[PATCH v2] ip6-manager: Fix SLAAC/DHCPv6 interaction

[Tore Anderson <tore fud no>]

This patch fixes NM's incorrect assumption that SLAAC and Stateful
DHCPv6 are mutually exclusive configuration methods. It does this by
lowering the initial target state of the device to "got-ra" rather than
the previous "got-address" (which implies SLAAC has been performed, not
DHCPv6). If an RA is seen containing a prefix with the Autonomous flag
set, the target state is increased to "got-address" so that NM will
expect the kernel to perform SLAAC.

A side-effect of lowering the initial target state to "got-ra" is that
will be possible for a connection to succeed even if NM has not
configured any (non-link-local) addresses. This will happen if the RA
received has the Managed flag unset, and also contains no Prefix
Information Options (or that all PIOs have the Autonomous flag unset).
While such a connection may be of questionable usability to an end user,
calling it a success it not really unreasonable; after all, NM will have
successfully configured the host according to the network admin's
specifications (which could include addition of a default routes,
on-link prefix routes, recursive DNS servers, and so forth).

It also improves some debugging output that incorrectly implied that
Stateful DHCPv6 supersede RA/SLAAC and that Information-Only DHCPv6 is
the only form of DHCPv6 that should be done in parallel with SLAAC.

The patch will not apply cleanly without "[PATCH] ip6-manager: Accept
RAs when forwarding". The two patches are functionally independent of
each other, though.

(rh #720188)
---
 src/ip6-manager/nm-ip6-manager.c |   33 ++++++++++++++++++++-------------
 1 files changed, 20 insertions(+), 13 deletions(-)

diff --git a/src/ip6-manager/nm-ip6-manager.c b/src/ip6-manager/nm-ip6-manager.c
index 03f5cc4..8ccdc11 100644
--- a/src/ip6-manager/nm-ip6-manager.c
+++ b/src/ip6-manager/nm-ip6-manager.c
@@ -41,6 +41,8 @@
 #define IF_RA_MANAGED   0x40
 #define IF_RA_RCVD      0x20
 #define IF_RS_SENT      0x10
+#define IF_PREFIX_ONLINK	0x01
+#define IF_PREFIX_AUTOCONF	0x02
 
 typedef struct {
 	NMNetlinkMonitor *monitor;
@@ -68,7 +70,7 @@ typedef enum {
 	NM_IP6_DEVICE_UNCONFIGURED,
 	NM_IP6_DEVICE_GOT_LINK_LOCAL,
 	NM_IP6_DEVICE_GOT_ROUTER_ADVERTISEMENT,
-	NM_IP6_DEVICE_GOT_ADDRESS,
+	NM_IP6_DEVICE_GOT_ADDRESS, /* Note: Used for SLAAC only, not DHCPv6 */
 	NM_IP6_DEVICE_TIMED_OUT
 } NMIP6DeviceState;
 
@@ -459,8 +461,7 @@ nm_ip6_device_sync_from_netlink (NMIP6Device *device, gboolean config_changed)
 	nm_log_dbg (LOGD_IP6, "(%s): addresses synced (state %s)",
 	            device->iface, state_to_string (device->state));
 
-	/* We only care about router advertisements if we want a real IPv6 address */
-	if (   (device->target_state == NM_IP6_DEVICE_GOT_ADDRESS)
+	if (   (device->target_state >= NM_IP6_DEVICE_GOT_ROUTER_ADVERTISEMENT)
 	    && (device->ra_flags & IF_RA_RCVD)) {
 
 		if (device->state < NM_IP6_DEVICE_GOT_ROUTER_ADVERTISEMENT)
@@ -468,27 +469,22 @@ nm_ip6_device_sync_from_netlink (NMIP6Device *device, gboolean config_changed)
 
 		if (device->ra_flags & IF_RA_MANAGED) {
 			dhcp_opts = IP6_DHCP_OPT_MANAGED;
-			nm_log_dbg (LOGD_IP6, "router advertisement deferred to DHCPv6");
+			nm_log_dbg (LOGD_IP6, "router advertisement requests Stateful DHCPv6");
 		} else if (device->ra_flags & IF_RA_OTHERCONF) {
 			dhcp_opts = IP6_DHCP_OPT_OTHERCONF;
-			nm_log_dbg (LOGD_IP6, "router advertisement requests parallel DHCPv6");
+			nm_log_dbg (LOGD_IP6, "router advertisement requests Information-Only DHCPv6");
 		}
 	}
 
 	if (!device->addrconf_complete) {
-		/* Managed mode (ie DHCP only) short-circuits automatic addrconf, so
-		 * we don't bother waiting for the device's target state to be reached
-		 * when the RA requests managed mode.
-		 */
-		if (   (device->state >= device->target_state)
-		    || (dhcp_opts == IP6_DHCP_OPT_MANAGED)) {
+		if (device->state >= device->target_state) {
 			/* device->finish_addrconf_id may currently be a timeout
 			 * rather than an idle, so we remove the existing source.
 			 */
 			if (device->finish_addrconf_id)
 				g_source_remove (device->finish_addrconf_id);
 
-			nm_log_dbg (LOGD_IP6, "(%s): reached target state or Managed-mode requested (state '%s') (dhcp opts 0x%X)",
+			nm_log_dbg (LOGD_IP6, "(%s): reached target state (state '%s') (dhcp opts 0x%X)",
 			            device->iface, state_to_string (device->state),
 			            dhcp_opts);
 
@@ -631,6 +627,12 @@ process_prefix (NMIP6Manager *manager, struct nl_msg *msg)
 		return NULL;
 	}
 
+	if(pmsg->prefix_flags & IF_PREFIX_AUTOCONF) {
+		nm_log_dbg (LOGD_IP6, "(%s): prefix requests stateless autoconf",
+			    device->iface);
+		device->target_state = NM_IP6_DEVICE_GOT_ADDRESS;
+	}
+
 	return device;
 }
 
@@ -1088,7 +1090,12 @@ nm_ip6_manager_prepare_interface (NMIP6Manager *manager,
 		device->target_state = NM_IP6_DEVICE_GOT_LINK_LOCAL;
 		nm_utils_do_sysctl (accept_ra_path, "0\n");
 	} else {
-		device->target_state = NM_IP6_DEVICE_GOT_ADDRESS;
+		/* To begin with, the target state is only got-ra. We will
+		 * increase it to got-address later, if we see a prefix
+		 * being advertised with the Autonomous flag set, cf.
+		 * process_prefix() above.
+		 */
+		device->target_state = NM_IP6_DEVICE_GOT_ROUTER_ADVERTISEMENT;
 		nm_utils_do_sysctl (accept_ra_path, "2\n");
 	}
 
-- 
1.7.6