feat(networkd): add ipv6 ra overrides (LP: #1973222) (#461)

Providing a new "ra-overrides" YAML setting:

  accept-ra: true
  ra-overrides:
    use-routes: false
    use-domains: false
    table: 127

COMMITS:
* feat(networkd): add ipv6 ra overrides
* refactor(networkd): use tristate for use_dns and enum for use_domains
* chore(networkd): make if statement more readable
* chore(docs): typo
* chore(docs): add older system path to rt_tables
* chore(docs): refine description for table in ipv6-ra-overrides
* chore(networkd): rename route_table to table
* chore(test): remove unnecessary workaround
* chore(abi): move ipv6_ra_overrides down
* refactor(parse): reuse handle_generic_bool function
* test(networkd): test ra overrides with all fields
* docs(networkd): remove confusing documentation
* refactor(parse): remove handle_generic_use_domains
* chore(networkd): rename ipv6_ra_overrides to ra_overrides
* fix struct ipv6_overrides -> ra_overrides naming
* doc: describe default value for ra-overrides.use-domains

doc/netplan-yaml.md

@@ -403,6 +403,11 @@ Match devices by MAC when setting options like: `wakeonlan` or `*-offload`.
   > respond to Router Advertisements.  If unset use the host kernel default
   > setting.
 
+- **`ra-overrides`** (mapping)
+
+  > (networkd back end only) Overrides default IPv6 Router Advertisement (RA)
+  > behaviour; see the `IPv6 Router Advertisement Overrides` section below.
+
 - **`addresses`** (sequence of scalars and mappings)
 
   > Add static addresses to the interface in addition to the ones received
@@ -697,6 +702,35 @@ client processes as specified in the Netplan YAML.
     >
     > **Requires feature: `dhcp-use-domains`**
 
+## IPv6 Router Advertisement Overrides
+Overrides for IPv6 Router Advertisement (RA) behaviour (only supported with
+networkd back end).
+
+- **`ra-overrides`** (mapping)
+
+  > The `ra-overrides` mappings override the default IPv6 Router
+  > Advertisement behaviour.
+
+  - **`use-dns`** (boolean)
+
+    > Default: `true`. When `true`, the DNS servers received from the
+    > Router Advertisement will be used. Currently only has an effect
+    > on the networkd back end.
+
+  - **`use-domains`** (scalar)
+
+    > Takes a boolean, or the special value `route`. When true, the domain
+    > name received from the Router Advertisement will be used as DNS search
+    > domain over this link. If set to `route`, the domain name received
+    > from the IPv6 RA will be used for routing DNS queries only, but not
+    > for searching. Defaults to `false`.
+
+  - **`table`** (scalar)
+
+    > The routing table number for routes received in the IPv6 RA.
+    > Allowed values are positive integers starting from 1.
+    > Some values are already in use to refer to specific routing tables:
+    > see `{/etc,/usr/share}/iproute2/rt_tables`.
 
 ## Routing
 

src/abi.h

@@ -32,6 +32,35 @@ typedef enum {
     NETPLAN_OPTIONAL_STATIC  = 1<<4,
 } NetplanOptionalAddressFlag;
 
+typedef enum
+{
+    /**
+     * @brief Tristate enum type
+     *
+     * This type defines a boolean which can be unset, i.e.
+     * this type has three states. The enum is ordered so
+     * that
+     *
+     * UNSET -> -1
+     * FALSE -> 0
+     * TRUE  -> 1
+     *
+     * And the integer values can be used directly when
+     * converting to string.
+     */
+    NETPLAN_TRISTATE_UNSET = -1, /* -1 */
+    NETPLAN_TRISTATE_FALSE,      /*  0 */
+    NETPLAN_TRISTATE_TRUE,       /*  1 */
+} NetplanTristate;
+
+typedef enum
+{
+    NETPLAN_USE_DOMAIN_MODE_UNSET = -1,
+    NETPLAN_USE_DOMAIN_MODE_FALSE,
+    NETPLAN_USE_DOMAIN_MODE_TRUE,
+    NETPLAN_USE_DOMAIN_MODE_ROUTE,
+} NetplanUseDomainMode;
+
 /* Fields below are valid for dhcp4 and dhcp6 unless otherwise noted. */
 typedef struct dhcp_overrides {
     gboolean use_dns;
@@ -45,6 +74,12 @@ typedef struct dhcp_overrides {
     guint metric;
 } NetplanDHCPOverrides;
 
+typedef struct ra_overrides {
+    NetplanTristate use_dns;
+    NetplanUseDomainMode use_domains;
+    guint table;
+} NetplanRAOverrides;
+
 typedef enum {
     NETPLAN_RA_MODE_KERNEL,
     NETPLAN_RA_MODE_ENABLED,
@@ -179,27 +214,6 @@ typedef struct netplan_backend_settings {
     GData* passthrough; /* See g_datalist* functions */
 } NetplanBackendSettings;
 
-typedef enum
-{
-    /**
-     * @brief Tristate enum type
-     *
-     * This type defines a boolean which can be unset, i.e.
-     * this type has three states. The enum is ordered so
-     * that
-     *
-     * UNSET -> -1
-     * FALSE -> 0
-     * TRUE  -> 1
-     *
-     * And the integer values can be used directly when
-     * converting to string.
-     */
-    NETPLAN_TRISTATE_UNSET = -1, /* -1 */
-    NETPLAN_TRISTATE_FALSE,      /*  0 */
-    NETPLAN_TRISTATE_TRUE,       /*  1 */
-} NetplanTristate;
-
 typedef struct netplan_vxlan NetplanVxlan;
 
 /* Keep 'struct netplan_net_definition' in a separate header file, to allow for
@@ -414,4 +428,6 @@ struct netplan_net_definition {
 
     NetplanTristate bridge_hairpin;
     NetplanTristate bridge_learning;
+
+    NetplanRAOverrides ra_overrides;
 };

src/netplan.c

@@ -500,6 +500,30 @@ write_dhcp_overrides(yaml_event_t* event, yaml_emitter_t* emitter, const char* k
 err_path: return FALSE; // LCOV_EXCL_LINE
 }
 
+STATIC gboolean
+write_ra_overrides(yaml_event_t* event, yaml_emitter_t* emitter, const char* key, const NetplanNetDefinition* def, const NetplanRAOverrides* data)
+{
+    if (DIRTY_COMPLEX(def, *data)
+        || data->use_dns != NETPLAN_TRISTATE_UNSET
+        || data->use_domains != NETPLAN_USE_DOMAIN_MODE_UNSET
+        || data->table != NETPLAN_ROUTE_TABLE_UNSPEC) {
+        YAML_SCALAR_PLAIN(event, emitter, key);
+        YAML_MAPPING_OPEN(event, emitter);
+        YAML_BOOL_TRISTATE(def, event, emitter, "use-dns", data->use_dns);
+        if (data->use_domains == NETPLAN_USE_DOMAIN_MODE_FALSE) {
+            YAML_STRING_PLAIN(def, event, emitter, "use-domains", "false");
+        } else if (data->use_domains == NETPLAN_USE_DOMAIN_MODE_TRUE) {
+            YAML_STRING_PLAIN(def, event, emitter, "use-domains", "true");
+        } else if (data->use_domains == NETPLAN_USE_DOMAIN_MODE_ROUTE) {
+            YAML_STRING_PLAIN(def, event, emitter, "use-domains", "route");
+        }
+        YAML_UINT_DEFAULT(def, event, emitter, "table", data->table, NETPLAN_ROUTE_TABLE_UNSPEC);
+        YAML_MAPPING_CLOSE(event, emitter);
+    }
+    return TRUE;
+err_path: return FALSE; // LCOV_EXCL_LINE
+}
+
 STATIC gboolean
 write_tunnel_settings(yaml_event_t* event, yaml_emitter_t* emitter, const NetplanNetDefinition* def)
 {
@@ -772,6 +796,7 @@ _serialize_yaml(
     } else if (def->accept_ra == NETPLAN_RA_MODE_DISABLED) {
         YAML_NONNULL_STRING_PLAIN(event, emitter, "accept-ra", "false");
     }
+    write_ra_overrides(event, emitter, "ra-overrides", def, &def->ra_overrides);
 
     YAML_STRING(def, event, emitter, "macaddress", def->set_mac);
     YAML_STRING(def, event, emitter, "set-name", def->set_name);

src/networkd.c

@@ -417,6 +417,18 @@ interval_has_suffix(const char* param) {
     return TRUE;
 }
 
+STATIC gboolean
+ra_overrides_is_dirty(const NetplanRAOverrides* overrides) {
+    if(overrides->use_dns != NETPLAN_TRISTATE_UNSET)
+        return TRUE;
+    if(overrides->use_domains != NETPLAN_USE_DOMAIN_MODE_UNSET)
+        return TRUE;
+    if(overrides->table != NETPLAN_ROUTE_TABLE_UNSPEC)
+        return TRUE;
+
+    return FALSE;
+}
+
 
 STATIC void
 write_bond_parameters(const NetplanNetDefinition* def, GString* s)
@@ -1059,6 +1071,25 @@ _netplan_netdef_write_network_file(
         g_string_append_printf(network, "\n[IPoIB]\nMode=%s\n", netplan_infiniband_mode_name(def->ib_mode));
     }
 
+    /* ra-overrides */
+    if (ra_overrides_is_dirty(&def->ra_overrides)) {
+        g_string_append(network, "\n[IPv6AcceptRA]\n");
+
+        if (def->ra_overrides.use_dns != NETPLAN_TRISTATE_UNSET) {
+            g_string_append_printf(network, "UseDNS=%s\n", def->ra_overrides.use_dns ? "true" : "false");
+        }
+        if (def->ra_overrides.use_domains == NETPLAN_USE_DOMAIN_MODE_FALSE) {
+            g_string_append_printf(network, "UseDomains=%s\n", "false");
+        } else if (def->ra_overrides.use_domains == NETPLAN_USE_DOMAIN_MODE_TRUE) {
+            g_string_append_printf(network, "UseDomains=%s\n", "true");
+        } else if (def->ra_overrides.use_domains == NETPLAN_USE_DOMAIN_MODE_ROUTE) {
+            g_string_append_printf(network, "UseDomains=%s\n", "route");
+        }
+        if (def->ra_overrides.table != NETPLAN_ROUTE_TABLE_UNSPEC) {
+            g_string_append_printf(network, "RouteTable=%d\n", def->ra_overrides.table);
+        }
+    }
+
     if (network->len > 0 || link->len > 0) {
         s = g_string_sized_new(200);
         append_match_section(def, s, TRUE);

src/parse.c

@@ -537,6 +537,7 @@ handle_generic_datalist(NetplanParser *npp, yaml_node_t* node, const char* key_p
     return TRUE;
 }
 
+
 /**
  * Generic handler for setting a npp->current.netdef string field from a scalar node
  * @data: offset into NetplanNetDefinition where the const char* field to write is
@@ -682,7 +683,7 @@ handle_netdef_bool(NetplanParser* npp, yaml_node_t* node, const void* data, GErr
 }
 
 /**
- * Generic handler for tri-state settings that can bei "UNSET", "TRUE", or "FALSE".
+ * Generic handler for tri-state settings that can be "UNSET", "TRUE", or "FALSE".
  * @data: offset into NetplanNetDefinition where the guint field to write is located
  */
 STATIC gboolean
@@ -800,6 +801,38 @@ handle_netdef_backend_settings_str(NetplanParser* npp, yaml_node_t* node, const
     return handle_generic_str(npp, node, npp->current.netdef, data, error);
 }
 
+/**
+ * Generic handler for setting a npp->current.netdef use-domains field from a scalar node
+ * @data: offset into NetplanNetDefinition where the use-domains field to write is located
+ */
+STATIC gboolean
+handle_netdef_use_domains(NetplanParser* npp, yaml_node_t* node, const void* data, GError** error)
+{
+    NetplanUseDomainMode v;
+    guint offset = GPOINTER_TO_UINT(data);
+    NetplanUseDomainMode* dest = ((void*) npp->current.netdef + offset);
+
+    gboolean ret = handle_generic_bool(npp, node, npp->current.netdef, data, NULL);
+
+    if (ret) {
+        if (*dest) {
+            v = NETPLAN_USE_DOMAIN_MODE_TRUE;
+        } else {
+            v = NETPLAN_USE_DOMAIN_MODE_FALSE;
+        }
+    } else if (g_ascii_strcasecmp(scalar(node), "route") == 0) {
+        v = NETPLAN_USE_DOMAIN_MODE_ROUTE;
+    } else {
+        return yaml_error(npp, node, error,
+                          "Invalid use-domains options '%s', must be a boolean, or the special value 'route'.",
+                          scalar(node));
+    }
+
+    *dest = v;
+    mark_data_as_dirty(npp, dest);
+    return TRUE;
+}
+
 /*
  * Check if the passthrough key format is incorrect and remove it from the list.
  * user_data is expected to contain a pointer to the GData list.
@@ -2876,6 +2909,13 @@ static const mapping_entry_handler dhcp6_overrides_handlers[] = {
     {NULL},
 };
 
+static const mapping_entry_handler ra_overrides_handlers[] = {
+    {"use-dns", YAML_SCALAR_NODE, {.generic=handle_netdef_tristate}, netdef_offset(ra_overrides.use_dns)},
+    {"use-domains", YAML_SCALAR_NODE, {.generic=handle_netdef_use_domains}, netdef_offset(ra_overrides.use_domains)},
+    {"table", YAML_SCALAR_NODE, {.generic=handle_netdef_guint}, netdef_offset(ra_overrides.table)},
+    {NULL},
+};
+
 /* Handlers shared by all link types */
 #define COMMON_LINK_HANDLERS \
     {"accept-ra", YAML_SCALAR_NODE, {.generic=handle_accept_ra}, netdef_offset(accept_ra)}, \
@@ -2888,6 +2928,7 @@ static const mapping_entry_handler dhcp6_overrides_handlers[] = {
     {"dhcp-identifier", YAML_SCALAR_NODE, {.generic=handle_dhcp_identifier}, NULL}, \
     {"dhcp4-overrides", YAML_MAPPING_NODE, {.map={.handlers=dhcp4_overrides_handlers}}, NULL}, \
     {"dhcp6-overrides", YAML_MAPPING_NODE, {.map={.handlers=dhcp6_overrides_handlers}}, NULL}, \
+    {"ra-overrides", YAML_MAPPING_NODE, {.map={.handlers=ra_overrides_handlers}}, NULL}, \
     {"gateway4", YAML_SCALAR_NODE, {.generic=handle_gateway4}, NULL}, \
     {"gateway6", YAML_SCALAR_NODE, {.generic=handle_gateway6}, NULL}, \
     {"ipv6-address-generation", YAML_SCALAR_NODE, {.generic=handle_netdef_addrgen}, NULL}, \

src/types.c

@@ -151,6 +151,14 @@ reset_dhcp_overrides(NetplanDHCPOverrides* overrides)
     overrides->metric = NETPLAN_METRIC_UNSPEC;
 }
 
+STATIC void
+reset_ra_overrides(NetplanRAOverrides* overrides)
+{
+    overrides->use_dns = NETPLAN_TRISTATE_UNSET;
+    overrides->use_domains = NETPLAN_USE_DOMAIN_MODE_UNSET;
+    overrides->table = NETPLAN_ROUTE_TABLE_UNSPEC;
+}
+
 void
 reset_ip_rule(NetplanIPRule* ip_rule)
 {
@@ -236,6 +244,7 @@ reset_netdef(NetplanNetDefinition* netdef, NetplanDefType new_type, NetplanBacke
     reset_dhcp_overrides(&netdef->dhcp4_overrides);
     reset_dhcp_overrides(&netdef->dhcp6_overrides);
     netdef->accept_ra = NETPLAN_RA_MODE_KERNEL;
+    reset_ra_overrides(&netdef->ra_overrides);
 
     free_garray_with_destructor(&netdef->ip4_addresses, g_free);
     free_garray_with_destructor(&netdef->ip6_addresses, g_free);