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core/pppd-plugin: wait to recover port settings before notifying death

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pppd restores the previous settings for the serial port it uses right
before exiting. It is especially important to do so because otherwise
ModemManager is not able to recover the port as it can receive a hangup
event from the port due to CLOCAL not being restored.  However, there is
currently a race condition that produces this issue. This is because
when PHASE_DEAD is notified, pppd still has not restored the port
settings - it does that a bit later, in the die() function.

This patch delays notifying PHASE_DEAD until when the exitnotify() hook
is called by pppd: when this happens the port settings have already been
restored.

There were previously efforts to fix this in commit fe090c34b7, so
PHASE_DEAD was used instead of PHASE_DISCONNECT to notify MM that the
port was disconnected, but that still early to ensure that the port
settings are restored.

The MM traces seen when the bug is triggered are:

ModemManager[2158]: <warn>  (ttyACM1): could not re-acquire serial port lock: (5) Input/output error
ModemManager[2158]: <warn>  Couldn't load Operator Code: 'Cannot run sequence: 'Could not open serial device ttyACM1: it has been forced close'

https://mail.gnome.org/archives/networkmanager-list/2019-June/msg00014.html

(cherry picked from commit a251712a72)
This commit is contained in:
Alfonso Sánchez-Beato 2019-06-13 18:23:21 +02:00 • committed by Thomas Haller
parent 5221af1123
commit 3caa065709
1 changed files with 18 additions and 3 deletions
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21
src/ppp/nm-pppd-plugin.c
View file

@ -49,7 +49,7 @@ char pppd_version[] = VERSION;
static GDBusProxy *proxy = NULL;
static void
nm_phasechange (void *data, int arg)
nm_phasechange (int arg)
{
NMPPPStatus ppp_status = NM_PPP_STATUS_UNKNOWN;
char new_name[IF_NAMESIZE];
@ -151,6 +151,16 @@ nm_phasechange (void *data, int arg)
}
}
static void
nm_phasechange_hook (void *data, int arg)
{
/* We send the nofication in exitnotify instead */
if (arg == PHASE_DEAD)
return;
nm_phasechange (arg);
}
static void
nm_ip_up (void *data, int arg)
{
@ -165,7 +175,7 @@ nm_ip_up (void *data, int arg)
if (!opts.ouraddr) {
g_warning ("nm-ppp-plugin: (%s): didn't receive an internal IP from pppd!", __func__);
nm_phasechange (NULL, PHASE_DEAD);
nm_phasechange (PHASE_DEAD);
return;
}
@ -357,6 +367,11 @@ nm_exit_notify (void *data, int arg)
{
g_return_if_fail (G_IS_DBUS_PROXY (proxy));
/* We wait until this point to notify dead phase to make sure that
* the serial port has recovered already its original settings.
*/
nm_phasechange (PHASE_DEAD);
g_message ("nm-ppp-plugin: (%s): cleaning up", __func__);
g_object_unref (proxy);
@ -424,7 +439,7 @@ plugin_init (void)
pap_passwd_hook = get_credentials;
pap_check_hook = get_pap_check;
add_notifier (&phasechange, nm_phasechange, NULL);
add_notifier (&phasechange, nm_phasechange_hook, NULL);
add_notifier (&ip_up_notifier, nm_ip_up, NULL);
add_notifier (&exitnotify, nm_exit_notify, proxy);
add_ip6_notifier ();