Add network PMTU support

include/zephyr/net/net_context.h

@@ -1292,7 +1292,8 @@
 	NET_OPT_TTL               = 16, /**< IPv4 unicast TTL */
 	NET_OPT_ADDR_PREFERENCES  = 17, /**< IPv6 address preference */
 	NET_OPT_TIMESTAMPING      = 18, /**< Packet timestamping */
+	NET_OPT_MTU               = 20, /**< IPv4 socket path MTU */
 };
 
 /**
  * @brief Set an connection option for this context.

include/zephyr/net/net_event.h

@@ -74,6 +74,7 @@
 	NET_EVENT_IPV6_CMD_PE_DISABLED,
 	NET_EVENT_IPV6_CMD_PE_FILTER_ADD,
 	NET_EVENT_IPV6_CMD_PE_FILTER_DEL,
+	NET_EVENT_IPV6_CMD_PMTU_CHANGED,
 };
 
 /* IPv4 Events*/
@@ -99,6 +100,7 @@
 	NET_EVENT_IPV4_CMD_ACD_SUCCEED,
 	NET_EVENT_IPV4_CMD_ACD_FAILED,
 	NET_EVENT_IPV4_CMD_ACD_CONFLICT,
+	NET_EVENT_IPV4_CMD_PMTU_CHANGED,
 };
 
 /* L4 network events */
@@ -237,6 +239,10 @@
 #define NET_EVENT_IPV6_PE_FILTER_DEL				\
 	(_NET_EVENT_IPV6_BASE | NET_EVENT_IPV6_CMD_PE_FILTER_DEL)
 
+/** IPv6 Path MTU is changed. */
+#define NET_EVENT_IPV6_PMTU_CHANGED				\
+	(_NET_EVENT_IPV6_BASE | NET_EVENT_IPV6_CMD_PMTU_CHANGED)
+
 /** Event emitted when an IPv4 address is added to the system. */
 #define NET_EVENT_IPV4_ADDR_ADD					\
 	(_NET_EVENT_IPV4_BASE | NET_EVENT_IPV4_CMD_ADDR_ADD)
@@ -296,6 +302,10 @@
 #define NET_EVENT_IPV4_ACD_CONFLICT				\
 	(_NET_EVENT_IPV4_BASE | NET_EVENT_IPV4_CMD_ACD_CONFLICT)
 
+/** IPv4 Path MTU is changed. */
+#define NET_EVENT_IPV4_PMTU_CHANGED				\
+	(_NET_EVENT_IPV4_BASE | NET_EVENT_IPV4_CMD_PMTU_CHANGED)
+
 /** Event emitted when the system is considered to be connected.
  * The connected in this context means that the network interface is up,
  * and the interface has either IPv4 or IPv6 address assigned to it.
@@ -441,6 +451,34 @@
 	bool is_deny_list;
 };
 
+/**
+ * @brief Network Management event information structure
+ * Used to pass information on network event
+ *   NET_EVENT_IPV4_PMTU_CHANGED
+ * when CONFIG_NET_MGMT_EVENT_INFO enabled and event generator pass the
+ * information.
+ */
+struct net_event_ipv4_pmtu_info {
+	/** IPv4 address */
+	struct in_addr dst;
+	/** New MTU */
+	uint16_t mtu;
+};
+
+/**
+ * @brief Network Management event information structure
+ * Used to pass information on network event
+ *   NET_EVENT_IPV6_PMTU_CHANGED
+ * when CONFIG_NET_MGMT_EVENT_INFO enabled and event generator pass the
+ * information.
+ */
+struct net_event_ipv6_pmtu_info {
+	/** IPv6 address */
+	struct in6_addr dst;
+	/** New MTU */
+	uint32_t mtu;
+};
+
 #ifdef __cplusplus
 }
 #endif

include/zephyr/net/net_pkt.h

@@ -342,6 +342,11 @@
 	uint8_t cooked_mode_pkt : 1;
 #endif /* CONFIG_NET_CAPTURE_COOKED_MODE */
 
+#if defined(CONFIG_NET_IPV4_PMTU)
+	/* Path MTU needed for this destination address */
+	uint8_t ipv4_pmtu : 1;
+#endif /* CONFIG_NET_IPV4_PMTU */
+
 	/* @endcond */
 };
 
@@ -783,6 +788,31 @@
 #endif
 }
 
+#if defined(CONFIG_NET_IPV4_PMTU)
+static inline bool net_pkt_ipv4_pmtu(struct net_pkt *pkt)
+{
+	return !!pkt->ipv4_pmtu;
+}
+
+static inline void net_pkt_set_ipv4_pmtu(struct net_pkt *pkt, bool value)
+{
+	pkt->ipv4_pmtu = value;
+}
+#else
+static inline bool net_pkt_ipv4_pmtu(struct net_pkt *pkt)
+{
+	ARG_UNUSED(pkt);
+
+	return false;
+}
+
+static inline void net_pkt_set_ipv4_pmtu(struct net_pkt *pkt, bool value)
+{
+	ARG_UNUSED(pkt);
+	ARG_UNUSED(value);
+}
+#endif /* CONFIG_NET_IPV4_PMTU */
+
 #if defined(CONFIG_NET_IPV4_FRAGMENT)
 static inline uint16_t net_pkt_ipv4_fragment_offset(struct net_pkt *pkt)
 {

include/zephyr/net/net_stats.h

@@ -198,6 +198,34 @@
 	net_stats_t sent;
 };
 
+/**
+ * @brief IPv6 Path MTU Discovery statistics
+ */
+struct net_stats_ipv6_pmtu {
+	/** Number of dropped IPv6 PMTU packets. */
+	net_stats_t drop;
+
+	/** Number of received IPv6 PMTU packets. */
+	net_stats_t recv;
+
+	/** Number of sent IPv6 PMTU packets. */
+	net_stats_t sent;
+};
+
+/**
+ * @brief IPv4 Path MTU Discovery statistics
+ */
+struct net_stats_ipv4_pmtu {
+	/** Number of dropped IPv4 PMTU packets. */
+	net_stats_t drop;
+
+	/** Number of received IPv4 PMTU packets. */
+	net_stats_t recv;
+
+	/** Number of sent IPv4 PMTU packets. */
+	net_stats_t sent;
+};
+
 /**
  * @brief IPv6 multicast listener daemon statistics
  */
@@ -379,6 +407,16 @@
 	struct net_stats_ipv6_nd ipv6_nd;
 #endif
 
+#if defined(CONFIG_NET_STATISTICS_IPV6_PMTU)
+	/** IPv6 Path MTU Discovery statistics */
+	struct net_stats_ipv6_pmtu ipv6_pmtu;
+#endif
+
+#if defined(CONFIG_NET_STATISTICS_IPV4_PMTU)
+	/** IPv4 Path MTU Discovery statistics */
+	struct net_stats_ipv4_pmtu ipv4_pmtu;
+#endif
+
 #if defined(CONFIG_NET_STATISTICS_MLD)
 	/** IPv6 MLD statistics */
 	struct net_stats_ipv6_mld ipv6_mld;
@@ -665,6 +703,8 @@
 	NET_REQUEST_STATS_CMD_GET_IPV4,
 	NET_REQUEST_STATS_CMD_GET_IPV6,
 	NET_REQUEST_STATS_CMD_GET_IPV6_ND,
+	NET_REQUEST_STATS_CMD_GET_IPV6_PMTU,
+	NET_REQUEST_STATS_CMD_GET_IPV4_PMTU,
 	NET_REQUEST_STATS_CMD_GET_ICMP,
 	NET_REQUEST_STATS_CMD_GET_UDP,
 	NET_REQUEST_STATS_CMD_GET_TCP,
@@ -732,6 +772,26 @@
 /** @endcond */
 #endif /* CONFIG_NET_STATISTICS_IPV6_ND */
 
+#if defined(CONFIG_NET_STATISTICS_IPV6_PMTU)
+/** Request IPv6 Path MTU Discovery statistics */
+#define NET_REQUEST_STATS_GET_IPV6_PMTU				\
+	(_NET_STATS_BASE | NET_REQUEST_STATS_CMD_GET_IPV6_PMTU)
+
+/** @cond INTERNAL_HIDDEN */
+NET_MGMT_DEFINE_REQUEST_HANDLER(NET_REQUEST_STATS_GET_IPV6_PMTU);
+/** @endcond */
+#endif /* CONFIG_NET_STATISTICS_IPV6_PMTU */
+
+#if defined(CONFIG_NET_STATISTICS_IPV4_PMTU)
+/** Request IPv4 Path MTU Discovery statistics */
+#define NET_REQUEST_STATS_GET_IPV4_PMTU				\
+	(_NET_STATS_BASE | NET_REQUEST_STATS_CMD_GET_IPV4_PMTU)
+
+/** @cond INTERNAL_HIDDEN */
+NET_MGMT_DEFINE_REQUEST_HANDLER(NET_REQUEST_STATS_GET_IPV4_PMTU);
+/** @endcond */
+#endif /* CONFIG_NET_STATISTICS_IPV4_PMTU */
+
 #if defined(CONFIG_NET_STATISTICS_ICMP)
 /** Request ICMPv4 and ICMPv6 statistics */
 #define NET_REQUEST_STATS_GET_ICMP				\

include/zephyr/net/socket.h

@@ -1190,6 +1190,12 @@ struct in_pktinfo {
 	struct in_addr ipi_addr;     /**< Header Destination address */
 };
 
+/** Retrieve the current known path MTU of the current socket. Returns an
+ *  integer. IP_MTU is valid only for getsockopt and can be employed only when
+ *  the socket has been connected.
+ */
+#define IP_MTU 14
+
 /** Set IPv4 multicast TTL value. */
 #define IP_MULTICAST_TTL 33
 /** Join IPv4 multicast group. */
@@ -1236,6 +1242,13 @@ struct ipv6_mreq {
 	int ipv6mr_ifindex;
 };
 
+/** For getsockopt(), retrieve the current known IPv6 path MTU of the given socket.
+ * Valid only when the socket has been connected.
+ * For setsockopt(), set the MTU to be used for the socket. The MTU is limited by
+ * the device MTU or the path MTU when path MTU discovery is enabled.
+ */
+#define IPV6_MTU 24
+
 /** Don't support IPv4 access */
 #define IPV6_V6ONLY 26
 

samples/net/stats/src/main.c

@@ -43,6 +43,12 @@
 	       GET_STAT(iface, ipv6_nd.sent),
 	       GET_STAT(iface, ipv6_nd.drop));
 #endif /* CONFIG_NET_IPV6_ND */
+#if defined(CONFIG_NET_IPV6_PMTU)
+	printk("IPv6 PMTU recv %d\tsent\t%d\tdrop\t%d\n",
+	       GET_STAT(iface, ipv6_pmtu.recv),
+	       GET_STAT(iface, ipv6_pmtu.sent),
+	       GET_STAT(iface, ipv6_pmtu.drop));
+#endif /* CONFIG_NET_IPV6_PMTU */
 #if defined(CONFIG_NET_STATISTICS_MLD)
 	printk("IPv6 MLD recv  %d\tsent\t%d\tdrop\t%d\n",
 	       GET_STAT(iface, ipv6_mld.recv),
@@ -68,6 +74,13 @@
 	       GET_STAT(iface, ip_errors.chkerr),
 	       GET_STAT(iface, ip_errors.protoerr));
 
+#if defined(CONFIG_NET_IPV4_PMTU)
+	printk("IPv4 PMTU recv %d\tsent\t%d\tdrop\t%d\n",
+	       GET_STAT(iface, ipv4_pmtu.recv),
+	       GET_STAT(iface, ipv4_pmtu.sent),
+	       GET_STAT(iface, ipv4_pmtu.drop));
+#endif /* CONFIG_NET_IPV4_PMTU */
+
 	printk("ICMP recv      %d\tsent\t%d\tdrop\t%d\n",
 	       GET_STAT(iface, icmp.recv),
 	       GET_STAT(iface, icmp.sent),

subsys/net/ip/CMakeLists.txt

@@ -42,6 +42,7 @@ zephyr_library_sources_ifdef(CONFIG_NET_IPV6_PE      ipv6_pe.c)
 zephyr_library_sources_ifdef(CONFIG_NET_IPV6_FRAGMENT     ipv6_fragment.c)
 zephyr_library_sources_ifdef(CONFIG_NET_IPV4_FRAGMENT     ipv4_fragment.c)
 zephyr_library_sources_ifdef(CONFIG_NET_MGMT_EVENT   net_mgmt.c)
+zephyr_library_sources_ifdef(CONFIG_NET_PMTU         pmtu.c)
 zephyr_library_sources_ifdef(CONFIG_NET_ROUTE        route.c)
 zephyr_library_sources_ifdef(CONFIG_NET_STATISTICS   net_stats.c)
 zephyr_library_sources_ifdef(CONFIG_NET_TCP          tcp.c)

subsys/net/ip/Kconfig

@@ -48,6 +48,22 @@ config NET_NATIVE_IPV4
 	depends on NET_NATIVE
 	default y if NET_IPV4
 
+config NET_PMTU
+	bool
+	select NET_MGMT
+	select NET_MGMT_EVENT
+	select NET_MGMT_EVENT_INFO
+	default y
+	depends on NET_IPV6_PMTU || NET_IPV4_PMTU
+
+if NET_PMTU
+module = NET_PMTU
+module-dep = NET_LOG
+module-str = Log level for PMTU
+module-help = Enables PMTU to output debug messages.
+source "subsys/net/Kconfig.template.log_config.net"
+endif # NET_PMTU
+
 config NET_NATIVE_TCP
 	bool
 	depends on NET_NATIVE
@@ -252,6 +268,11 @@ config NET_SHELL_PKT_ALLOC_SUPPORTED
 	default y
 	depends on NET_SHELL_SHOW_DISABLED_COMMANDS || NET_DEBUG_NET_PKT_ALLOC
 
+config NET_SHELL_PMTU_SUPPORTED
+	bool "PMTU config"
+	default y
+	depends on NET_SHELL_SHOW_DISABLED_COMMANDS || NET_PMTU
+
 config NET_SHELL_PPP_SUPPORTED
 	bool "PPP config"
 	default y

subsys/net/ip/Kconfig.ipv4

@@ -151,6 +151,18 @@ config NET_IPV4_FRAGMENT_TIMEOUT
 	  How long to wait for IPv4 fragment to arrive before the reassembly
 	  will timeout. This value is in seconds.
 
+config NET_IPV4_PMTU
+	bool "IPv4 Path MTU Discovery"
+	help
+	  Enables IPv4 Path MTU Discovery (see RFC 1191)
+
+config NET_IPV4_PMTU_DESTINATION_CACHE_ENTRIES
+	int "Number of IPv4 PMTU destination cache entries"
+	default 3
+	depends on NET_IPV4_PMTU
+	help
+	  How many PMTU entries we can track for each destination address.
+
 module = NET_IPV4
 module-dep = NET_LOG
 module-str = Log level for core IPv4

subsys/net/ip/Kconfig.ipv6

@@ -46,6 +46,18 @@ config NET_IPV6_MTU
 	  The value should normally be 1280 which is the minimum IPv6 packet
 	  size that implementations need to support without fragmentation.
 
+config NET_IPV6_PMTU
+	bool "IPv6 Path MTU Discovery"
+	help
+	  Enables IPv6 Path MTU Discovery (see RFC 8201)
+
+config NET_IPV6_PMTU_DESTINATION_CACHE_ENTRIES
+	int "Number of IPv6 PMTU destination cache entries"
+	default 3
+	depends on NET_IPV6_PMTU
+	help
+	  How many PMTU entries we can track for each destination address.
+
 config NET_INITIAL_HOP_LIMIT
 	int "Initial IPv6 hop limit value for unicast packets"
 	default 64

subsys/net/ip/Kconfig.stats

@@ -57,6 +57,20 @@ config NET_STATISTICS_IPV6_ND
 	help
 	  Keep track of IPv6 Neighbor Discovery related statistics
 
+config NET_STATISTICS_IPV6_PMTU
+	bool "IPv6 PMTU statistics"
+	depends on NET_IPV6_PMTU
+	default y
+	help
+	  Keep track of IPv6 Path MTU Discovery related statistics
+
+config NET_STATISTICS_IPV4_PMTU
+	bool "IPv4 PMTU statistics"
+	depends on NET_IPV4_PMTU
+	default y
+	help
+	  Keep track of IPv4 Path MTU Discovery related statistics
+
 config NET_STATISTICS_ICMP
 	bool "ICMP statistics"
 	depends on NET_IPV6 || NET_IPV4