dhcp: treat lease expiry as failure (rh #1139326)

System Internals / NetworkManager - Dan Williams [redhat.com] - 2 October 2014 15:02 UTC

Lease expiry means that the DHCP configuration is no longer valid, and that all attempts to renew/rebind the lease have failed. The IP config needs to be removed. NetworkManager also sets prefered/valid lifetimes on addresses, so the kernel will remove them when the lease expires anyway. That causes removal of the default route, if the default route was through the device whose config has now expired.

DHCP clients will typically move to the 'renew' or 'rebind' states when nearing lease expiry, then if no answer is received move to the 'expire' state. Eventually they move to the 'fail' state when all attempts to contact the server have failed.

Previously, since NM ignored the 'expire' DHCP state it would not clear out the DHCP IP4 config immediately when the lease expired, instead waiting for the DHCP client to move to the 'fail' state. But if the DHCP server appeared between the 'expire' and 'fail' states, NM would not notice and the device's NMIP4Config would not change, and thus the Policy would not get the "ip4-config-changed" signal to re-add the default route that the kernel had previously removed due to the valid lifetime reaching zero when the lease expired.

https://bugzilla.redhat.com/show_bug.cgi?id=1139326

90a7756 dhcp: treat lease expiry as failure (rh #1139326)
src/dhcp-manager/nm-dhcp-client.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

Upstream: cgit.freedesktop.org

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