From 401fee7c2040e87d7f9c83fd350733b0f538d578 Mon Sep 17 00:00:00 2001
From: Tom Gundersen <teg@jklm.no>
Date: Tue, 21 May 2019 21:52:44 +0200
Subject: dhcp: support notifying the client of the result of DAD

The DHCP client is not meant to use the assigned address before DAD
has completed successfully, if enabled. And if DAD fails, the server
should be notified with a DECLINE, in order to potentially blacklist
the address.

Currently, none of the clients support this, but add the required
callbacks, and allow clients to opt in if they want.
---
 src/devices/nm-device.c   |  8 ++++++--
 src/dhcp/nm-dhcp-client.c | 30 ++++++++++++++++++++++++++++++
 src/dhcp/nm-dhcp-client.h | 14 ++++++++++++++
 3 files changed, 50 insertions(+), 2 deletions(-)

diff --git a/src/devices/nm-device.c b/src/devices/nm-device.c
index abcff229bf..e649d267fe 100644
--- a/src/devices/nm-device.c
+++ b/src/devices/nm-device.c
@@ -7694,9 +7694,13 @@ clear_config:
 static void
 dhcp4_dad_cb (NMDevice *self, NMIP4Config **configs, gboolean success)
 {
-	if (success)
+	NMDevicePrivate *priv = NM_DEVICE_GET_PRIVATE (self);
+
+	if (success) {
+		nm_dhcp_client_accept (priv->dhcp4.client, NULL);
 		nm_device_activate_schedule_ip_config_result (self, AF_INET, NM_IP_CONFIG_CAST (configs[1]));
-	else {
+	} else {
+		nm_dhcp_client_decline (priv->dhcp4.client, "Address conflict detected", NULL);
 		nm_device_ip_method_failed (self, AF_INET,
 		                            NM_DEVICE_STATE_REASON_IP_ADDRESS_DUPLICATE);
 	}
diff --git a/src/dhcp/nm-dhcp-client.c b/src/dhcp/nm-dhcp-client.c
index 6c95d5790c..4dca4750e7 100644
--- a/src/dhcp/nm-dhcp-client.c
+++ b/src/dhcp/nm-dhcp-client.c
@@ -530,6 +530,36 @@ nm_dhcp_client_start_ip4 (NMDhcpClient *self,
 	                                                   error);
 }
 
+gboolean
+nm_dhcp_client_accept (NMDhcpClient *self,
+                       GError **error)
+{
+	g_return_val_if_fail (NM_IS_DHCP_CLIENT (self), FALSE);
+
+	if (NM_DHCP_CLIENT_GET_CLASS (self)->accept) {
+		return NM_DHCP_CLIENT_GET_CLASS (self)->accept (self,
+		                                                error);
+	}
+
+	return TRUE;
+}
+
+gboolean
+nm_dhcp_client_decline (NMDhcpClient *self,
+                        const char *error_message,
+                        GError **error)
+{
+	g_return_val_if_fail (NM_IS_DHCP_CLIENT (self), FALSE);
+
+	if (NM_DHCP_CLIENT_GET_CLASS (self)->decline) {
+		return NM_DHCP_CLIENT_GET_CLASS (self)->decline (self,
+		                                                 error_message,
+		                                                 error);
+	}
+
+	return TRUE;
+}
+
 static GBytes *
 get_duid (NMDhcpClient *self)
 {
diff --git a/src/dhcp/nm-dhcp-client.h b/src/dhcp/nm-dhcp-client.h
index 1a8ccaba2b..33030a4f23 100644
--- a/src/dhcp/nm-dhcp-client.h
+++ b/src/dhcp/nm-dhcp-client.h
@@ -82,6 +82,13 @@ typedef struct {
 	                           const char *last_ip4_address,
 	                           GError **error);
 
+	gboolean (*accept)        (NMDhcpClient *self,
+	                           GError **error);
+
+	gboolean (*decline)       (NMDhcpClient *self,
+	                           const char *error_message,
+	                           GError **error);
+
 	gboolean (*ip6_start)     (NMDhcpClient *self,
 	                           const char *anycast_addr,
 	                           const struct in6_addr *ll_addr,
@@ -155,6 +162,13 @@ gboolean nm_dhcp_client_start_ip6 (NMDhcpClient *self,
                                    guint needed_prefixes,
                                    GError **error);
 
+gboolean nm_dhcp_client_accept (NMDhcpClient *self,
+                                GError **error);
+
+gboolean nm_dhcp_client_decline (NMDhcpClient *self,
+                                 const char *error_message,
+                                 GError **error);
+
 void nm_dhcp_client_stop (NMDhcpClient *self, gboolean release);
 
 /* Backend helpers for subclasses */
-- 
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