patches/inetutils/0011-telnetd-Premature-connection-closure.patch

   1 From bc5dc7af74e6fa1c70aa4bbb1e482fd0c3663af3 Mon Sep 17 00:00:00 2001
   2 From: Mats Erik Andersson <gnu@gisladisker.se>
   3 Date: Sat, 15 Aug 2015 20:56:26 +0200
   4 Subject: [PATCH 11/60] telnetd: Premature connection closure.
   5
   6 A change, part of 0b7e8687, but secondary to its
   7 intention, turned out to cause service rejects during
   8 conditions akin to connection flooding.  Revert this
   9 particular part to gain established, good behaviour
  10 on GNU/Linux.
  11 Reported in `bug-inetutils/2015-07/msg00006.html'.
  12 ---
  13  ChangeLog         | 18 ++++++++++++++++++
  14  telnetd/telnetd.c |  8 +++++++-
  15  telnetd/utility.c |  8 ++++++++
  16  3 files changed, 33 insertions(+), 1 deletion(-)
  17
  18 diff --git a/ChangeLog b/ChangeLog
  19 index 73b281b9..03bb8a78 100644
  20 --- a/ChangeLog
  21 +++ b/ChangeLog
  22 @@ -1,3 +1,21 @@
  23 +2015-08-15  Mats Erik Andersson  <gnu@gisladisker.se>
  24 +
  25 +       telnetd: Premature connection closure.
  26 +       When many connections are attempted in quick succession,
  27 +       a substantial number of them are cancelled.  This does not
  28 +       appear for manual use cases, but for contrived automated
  29 +       set-ups.  The cause seems to be a change in the evaluation
  30 +       of pty_read(), which was done to coincide with the condition
  31 +       in use by the original BSD implementation.  Issue reported and
  32 +       suggested by Chris Severance in
  33 +       http://lists.gnu.org/archive/html/bug-inetutils/2015-07/msg00006.html
  34 +
  35 +       * telnetd/telnetd.c (telnetd_run): Break the loop only by the
  36 +       stronger condition `pty_read() < 0', i.e., only on non-masked
  37 +       read errors.  This reverts a change introduced in 2015-03-15.
  38 +       * telnetd/utility.c (pty_read): Add a comment that the read
  39 +       errors EWOULDBLOCK, EAGAIN, and EIO are treated specially.
  40 +
  41  2015-08-07  Mats Erik Andersson  <gnu@gisladisker.se>
  42
  43         ifconfig: Statistics for BSD systems.
  44 diff --git a/telnetd/telnetd.c b/telnetd/telnetd.c
  45 index faecc072..0bf102ac 100644
  46 --- a/telnetd/telnetd.c
  47 +++ b/telnetd/telnetd.c
  48 @@ -662,7 +662,13 @@ telnetd_run (void)
  49        if (FD_ISSET (pty, &ibits))
  50         {
  51           /* Something to read from the pty... */
  52 -         if (pty_read () <= 0)
  53 +
  54 +         /* Observe that pty_read() is masking a few select
  55 +          * read errors with the return value 0.  Let them
  56 +          * pass for further manipulation.  Issue reported in
  57 +          * http://lists.gnu.org/archive/html/bug-inetutils/2015-07/msg00006.html
  58 +          */
  59 +         if (pty_read () < 0)
  60             break;
  61
  62           /* The first byte is now TIOCPKT data.  Peek at it.  */
  63 diff --git a/telnetd/utility.c b/telnetd/utility.c
  64 index e7ffb8ed..e493dff2 100644
  65 --- a/telnetd/utility.c
  66 +++ b/telnetd/utility.c
  67 @@ -372,6 +372,14 @@ pty_input_putback (const char *str, size_t len)
  68    return 0;
  69  }
  70
  71 +/* pty_read()
  72 + *
  73 + * Read errors EWOULDBLOCK, EAGAIN, and EIO are
  74 + * tweeked into reporting zero bytes input.
  75 + * In particular, EIO is known to appear when
  76 + * reading off the master side, before having
  77 + * an active slave side.
  78 + */
  79  int
  80  pty_read (void)
  81  {
  82 --
  83 2.26.0.292.g33ef6b2f38
  84