mwiede#411 add flush operation from is/jsch#39, with new config option to allow disabling in case it causes regressions.

Author: norrisjeremy

src/main/java/com/jcraft/jsch/Channel.java

@@ -67,7 +67,11 @@ static Channel getChannel(String type, Session session) {
       ret = new ChannelForwardedTCPIP();
     }
     if (type.equals("sftp")) {
-      ret = new ChannelSftp();
+      ChannelSftp sftp = new ChannelSftp();
+      boolean useWriteFlushWorkaround =
+          session.getConfig("use_sftp_write_flush_workaround").equals("yes");
+      sftp.setUseWriteFlushWorkaround(useWriteFlushWorkaround);
+      ret = sftp;
     }
     if (type.equals("subsystem")) {
       ret = new ChannelSubsystem();

src/main/java/com/jcraft/jsch/ChannelSftp.java

@@ -157,6 +157,8 @@ public class ChannelSftp extends ChannelSession {
   private Charset fEncoding = StandardCharsets.UTF_8;
   private boolean fEncoding_is_utf8 = true;
 
+  private boolean useWriteFlushWorkaround = true;
+
   private RequestQueue rq = new RequestQueue(16);
 
   /**
@@ -181,6 +183,14 @@ public int getBulkRequests() {
     return rq.size();
   }
 
+  public void setUseWriteFlushWorkaround(boolean useWriteFlushWorkaround) {
+    this.useWriteFlushWorkaround = useWriteFlushWorkaround;
+  }
+
+  public boolean getUseWriteFlushWorkaround() {
+    return useWriteFlushWorkaround;
+  }
+
   public ChannelSftp() {
     super();
     lwsize_max = LOCAL_WINDOW_SIZE_MAX;
@@ -754,6 +764,9 @@ public void write(byte[] d, int s, int len) throws IOException {
           try {
             int _len = len;
             while (_len > 0) {
+              if (useWriteFlushWorkaround && rwsize < 21 + handle.length + _len + 4) {
+                flush();
+              }
               int sent = sendWRITE(handle, _offset[0], d, s, _len);
               writecount++;
               _offset[0] += sent;

src/main/java/com/jcraft/jsch/JSch.java

@@ -228,6 +228,8 @@ public class JSch {
     config.put("try_additional_pubkey_algorithms",
         Util.getSystemProperty("jsch.try_additional_pubkey_algorithms", "yes"));
     config.put("enable_auth_none", Util.getSystemProperty("jsch.enable_auth_none", "yes"));
+    config.put("use_sftp_write_flush_workaround",
+        Util.getSystemProperty("jsch.use_sftp_write_flush_workaround", "yes"));
 
     config.put("CheckCiphers",
         Util.getSystemProperty("jsch.check_ciphers", "chacha20-poly1305@openssh.com"));

src/main/java/com/jcraft/jsch/Session.java

@@ -3069,6 +3069,7 @@ private void applyConfig() throws JSchException {
     checkConfig(config, "enable_pubkey_auth_query");
     checkConfig(config, "try_additional_pubkey_algorithms");
     checkConfig(config, "enable_auth_none");
+    checkConfig(config, "use_sftp_write_flush_workaround");
 
     checkConfig(config, "cipher.c2s");
     checkConfig(config, "cipher.s2c");