Commit 763d7223 authored by David Goulet's avatar David Goulet 🐼
Browse files

kist: Don't try to flush empty outbuf 



It is possible that a scheduled channel ended up with 0 bytes in its
outbuf after the scheduling loop and having an outbuf table entry
indicating that we need to flush bytes on the wire after the loop.

This lead to attempt to write 0 bytes up to the TLS layer that would
prevent such action.

All in all, this fixes wasted CPU cycles on attempting to flush nothing.

Fixes #40548

Signed-off-by: David Goulet's avatarDavid Goulet <dgoulet@torproject.org>
parent 9bf4a9e1

changes/ticket40548

0 → 100644
+4 −0
Original line number Diff line number Diff line 
  o Minor bugfixes (cell scheduling):

    - Don't attempt to write 0 bytes after a cell scheduling loop. No empty

      payload was put on the wire. Fixes bug 40548; bugfix on 0.3.5.1-alpha.

    - Avoid writing empty payload with NSS write.

src/core/or/scheduler_kist.c

+10 −2
Original line number Diff line number Diff line
@@ -465,9 +465,17 @@ MOCK_IMPL(int, channel_should_write_to_kernel, 
MOCK_IMPL(void, channel_write_to_kernel, (channel_t *chan))

{

  tor_assert(chan);



  /* This is possible because a channel might have an outbuf table entry even

   * though it has no more cells in its outbuf. Just move on. */

  size_t outbuf_len = channel_outbuf_length(chan);

  if (outbuf_len == 0) {

    return;

  }



  log_debug(LD_SCHED, "Writing %lu bytes to kernel for chan %" PRIu64,

            (unsigned long)channel_outbuf_length(chan),

            chan->global_identifier);

            (unsigned long) outbuf_len, chan->global_identifier);



  /* Note that 'connection_handle_write()' may change the scheduler state of

   * the channel during the scheduling loop with

   * 'connection_or_flushed_some()' -> 'scheduler_channel_wants_writes()'.