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client: fallback to CLOCK_MONOTONIC for timerfd

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RHEL7 supports clock_gettime(CLOCK_BOOTIME), but it does not support
timerfd_create(CLOCK_BOOTIME). Creating a timerfd will fail with EINVAL.
Fallback to CLOCK_MONOTONIC.

Compare this to n-acd which also has compatibility code to fallback to
CLOCK_MONOTONIC. However when n-acd falls back to CLOCK_MONOTONIC, it uses
monotonic clock also for clock_gettime().

For n-dhcp4, the timestamps are also exposed in the public API
(n_dhcp4_client_lease_get_lifetime()). Hence, for timestamps n-dhcp4
still uses and requires clock_gettime(CLOCK_BOOTIME). Only the internal
timeout handling with the timerfd falls back to CLOCK_MONOTONIC.

https://github.com/nettools/n-dhcp4/pull/13
https://gitlab.freedesktop.org/NetworkManager/NetworkManager/merge_requests/362
(cherry picked from commit a1771c738d)
This commit is contained in:
Thomas Haller
2019-12-15 10:33:28 +01:00
parent 944ff9f9dc
commit f49ce41214
2 changed files with 27 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

30
shared/n-dhcp4/src/n-dhcp4-client.c
View File

@@ -388,8 +388,14 @@ _c_public_ int n_dhcp4_client_new(NDhcp4Client **clientp, NDhcp4ClientConfig *co
return -errno;
client->fd_timer = timerfd_create(CLOCK_BOOTTIME, TFD_CLOEXEC | TFD_NONBLOCK);
if (client->fd_timer < 0)
return -errno;
if (client->fd_timer < 0) {
if (errno != EINVAL)
return -errno;
client->fd_timer = timerfd_create(CLOCK_MONOTONIC, TFD_CLOEXEC | TFD_NONBLOCK);
if (client->fd_timer < 0)
return -errno;
client->timerfd_is_monotonic = true;
}
ev.data.u32 = N_DHCP4_CLIENT_EPOLL_TIMER;
r = epoll_ctl(client->fd_epoll, EPOLL_CTL_ADD, client->fd_timer, &ev);
@@ -499,8 +505,24 @@ void n_dhcp4_client_arm_timer(NDhcp4Client *client) {
n_dhcp4_client_probe_get_timeout(client->current_probe, &timeout);
if (timeout != client->scheduled_timeout) {
uint64_t scheduled_timeout = timeout;
int flags = TFD_TIMER_ABSTIME;
if ( timeout != 0
&& client->timerfd_is_monotonic) {
uint64_t now;
/* the timerfd ticks with CLOCK_MONOTONIC. Calculate and set the relative
* timeout. */
now = n_dhcp4_gettime(CLOCK_BOOTTIME);
if (timeout <= now)
timeout = 1;
else
timeout = timeout - now;
flags = 0;
}
r = timerfd_settime(client->fd_timer,
TFD_TIMER_ABSTIME,
flags,
&(struct itimerspec){
.it_value = {
.tv_sec = timeout / UINT64_C(1000000000),
@@ -510,7 +532,7 @@ void n_dhcp4_client_arm_timer(NDhcp4Client *client) {
NULL);
c_assert(r >= 0);
client->scheduled_timeout = timeout;
client->scheduled_timeout = scheduled_timeout;
}
}

1
shared/n-dhcp4/src/n-dhcp4-private.h
View File

@@ -332,6 +332,7 @@ struct NDhcp4Client {
uint64_t scheduled_timeout;
bool preempted : 1;
bool timerfd_is_monotonic : 1;
};
#define N_DHCP4_CLIENT_NULL(_x) { \