dhcp6: don't require a hardware address

The systemd DHCPv6 client requires a hardware address only to
determine the IAID; NM always overrides the IAID with its own and
therefore the hwaddr is not used.

Removing such requirement allows DHCPv6 to run over PPP, which is
useful with DHCPv6-PD to get a prefix from the ISP.

To test this, I set up a server with pppoe-server, radvd and the Wide
DHCPv6 server providing an address and a prefix. On the client, NM was
able to obtain a prefix using both dhcp=dhclient and dhcp=systemd.

Note that if there is no hardware address and you specify
ipv6.dhcp-duid=ll or ipv6.dhcp-iaid=mac, a warning will be emitted and
NM will use a random DUID/IAID.

https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/issues/478
(cherry picked from commit 76a6a30577e7748a67d5ee0c3f5c252b751db81c)
(cherry picked from commit 905d4eb36e82499bbae4136253223ca04c4bcd77)

4 files changed, 24 insertions, 49 deletions

diff --git a/src/devices/nm-device.c b/src/devices/nm-device.c
index e6b3624c73..8dee90fbe1 100644
--- a/src/devices/nm-device.c
+++ b/src/devices/nm-device.c
@@ -9266,7 +9266,6 @@ dhcp6_start_with_link_ready (NMDevice *self, NMConnection *connection)
 	NMDevicePrivate *priv = NM_DEVICE_GET_PRIVATE (self);
 	NMSettingIPConfig *s_ip6;
 	gs_unref_bytes GBytes *hwaddr = NULL;
-	gs_unref_bytes GBytes *bcast_hwaddr = NULL;
 	gs_unref_bytes GBytes *duid = NULL;
 	gboolean enforce_duid = FALSE;
 	const NMPlatformLink *pllink;
@@ -9292,20 +9291,16 @@ dhcp6_start_with_link_ready (NMDevice *self, NMConnection *connection)
 	}
 
 	pllink = nm_platform_link_get (nm_device_get_platform (self), nm_device_get_ip_ifindex (self));
-	if (pllink) {
+	if (pllink)
 		hwaddr = nmp_link_address_get_as_bytes (&pllink->l_address);
-		bcast_hwaddr = nmp_link_address_get_as_bytes (&pllink->l_broadcast);
-	}
 
 	iaid = dhcp_get_iaid (self, AF_INET6, connection, &iaid_explicit);
-
 	duid = dhcp6_get_duid (self, connection, hwaddr, &enforce_duid);
+
 	priv->dhcp_data_6.client = nm_dhcp_manager_start_ip6 (nm_dhcp_manager_get (),
 	                                                      nm_device_get_multi_index (self),
 	                                                      nm_device_get_ip_iface (self),
 	                                                      nm_device_get_ip_ifindex (self),
-	                                                      hwaddr,
-	                                                      bcast_hwaddr,
 	                                                      &ll_addr->address,
 	                                                      nm_connection_get_uuid (connection),
 	                                                      nm_device_get_route_table (self, AF_INET6),
diff --git a/src/dhcp/nm-dhcp-manager.c b/src/dhcp/nm-dhcp-manager.c
index 333744dd31..2d6323b8c0 100644
--- a/src/dhcp/nm-dhcp-manager.c
+++ b/src/dhcp/nm-dhcp-manager.c
@@ -239,21 +239,27 @@ client_start (NMDhcpManager *self,
 	g_return_val_if_fail (!dhcp_client_id || g_bytes_get_size (dhcp_client_id) >= 2, NULL);
 	g_return_val_if_fail (!error || !*error, NULL);
 
-	if (!hwaddr || !bcast_hwaddr) {
-		nm_utils_error_set (error,
-		                    NM_UTILS_ERROR_UNKNOWN,
-		                    "missing %s address",
-		                    hwaddr ? "broadcast" : "MAC");
-		return NULL;
-	}
+	if (addr_family == AF_INET) {
+		if (!hwaddr || !bcast_hwaddr) {
+			nm_utils_error_set (error,
+			                    NM_UTILS_ERROR_UNKNOWN,
+			                    "missing %s address",
+			                    hwaddr ? "broadcast" : "MAC");
+			return NULL;
+		}
 
-	hwaddr_len = g_bytes_get_size (hwaddr);
-	if (   hwaddr_len == 0
-	    || hwaddr_len > NM_UTILS_HWADDR_LEN_MAX) {
-		nm_utils_error_set (error,
-		                    NM_UTILS_ERROR_UNKNOWN,
-		                    "invalid MAC address");
-		g_return_val_if_reached (NULL) ;
+		hwaddr_len = g_bytes_get_size (hwaddr);
+		if (   hwaddr_len == 0
+		    || hwaddr_len > NM_UTILS_HWADDR_LEN_MAX) {
+			nm_utils_error_set (error,
+			                    NM_UTILS_ERROR_UNKNOWN,
+			                    "invalid MAC address");
+			g_return_val_if_reached (NULL) ;
+		}
+		nm_assert (g_bytes_get_size (hwaddr) == g_bytes_get_size (bcast_hwaddr));
+	} else {
+		hwaddr = NULL;
+		bcast_hwaddr = NULL;
 	}
 
 	if (hostname) {
@@ -267,8 +273,6 @@ client_start (NMDhcpManager *self,
 		}
 	}
 
-	nm_assert (g_bytes_get_size (hwaddr) == g_bytes_get_size (bcast_hwaddr));
-
 	priv = NM_DHCP_MANAGER_GET_PRIVATE (self);
 
 	/* Kill any old client instance */
@@ -453,8 +457,6 @@ nm_dhcp_manager_start_ip6 (NMDhcpManager *self,
                            NMDedupMultiIndex *multi_idx,
                            const char *iface,
                            int ifindex,
-                           GBytes *hwaddr,
-                           GBytes *bcast_hwaddr,
                            const struct in6_addr *ll_addr,
                            const char *uuid,
                            guint32 route_table,
@@ -488,8 +490,8 @@ nm_dhcp_manager_start_ip6 (NMDhcpManager *self,
 	                     multi_idx,
 	                     iface,
 	                     ifindex,
-	                     hwaddr,
-	                     bcast_hwaddr,
+	                     NULL,
+	                     NULL,
 	                     uuid,
 	                     route_table,
 	                     route_metric,
diff --git a/src/dhcp/nm-dhcp-manager.h b/src/dhcp/nm-dhcp-manager.h
index 1b793c22f8..265cf01853 100644
--- a/src/dhcp/nm-dhcp-manager.h
+++ b/src/dhcp/nm-dhcp-manager.h
@@ -53,8 +53,6 @@ NMDhcpClient * nm_dhcp_manager_start_ip6     (NMDhcpManager *manager,
                                               struct _NMDedupMultiIndex *multi_idx,
                                               const char *iface,
                                               int ifindex,
-                                              GBytes *hwaddr,
-                                              GBytes *bcast_hwaddr,
                                               const struct in6_addr *ll_addr,
                                               const char *uuid,
                                               guint32 route_table,
diff --git a/src/dhcp/nm-dhcp-systemd.c b/src/dhcp/nm-dhcp-systemd.c
index 23862e9e9b..c0b7a28c78 100644
--- a/src/dhcp/nm-dhcp-systemd.c
+++ b/src/dhcp/nm-dhcp-systemd.c
@@ -892,15 +892,11 @@ ip6_start (NMDhcpClient *client,
 	NMDhcpSystemd *self = NM_DHCP_SYSTEMD (client);
 	NMDhcpSystemdPrivate *priv = NM_DHCP_SYSTEMD_GET_PRIVATE (self);
 	nm_auto (sd_dhcp6_client_unrefp) sd_dhcp6_client *sd_client = NULL;
-	GBytes *hwaddr;
 	const char *hostname;
 	int r, i;
 	const guint8 *duid_arr;
 	gsize duid_len;
 	GBytes *duid;
-	const uint8_t *hwaddr_arr;
-	gsize hwaddr_len;
-	int arp_type;
 
 	g_return_val_if_fail (!priv->client4, FALSE);
 	g_return_val_if_fail (!priv->client6, FALSE);
@@ -945,22 +941,6 @@ ip6_start (NMDhcpClient *client,
 		return FALSE;
 	}
 
-	hwaddr = nm_dhcp_client_get_hw_addr (client);
-	if (   !hwaddr
-	    || !(hwaddr_arr = g_bytes_get_data (hwaddr, &hwaddr_len))
-	    || (arp_type = nm_utils_arp_type_detect_from_hwaddrlen (hwaddr_len)) < 0) {
-		nm_utils_error_set_literal (error, NM_UTILS_ERROR_UNKNOWN, "invalid MAC address");
-		return FALSE;
-	}
-	r = sd_dhcp6_client_set_mac (sd_client,
-	                             hwaddr_arr,
-	                             hwaddr_len,
-	                             (guint16) arp_type);
-	if (r < 0) {
-		nm_utils_error_set_errno (error, r, "failed to set MAC address: %s");
-		return FALSE;
-	}
-
 	r = sd_dhcp6_client_set_ifindex (sd_client,
 	                                 nm_dhcp_client_get_ifindex (client));
 	if (r < 0) {