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#ifndef IP_H
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#define IP_H
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#include "net.h"
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/**
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\file ip.h
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\brief IP Packet header
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This file contains the memory map and associated functions for IP packet header
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creation and deconstruction.
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*/
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#define ETHERTYPE_IPV4 0x0800
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#define ETHERTYPE_IPV6 0x86DD
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/// IP Address memory map
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typedef struct {
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unsigned char octet[4]; ///< Individual address octets
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} IP_Address;
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/// IP Packet memory map
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typedef struct {
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/// 4 bits that contain the version, that specifies if it's an IPv4 or IPv6 packet,
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unsigned version:4; // Only 0x4 supported
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/// 4 bits that contain the Internet Header Length which is the length of the header in multiples of 4 bytes (eg. 5 means 20 bytes).
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unsigned header_bytes_div4:4;
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/// 8 bits that contain the Type of Service, also referred to as Quality of Service (QoS), which describes what priority the packet should have,
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unsigned tos:8;
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/// 16 bits that contain the total length of the IP packet (datagram) in bytes,
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u16 packet_bytes;
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/// 16 bits that contain an identification tag to help reconstruct the packet from several fragments,
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u16 fragment_id;
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/// 3 bits that contain a zero, a flag that says whether the packet is allowed to be fragmented or not (DF: Don't fragment), and a flag to state whether more fragments of a packet follow (MF: More Fragments)
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unsigned unused_0:1;
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unsigned dont_fragment:1;
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unsigned more_follow:1;
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/// 13 bits that contain the fragment offset, a field to identify position of fragment within original packet
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unsigned fragment_offset:13; ///< This and the ones above may not work properly due to endianness
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/// 8 bits that contain the Time to live (TTL) which is the number of hops (router, computer or device along a network) the packet is allowed to pass before it dies (for example, a packet with a TTL of 16 will be allowed to go across 16 routers to get to its destination before it is discarded),
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unsigned ttl:8;
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/// 8 bits that contain the protocol (TCP, UDP, ICMP, etc...)
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/// 0x01 ICMP
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/// 0x06 TCP
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/// 0x11 UDP
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unsigned protocol:8;
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/// 16 bits that contain the Header Checksum, a number used in error detection,
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u16 header_checksum;
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/// 32 bits that contain the source IP address,
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IP_Address source;
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/// 32 bits that contain the destination address.
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IP_Address destination;
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/// Zero-length field for memory mapping the packet data
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unsigned char data[];
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} IP_PacketHeader;
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/// Convert from wire to host or host to wire endianness
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inline void fix_endian_ip(IP_PacketHeader *packet)
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{
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packet->version ^= packet->header_bytes_div4;
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packet->header_bytes_div4 ^= packet->version;
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packet->version ^= packet->header_bytes_div4;
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fix_endian_u16(&packet->packet_bytes);
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fix_endian_u16(&packet->fragment_id);
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// Don't fix checksums; they are done bitwise
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}
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/// Get a constant string of the given IP protocol (e.g. "ICMP", "TCP", "UDP") if known
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inline const char *ipproto2name(u8 proto)
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{
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switch (proto)
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{
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case 0x01: return "ICMP";
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case 0x02: return "IGMP";
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case 0x06: return "TCP";
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case 0x11: return "UDP";
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}
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return "<UNKNOWN>";
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}
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/// Parse the string (in decimal triple-dot notation) into the IP address structure
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inline void str2ipaddr(const char *ip, IP_Address *addr)
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{
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static short a,b,c,d;
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sscanf(ip, "%3hd.%3hd.%3hd.%3hd", &a, &b, &c, &d);
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addr->octet[0] = a;
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addr->octet[1] = b;
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addr->octet[2] = c;
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addr->octet[3] = d;
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}
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#endif |
Kyle Lemons