Many networking tweaks

- Simple path MTU
- ICMP error handling
- DNS cname chasing
- DNS buffer strengthening
- IP protocol registration system
- ICMP port unreachable replies
- ICMP rate limiting for unreachables

Author: braindigitalis

include/dns.h

@@ -46,6 +46,12 @@ enum query_type_t {
 	DNS_QUERY_PTR6	= 0xFFFE
 };
 
+#define DNS_HEADER_SIZE 12
+
+#define DNS_RR_FIXED_SIZE 10
+
+#define DNS_RESULT_MAX 1023
+
 /** Represents a dns request/reply header, and its payload as opaque data.
  */
 typedef struct dns_header {

include/ethernet.h

@@ -16,15 +16,25 @@ typedef void (*ethernet_protocol_t)(void*, int);
 #define HARDWARE_TYPE_ETHERNET 0x01
 
 /**
- * @brief There is actually more to an ethernet frame than this
- * (see the STD documents!) but we don't have access to it from the
- * software.
+ * @brief Ethernet II frame header visible to the network stack
+ *
+ * Real Ethernet frames also contain a preamble, start frame delimiter,
+ * frame check sequence and inter-frame gap. Those fields are handled by
+ * the NIC/MAC layer and are not normally present in the packet buffer
+ * delivered to software.
  */
 typedef struct ethernet_frame {
-	uint8_t dst_mac_addr[6]; // Destination MAC address
-	uint8_t src_mac_addr[6]; // Source MAC address
-	uint16_t type; // Packet type
-	uint8_t data[]; // Raw data
+	/** Destination MAC address */
+	uint8_t dst_mac_addr[6];
+
+	/** Source MAC address */
+	uint8_t src_mac_addr[6];
+
+	/** EtherType field */
+	uint16_t type;
+
+	/** Ethernet payload */
+	uint8_t data[];
 } __attribute__((packed)) ethernet_frame_t;
 
 /**
@@ -36,15 +46,15 @@ typedef struct ethernet_frame {
  * @param protocol protocol type
  * @return int nonzero on successful queue of packet
  */
-int ethernet_send_packet(uint8_t* dst_mac_addr, uint8_t* data, uint32_t len, uint16_t protocol);
+int ethernet_send_packet(const uint8_t* dst_mac_addr, const uint8_t* data, size_t len, uint16_t protocol);
 
 /**
  * @brief Handle inbound packet via interrupt from network card driver
  * 
  * @param packet raw packet data
  * @param len packet data length
  */
-void ethernet_handle_packet(ethernet_frame_t * packet, int len);
+void ethernet_handle_packet(ethernet_frame_t * packet, size_t len);
 
 /**
  * @brief Register a protocol with the ethernet layer

include/icmp.h

@@ -7,111 +7,305 @@
 
 #include "kernel.h"
 
+/**
+ * @brief ICMP packet types
+ */
 enum icmp_type_t {
+	/** Echo reply */
 	ICMP_ECHO_REPLY = 0,
+
+	/** Destination unreachable */
 	ICMP_DESTINATION_UNREACHABLE = 3,
+
+	/** Source quench, deprecated */
 	ICMP_SOURCE_QUENCH = 4,
+
+	/** Redirect */
 	ICMP_REDIRECT = 5,
+
+	/** Echo request */
 	ICMP_ECHO = 8,
+
+	/** Time exceeded */
 	ICMP_TIME_EXCEEDED = 11,
+
+	/** Parameter problem */
 	ICMP_PARAMETER_PROBLEM = 12,
+
+	/** Timestamp request */
 	ICMP_TIMESTAMP = 13,
+
+	/** Timestamp reply */
 	ICMP_TIMESTAMP_REPLY = 14,
+
+	/** Information request */
 	ICMP_INFORMATION_REQUEST = 15,
+
+	/** Information reply */
 	ICMP_INFORMATION_REPLY = 16,
 };
 
+/**
+ * @brief ICMP destination unreachable reason codes
+ */
 enum icmp_unreachable_code_t {
+	/** Destination network is unreachable */
 	ICMP_NET_UNREACHABLE = 0,
+
+	/** Destination host is unreachable */
 	ICMP_HOST_UNREACHABLE = 1,
+
+	/** Destination protocol is unreachable */
 	ICMP_PROTOCOL_UNREACHABLE = 2,
+
+	/** Destination port is unreachable */
 	ICMP_PORT_UNREACHABLE = 3,
+
+	/** Fragmentation is required but the IPv4 DF bit was set */
 	ICMP_FRAGMENTATION_NEEDED = 4,
+
+	/** Source route failed */
 	ICMP_SOURCE_ROUTE_FAILED = 5,
 };
 
+/**
+ * @brief ICMP time exceeded reason codes
+ */
 enum icmp_time_exceeded_code_t {
+	/** Packet TTL expired in transit */
 	ICMP_TTL_EXCEEDED = 0,
+
+	/** Fragment reassembly timeout expired */
 	ICMP_FRAGMENT_REASSEMBLY_TIME_EXCEEDED = 1,
 };
 
+/**
+ * @brief ICMP redirect reason codes
+ */
 enum icmp_redirect_code_t {
+	/** Redirect traffic for a network */
 	ICMP_REDIRECT_NETWORK = 0,
+
+	/** Redirect traffic for a host */
 	ICMP_REDIRECT_HOST = 1,
+
+	/** Redirect traffic for a TOS/network combination */
 	ICMP_REDIRECT_TOS_NETWORK = 2,
+
+	/** Redirect traffic for a TOS/host combination */
 	ICMP_REDIRECT_TOS_HOST = 3,
 };
 
+/**
+ * @brief Generic ICMP packet carrying a quoted IPv4 datagram
+ *
+ * Used for destination unreachable and time exceeded messages. For
+ * fragmentation-needed messages, unused carries the next-hop MTU in network
+ * byte order.
+ */
 typedef struct icmp_packet {
+	/** ICMP packet type */
 	uint8_t type;
+
+	/** ICMP type-specific code */
 	uint8_t code;
+
+	/** Internet checksum of the ICMP packet */
 	uint16_t checksum;
+
+	/** Type-specific auxiliary field */
 	uint32_t unused;
+
+	/** Quoted IPv4 datagram that triggered the ICMP message */
 	ip_packet_t original_datagram;
 } __attribute__((packed)) icmp_packet_t;
 
+/**
+ * @brief ICMP redirect packet
+ */
 typedef struct icmp_redirect_packet {
+	/** ICMP packet type */
 	uint8_t type;
+
+	/** ICMP redirect reason code */
 	uint8_t code;
+
+	/** Internet checksum of the ICMP packet */
 	uint16_t checksum;
+
+	/** Replacement gateway IPv4 address */
 	uint32_t gateway;
+
+	/** Quoted IPv4 datagram that triggered the redirect */
 	ip_packet_t original_datagram;
 } __attribute__((packed)) icmp_redirect_packet_t;
 
+/**
+ * @brief ICMP information request/reply packet
+ */
 typedef struct icmp_information {
+	/** ICMP packet type */
 	uint8_t type;
+
+	/** ICMP type-specific code */
 	uint8_t code;
+
+	/** Internet checksum of the ICMP packet */
 	uint16_t checksum;
+
+	/** Request identifier */
 	uint16_t id;
+
+	/** Request sequence number */
 	uint16_t seq;
 } __attribute__((packed)) icmp_information_t;
 
+/**
+ * @brief ICMP parameter problem packet
+ */
 typedef struct icmp_parameter_problem_packet {
+	/** ICMP packet type */
 	uint8_t type;
+
+	/** ICMP parameter problem code */
 	uint8_t code;
+
+	/** Internet checksum of the ICMP packet */
 	uint16_t checksum;
+
+	/** Offset of invalid byte within the IPv4 header */
 	uint8_t problem_ptr;
+
+	/** Reserved field */
 	uint16_t unused1;
+
+	/** Reserved field */
 	uint16_t unused2;
+
+	/** Quoted IPv4 datagram containing the invalid header */
 	ip_packet_t original_datagram;
 } __attribute__((packed)) icmp_parameter_problem_packet_t;
 
+/**
+ * @brief ICMP echo request/reply packet
+ */
 typedef struct icmp_echo_packet {
+	/** ICMP packet type */
 	uint8_t type;
+
+	/** ICMP type-specific code */
 	uint8_t code;
+
+	/** Internet checksum of the ICMP packet */
 	uint16_t checksum;
+
+	/** Echo identifier */
 	uint16_t id;
+
+	/** Echo sequence number */
 	uint16_t seq;
 } __attribute__((packed)) icmp_echo_packet_t;
 
+/**
+ * @brief ICMP timestamp request/reply packet
+ */
 typedef struct icmp_timestamp_packet {
+	/** ICMP packet type */
 	uint8_t type;
+
+	/** ICMP type-specific code */
 	uint8_t code;
+
+	/** Internet checksum of the ICMP packet */
 	uint16_t checksum;
+
+	/** Request identifier */
 	uint16_t id;
+
+	/** Request sequence number */
 	uint16_t seq;
+
+	/** Sender originate timestamp */
 	uint32_t originate_timestamp;
+
+	/** Receiver receive timestamp */
 	uint32_t receive_timestamp;
+
+	/** Sender transmit timestamp */
 	uint32_t transmit_timestamp;
 } __attribute__((packed)) icmp_timestamp_packet_t;
 
 /**
- * @brief Handle ICMP packet from the IP driver
- * 
- * @param ip Encapsulating IP packet
- * @param packet raw ICMP packet
- * @param length ICMP packet length
+ * @brief Callback for protocol handlers interested in ICMP unreachable messages
+ *
+ * The quoted IPv4 datagram identifies the protocol endpoint that triggered the
+ * ICMP error. The MTU value is only meaningful for ICMP_FRAGMENTATION_NEEDED.
+ *
+ * @param quoted_ip Quoted IPv4 datagram from the ICMP payload
+ * @param code ICMP unreachable reason code
+ * @param mtu Path MTU for ICMP_FRAGMENTATION_NEEDED, otherwise zero
+ */
+typedef void (*icmp_unreachable_handler_t)(ip_packet_t*, uint8_t, uint16_t);
+
+/**
+ * @brief Register a handler for ICMP unreachable notifications
+ *
+ * @param protocol IP protocol number to register for
+ * @param handler Callback function
  */
-void icmp_handle_packet([[maybe_unused]] ip_packet_t* encap_packet, icmp_packet_t* packet, size_t len);
+void icmp_register_unreachable_handler(uint8_t protocol, icmp_unreachable_handler_t handler);
 
+/**
+ * @brief Send an ICMP echo request
+ *
+ * @param destination Destination IPv4 address
+ * @param id Echo identifier
+ * @param seq Echo sequence number
+ */
 void icmp_send_echo(uint8_t* destination, uint16_t id, uint16_t seq);
 
+/**
+ * @brief Send an ICMP time exceeded packet
+ *
+ * @param original_ip Original IPv4 packet that triggered the error
+ * @param code ICMP time exceeded reason code
+ */
 void icmp_send_time_exceeded(ip_packet_t* original_ip, uint8_t code);
 
+/**
+ * @brief Send an ICMP destination unreachable packet
+ *
+ * @param original_ip Original IPv4 packet that triggered the error
+ * @param code ICMP unreachable reason code
+ */
 void icmp_send_destination_unreachable(ip_packet_t* original_ip, uint8_t code);
 
+/**
+ * @brief Send an ICMP parameter problem packet
+ *
+ * @param original_ip Original IPv4 packet that triggered the error
+ * @param pointer_offset Offset of invalid byte within the IPv4 header
+ */
 void icmp_send_parameter_problem(ip_packet_t* original_ip, uint8_t pointer_offset);
 
+/**
+ * @brief Send an ICMP redirect packet
+ *
+ * @param original_ip Original IPv4 packet that triggered the redirect
+ * @param code ICMP redirect reason code
+ * @param new_gateway_ip Replacement gateway IPv4 address
+ */
 void icmp_send_redirect(ip_packet_t* original_ip, uint8_t code, uint32_t new_gateway_ip);
 
+/**
+ * @brief Send an ICMP fragmentation needed packet
+ *
+ * @param original_ip Original IPv4 packet that could not be forwarded
+ * @param mtu Path MTU required for successful forwarding
+ */
 void icmp_send_fragmentation_needed(ip_packet_t* original_ip, uint16_t mtu);
+
+/**
+ * @brief Initialise the ICMP subsystem
+ */
+void icmp_init();

include/ip.h

@@ -102,6 +102,20 @@ typedef struct packet_queue_item {
 	struct packet_queue_item* next;
 } packet_queue_item_t;
 
+typedef void (*ip_protocol_handler_t)(ip_packet_t*, void*, size_t);
+
+typedef enum {
+	IP_ERROR_PROTOCOL_UNREACHABLE,
+} ip_error_t;
+
+typedef void (*ip_error_handler_t)(ip_packet_t *packet, ip_error_t error);
+
+bool ip_register_protocol(uint8_t protocol_number, ip_protocol_handler_t handler);
+
+bool ip_unregister_protocol(uint8_t protocol_number);
+
+void ip_register_error_handler(ip_error_handler_t handler);
+
 /**
  * @brief Convert network byte order IP to a string form for display
  *