoded, isTemp: false, affectedMsg: message}