1 files changed, 178 insertions, 0 deletions
diff --git a/worker/imap/connect.go b/worker/imap/connect.go
new file mode 100644
index 00000000..9cc394b4
--- /dev/null
+++ b/worker/imap/connect.go
@@ -0,0 +1,178 @@
+package imap
+
+import (
+	"crypto/tls"
+	"fmt"
+	"net"
+	"time"
+
+	"git.sr.ht/~rjarry/aerc/lib"
+	"github.com/emersion/go-imap"
+	"github.com/emersion/go-imap/client"
+)
+
+// connect establishes a new tcp connection to the imap server, logs in and
+// selects the default inbox. If no error is returned, the imap client will be
+// in the imap.SelectedState.
+func (w *IMAPWorker) connect() (*client.Client, error) {
+
+	var (
+		conn *net.TCPConn
+		err  error
+		c    *client.Client
+	)
+
+	conn, err = newTCPConn(w.config.addr, w.config.connection_timeout)
+	if conn == nil || err != nil {
+		return nil, err
+	}
+
+	if w.config.connection_timeout > 0 {
+		end := time.Now().Add(w.config.connection_timeout)
+		err = conn.SetDeadline(end)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	if w.config.keepalive_period > 0 {
+		err = w.setKeepaliveParameters(conn)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	serverName, _, _ := net.SplitHostPort(w.config.addr)
+	tlsConfig := &tls.Config{ServerName: serverName}
+
+	switch w.config.scheme {
+	case "imap":
+		c, err = client.New(conn)
+		if err != nil {
+			return nil, err
+		}
+		if !w.config.insecure {
+			if err = c.StartTLS(tlsConfig); err != nil {
+				return nil, err
+			}
+		}
+	case "imaps":
+		tlsConn := tls.Client(conn, tlsConfig)
+		c, err = client.New(tlsConn)
+		if err != nil {
+			return nil, err
+		}
+	default:
+		return nil, fmt.Errorf("Unknown IMAP scheme %s", w.config.scheme)
+	}
+
+	c.ErrorLog = w.worker.Logger
+
+	if w.config.user != nil {
+		username := w.config.user.Username()
+		password, hasPassword := w.config.user.Password()
+		if !hasPassword {
+			// TODO: ask password
+		}
+
+		if w.config.oauthBearer.Enabled {
+			if err := w.config.oauthBearer.Authenticate(
+				username, password, c); err != nil {
+				return nil, err
+			}
+		} else if err := c.Login(username, password); err != nil {
+			return nil, err
+		}
+	}
+
+	c.SetDebug(w.worker.Logger.Writer())
+
+	if _, err := c.Select(imap.InboxName, false); err != nil {
+		return nil, err
+	}
+
+	return c, nil
+}
+
+// newTCPConn establishes a new tcp connection. Timeout will ensure that the
+// function does not hang when there is no connection. If there is a timeout,
+// but a valid connection is eventually returned, ensure that it is properly
+// closed.
+func newTCPConn(addr string, timeout time.Duration) (*net.TCPConn, error) {
+
+	var errTCPTimeout = fmt.Errorf("tcp connection timeout")
+
+	type tcpConn struct {
+		conn *net.TCPConn
+		err  error
+	}
+
+	done := make(chan tcpConn)
+	go func() {
+		addr, err := net.ResolveTCPAddr("tcp", addr)
+		if err != nil {
+			done <- tcpConn{nil, err}
+			return
+		}
+
+		newConn, err := net.DialTCP("tcp", nil, addr)
+		if err != nil {
+			done <- tcpConn{nil, err}
+			return
+		}
+
+		done <- tcpConn{newConn, nil}
+		return
+	}()
+
+	select {
+	case <-time.After(timeout):
+		go func() {
+			if tcpResult := <-done; tcpResult.conn != nil {
+				tcpResult.conn.Close()
+			}
+		}()
+		return nil, errTCPTimeout
+	case tcpResult := <-done:
+		if tcpResult.conn == nil || tcpResult.err != nil {
+			return nil, tcpResult.err
+		}
+		return tcpResult.conn, nil
+	}
+}
+
+// Set additional keepalive parameters.
+// Uses new interfaces introduced in Go1.11, which let us get connection's file
+// descriptor, without blocking, and therefore without uncontrolled spawning of
+// threads (not goroutines, actual threads).
+func (w *IMAPWorker) setKeepaliveParameters(conn *net.TCPConn) error {
+	err := conn.SetKeepAlive(true)
+	if err != nil {
+		return err
+	}
+	// Idle time before sending a keepalive probe
+	err = conn.SetKeepAlivePeriod(w.config.keepalive_period)
+	if err != nil {
+		return err
+	}
+	rawConn, e := conn.SyscallConn()
+	if e != nil {
+		return e
+	}
+	err = rawConn.Control(func(fdPtr uintptr) {
+		fd := int(fdPtr)
+		// Max number of probes before failure
+		err := lib.SetTcpKeepaliveProbes(fd, w.config.keepalive_probes)
+		if err != nil {
+			w.worker.Logger.Printf(
+				"cannot set tcp keepalive probes: %v\n", err)
+		}
+		// Wait time after an unsuccessful probe
+		err = lib.SetTcpKeepaliveInterval(fd, w.config.keepalive_interval)
+		if err != nil {
+			w.worker.Logger.Printf(
+				"cannot set tcp keepalive interval: %v\n", err)
+		}
+	})
+	return err
+}