From 534d32cf810cbdfc771ced5db0d5b208c4cf679b Mon Sep 17 00:00:00 2001
From: Beniamino Galvani <bgalvani@redhat.com>
Date: Sun, 5 Oct 2025 12:03:08 +0200
Subject: [PATCH] ipv4: improve logging for ipv4.dhcp-ipv6-only-preferred

---
 src/core/devices/nm-device.c   | 17 ++++++++++++-----
 src/core/dhcp/nm-dhcp-client.c |  4 +++-
 2 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/src/core/devices/nm-device.c b/src/core/devices/nm-device.c
index 4f0ea9c1e4..143ac587c5 100644
--- a/src/core/devices/nm-device.c
+++ b/src/core/devices/nm-device.c
@@ -1944,12 +1944,14 @@ _prop_get_ipvx_may_fail_cached(NMDevice *self, int addr_family, NMTernary *cache
 }
 
 static gboolean
-_prop_get_ipv4_dhcp_ipv6_only_preferred(NMDevice *self)
+_prop_get_ipv4_dhcp_ipv6_only_preferred(NMDevice *self, gboolean *out_is_auto)
 {
     NMDevicePrivate                  *priv = NM_DEVICE_GET_PRIVATE(self);
     NMSettingIP4Config               *s_ip4;
     NMSettingIP4DhcpIpv6OnlyPreferred ipv6_only;
 
+    NM_SET_OUT(out_is_auto, FALSE);
+
     s_ip4 = nm_device_get_applied_setting(self, NM_TYPE_SETTING_IP4_CONFIG);
     if (!s_ip4)
         return FALSE;
@@ -1976,6 +1978,8 @@ _prop_get_ipv4_dhcp_ipv6_only_preferred(NMDevice *self)
         return ipv6_only == NM_SETTING_IP4_DHCP_IPV6_ONLY_PREFERRED_YES;
 
     /* auto */
+    NM_SET_OUT(out_is_auto, TRUE);
+
     if (nm_streq0(priv->ipv6_method, NM_SETTING_IP6_CONFIG_METHOD_AUTO)
         && _prop_get_ipv6_clat(self, nm_device_get_applied_connection(self))
                != NM_SETTING_IP6_CONFIG_CLAT_NO) {
@@ -11833,8 +11837,9 @@ _dev_ipdhcpx_start(NMDevice *self, int addr_family)
         gboolean               hostname_is_fqdn;
         gboolean               send_client_id;
         guint8                 dscp;
-        gboolean               dscp_explicit  = FALSE;
-        gboolean               ipv6_only_pref = FALSE;
+        gboolean               dscp_explicit       = FALSE;
+        gboolean               ipv6_only_pref      = FALSE;
+        gboolean               ipv6_only_pref_auto = FALSE;
 
         client_id = _prop_get_ipv4_dhcp_client_id(self, connection, hwaddr, &send_client_id);
         dscp      = _prop_get_ipv4_dhcp_dscp(self, &dscp_explicit);
@@ -11853,13 +11858,15 @@ _dev_ipdhcpx_start(NMDevice *self, int addr_family)
             hostname         = nm_setting_ip_config_get_dhcp_hostname(s_ip);
         }
 
-        if (_prop_get_ipv4_dhcp_ipv6_only_preferred(self)) {
+        if (_prop_get_ipv4_dhcp_ipv6_only_preferred(self, &ipv6_only_pref_auto)) {
             if (nm_streq0(priv->ipv6_method, NM_SETTING_IP6_CONFIG_METHOD_DISABLED)) {
                 _LOGI_ipdhcp(
                     addr_family,
                     "not requesting the \"IPv6-only preferred\" option because IPv6 is disabled");
             } else {
-                _LOGD_ipdhcp(addr_family, "requesting the \"IPv6-only preferred\" option");
+                _LOGD_ipdhcp(addr_family,
+                             "requesting the \"IPv6-only preferred\" option (%s enabled)",
+                             ipv6_only_pref_auto ? "automatically" : "explicitly");
                 ipv6_only_pref = TRUE;
             }
         }
diff --git a/src/core/dhcp/nm-dhcp-client.c b/src/core/dhcp/nm-dhcp-client.c
index 18ad4024b4..cc6dccdfa4 100644
--- a/src/core/dhcp/nm-dhcp-client.c
+++ b/src/core/dhcp/nm-dhcp-client.c
@@ -1460,7 +1460,9 @@ nm_dhcp_client_schedule_ipv6_only_restart(NMDhcpClient *self, guint timeout)
     nm_assert(!priv->is_stopped);
 
     timeout = NM_MAX(priv->v4.ipv6_only_min_wait, timeout);
-    _LOGI("received option \"ipv6-only-preferred\": stopping DHCPv4 for %u seconds", timeout);
+    _LOGI("received option \"ipv6-only-preferred\": stopping DHCPv4 for %u seconds. Set "
+          "ipv4.dhcp-ipv6-only-preferred=no to force the use of IPv4 on this IPv6-mostly network",
+          timeout);
 
     nm_dhcp_client_stop(self, FALSE);
     nm_clear_g_source_inst(&priv->no_lease_timeout_source);