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Fix problem where TLS connections would sometimes hang

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* src/process.c (wait_reading_process_output): Before the select,
check every interesting gnutls stream for available data in the
buffer.  If some of them hit, and either there is no wait_proc or
the wait_proc is one of the gnutls streams with new data, set the
select timeout to 0 after the select, and merge the gnutls buffer
status into the select returns (bug#40665).  This fixes a problem
where TLS connections would sometimes hang.
This commit is contained in:
Derek Zhou 2020-08-03 07:56:22 +02:00 • committed by Lars Ingebrigtsen
parent a325584281
commit f921feceb8
1 changed files with 46 additions and 51 deletions
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97
src/process.c
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@ -5491,6 +5491,10 @@ wait_reading_process_output (intmax_t time_limit, int nsecs, int read_kbd,
}
else
{
#ifdef HAVE_GNUTLS
int tls_nfds;
fd_set tls_available;
#endif
/* Set the timeout for adaptive read buffering if any
process has non-zero read_output_skip and non-zero
read_output_delay, and we are not reading output for a
@ -5560,7 +5564,36 @@ wait_reading_process_output (intmax_t time_limit, int nsecs, int read_kbd,
}
#endif
/* Non-macOS HAVE_GLIB builds call thread_select in xgselect.c. */
#ifdef HAVE_GNUTLS
/* GnuTLS buffers data internally. We need to check if some
data is available in the buffers manually before the select.
And if so, we need to skip the select which could block. */
FD_ZERO (&tls_available);
tls_nfds = 0;
for (channel = 0; channel < FD_SETSIZE; ++channel)
if (! NILP (chan_process[channel])
&& FD_ISSET (channel, &Available))
{
struct Lisp_Process *p = XPROCESS (chan_process[channel]);
if (p
&& p->gnutls_p && p->gnutls_state
&& emacs_gnutls_record_check_pending (p->gnutls_state) > 0)
{
tls_nfds++;
eassert (p->infd == channel);
FD_SET (p->infd, &tls_available);
}
}
/* If wait_proc is somebody else, we have to wait in select
as usual. Otherwise, clobber the timeout. */
if (tls_nfds > 0
&& (!wait_proc ||
(wait_proc->infd >= 0
&& FD_ISSET (wait_proc->infd, &tls_available))))
timeout = make_timespec (0, 0);
#endif
/* Non-macOS HAVE_GLIB builds call thread_select in xgselect.c. */
#if defined HAVE_GLIB && !defined HAVE_NS
nfds = xg_select (max_desc + 1,
&Available, (check_write ? &Writeok : 0),
@ -5578,59 +5611,21 @@ wait_reading_process_output (intmax_t time_limit, int nsecs, int read_kbd,
#endif /* !HAVE_GLIB */
#ifdef HAVE_GNUTLS
/* GnuTLS buffers data internally. In lowat mode it leaves
some data in the TCP buffers so that select works, but
with custom pull/push functions we need to check if some
data is available in the buffers manually. */
if (nfds == 0)
/* Merge tls_available into Available. */
if (tls_nfds > 0)
{
fd_set tls_available;
int set = 0;
FD_ZERO (&tls_available);
if (! wait_proc)
if (nfds == 0 || (nfds < 0 && errno == EINTR))
{
/* We're not waiting on a specific process, so loop
through all the channels and check for data.
This is a workaround needed for some versions of
the gnutls library -- 2.12.14 has been confirmed
to need it. */
for (channel = 0; channel < FD_SETSIZE; ++channel)
if (! NILP (chan_process[channel]))
{
struct Lisp_Process *p =
XPROCESS (chan_process[channel]);
if (p && p->gnutls_p && p->gnutls_state
&& ((emacs_gnutls_record_check_pending
(p->gnutls_state))
> 0))
{
nfds++;
eassert (p->infd == channel);
FD_SET (p->infd, &tls_available);
set++;
}
}
/* Fast path, just copy. */
nfds = tls_nfds;
Available = tls_available;
}
else
{
/* Check this specific channel. */
if (wait_proc->gnutls_p /* Check for valid process. */
&& wait_proc->gnutls_state
/* Do we have pending data? */
&& ((emacs_gnutls_record_check_pending
(wait_proc->gnutls_state))
> 0))
{
nfds = 1;
eassert (0 <= wait_proc->infd);
/* Set to Available. */
FD_SET (wait_proc->infd, &tls_available);
set++;
}
}
if (set)
Available = tls_available;
else if (nfds > 0)
/* Slow path, merge one by one. Note: nfds does not need
to be accurate, just positive is enough. */
for (channel = 0; channel < FD_SETSIZE; ++channel)
if (FD_ISSET(channel, &tls_available))
FD_SET(channel, &Available);
}
#endif
}