Merge pull request #15508 from namib-project/dhcp-mud-support

Add MUD URL option to DHCPv6 client

makefiles/pseudomodules.inc.mk

@@ -26,6 +26,7 @@ PSEUDOMODULES += evtimer_mbox
 PSEUDOMODULES += evtimer_on_ztimer
 PSEUDOMODULES += fmt_%
 PSEUDOMODULES += gnrc_dhcpv6_%
+PSEUDOMODULES += gnrc_dhcpv6_client_mud_url
 PSEUDOMODULES += gnrc_ipv6_default
 PSEUDOMODULES += gnrc_ipv6_ext_frag_stats
 PSEUDOMODULES += gnrc_ipv6_router

sys/include/net/dhcpv6.h

@@ -69,6 +69,7 @@ extern "C" {
                                              *   delegation (IA_PD) option */
 #define DHCPV6_OPT_IAPFX            (26U)   /**< IA prefix option */
 #define DHCPV6_OPT_SMR              (82U)   /**< SOL_MAX_RT option */
+#define DHCPV6_OPT_MUD_URL          (112U)  /**< MUD URL option (see RFC 8520) */
 /** @} */
 
 /**

sys/include/net/dhcpv6/client.h

@@ -45,7 +45,7 @@ extern "C" {
  * @brief   Static length of the DUID
  */
 #define DHCPV6_CLIENT_DUID_LEN      (sizeof(dhcpv6_duid_l2_t) + 8U)
-#define DHCPV6_CLIENT_BUFLEN        (256)   /**< length for send and receive buffer */
+#define DHCPV6_CLIENT_BUFLEN        (256)   /**< default length for send and receive buffer */
 
 /**
  * @defgroup net_dhcpv6_conf DHCPv6 client compile configurations
@@ -58,6 +58,15 @@ extern "C" {
 #ifndef CONFIG_DHCPV6_CLIENT_PFX_LEASE_MAX
 #define CONFIG_DHCPV6_CLIENT_PFX_LEASE_MAX (1U)
 #endif
+
+/**
+ * @brief   MUD URL (must use the https:// scheme)
+ * For more info, see the [definitions](@ref net_dhcpv6_mud_url_option) below
+ */
+#ifndef CONFIG_DHCPV6_CLIENT_MUD_URL
+#define CONFIG_DHCPV6_CLIENT_MUD_URL "https://example.org"
+#endif
+
 /** @} */
 
 /**
@@ -167,6 +176,31 @@ uint32_t dhcpv6_client_prefix_valid_until(unsigned netif,
                                           unsigned pfx_len);
 /** @} */
 
+/**
+ * @name DHCPv6 Manufacturer Usage Description (MUD) URL option definitions
+ * @see [RFC 8520, section 10](https://tools.ietf.org/html/rfc8520#section-10)
+ * @anchor  net_dhcpv6_mud_url_option
+ * @{
+ */
+
+/**
+ * @brief   Length for the send buffer if a MUD URL is included in the DHCP client's packets
+ *
+ * @note    Only (re)defined by the `gnrc_dhcpv6_client_mud_url` pseudo-module.
+ */
+#if defined(MODULE_GNRC_DHCPV6_CLIENT_MUD_URL) || defined(DOXYGEN)
+#define DHCPV6_CLIENT_SEND_BUFLEN        (DHCPV6_CLIENT_BUFLEN + 256)
+#else
+#define DHCPV6_CLIENT_SEND_BUFLEN        (DHCPV6_CLIENT_BUFLEN)
+#endif
+
+/**
+ * @brief   Maximal length of a MUD URL
+ */
+#define MAX_MUD_URL_LENGTH (0xFF - sizeof(dhcpv6_opt_mud_url_t))
+
+/** @} */
+
 #ifdef __cplusplus
 }
 #endif

sys/net/application_layer/dhcpv6/Kconfig

@@ -16,4 +16,19 @@ config DHCPV6_CLIENT_PFX_LEASE_MAX
     int "Maximum number of prefix leases to be stored"
     default 1
 
+menuconfig KCONFIG_USEMODULE_GNRC_DHCPV6_CLIENT_MUD_URL
+    bool "Enable DHCPv6 Client MUD URL"
+    help
+        Enable the inclusion of a MUD URL in DHCPv6 packets
+        as specified in RFC 8520, section 10. This URL
+        has to point to a MUD file containing YANG-based JSON
+        with a description of the device and its suggested
+        network behavior. The URL must use the "https" scheme.
+
+if KCONFIG_USEMODULE_GNRC_DHCPV6_CLIENT_MUD_URL
+
+config CONFIG_DHCPV6_CLIENT_MUD_URL
+    string "URL pointing to a Manufacturer Usage Description file"
+
+endif # KCONFIG_USEMODULE_GNRC_DHCPV6_CLIENT_MUD_URL
 endif # KCONFIG_USEMODULE_DHCPv6

sys/net/application_layer/dhcpv6/_dhcpv6.h

@@ -28,7 +28,6 @@
 extern "C" {
 #endif
 
-
 /**
  * @name    DHCPv6 multicast addresses
  * @see [RFC 8415, section 7.1]
@@ -214,6 +213,17 @@ typedef struct __attribute__((packed)) {
     network_uint32_t value;         /**< overriding value for SOL_MAX_RT (in sec) */
 } dhcpv6_opt_smr_t;
 
+/**
+ * @brief   MUD URL DHCPv6 option format
+ * @see [RFC 8520, section 10]
+ *      (https://tools.ietf.org/html/rfc8520#section-10)
+ */
+typedef struct __attribute__((packed)) {
+    network_uint16_t type;  /**< @ref DHCPV6_OPT_MUD_URL */
+    network_uint16_t len;   /**< length of the MUDstring in octets. */
+    char mudString[];       /**< MUD URL using the "https" scheme */
+} dhcpv6_opt_mud_url_t;
+
 #ifdef __cplusplus
 }
 #endif

sys/net/application_layer/dhcpv6/client.c

@@ -65,7 +65,7 @@ typedef struct {
     uint8_t duid_len;
 } server_t;
 
-static uint8_t send_buf[DHCPV6_CLIENT_BUFLEN];
+static uint8_t send_buf[DHCPV6_CLIENT_SEND_BUFLEN];
 static uint8_t recv_buf[DHCPV6_CLIENT_BUFLEN];
 static uint8_t best_adv[DHCPV6_CLIENT_BUFLEN];
 static uint8_t duid[DHCPV6_CLIENT_DUID_LEN];
@@ -247,6 +247,22 @@ static inline size_t _compose_elapsed_time_opt(dhcpv6_opt_elapsed_time_t *time)
     return len + sizeof(dhcpv6_opt_t);
 }
 
+static inline size_t _compose_mud_url_opt(dhcpv6_opt_mud_url_t *mud_url_opt,
+                                          const char *mud_url, size_t len_max)
+{
+    uint16_t len = strlen(mud_url);
+
+    if (len > len_max) {
+        assert(0);
+        return 0;
+    }
+
+    mud_url_opt->type = byteorder_htons(DHCPV6_OPT_MUD_URL);
+    mud_url_opt->len = byteorder_htons(len);
+    strncpy(mud_url_opt->mudString, mud_url, len_max);
+    return len + sizeof(dhcpv6_opt_mud_url_t);
+}
+
 static inline size_t _compose_oro_opt(dhcpv6_opt_oro_t *oro, uint16_t *opts,
                                         unsigned opts_num)
 {
@@ -273,7 +289,7 @@ static inline size_t _compose_ia_pd_opt(dhcpv6_opt_ia_pd_t *ia_pd,
     return len + sizeof(dhcpv6_opt_t);
 }
 
-static inline size_t _add_ia_pd_from_config(uint8_t *buf)
+static inline size_t _add_ia_pd_from_config(uint8_t *buf, size_t len_max)
 {
     size_t msg_len = 0;
 
@@ -285,6 +301,12 @@ static inline size_t _add_ia_pd_from_config(uint8_t *buf)
             msg_len += _compose_ia_pd_opt(ia_pd, ia_id, 0U);
         }
     }
+
+    if (msg_len > len_max) {
+        assert(0);
+        return 0;
+    }
+
     return msg_len;
 }
 
@@ -707,7 +729,16 @@ static void _solicit_servers(event_t *event)
     msg_len += _compose_elapsed_time_opt(time);
     msg_len += _compose_oro_opt((dhcpv6_opt_oro_t *)&send_buf[msg_len], oro_opts,
                                 ARRAY_SIZE(oro_opts));
-    msg_len += _add_ia_pd_from_config(&send_buf[msg_len]);
+
+    if (IS_USED(MODULE_GNRC_DHCPV6_CLIENT_MUD_URL)) {
+        const char mud_url[] = CONFIG_DHCPV6_CLIENT_MUD_URL;
+        assert(strlen(mud_url) <= MAX_MUD_URL_LENGTH);
+        assert(strncmp(mud_url, "https://", 8) == 0);
+        msg_len += _compose_mud_url_opt((dhcpv6_opt_mud_url_t *)&send_buf[msg_len],
+                                        mud_url, sizeof(send_buf) - msg_len);
+    }
+
+    msg_len += _add_ia_pd_from_config(&send_buf[msg_len], sizeof(send_buf) - msg_len);
     DEBUG("DHCPv6 client: send SOLICIT\n");
     _flush_stale_replies(&sock);
     res = sock_udp_send(&sock, send_buf, msg_len, &remote);
@@ -815,7 +846,7 @@ static void _request_renew_rebind(uint8_t type)
     msg_len += _compose_elapsed_time_opt(time);
     msg_len += _compose_oro_opt((dhcpv6_opt_oro_t *)&send_buf[msg_len], oro_opts,
                                 ARRAY_SIZE(oro_opts));
-    msg_len += _add_ia_pd_from_config(&send_buf[msg_len]);
+    msg_len += _add_ia_pd_from_config(&send_buf[msg_len], sizeof(send_buf) - msg_len);
     _flush_stale_replies(&sock);
     while (sock_udp_send(&sock, send_buf, msg_len, &remote) <= 0) {}
     while (((res = sock_udp_recv(&sock, recv_buf, sizeof(recv_buf),

tests/gnrc_dhcpv6_client_6lbr/Makefile

@@ -5,6 +5,7 @@ export TAP ?= tap0
 
 USEMODULE += auto_init_gnrc_netif
 USEMODULE += gnrc_dhcpv6_client_6lbr
+USEMODULE += gnrc_dhcpv6_client_mud_url
 USEMODULE += gnrc_netdev_default
 USEMODULE += gnrc_pktdump
 USEMODULE += gnrc_sixlowpan_border_router_default

tests/gnrc_dhcpv6_client_6lbr/tests/01-run.py

@@ -14,13 +14,19 @@ import time
 
 from scapy.all import AsyncSniffer, sendp, Ether, IPv6, UDP
 from scapy.all import DHCP6_Solicit, DHCP6_Advertise, DHCP6_Request, DHCP6_Reply
-from scapy.all import DHCP6OptClientId, DHCP6OptServerId, DHCP6OptIA_PD
+from scapy.all import DHCP6OptClientId, DHCP6OptServerId, DHCP6OptIA_PD, DHCP6OptUnknown
 from scapy.all import DUID_LL, DHCP6OptIAPrefix
 from testrunner import run
 
 
 TIMEOUT = 1
 
+MUD_OPTION_CODE = 112
+MUD_TEST_URL = b'https://example.org'
+
+# MUD URL option in DHCPv6 is not yet supported by scapy
+DHCP6OptMUD = DHCP6OptUnknown
+
 
 def get_upstream_netif(child):
     child.sendline("ifconfig")
@@ -123,6 +129,12 @@ def testfunc(child):
     # and it is asking for a prefix delegation
     assert DHCP6OptIA_PD in pkt
 
+    assert DHCP6OptMUD in pkt
+    mud_packet = pkt[DHCP6OptMUD]
+    assert mud_packet.optcode == 112
+    assert mud_packet.optlen == len(MUD_TEST_URL)
+    assert mud_packet.data == MUD_TEST_URL
+
     # reply to solicit with advertise and a prefix provided
     trid = pkt[DHCP6_Solicit].trid
     srv_duid = "aa:bb:cc:dd:ee:ff"