dhcp: fix "ipv6.dhcp-duid=lease" for dhclient DHCPv6 client

The "lease" mode is unusual, because it means to prefer the DUID
configuration from the DHCP plugin over the explicit configuration in
NetworkManager. It is only for the DHCPv6 DUID and not for the IPv4
client-id. It also is only special for the "dhclient" plugin, because
with the internal plugin, this always corresponds to a generated, stable
DUID.

Commit 58287cbcc0c8 ('core: rework IP configuration in NetworkManager
using layer 3 configuration') broke this. The commit refactored the code
to track the effective-client-id separately. Previously, the client-id which
was read from the dhclient lease, was overwriting NMDhcpClient.client_id. But
with the refactor, it broke because nm_dhcp_client_get_effective_client_id()
was never called.

Fix that.

Fixes: 58287cbcc0c8 ('core: rework IP configuration in NetworkManager using layer 3 configuration')

2 files changed, 23 insertions, 8 deletions

diff --git a/src/core/dhcp/nm-dhcp-dhclient-utils.c b/src/core/dhcp/nm-dhcp-dhclient-utils.c
index 74e6b90507..72dbc7885e 100644
--- a/src/core/dhcp/nm-dhcp-dhclient-utils.c
+++ b/src/core/dhcp/nm-dhcp-dhclient-utils.c
@@ -399,6 +399,7 @@ nm_dhcp_dhclient_create_config(const char         *interface,
                 if (out_new_client_id)
                     nm_clear_pointer(out_new_client_id, g_bytes_unref);
                 NM_SET_OUT(out_new_client_id, read_client_id(p));
+                /* fall-through. We keep the line... */
             }
 
             /* Override config file hostname and use one from the connection */
@@ -656,6 +657,7 @@ nm_dhcp_dhclient_save_duid(const char *leasefile, GBytes *duid, GError **error)
     gsize                         len = 0;
 
     g_return_val_if_fail(leasefile != NULL, FALSE);
+
     if (!duid) {
         nm_utils_error_set_literal(error, NM_UTILS_ERROR_UNKNOWN, "missing duid");
         g_return_val_if_reached(FALSE);
diff --git a/src/core/dhcp/nm-dhcp-dhclient.c b/src/core/dhcp/nm-dhcp-dhclient.c
index 92b4332a74..34aa7d44e0 100644
--- a/src/core/dhcp/nm-dhcp-dhclient.c
+++ b/src/core/dhcp/nm-dhcp-dhclient.c
@@ -82,6 +82,10 @@ G_DEFINE_TYPE(NMDhcpDhclient, nm_dhcp_dhclient, NM_TYPE_DHCP_CLIENT)
 
 /*****************************************************************************/
 
+static GBytes *read_duid_from_lease(NMDhcpDhclient *self);
+
+/*****************************************************************************/
+
 static const char *
 nm_dhcp_dhclient_get_path(void)
 {
@@ -332,6 +336,7 @@ static gboolean
 dhclient_start(NMDhcpClient *client,
                gboolean      set_mode,
                gboolean      release,
+               gboolean      set_duid,
                pid_t        *out_pid,
                GError      **error)
 {
@@ -410,8 +415,10 @@ dhclient_start(NMDhcpClient *client,
     }
 
     /* Save the DUID to the leasefile dhclient will actually use */
-    if (addr_family == AF_INET6) {
-        if (!nm_dhcp_dhclient_save_duid(priv->lease_file, client_config->client_id, &local)) {
+    if (set_duid && addr_family == AF_INET6) {
+        if (!nm_dhcp_dhclient_save_duid(priv->lease_file,
+                                        nm_dhcp_client_get_effective_client_id(client),
+                                        &local)) {
             nm_utils_error_set(error,
                                NM_UTILS_ERROR_UNKNOWN,
                                "failed to save DUID to '%s': %s",
@@ -560,6 +567,7 @@ ip6_start(NMDhcpClient *client, const struct in6_addr *ll_addr, GError **error)
     NMDhcpDhclient           *self = NM_DHCP_DHCLIENT(client);
     NMDhcpDhclientPrivate    *priv = NM_DHCP_DHCLIENT_GET_PRIVATE(self);
     const NMDhcpClientConfig *config;
+    gs_unref_bytes GBytes    *effective_client_id = NULL;
 
     config = nm_dhcp_client_get_config(client);
 
@@ -586,7 +594,12 @@ ip6_start(NMDhcpClient *client, const struct in6_addr *ll_addr, GError **error)
         return FALSE;
     }
 
-    return dhclient_start(client, TRUE, FALSE, NULL, error);
+    nm_assert(config->client_id);
+    if (!config->v6.enforce_duid)
+        effective_client_id = read_duid_from_lease(self);
+    nm_dhcp_client_set_effective_client_id(client, effective_client_id ?: config->client_id);
+
+    return dhclient_start(client, TRUE, FALSE, TRUE, NULL, error);
 }
 
 static void
@@ -620,18 +633,18 @@ stop(NMDhcpClient *client, gboolean release)
     if (release) {
         pid_t rpid = -1;
 
-        if (dhclient_start(client, FALSE, TRUE, &rpid, NULL)) {
+        if (dhclient_start(client, FALSE, TRUE, FALSE, &rpid, NULL)) {
             /* Wait a few seconds for the release to happen */
             nm_dhcp_client_stop_pid(rpid, nm_dhcp_client_get_iface(client));
         }
     }
 }
 
-_nm_unused static GBytes *
-get_duid(NMDhcpClient *client)
+static GBytes *
+read_duid_from_lease(NMDhcpDhclient *self)
 {
-    NMDhcpDhclient           *self = NM_DHCP_DHCLIENT(client);
-    NMDhcpDhclientPrivate    *priv = NM_DHCP_DHCLIENT_GET_PRIVATE(self);
+    NMDhcpClient             *client = NM_DHCP_CLIENT(self);
+    NMDhcpDhclientPrivate    *priv   = NM_DHCP_DHCLIENT_GET_PRIVATE(self);
     const NMDhcpClientConfig *client_config;
     GBytes                   *duid      = NULL;
     gs_free char             *leasefile = NULL;