device: restart DHCP when the MAC changesbg/restart-dhcp-on-mac-change

If the MAC changes there is the possibility that the DHCP client will
not be able to renew the address because it uses the old MAC as
CHADDR. Depending on the implementation, the DHCP server might use
CHADDR (so, the old address) as the destination MAC for DHCP replies,
and those packets will be lost.

To avoid this problem, restart the DHCP client when the MAC changes.

https://bugzilla.redhat.com/show_bug.cgi?id=2110000

1 files changed, 4 insertions, 1 deletions

diff --git a/src/core/devices/nm-device.c b/src/core/devices/nm-device.c
index 96b4a1d26b..16a8e9028a 100644
--- a/src/core/devices/nm-device.c
+++ b/src/core/devices/nm-device.c
@@ -6637,6 +6637,7 @@ device_link_changed(gpointer user_data)
     NMDeviceClass                  *klass             = NM_DEVICE_GET_CLASS(self);
     NMDevicePrivate                *priv              = NM_DEVICE_GET_PRIVATE(self);
     gboolean                        ip_ifname_changed = FALSE;
+    gboolean                        hw_addr_changed   = FALSE;
     nm_auto_nmpobj const NMPObject *pllink_keep_alive = NULL;
     const NMPlatformLink           *pllink;
     const char                     *str;
@@ -6684,7 +6685,7 @@ device_link_changed(gpointer user_data)
         _stats_update_counters_from_pllink(self, pllink);
 
     had_hw_addr = (priv->hw_addr != NULL);
-    nm_device_update_hw_address(self);
+    hw_addr_changed = nm_device_update_hw_address(self);
     got_hw_addr = (!had_hw_addr && priv->hw_addr);
     nm_device_update_permanent_hw_address(self, FALSE);
 
@@ -6736,6 +6737,8 @@ device_link_changed(gpointer user_data)
     /* Update DHCP, etc, if needed */
     if (ip_ifname_changed)
         nm_device_update_dynamic_ip_setup(self, "IP interface changed");
+    else if (hw_addr_changed)
+        nm_device_update_dynamic_ip_setup(self, "hw-address changed");
 
     was_up   = priv->up;
     priv->up = NM_FLAGS_HAS(pllink->n_ifi_flags, IFF_UP);