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port: should check the new phc_index before switching 

In logic, when we want to switch phc, we should check if the new phc
index is valid instead of checking the previous one.

In reality, if we use linux team interface with activebackup mode. As
teamd is a userspace tool, it sets the new slave as active port after
receiving link change message. If we set current active port down and
another slave up. There is a race that we receive the new slave's link
up message while active port(ts_index) is still the old one. This means
we may use a link down interface as ts_index and get phc_index with -1.

If we update the p->phc_index to -1, there will be no possibility to
change it back to other value as we swith phc only when p->phc_index >= 0.

With this fix, we will not switch phc_index until receiving the real
active port(p->iface->ts_info.phc_index >= 0) update message.

Reported-by: Miroslav Lichvar <mlichvar@redhat.com>
Fixes: 536a71031d ("ptp4l: use ts label to get ts info")
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
master
Hangbin Liu 2019-03-20 14:44:13 +08:00 committed by Richard Cochran
parent 6b61ba29c7
commit 51d76bdfb7
1 changed files with 1 additions and 1 deletions
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2
port.c
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@ -2442,7 +2442,7 @@ void port_link_status(void *ctx, int linkup, int ts_index)
sk_get_ts_info(p->iface->ts_label, &p->iface->ts_info); sk_get_ts_info(p->iface->ts_label, &p->iface->ts_info);
/* Only switch phc with HW time stamping mode */ /* Only switch phc with HW time stamping mode */
if (p->phc_index >= 0 && p->iface->ts_info.valid) { if (p->iface->ts_info.valid && p->iface->ts_info.phc_index >= 0) {
required_modes = clock_required_modes(p->clock); required_modes = clock_required_modes(p->clock);
if ((p->iface->ts_info.so_timestamping & required_modes) != required_modes) { if ((p->iface->ts_info.so_timestamping & required_modes) != required_modes) {
pr_err("interface '%s' does not support requested " pr_err("interface '%s' does not support requested "