Ethernet II, IPv4, UDP packet parsers added (not complete)

Doxyfile

@@ -2453,7 +2453,7 @@ UML_LIMIT_NUM_FIELDS   = 10
 DOT_UML_DETAILS        = NO
 
 # The DOT_WRAP_THRESHOLD tag can be used to set the maximum number of characters
-# to display on a single line. If the actual line length exceeds this threshold
+# to display on a single line. If the actual line length_type exceeds this threshold
 # significantly it will wrapped across multiple lines. Some heuristics are apply
 # to avoid ugly line breaks.
 # Minimum value: 0, maximum value: 1000, default value: 17.

global_state.c

@@ -1,8 +1,67 @@
+#include <stddef.h>
 #include "global_state.h"
 #include "dynmem.h"
 
+#include "prefab/prefab.h"
+
 EthState gEthState;
 
+static void register_packet_parsers() {
+    PcktClassDesc cdesc;
+    // Ethernet frame parser
+    cdesc.class = 0;
+    cdesc.containerClass = 0;
+    cdesc.procFun = parse_ethernet;
+    cdesc.propertySize = sizeof(EthernetProps);
+    packreg_add(E.pcktReg, &cdesc);
+
+    // IPv4 packet parser
+    cdesc.class = ETH_IPv4_PACKET_CLASS;
+    cdesc.containerClass = 0;
+    cdesc.procFun = parse_ipv4;
+    cdesc.propertySize = sizeof(IPv4Props);
+    packreg_add(E.pcktReg, &cdesc);
+
+    // UDP packet parser
+    cdesc.class = ETH_UDP_PACKET_CLASS;
+    cdesc.containerClass = ETH_IPv4_PACKET_CLASS;
+    cdesc.procFun = parse_udp;
+    cdesc.propertySize = sizeof(UDPProps);
+    packreg_add(E.pcktReg, &cdesc);
+}
+
 void ethlib_init() {
     dynmem_init(); // initialize dynamic memory subsystem
+    E.pcktReg = packreg_new(); // create new packet registry
+    register_packet_parsers(); // register packet parsers
+}
+
+void process_raw_packet(const uint8_t * data, uint32_t size) {
+    uint16_t ownClass = 0, containerClass = 0; // Ethernet...
+    uint16_t offset = 0;
+    PcktProps * props = NULL;
+    do {
+        // get packet descriptor
+        const PcktClassDesc * cdesc = packreg_get_by_class(E.pcktReg, ownClass, containerClass);
+        if (cdesc == NULL) {
+            break;
+        }
+
+        // allocate property object
+        props = (PcktProps *) dynmem_alloc(cdesc->propertySize);
+
+        // call parsing function
+        cdesc->procFun(data + offset, size - offset, props);
+        uint16_t containedClass = props->containedPacketClass;
+        if (containedClass != 0) {
+            containerClass = ownClass;
+            offset += props->headerSize;
+            dynmem_free(props);
+        }
+        ownClass = containedClass;
+    } while (ownClass != 0);
+
+    // TODO process innermost packet
+
+    return;
 }

global_state.h

@@ -8,8 +8,8 @@
  * Global EtherLib state.
  */
 typedef struct {
-    MP * mp; ///< Memory pool for synamic allocations.
+    MP * mp; ///< Memory pool for dynamic allocations
-    PcktRegistry pcktReg; ///< Packet registry.
+    PcktRegistry * pcktReg; ///< Packet registry
 } EthState;
 
 extern EthState gEthState;
@@ -20,4 +20,6 @@ extern EthState gEthState;
  */
 void ethlib_init();
 
+void process_raw_packet(const uint8_t * data, uint32_t size);
+
 #endif //ETHERLIB_GLOBAL_STATE_H

packet_registry.c

@@ -34,6 +34,13 @@ void packreg_add(PcktRegistry * packReg, const PcktClassDesc * classDesc) {
     packReg->entCnt++;
 }
 
-void packreg_get_by_class(uint16_t class) {
+const PcktClassDesc * packreg_get_by_class(const PcktRegistry * packReg, uint16_t ownClass, uint16_t containerClass)  {
-
+    uint32_t i;
+    for (i = 0; i < packReg->entCnt; i++) {
+        const PcktClassDesc * cdesc = packReg->ents + i;
+        if ((cdesc->class == ownClass) && ((cdesc->containerClass == containerClass) || (containerClass == 0))) {
+            return cdesc;
+        }
+    }
+    return NULL;
 }

packet_registry.h

@@ -17,24 +17,29 @@ typedef uint8_t bool8_t;
  * to be aligned to 32-bit boundary and so must be guaranteed by extending
  * as well. (The size of the packet is divisible by 4.)
  */
+
+#define PcktPropsHeader \
+    uint16_t headerSize; /*< Header size in bytes */ \
+    uint16_t containedPacketClass; /*< ID of contained packet. Zero if no packet contained. */ \
+    bool8_t validityOK; /*< Indicates that checksum is OK. */ \
+
+
 typedef struct {
-    uint16_t headerSize; ///< Header size in bytes
+    PcktPropsHeader
-    uint16_t containedPacketClass; ///< ID of contained packet. Zero if no packet contained.
-    bool8_t checksumOK; ///< Indicates that checksum is OK.
 } PcktProps;
 
 /**
  * @typedef int (*PcktProcFn)(const uint8_t *pHdr, uint32_t size, uint8_t *pPcktProps);
  * @brief Pckt processing function template.
- * @param pHdr: pointer to the packet header
+ * @param hdr: pointer to the packet header
  * @param size: remaining packet size counted from pHdr
- * @param pPcktProps: pointer to existing structure to store
+ * @param props: pointer to existing structure to store
  *      packet properties to (e.g. source address, port etc.)
  * @return packet class of contained packet, or -1 on failure or
  *      0 if no more standard packet contained (e.g. UDP packet contains
  *      user data)
  */
-typedef int (*PcktProcFn)(const uint8_t *pHdr, uint32_t size, uint8_t *pProps);
+typedef int (*PcktProcFn)(const uint8_t *hdr, uint32_t size, PcktProps *props);
 
 /**
  * @struct PcktClassDesc
@@ -45,6 +50,7 @@ typedef struct {
     uint16_t class; ///< Type identification of the packet 'class' (unique!)
     uint16_t containerClass; ///< Type of container packet packet (e.g.: IPv4 in case of UDP)
     PcktProcFn procFun; ///< Pckt processing function
+    uint16_t propertySize; ///< Size of property structure
 } PcktClassDesc;
 
 /**
@@ -70,5 +76,13 @@ PcktRegistry * packreg_new();
  */
 void packreg_add(PcktRegistry * packReg, const PcktClassDesc * classDesc);
 
+/**
+ * Get packet descriptor by own class and container class.
+ * @param packReg pointer to Packet Registry object
+ * @param ownClass packet's own class
+ * @param containerClass container packet's class (if 0, then search by container class is not considered)
+ * @return pointer to descriptor on success or NULL on failure
+ */
+const PcktClassDesc * packreg_get_by_class(const PcktRegistry * packReg, uint16_t ownClass, uint16_t containerClass);
 
 #endif //ETHERLIB_PACKET_REGISTRY_H

prefab/packet_parsers/ethernet_frame.c

@@ -0,0 +1,26 @@
+//
+// Created by epagris on 2022.11.03..
+//
+
+#include <memory.h>
+#include <stdbool.h>
+#include "ethernet_frame.h"
+#include "etherlib/utils.h"
+
+#define ETH_ETHERTYPE_LENGTH_THRESHOLD (1500)
+#define ETH_ETHERNET_HEADER_SIZE (14)
+
+int parse_ethernet(const uint8_t *hdr, uint32_t size, PcktProps * props) {
+    EthernetProps * frameProps = (EthernetProps *)props;
+    COPY_ADVANCE(frameProps->destAddr, hdr, ETH_HW_ADDR_LEN); // copy destination address
+    COPY_ADVANCE(frameProps->sourceAddr, hdr, ETH_HW_ADDR_LEN); // copy destination address
+    COPY_WORD_H2N_ADVANCE(&frameProps->length_type, hdr); // copy length/type field
+
+    // fill-in packet property header fields
+    frameProps->validityOK = true;
+    frameProps->containedPacketClass =
+            frameProps->length_type <= ETH_ETHERTYPE_LENGTH_THRESHOLD ? 0 : frameProps->length_type;
+    frameProps->headerSize = ETH_ETHERNET_HEADER_SIZE;
+
+    return frameProps->containedPacketClass;
+}

prefab/packet_parsers/ethernet_frame.h

@@ -0,0 +1,33 @@
+//
+// Created by epagris on 2022.11.03..
+//
+
+#ifndef ETHERLIB_ETHERNET_FRAME_H
+#define ETHERLIB_ETHERNET_FRAME_H
+
+#include <stdint.h>
+#include "etherlib/packet_registry.h"
+
+#define ETH_HW_ADDR_LEN (6)
+
+/**
+ * @struct EthernetProps
+ * Ethernet frame properties
+ */
+typedef struct {
+    PcktPropsHeader
+    uint8_t destAddr[ETH_HW_ADDR_LEN]; ///< destination address
+    uint8_t sourceAddr[ETH_HW_ADDR_LEN]; ///< source address
+    uint16_t length_type; /// < frame length_type
+} EthernetProps;
+
+/**
+ * Parse raw Ethernet frames.
+ * @param hdr pointer to the Ethernet packet header
+ * @param size total frame size
+ * @param props pointer to property storage
+ * @return EtherType or 0 (if size is less than 1500) on success or -1 on error
+ */
+int parse_ethernet(const uint8_t *hdr, uint32_t size, PcktProps * props);
+
+#endif //ETHERLIB_ETHERNET_FRAME_H

prefab/packet_parsers/ipv4_packet.c

@@ -0,0 +1,69 @@
+//
+// Created by epagris on 2022.11.03..
+//
+
+#include <stdbool.h>
+#include "ipv4_packet.h"
+#include "etherlib/utils.h"
+
+static uint16_t ip_checksum(const IPv4Props * ipProps) {
+    // sum fields
+    uint32_t sum = 0;
+    const uint16_t * pField = (const uint16_t *) &ipProps;
+    for (uint8_t i = 0; i < ipProps->IHL * 2; i++) {
+        if (i != 5) { // 6. 16-bit long field is the checksum itself, do not count int
+            sum += pField[i];
+        }
+    }
+
+    // 16-31 bit carry
+    uint16_t carry = sum >> 16;
+
+    // add carry
+    sum += carry;
+
+    // if a new carry bit arisen, then
+    // add to the sum
+    sum = (sum & 0xFFFF) + (sum >> 16);
+
+    // invert result
+    uint16_t sum16 = sum ^ 0xFFFF;
+    return sum16;
+}
+
+#define ETH_IP_HEADER_LENGTH (20)
+
+static bool check_ipv4_validity(const IPv4Props * ipProps) {
+    bool valid =
+            ipProps->Version != 4 &&
+            ipProps->IHL == ETH_IP_HEADER_LENGTH &&
+            ipProps->HeaderChecksum == ip_checksum(ipProps);
+    return valid;
+}
+
+int parse_ipv4(const uint8_t *hdr, uint32_t size, PcktProps * props) {
+    IPv4Props * ipProps = (IPv4Props *)props;
+    uint8_t version_length;
+    COPY_ADVANCE(&version_length, hdr, 1);
+    ipProps->Version = (version_length) >> 4;
+    ipProps->IHL = (version_length) & 0x0F;
+    COPY_ADVANCE(&ipProps->DSF, hdr, 1);
+    COPY_WORD_H2N_ADVANCE(&ipProps->TotalLength, hdr);
+    COPY_WORD_H2N_ADVANCE(&ipProps->Identification, hdr);
+    uint16_t flags_fragOffset;
+    COPY_WORD_H2N_ADVANCE(&flags_fragOffset, hdr);
+    ipProps->Flags = (flags_fragOffset >> 13) & 0x07;
+    ipProps->FragmentOffset = (flags_fragOffset & ~(0x07 << 13));
+    COPY_ADVANCE(&ipProps->TTL, hdr, 1);
+    COPY_ADVANCE(&ipProps->Protocol, hdr, 1);
+    COPY_WORD_H2N_ADVANCE(&ipProps->HeaderChecksum, hdr);
+    COPY_DWORD_H2N_ADVANCE(&ipProps->SourceIPAddr, hdr);
+    COPY_DWORD_H2N_ADVANCE(&ipProps->DestIPAddr, hdr);
+
+    // fill-in common packet header fields
+    ipProps->validityOK = check_ipv4_validity(ipProps);
+    ipProps->containedPacketClass = ipProps->Protocol;
+    ipProps->headerSize = ETH_IP_HEADER_LENGTH;
+
+    return ipProps->validityOK ? ipProps->Protocol : -1;
+}

prefab/packet_parsers/ipv4_packet.h

@@ -0,0 +1,43 @@
+#ifndef ETHERLIB_IPV4_PACKET_H
+#define ETHERLIB_IPV4_PACKET_H
+
+#include <stdint.h>
+#include "etherlib/packet_registry.h"
+
+#define ETH_IPv4_PACKET_CLASS (0x0800)
+
+// IPv4 fejlécet leíró struktúra
+typedef struct {
+    PcktPropsHeader
+
+    // 1. 32-bit
+    uint8_t IHL; ///< header size
+    uint8_t Version; ///< version (always 4)
+    uint8_t DSF; ///< service type
+    uint16_t TotalLength; ///< total packet length
+
+    // 2. 32-bit
+    uint16_t Identification; ///< identification
+    uint8_t Flags; ///< packet flags
+    uint16_t FragmentOffset; ///< packet fragmentation offset
+
+    // 3. 32-bit
+    uint8_t TTL; // Time-To-Live
+    uint8_t Protocol; ///< Protocol
+    uint16_t HeaderChecksum; ///< header IP-checksum
+
+    // 4. 32-bit
+    uint32_t SourceIPAddr; ///< source IP-address
+    uint32_t DestIPAddr; ///< destination IP-address
+} IPv4Props;
+
+/**
+ * Parse raw IPv4 packets.
+ * @param hdr pointer to the IPv4 packet header
+ * @param size total packet size
+ * @param props pointer to property storage
+ * @return Protocol on success or -1 on failure
+ */
+int parse_ipv4(const uint8_t *hdr, uint32_t size, PcktProps * props);
+
+#endif //ETHERLIB_IPV4_PACKET_H

prefab/packet_parsers/packet_parsers.c

@@ -0,0 +1 @@
+#include "packet_parsers.h"

prefab/packet_parsers/packet_parsers.h

@@ -0,0 +1,8 @@
+#ifndef ETHERLIB_PACKET_PARSERS_H
+#define ETHERLIB_PACKET_PARSERS_H
+
+#include "ethernet_frame.h"
+#include "ipv4_packet.h"
+#include "udp_packet.h"
+
+#endif //ETHERLIB_PACKET_PARSERS_H

prefab/packet_parsers/udp_packet.c

@@ -0,0 +1,20 @@
+#include <stdbool.h>
+#include "udp_packet.h"
+#include "etherlib/utils.h"
+
+#define ETH_UDP_HEADER_SIZE (8)
+
+int parse_udp(const uint8_t *hdr, uint32_t size, PcktProps * props) {
+    UDPProps * udpProps = (UDPProps *)props;
+    COPY_WORD_H2N_ADVANCE(&udpProps->SourcePort, hdr);
+    COPY_WORD_H2N_ADVANCE(&udpProps->DestinationPort, hdr);
+    COPY_WORD_H2N_ADVANCE(&udpProps->Length, hdr);
+    COPY_WORD_H2N_ADVANCE(&udpProps->Checksum, hdr);
+
+    // common fields...
+    udpProps->headerSize = ETH_UDP_HEADER_SIZE;
+    udpProps->validityOK = size == udpProps->Length; // TODO UDP checksum validation!
+    udpProps->containedPacketClass = 0;
+
+    return udpProps->validityOK ? 0 : -1;
+}

prefab/packet_parsers/udp_packet.h

@@ -0,0 +1,31 @@
+#ifndef ETHERLIB_UDP_PACKET_H
+#define ETHERLIB_UDP_PACKET_H
+
+#include <stdint.h>
+#include "etherlib/packet_registry.h"
+
+#define ETH_UDP_PACKET_CLASS (17)
+
+/**
+ * @struct UDPProps
+ * UDP packet properties.
+ */
+typedef struct {
+    PcktPropsHeader
+
+    uint16_t SourcePort; ///> source port
+    uint16_t DestinationPort; ///> destination port
+    uint16_t Length; ///> packet size
+    uint16_t Checksum; ///> UDP checksum
+} UDPProps;
+
+/**
+ * Parse raw UDP packets.
+ * @param hdr pointer to the UDP packet header
+ * @param size total packet size
+ * @param props pointer to property storage
+ * @return 0 on success or -1 on failure
+ */
+int parse_udp(const uint8_t *hdr, uint32_t size, PcktProps * props);
+
+#endif //ETHERLIB_UDP_PACKET_H

prefab/prefab.h

@@ -0,0 +1,6 @@
+#ifndef ETHERLIB_PREFAB_H
+#define ETHERLIB_PREFAB_H
+
+#include "packet_parsers/packet_parsers.h"
+
+#endif //ETHERLIB_PREFAB_H

utils.c

@@ -3,3 +3,59 @@
 //
 
 #include "utils.h"
+
+static uint32_t crc32table[] = { /* CRC polynomial */
+        0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f,
+        0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988,
+        0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91, 0x1db71064, 0x6ab020f2,
+        0xf3b97148, 0x84be41de, 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
+        0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
+        0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172,
+        0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b, 0x35b5a8fa, 0x42b2986c,
+        0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
+        0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423,
+        0xcfba9599, 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
+        0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190, 0x01db7106,
+        0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433,
+        0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d,
+        0x91646c97, 0xe6635c01, 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e,
+        0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
+        0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,
+        0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, 0x4adfa541, 0x3dd895d7,
+        0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0,
+        0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa,
+        0xbe0b1010, 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
+        0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81,
+        0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a,
+        0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683, 0xe3630b12, 0x94643b84,
+        0x0d6d6a3e, 0x7a6a5aa8, 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1,
+        0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
+        0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc,
+        0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5, 0xd6d6a3e8, 0xa1d1937e,
+        0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
+        0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55,
+        0x316e8eef, 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
+        0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe, 0xb2bd0b28,
+        0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,
+        0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a, 0x9c0906a9, 0xeb0e363f,
+        0x72076785, 0x05005713, 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38,
+        0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
+        0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
+        0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff, 0xf862ae69,
+        0x616bffd3, 0x166ccf45, 0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2,
+        0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc,
+        0x40df0b66, 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
+        0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605, 0xcdd70693,
+        0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94,
+        0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d
+};
+
+uint32_t crc32(const uint8_t * data, uint32_t size) {
+    uint32_t checksum = ~0;
+    uint32_t i;
+    for (i = 0; i < size; i++) {
+        checksum = (checksum >> 8) ^ crc32table[checksum ^ data[i]];
+    }
+    checksum = ~checksum;
+    return checksum;
+}

utils.h

@@ -6,6 +6,30 @@
 #define ETHERLIB_UTILS_H
 
 #include <stdio.h>
+#include <stdint.h>
+#include <memory.h>
+
+#ifndef htonl
+#define htonl(a)                    \
+        ((((a) >> 24) & 0x000000ff) |   \
+         (((a) >>  8) & 0x0000ff00) |   \
+         (((a) <<  8) & 0x00ff0000) |   \
+         (((a) << 24) & 0xff000000))
+#endif
+
+#ifndef ntohl
+#define ntohl(a)    htonl((a))
+#endif
+
+#ifndef htons
+#define htons(a)                \
+        ((((a) >> 8) & 0x00ff) |    \
+         (((a) << 8) & 0xff00))
+#endif
+
+#ifndef ntohs
+#define ntohs(a)    htons((a))
+#endif
 
 #define ERROR(...) printf(__VA_ARGS__)
 #define INFO(...) printf(__VA_ARGS__)
@@ -15,4 +39,18 @@
 
 #define ALIGN(p,t) (((size_t)(p) + (sizeof(t) - 1)) & ~(sizeof(t) - 1))
 
+#define COPY_ADVANCE(dst,src,n) memcpy((dst), (src), n), src += n
+#define COPY_WORD_H2N_ADVANCE(dst,w) { uint16_t u; memcpy(&u, w, 2); u = htons(u); memcpy((dst), &u, 2); w += 2; }
+#define COPY_DWORD_H2N_ADVANCE(dst,dw) { uint32_t du; memcpy(&du, dw, 4); du = htonl(du); memcpy((dst), &du, 4); dw += 4; }
+
+// ------------------
+
+/**
+ * Compute CRC-32 checksum.
+ * @param data Data from which the checksum is being calculated.
+ * @param size Size of data byte array.
+ * @return checksum
+ */
+uint32_t crc32(const uint8_t * data, uint32_t size);
+
 #endif //ETHERLIB_UTILS_H