Merge pull request #6 from cilium/add-send-context

dns: Add SendContext()

client.go

@@ -210,6 +210,32 @@ func (c *Client) exchangeWithConnContext(ctx context.Context, m *Msg, conn *Conn
 }
 
 func (c *Client) exchangeContext(ctx context.Context, m *Msg, co *Conn) (r *Msg, rtt time.Duration, err error) {
+	start := time.Now()
+	err = c.SendContext(ctx, m, co, start)
+	if err != nil {
+		return nil, 0, err
+	}
+
+	if isPacketConn(co.Conn) {
+		for {
+			r, err = co.ReadMsg()
+			// Ignore replies with mismatched IDs because they might be
+			// responses to earlier queries that timed out.
+			if err != nil || r.Id == m.Id {
+				break
+			}
+		}
+	} else {
+		r, err = co.ReadMsg()
+		if err == nil && r.Id != m.Id {
+			err = ErrId
+		}
+	}
+
+	return r, time.Since(start), err
+}
+
+func (c *Client) SendContext(ctx context.Context, m *Msg, co *Conn, t time.Time) error {
 	opt := m.IsEdns0()
 	// If EDNS0 is used use that for size.
 	if opt != nil && opt.UDPSize() >= MinMsgSize {
@@ -221,7 +247,6 @@ func (c *Client) exchangeContext(ctx context.Context, m *Msg, co *Conn) (r *Msg,
 	}
 
 	// write with the appropriate write timeout
-	t := time.Now()
 	writeDeadline := t.Add(c.getTimeoutForRequest(c.writeTimeout()))
 	readDeadline := t.Add(c.getTimeoutForRequest(c.readTimeout()))
 	if deadline, ok := ctx.Deadline(); ok {
@@ -237,27 +262,7 @@ func (c *Client) exchangeContext(ctx context.Context, m *Msg, co *Conn) (r *Msg,
 
 	co.TsigSecret, co.TsigProvider = c.TsigSecret, c.TsigProvider
 
-	if err = co.WriteMsg(m); err != nil {
-		return nil, 0, err
-	}
-
-	if isPacketConn(co.Conn) {
-		for {
-			r, err = co.ReadMsg()
-			// Ignore replies with mismatched IDs because they might be
-			// responses to earlier queries that timed out.
-			if err != nil || r.Id == m.Id {
-				break
-			}
-		}
-	} else {
-		r, err = co.ReadMsg()
-		if err == nil && r.Id != m.Id {
-			err = ErrId
-		}
-	}
-	rtt = time.Since(t)
-	return r, rtt, err
+	return co.WriteMsg(m)
 }
 
 // ReadMsg reads a message from the connection co.