Merge pull request #16568 from benpicco/gnrc_ipv6_nib-rio

gnrc_ipv6_nib: handle route information option and add config to add to final RAs

makefiles/pseudomodules.inc.mk

@@ -43,6 +43,7 @@ PSEUDOMODULES += gnrc_ipv6_nib_6lbr
 PSEUDOMODULES += gnrc_ipv6_nib_6ln
 PSEUDOMODULES += gnrc_ipv6_nib_6lr
 PSEUDOMODULES += gnrc_ipv6_nib_dns
+PSEUDOMODULES += gnrc_ipv6_nib_rio
 PSEUDOMODULES += gnrc_ipv6_nib_router
 PSEUDOMODULES += gnrc_netdev_default
 PSEUDOMODULES += gnrc_neterr

sys/include/net/gnrc/ipv6/nib/conf.h

@@ -138,6 +138,17 @@ extern "C" {
 #endif
 #endif
 
+/**
+ * @brief   Include a Route Information Option for subnets
+ *          on other interfaces in the last Router Advertisement
+ *          generated by @ref gnrc_ipv6_nib_change_rtr_adv_iface
+ *
+ *          Requires the `gnrc_ipv6_nib_rio` module.
+ */
+#ifndef CONFIG_GNRC_IPV6_NIB_ADD_RIO_IN_LAST_RA
+#define CONFIG_GNRC_IPV6_NIB_ADD_RIO_IN_LAST_RA       0
+#endif
+
 /**
  * @brief   (de-)activate NDP address resolution state-machine
  */

sys/include/net/gnrc/ndp.h

@@ -232,6 +232,35 @@ gnrc_pktsnip_t *gnrc_ndp_opt_pi_build(const ipv6_addr_t *prefix,
                                       uint8_t prefix_len,
                                       uint32_t valid_ltime, uint32_t pref_ltime,
                                       uint8_t flags, gnrc_pktsnip_t *next);
+/**
+ * @brief   Builds the route information option.
+ *
+ * @pre `prefix != NULL`
+ * @pre `!ipv6_addr_is_link_local(prefix) && !ipv6_addr_is_multicast(prefix)`
+ * @pre `prefix_len <= 128`
+ *
+ * @see [RFC 4191, section 2.3](https://tools.ietf.org/html/rfc4191#section-2.3)
+ *
+ * @note    Should only be used with router advertisemnents. This is not checked
+ *          however, since nodes should silently ignore it in other NDP messages.
+ *
+ * @param[in] prefix        An IPv6 address or a prefix of an IPv6 address.
+ *                          Must not be NULL or be a link-local or
+ *                          multicast address.
+ * @param[in] prefix_len    The length of @p prefix in bits. Must be between
+ *                          0 and 128.
+ * @param[in] route_ltime   Length of time in seconds that @p prefix is valid.
+ *                          UINT32_MAX represents infinity.
+ * @param[in] flags         Flags as defined in net/ndp.h.
+ * @param[in] next          More options in the packet. NULL, if there are none.
+ *
+ * @return  The packet snip list of options, on success
+ * @return  NULL, if packet buffer is full
+ */
+gnrc_pktsnip_t *gnrc_ndp_opt_ri_build(const ipv6_addr_t *prefix,
+                                      uint8_t prefix_len,
+                                      uint32_t route_ltime,
+                                      uint8_t flags, gnrc_pktsnip_t *next);
 
 /**
  * @brief   Builds the MTU option.

sys/include/net/ndp.h

@@ -88,6 +88,7 @@ extern "C" {
 #define NDP_OPT_PI                  (3)     /**< prefix information option */
 #define NDP_OPT_RH                  (4)     /**< redirected option */
 #define NDP_OPT_MTU                 (5)     /**< MTU option */
+#define NDP_OPT_RI                  (24)    /**< Route Information Option */
 #define NDP_OPT_RDNSS               (25)    /**< recursive DNS server option */
 #define NDP_OPT_AR                  (33)    /**< address registration option */
 #define NDP_OPT_6CTX                (34)    /**< 6LoWPAN context option */
@@ -103,6 +104,17 @@ extern "C" {
 #define NDP_OPT_PI_FLAGS_A          (0x40)  /**< autonomous address configuration */
 /** @} */
 
+/**
+ * @{
+ * @name    Flags for route information option
+ */
+#define NDP_OPT_RI_FLAGS_MASK       (0x18)
+#define NDP_OPT_RI_FLAGS_PRF_NONE   (0x10)  /**< ignore preference */
+#define NDP_OPT_RI_FLAGS_PRF_NEG    (0x18)  /**< negative preference */
+#define NDP_OPT_RI_FLAGS_PRF_ZERO   (0x0)   /**< zero preference */
+#define NDP_OPT_RI_FLAGS_PRF_POS    (0x8)   /**< positive preference */
+/** @} */
+
 /**
  * @{
  * @name    Prefix information option constants
@@ -308,6 +320,21 @@ typedef struct __attribute__((packed)) {
     ipv6_addr_t prefix;             /**< prefix */
 } ndp_opt_pi_t;
 
+/**
+ * @brief   Route information option format
+ * @extends ndp_opt_t
+ *
+ * @see     [RFC 4191, section 2.3](https://tools.ietf.org/html/rfc4191#section-2.3)
+ */
+typedef struct __attribute__((packed)) {
+    uint8_t type;                   /**< option type */
+    uint8_t len;                    /**< length in units of 8 octets */
+    uint8_t prefix_len;             /**< prefix length */
+    uint8_t flags;                  /**< flags */
+    network_uint32_t route_ltime;   /**< route lifetime */
+    ipv6_addr_t prefix;             /**< prefix */
+} ndp_opt_ri_t;
+
 /**
  * @brief   Redirected header option format
  * @extends ndp_opt_t

sys/net/gnrc/Makefile.dep

@@ -247,6 +247,7 @@ ifneq (,$(filter gnrc_ipv6_default,$(USEMODULE)))
 endif
 
 ifneq (,$(filter gnrc_ipv6_router_default,$(USEMODULE)))
+  USEMODULE += gnrc_ipv6_nib_rio
   USEMODULE += gnrc_ipv6_router
   USEMODULE += gnrc_icmpv6
 endif

sys/net/gnrc/network_layer/ipv6/nib/_nib-router.c

@@ -215,6 +215,52 @@ static gnrc_pktsnip_t *_build_ext_opts(gnrc_netif_t *netif,
     return ext_opts;
 }
 
+/* Sending a RA with ltime = 0 causes the router to be removed from the
+ * default router list, but options are still parsed.
+ * This allows us to add downstream subnets that should be routed through
+ * this router, but the router is not an upstream / default router for
+ * this link. */
+static gnrc_pktsnip_t *_build_final_ext_opts(gnrc_netif_t *netif)
+{
+    gnrc_pktsnip_t *ext_opts = NULL;
+    _nib_offl_entry_t *entry = NULL;
+
+    if (!IS_USED(MODULE_GNRC_IPV6_NIB_RIO) ||
+        !IS_ACTIVE(CONFIG_GNRC_IPV6_NIB_ADD_RIO_IN_LAST_RA)) {
+        return NULL;
+    }
+
+    DEBUG("nib: sending final RA on interface %u\n", netif->pid);
+
+    uint32_t now = evtimer_now_msec();
+    while ((entry = _nib_offl_iter(entry))) {
+
+        unsigned id = netif->pid;
+        if (_nib_onl_get_if(entry->next_hop) == id) {
+            continue;
+        }
+
+        if ((entry->mode & _PL) && (entry->flags & _PFX_ON_LINK)) {
+            DEBUG("nib: adding downstream subnet to RA\n");
+            uint32_t valid_ltime = (entry->valid_until == UINT32_MAX) ? UINT32_MAX :
+                                   ((entry->valid_until - now) / MS_PER_SEC);
+            gnrc_pktsnip_t *snip  = gnrc_ndp_opt_ri_build(&entry->pfx,
+                                                          entry->pfx_len,
+                                                          valid_ltime,
+                                                          NDP_OPT_RI_FLAGS_PRF_NONE,
+                                                          ext_opts);
+            if (snip != NULL) {
+                ext_opts = snip;
+            } else {
+                DEBUG_PUTS("nib: can't add RIO to RA - out of memory");
+                break;
+            }
+        }
+    }
+
+    return ext_opts;
+}
+
 void _set_rtr_adv(gnrc_netif_t *netif)
 {
     DEBUG("nib: set RTR_ADV flag for interface %i\n", netif->pid);
@@ -228,7 +274,9 @@ static void _snd_ra(gnrc_netif_t *netif, const ipv6_addr_t *dst,
 {
     gnrc_pktsnip_t *ext_opts = NULL;
 
-    if (!final) {
+    if (final) {
+        ext_opts = _build_final_ext_opts(netif);
+    } else {
         ext_opts = _build_ext_opts(netif, abr);
     }
 

sys/net/gnrc/network_layer/ipv6/nib/nib.c

@@ -461,6 +461,8 @@ static uint32_t _handle_pio(gnrc_netif_t *netif, const icmpv6_hdr_t *icmpv6,
 static uint32_t _handle_pio(gnrc_netif_t *netif, const icmpv6_hdr_t *icmpv6,
                             const ndp_opt_pi_t *pio);
 #endif  /* CONFIG_GNRC_IPV6_NIB_MULTIHOP_P6C */
+static uint32_t _handle_rio(gnrc_netif_t *netif, const ipv6_hdr_t *ipv6,
+                            const ndp_opt_ri_t *pio);
 /** @} */
 
 /* Iterator for NDP options in a packet */
@@ -738,6 +740,9 @@ static void _handle_rtr_adv(gnrc_netif_t *netif, const ipv6_hdr_t *ipv6,
                 _handle_mtuo(netif, (const icmpv6_hdr_t *)rtr_adv,
                              (ndp_opt_mtu_t *)opt);
                 break;
+            case NDP_OPT_RI:
+                _handle_rio(netif, ipv6, (ndp_opt_ri_t *)opt);
+                break;
             case NDP_OPT_PI: {
                 uint32_t min_pfx_timeout;
 #if IS_ACTIVE(CONFIG_GNRC_IPV6_NIB_MULTIHOP_P6C)
@@ -1584,4 +1589,55 @@ static uint32_t _handle_pio(gnrc_netif_t *netif, const icmpv6_hdr_t *icmpv6,
     return UINT32_MAX;
 }
 
+static const char *_prio_string(uint8_t prio)
+{
+    switch (prio & NDP_OPT_RI_FLAGS_MASK) {
+    case NDP_OPT_RI_FLAGS_PRF_NONE:
+        return "none";
+    case NDP_OPT_RI_FLAGS_PRF_NEG:
+        return "-1";
+    case NDP_OPT_RI_FLAGS_PRF_ZERO:
+        return "0";
+    case NDP_OPT_RI_FLAGS_PRF_POS:
+        return "1";
+    }
+
+    return "invalid";
+}
+
+static uint32_t _handle_rio(gnrc_netif_t *netif, const ipv6_hdr_t *ipv6,
+                            const ndp_opt_ri_t *rio)
+{
+    if (!IS_USED(MODULE_GNRC_IPV6_NIB_RIO)) {
+        return 0;
+    }
+
+    uint32_t route_ltime = byteorder_ntohl(rio->route_ltime);
+
+    if (ipv6_addr_is_link_local(&rio->prefix)) {
+        DEBUG("nib: ignoring RIO with invalid data\n");
+        return UINT32_MAX;
+    }
+    DEBUG("nib: received valid Route Information option:\n");
+    DEBUG("     - Prefix: %s/%u\n",
+          ipv6_addr_to_str(addr_str, &rio->prefix, sizeof(addr_str)),
+          rio->prefix_len);
+    DEBUG("     - Priority: %s\n", _prio_string(rio->flags));
+    DEBUG("     - Route lifetime: %" PRIu32 "\n",
+          byteorder_ntohl(rio->route_ltime));
+
+    if (route_ltime < UINT32_MAX) { /* UINT32_MAX means infinite lifetime */
+        /* the valid lifetime is given in seconds, but our timers work in
+         * microseconds, so we have to scale down to the smallest possible
+         * value (UINT32_MAX - 1). This is however alright since we ask for
+         * a new router advertisement before this timeout expires */
+        route_ltime = (route_ltime > (UINT32_MAX / MS_PER_SEC)) ?
+                      (UINT32_MAX - 1) : route_ltime * MS_PER_SEC;
+    }
+
+    gnrc_ipv6_nib_ft_add(&rio->prefix, rio->prefix_len, &ipv6->src,
+                         netif->pid, route_ltime);
+
+    return route_ltime;
+}
 /** @} */

sys/net/gnrc/network_layer/ndp/gnrc_ndp.c

@@ -201,6 +201,30 @@ gnrc_pktsnip_t *gnrc_ndp_opt_pi_build(const ipv6_addr_t *prefix,
     return pkt;
 }
 
+gnrc_pktsnip_t *gnrc_ndp_opt_ri_build(const ipv6_addr_t *prefix,
+                                      uint8_t prefix_len,
+                                      uint32_t route_ltime,
+                                      uint8_t flags, gnrc_pktsnip_t *next)
+{
+    assert(prefix != NULL);
+    assert(!ipv6_addr_is_link_local(prefix) && !ipv6_addr_is_multicast(prefix));
+    assert(prefix_len <= 128);
+    gnrc_pktsnip_t *pkt = gnrc_ndp_opt_build(NDP_OPT_RI, sizeof(ndp_opt_ri_t),
+                                             next);
+
+    if (pkt != NULL) {
+        ndp_opt_ri_t *ri_opt = pkt->data;
+
+        ri_opt->prefix_len = prefix_len;
+        ri_opt->flags = (flags & NDP_OPT_PI_FLAGS_MASK);
+        ri_opt->route_ltime = byteorder_htonl(route_ltime);
+        /* Bits beyond prefix_len MUST be 0 */
+        ipv6_addr_set_unspecified(&ri_opt->prefix);
+        ipv6_addr_init_prefix(&ri_opt->prefix, prefix, prefix_len);
+    }
+    return pkt;
+}
+
 gnrc_pktsnip_t *gnrc_ndp_opt_mtu_build(uint32_t mtu, gnrc_pktsnip_t *next)
 {
     gnrc_pktsnip_t *pkt = gnrc_ndp_opt_build(NDP_OPT_MTU,