diff --git a/arp_cache.c b/arp_cache.c
new file mode 100644
index 0000000..a32a89d
--- /dev/null
+++ b/arp_cache.c
@@ -0,0 +1,42 @@
+//
+// Created by epagris on 2022.12.10..
+//
+
+#include <memory.h>
+#include "arp_cache.h"
+#include "dynmem.h"
+
+ArpCache *arpc_new(uint16_t size) {
+    ArpCache * arcp = (ArpCache *) dynmem_alloc(2 * sizeof(uint16_t) + size * sizeof(ArpEntry));
+    arcp->size = size;
+    arcp->fill = 0;
+    return arcp;
+}
+
+void arpc_free(ArpCache *aprc) {
+    dynmem_free(aprc);
+}
+
+void arpc_learn(ArpCache *arpc, const ArpEntry *newEntry) {
+    // TODO: nagyon dummy...
+    for (uint16_t i = 0; i < arpc->fill; i++) {
+        ArpEntry * entry = arpc->entries + i;
+        if (!memcmp(entry->eth, newEntry->eth, ETH_HW_ADDR_LEN) && (entry->ip == newEntry->ip)) {
+            return;
+        }
+    }
+
+    // if not found...
+    arpc->entries[arpc->fill++] = *newEntry;
+}
+
+const ArpEntry *arpc_get(ArpCache *arpc, ip4_addr ip) {
+    for (uint16_t i = 0; i < arpc->fill; i++) {
+        ArpEntry * entry = arpc->entries + i;
+        if (entry->ip == ip) {
+            return entry;
+        }
+    }
+
+    return NULL;
+}
diff --git a/arp_cache.h b/arp_cache.h
new file mode 100644
index 0000000..d1fc6ea
--- /dev/null
+++ b/arp_cache.h
@@ -0,0 +1,51 @@
+#ifndef ETHERLIB_TEST_ARP_CACHE_H
+#define ETHERLIB_TEST_ARP_CACHE_H
+
+#include "prefab/packet_parsers/ethernet_frame.h"
+#include "prefab/packet_parsers/ipv4_types.h"
+
+/**
+ * ARP cache entry record.
+ */
+typedef struct {
+    EthernetAddress eth; ///< Ethernet address
+    ip4_addr ip; ///< IPv4 address
+} ArpEntry;
+
+/**
+ * ARP cache class.
+ */
+typedef struct {
+    uint16_t size; ///< Number of cache entries
+    uint16_t fill; ///< Fill level
+    ArpEntry entries[]; ///< Cache entries
+} ArpCache;
+
+/**
+ * Create new ARP cache table.
+ * @param size Number of available entries
+ * @return Pointer to newly allocated ARP cache
+ */
+ArpCache * arpc_new(uint16_t size);
+
+/**
+ * Learn new assignment.
+ * @param arpc Pointer to ARP cache
+ * @param newEntry Pointer to map newEntry
+ */
+void arpc_learn(ArpCache * arpc, const ArpEntry * newEntry);
+
+/**
+ * Get entry by IP-address.
+ * @param ip IP address
+ * @return Pointer to matching entry OR NULL if not found
+ */
+const ArpEntry *arpc_get(ArpCache *arpc, ip4_addr ip);
+
+/**
+ * Free ARP cache.
+ * @param aprc Pointer to existing ARP cache.
+ */
+void arpc_free(ArpCache * aprc);
+
+#endif //ETHERLIB_TEST_ARP_CACHE_H
diff --git a/connection_block.h b/connection_block.h
index 65c2200..94a1d82 100644
--- a/connection_block.h
+++ b/connection_block.h
@@ -8,6 +8,9 @@ struct ConnBlock_;
 
 typedef int (*ConnBlockTransmitFn)(EthInterface * intf, const uint8_t * data, uint32_t size, const struct ConnBlock_ * connBlock);
 
+/**
+ * Connection block.
+ */
 typedef struct ConnBlock_ {
     EthInterface * intf; ///< Ethernet interface
     PcktSieveLayer * sieveLayer; ///< Sieve layer
diff --git a/docs/.$PacketSieve.bkp b/docs/.$PacketSieve.bkp
new file mode 100644
index 0000000..1a485c6
--- /dev/null
+++ b/docs/.$PacketSieve.bkp
@@ -0,0 +1 @@
+<mxfile host="Electron" modified="2022-12-09T10:36:11.906Z" agent="5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) draw.io/20.3.0 Chrome/104.0.5112.114 Electron/20.1.3 Safari/537.36" etag="y_61wgbl8uiCwZsw6xJH" version="20.3.0" type="device"><diagram id="apy941U9fxJ8yi3WkWR-" name="PacketSieve">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</diagram></mxfile>
\ No newline at end of file
diff --git a/docs/PacketSieve b/docs/PacketSieve
new file mode 100644
index 0000000..12dca50
--- /dev/null
+++ b/docs/PacketSieve
@@ -0,0 +1 @@
+<mxfile host="Electron" modified="2022-12-09T11:34:28.143Z" agent="5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) draw.io/20.3.0 Chrome/104.0.5112.114 Electron/20.1.3 Safari/537.36" etag="ODecaFkfpWYIbJyWGB1x" version="20.3.0" type="device"><diagram id="apy941U9fxJ8yi3WkWR-" name="PacketSieve">7Vpbk6I6EP41Po5FEoj4OOM4e6nZ3TnHmr08bSEEYReIFePt/PoTJAxiMsooous6U2XRTW701193h9BCvXjxjjnj4BP1SNSChrdoofsWhF0biN9UscwUGONMMWKhl6lAoRiE/xGpNKR2GnpkUmrIKY14OC4rXZokxOUlncMYnZeb+TQqzzp2RkRRDFwnUrXfQo8Hmda2jEL/noSjIJ8ZGPJO7OSNpWISOB6dr6lQv4V6jFKeXcWLHolS2+V2yfo9vHL3ZWGMJLxKhy83/3Zp3EePH+mtO/j67HbZ4AbIYWZONJVPLFfLl7kJiCcsIkXKeEBHNHGifqG9c6dsRtJpgBAYnSbeSjKEVHR4pHQsm/winC8l1s6UU6EKeBzJuz5N+IMTh1HqMj06ZSFhYkWfyVzelD1tIapGkA80Ef1csu3JpTM5bET4lnbSXVMjrE0gTfyO0JhwthQNGIkcHs7KbuNI7xu9tCsAEhcSo7fgpcDV5wFhiXiETdjmQcjJYOysrDAX5HyLlcMo6tGIstVQyHOI7btCP+GM/iZrd7Brk6G/DYgZYZwstppO3oU5qWSoECzL5HlBvI5sEqxxDhmHG3vy6+vnj48+NR65gfv//ERd8/kGwPMjh9Yb92OAqTJAb4aTerypYPDhaWYe1dstYnumztttOEQif9Xi7Sbe8Pbc+3d4O6zB2/WhRTVq084trMmW32X/lfAjFdpWLt4v1m/eL6X0loxBFiH/ns8nrrMZoCXFYoZUyCfYn2S4YpoxT5Vm9JTfwxUOR1+LTGc7Mvu6TMlxawyqVfEG1imDKlaCKujCNsB2G7TTyhtHYu13Q0EiPEqvRLhqG+Jf9QsR7XgZxnLUTGhCNkKsVDlROEqEyLLYdpeGzlAU3rdSH4eet3IsXWgvO9tb+M8oFwamyS5mV4/kSKlbcNu2qwVznEae42DcPb/ipZnKvlOVgmdV2XcUuB7CiBMm7A2NYboOOk/Eb1HvG59uezeO5zEymaQrStKW8TRKWTRR9wOHM9UVUAjA/mCqgk2qdjrtapsMswaaalPtGdK0xnQIrIqbDHxK7uWrvPhNBoKwor/Xsc3QAq3uqZ/vn45pad/3oat9eeHhIbYKSytm1Rj/VUtjcHaWRjuKvNrzQ0T8UxdyB2GobMnNaltycCwE1XcfxyzELw0+BKpS8GgA5gP/+dn99aRdIbnDhpL7tkWuQYBA50ofhT6WUivoamPYKH3UAHhJ9MkP33a/gUenJJDmjNA0jGsBsZtC0FIJhBolkFoDXmS13eThid7Q6g7yypFq0GmK7GY5ci0Q9tziauvrZgsE9a2pWiAk3m36IVABiOdMgpeCYA3QsrH3OiFSjbdmGktjmlxXOZXLGZ5omPACG2i/EhDzIbJiRPYqrL5zIIA3BsqKFWWgFXwvj30AovYV0Sx9dM12BxjFn1kGePOrl6oAm13rtABXeeH9NwCMzTLAqB58sXlafPP4rxxkteQx1oendDH5sVXtWbaOQ6oakiXahMFWyxxb41xH+5gNqru4Mi5jsRm+XDws1BgeQiy+6s1oVXwajfr/Aw==</diagram></mxfile>
\ No newline at end of file
diff --git a/eth_interface.c b/eth_interface.c
index a244b6b..3693dcf 100644
--- a/eth_interface.c
+++ b/eth_interface.c
@@ -5,6 +5,7 @@
 #include "eth_interface.h"
 #include "dynmem.h"
 #include "utils.h"
+#include "etherlib_options.h"
 
 static int ethintf_llrecv(EthIODef * io, const RawPckt * pckt) {
     ethinf_receive((EthInterface *) io->tag, pckt);
@@ -21,14 +22,17 @@ EthInterface *ethintf_new(EthIODef * io) {
     ASSERT_NULL(ethIntf);
     memset(&ethIntf->sieve.layer0, 0, sizeof(PcktSieveLayer));
     ethIntf->ioDef = io;
+    ethIntf->ip = 0;
+    ethIntf->arpc = arpc_new(ETHLIB_ARPCACHE_SIZE);
+    ASSERT_NULL(ethIntf->arpc);
     ethintf_register(ethIntf);
     return ethIntf;
 }
 
 void ethinf_receive(EthInterface *intf, const RawPckt *rawPckt) {
-    packsieve_input(&intf->sieve, rawPckt);
+    packsieve_input(&intf->sieve, rawPckt, intf);
 }
 
 void ethinf_transmit(EthInterface *intf, const RawPckt *rawPckt) {
-    intf->ioDef->llTx(&(intf->ioDef), rawPckt);
+    intf->ioDef->llTx(intf->ioDef, rawPckt);
 }
diff --git a/eth_interface.h b/eth_interface.h
index fcbe18f..2b66c0f 100644
--- a/eth_interface.h
+++ b/eth_interface.h
@@ -3,7 +3,12 @@
 
 #include "packet_sieve.h"
 #include "prefab/packet_parsers/packet_parsers.h"
+#include "prefab/packet_parsers/ipv4_types.h"
+#include "arp_cache.h"
 
+/**
+ * Ethernet interface low level definition.
+ */
 typedef struct EthIODef_ {
     int (*llTx)(struct EthIODef_ * io, const RawPckt * rawPckt); ///< Function pointer to low-level transmit function
     int (*llTxDone)(struct EthIODef_ * io, const RawPckt * rawPckt); ///< Transmission done (interrupt) callback
@@ -14,10 +19,15 @@ typedef struct EthIODef_ {
 
 } EthIODef;
 
+/**
+ * Ethernet interface representation.
+ */
 typedef struct EthInterface_ {
     PcktSieve sieve; ///< Packet sieve
     EthIODef * ioDef; ///< Low-level IO definitions
     EthernetAddress mac; ///< Ethernet address
+    ip4_addr ip; ///< IP address
+    ArpCache * arpc; ///< ARP cache
 } EthInterface;
 
 /**
diff --git a/packet_registry.c b/packet_registry.c
index 3facbe5..4cc884b 100644
--- a/packet_registry.c
+++ b/packet_registry.c
@@ -3,6 +3,8 @@
 #include "dynmem.h"
 #include "utils.h"
 
+#include "packet_sieve.h"
+
 #include <stddef.h>
 #include <memory.h>
 
diff --git a/packet_registry.h b/packet_registry.h
index 7a0bed8..2d0cb2a 100644
--- a/packet_registry.h
+++ b/packet_registry.h
@@ -14,7 +14,7 @@ typedef uint8_t bool8_t;
  *
  * Every packet property structure must extend this base structure,
  * so that, must begin with fields defined here. PcktProps is guaranteed
- * to be aligned to 32-bit boundary and so must be guaranteed by extending
+ * to be aligned to 32-bit boundary and so must be kept so by extending
  * as well. (The size of the packet is divisible by 4.)
  */
 
@@ -33,6 +33,9 @@ typedef struct {
     PcktPropsHeader
 } PcktProps;
 
+struct EthInterface_;
+struct PcktHeaderElement_;
+
 /**
  * @typedef int (*PcktProcFn)(const uint8_t *pHdr, uint32_t size, uint8_t *pPcktProps);
  * @brief Pckt processing function template.
@@ -40,11 +43,12 @@ typedef struct {
  * @param size: remaining packet size counted from pHdr
  * @param props: pointer to existing structure to store
  *      packet properties to (e.g. source address, port etc.)
+ * @param intf associeated Ethernet interface
  * @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 *hdr, uint32_t size, PcktProps *props);
+typedef int (*PcktProcFn)(const uint8_t *hdr, uint32_t size, struct PcktHeaderElement_ * pcktHdrLe, struct EthInterface_ * intf);
 
 /**
  * @struct PcktClassDesc
diff --git a/packet_sieve.c b/packet_sieve.c
index 6743eca..d0249f2 100644
--- a/packet_sieve.c
+++ b/packet_sieve.c
@@ -23,7 +23,7 @@ PcktSieve *packsieve_new() {
     return sieve;
 }
 
-void packsieve_input(const PcktSieve *sieve, const RawPckt * rawPckt) {
+void packsieve_input(const PcktSieve *sieve, const RawPckt *rawPckt, struct EthInterface_ *intf) {
     // extract fields
     uint8_t * data = rawPckt->payload;
     uint32_t size = rawPckt->size;
@@ -53,7 +53,7 @@ void packsieve_input(const PcktSieve *sieve, const RawPckt * rawPckt) {
         }
 
         // call parsing function
-        cdesc->procFun(data + offset, size - offset, &header->props);
+        cdesc->procFun(data + offset, size - offset, header, intf);
         uint16_t containedClass = header->props.containedPacketClass;
         if (containedClass != 0) {
             containerClass = ownClass;
@@ -80,7 +80,7 @@ void packsieve_input(const PcktSieve *sieve, const RawPckt * rawPckt) {
         const PcktSieveLayer * nodeIter = layer->nodes;
         found = false;
         while (nodeIter && !found) {
-            found |= nodeIter->filtFn(&nodeIter->filtCond, &headerIter->props, &headerIter->next->props);
+            found |= nodeIter->matchAny || nodeIter->filtFn(&nodeIter->filtCond, &headerIter->props, &headerIter->next->props); // specific or general match
             if (found) {
                 layer = nodeIter; // advance in the sieve tree
                 const PcktHeaderElement * containedHeader = headerIter->next; // advance on headers
@@ -108,12 +108,12 @@ void packsieve_input(const PcktSieve *sieve, const RawPckt * rawPckt) {
     return;
 }
 
-PcktSieveLayer *packsieve_new_layer(PcktSieveLayer *parent, const PcktSieveFilterCondition *filtCond, SieveFilterFn filtFn, SieveCallBackFn cbFn, PcktSieveLayerTag tag, uint16_t pcktClass) {
+PcktSieveLayer *packsieve_new_layer(PcktSieveLayer *parent, const PcktSieveFilterCondition *filtCond, bool matchAny, SieveFilterFn filtFn, SieveCallBackFn cbFn, PcktSieveLayerTag tag, uint16_t pcktClass) {
     // search for matching layer
     PcktSieveLayer * nodeIter = parent->nodes;
     bool alreadyExists = false;
     while (nodeIter != NULL && !alreadyExists) {
-        if (packfiltcond_cmp(&nodeIter->filtCond, filtCond) && (nodeIter->filtFn == filtFn)) { // if matching...
+        if ((packfiltcond_cmp(&nodeIter->filtCond, filtCond) || (nodeIter->matchAny && matchAny)) && (nodeIter->filtFn == filtFn)) { // if matching... [search for specific match OR any match]
             alreadyExists = true;
         } else {
             nodeIter = nodeIter->next;
@@ -128,19 +128,33 @@ PcktSieveLayer *packsieve_new_layer(PcktSieveLayer *parent, const PcktSieveFilte
         ASSERT_NULL(layer);
 
         PcktSieveLayer *oldListFirst = parent->nodes;
-        parent->nodes = layer; // replace first element (it's the fastest way of new element insertion, since element position does not carry any meaning this case)
         layer->packetClass = pcktClass;
         layer->parent = parent;
-        layer->prev = NULL;
-        layer->next = oldListFirst;
-        if (oldListFirst != NULL) {
-            layer->prev = layer;
+
+        if (!matchAny || (oldListFirst == NULL)) { // for specific match or on first node insertion...
+            layer->prev = NULL;
+            parent->nodes = layer; // ...replace first element (it's the fastest way of new element insertion, since element position does not carry any meaning in general case)
+            layer->next = oldListFirst;
+            if (oldListFirst != NULL) {
+                layer->prev = layer;
+            }
+        } else { // for 'any' match if at least a single node is already present
+            PcktSieveLayer * iter = parent->nodes;
+            while (iter->next != NULL) { // find the last node
+                iter = iter->next;
+            }
+            iter->next = layer;
+            layer->prev = iter;
+            layer->next = NULL;
         }
+
         layer->nodes = NULL;
         layer->filtCond = *filtCond;
+        layer->matchAny = matchAny;
         layer->filtFn = filtFn;
         layer->cbFn = cbFn;
         layer->tag = tag;
+        layer->infoTag[0] = '\0';
         return layer;
     }
 }
@@ -181,7 +195,11 @@ bool packsieve_remove_layer(PcktSieveLayer * layer) {
 #define ETH_SIEVE_LAYER_INDENT_PER_LEVEL (4)
 
 void packsieve_report(const PcktSieveLayer *layer, uint32_t indent) {
-    INFO("%*c\\--|%d|---\n", indent, ' ', layer->packetClass);
+    if (*layer->infoTag != '\0') {
+        INFO("%*c\\--|%s|---\n", indent, ' ', layer->infoTag);
+    } else {
+        INFO("%*c\\--|%d|---\n", indent, ' ', layer->packetClass);
+    }
     const PcktSieveLayer * nodeIter = layer->nodes;
     while(nodeIter) {
         packsieve_report(nodeIter, indent + ETH_SIEVE_LAYER_INDENT_PER_LEVEL);
diff --git a/packet_sieve.h b/packet_sieve.h
index f2565d7..c359bef 100644
--- a/packet_sieve.h
+++ b/packet_sieve.h
@@ -6,6 +6,9 @@
 #include "packet_registry.h"
 #include "packet.h"
 
+/**
+ * Packet header information.
+ */
 typedef struct PcktHeaderElement_ {
     struct PcktHeaderElement_ * next, * prev; ///< Next and previous header in the linked list
     PcktProps props; ///< Properties (allocated to appropriate size)
@@ -41,10 +44,16 @@ bool packfiltcond_cmp(const PcktSieveFilterCondition * c1, const PcktSieveFilter
  */
 void packfiltcond_zero(PcktSieveFilterCondition * cond);
 
+/**
+ * Sieve filter function type.
+ */
 typedef bool (*SieveFilterFn)(const PcktSieveFilterCondition * filtCond, const PcktProps * contProps, const PcktProps * ownProps);
 
 struct PcktSieveLayer_;
 
+/**
+ * Callback function type for packet sieve match.
+ */
 typedef int (*SieveCallBackFn)(const Pckt * pckt);
 
 typedef union {
@@ -52,17 +61,29 @@ typedef union {
     uint32_t u;
 } PcktSieveLayerTag;
 
+#define PCKT_SIEVE_INFOTAG_LEN (24)
+
+/**
+ * Packet sieve layer structure.
+ */
 typedef struct PcktSieveLayer_ {
     uint16_t packetClass; ///< Packet class (e.g. IP)
     PcktSieveFilterCondition filtCond; ///< Filter condition, arbitrary type (e.g. destination IP-address)
+    bool matchAny; ///< Match any packet, don't test against filter condition
     SieveFilterFn filtFn; ///< Filter function pointer
     SieveCallBackFn cbFn; ///< Associated callback function
     PcktSieveLayerTag tag; ///< Layer tag (arbitrary information)
     struct PcktSieveLayer_ * parent; ///< Pointer to parent node in the sieve tree
     struct PcktSieveLayer_ * next, * prev; ///< Next and previous sieve layer on the same level
-    struct PcktSieveLayer_ * nodes; ///< Subnodes on the sieve tree
+    struct PcktSieveLayer_ * nodes; ///< Subnodes in the sieve tree
+    char infoTag[PCKT_SIEVE_INFOTAG_LEN]; ///< Info tag length
 } PcktSieveLayer;
 
+struct EthInterface_;
+
+/**
+ * Packet sieve class.
+ */
 typedef struct {
     PcktSieveLayer layer0; ///< Top of sieve tree
 } PcktSieve;
@@ -79,14 +100,14 @@ PcktSieve * packsieve_new();
  * @param data
  * @param size
  */
-void packsieve_input(const PcktSieve * sieve, const RawPckt * rawPckt);
+void packsieve_input(const PcktSieve *sieve, const RawPckt *rawPckt, struct EthInterface_ *intf);
 
 /**
  * Create a new sieve filter layer.
  * @param parent parent layer
  * @return pointer to new layer object or NULL on failure
  */
-PcktSieveLayer *packsieve_new_layer(PcktSieveLayer *parent, const PcktSieveFilterCondition *filtCond, SieveFilterFn filtFn, SieveCallBackFn cbFn, PcktSieveLayerTag tag, uint16_t pcktClass);
+PcktSieveLayer *packsieve_new_layer(PcktSieveLayer *parent, const PcktSieveFilterCondition *filtCond, bool matchAny, SieveFilterFn filtFn, SieveCallBackFn cbFn, PcktSieveLayerTag tag, uint16_t pcktClass);
 
 /**
  * Remove sieve layer from packet sieve.
diff --git a/prefab/conn_blocks/ipv4_connblock.c b/prefab/conn_blocks/ipv4_connblock.c
index 2a2263e..bd3895c 100644
--- a/prefab/conn_blocks/ipv4_connblock.c
+++ b/prefab/conn_blocks/ipv4_connblock.c
@@ -11,17 +11,28 @@ static bool filtIPv4(const PcktSieveFilterCondition * filtCond, const PcktProps
     EthernetProps * etherProps = (EthernetProps *) contProps;
     IPv4Props * ipProps = (IPv4Props *) ownProps;
 
-    return etherProps->length_type == ETH_IPv4_PACKET_CLASS && filtCond->u[0] == ipProps->DestIPAddr;
+    return etherProps->length_type == ETH_IPv4_PACKET_CLASS && IP_ADDR_FROM_FILTCOND(filtCond) == ipProps->DestIPAddr;
 }
 
 ConnBlock ipv4_new_connblock(EthInterface *intf, ip4_addr ipAddr, SieveCallBackFn cbFn) {
     ConnBlock connb;
     PcktSieveFilterCondition filtCond;
     packfiltcond_zero(&filtCond);
-    filtCond.u[0] = ipAddr;
+    IP_ADDR_TO_FILTCOND(&filtCond, ipAddr);
     PcktSieveLayerTag tag;
     tag.u = 0;
-    connb.sieveLayer = packsieve_new_layer(&intf->sieve.layer0, &filtCond, filtIPv4, cbFn, tag, ETH_IPv4_PACKET_CLASS);
+    bool matchAny = ipAddr == IPv4_ANY_ADDR;
+    connb.sieveLayer = packsieve_new_layer(&intf->sieve.layer0, &filtCond, matchAny, filtIPv4, cbFn, tag, ETH_IPv4_PACKET_CLASS);
     ASSERT_NULL(connb.sieveLayer);
+
+    connb.intf = intf;
+
+    if (!matchAny) {
+        SNPRINTF(connb.sieveLayer->infoTag, PCKT_SIEVE_INFOTAG_LEN, "IP: %u.%u.%u.%u",
+                 (ipAddr & 0xFF), ((ipAddr >> 8) & 0xFF), ((ipAddr >> 16) & 0xFF), ((ipAddr >> 24) & 0xFF));
+    } else {
+        SNPRINTF(connb.sieveLayer->infoTag, PCKT_SIEVE_INFOTAG_LEN, "IP: ANY");
+    }
+
     return connb;
 }
diff --git a/prefab/conn_blocks/ipv4_connblock.h b/prefab/conn_blocks/ipv4_connblock.h
index f69e039..9a670fa 100644
--- a/prefab/conn_blocks/ipv4_connblock.h
+++ b/prefab/conn_blocks/ipv4_connblock.h
@@ -4,8 +4,10 @@
 #include <stdint.h>
 #include "../../connection_block.h"
 #include "../../eth_interface.h"
+#include "../packet_parsers/ipv4_types.h"
 
-typedef uint32_t ip4_addr;
+#define IP_ADDR_FROM_FILTCOND(fc) ((fc)->u[0])
+#define IP_ADDR_TO_FILTCOND(fc,addr) (((fc)->u[0]) = (addr))
 
 /**
  * Create new IPv4 connection block.
diff --git a/prefab/conn_blocks/udp_connblock.c b/prefab/conn_blocks/udp_connblock.c
index 3781e4b..c14ccb3 100644
--- a/prefab/conn_blocks/udp_connblock.c
+++ b/prefab/conn_blocks/udp_connblock.c
@@ -14,7 +14,7 @@ static bool filtUdp(const PcktSieveFilterCondition * filtCond, const PcktProps *
     IPv4Props * ipProps = (IPv4Props *) contProps;
     UdpProps * udpProps = (UdpProps *) ownProps;
 
-    return ipProps->Protocol == ETH_UDP_PACKET_CLASS && filtCond->uw[0] == udpProps->DestinationPort;
+    return ipProps->Protocol == ETH_UDP_PACKET_CLASS && (UDP_PORT_FROM_FILTCOND(filtCond) == udpProps->DestinationPort);
 }
 
 ConnBlock udp_new_connblock(EthInterface * intf, ip4_addr ipAddr, uint16_t port, SieveCallBackFn cbFn) {
@@ -23,18 +23,22 @@ ConnBlock udp_new_connblock(EthInterface * intf, ip4_addr ipAddr, uint16_t port,
 
     PcktSieveFilterCondition filtCond;
     packfiltcond_zero(&filtCond);
-    filtCond.uw[0] = port;
+    UDP_PORT_TO_FILTCOND(&filtCond, port);
     PcktSieveLayerTag tag;
     tag.u = 0;
-    udpConnB.sieveLayer = packsieve_new_layer(ipConnB.sieveLayer, &filtCond, filtUdp, cbFn, tag, ETH_UDP_PACKET_CLASS);
+    udpConnB.sieveLayer = packsieve_new_layer(ipConnB.sieveLayer, &filtCond, false, filtUdp, cbFn, tag, ETH_UDP_PACKET_CLASS);
     ASSERT_NULL(udpConnB.sieveLayer);
+
+    udpConnB.intf = intf;
+
+    SNPRINTF(udpConnB.sieveLayer->infoTag, PCKT_SIEVE_INFOTAG_LEN, "UDP port: %d", port);
+
     return udpConnB;
 }
 
 #define ALLOC_HEADER_ELEMENT(T) (PcktHeaderElement *) dynmem_alloc(ETH_PCKT_HEADER_ELEMENT_HEAD_SIZE + sizeof(T))
-#define HEADER_FETCH_PROPS(T,h) (T *)(&h->props)
 
-int udp_send(const struct ConnBlock_ * connBlock, const uint8_t *data, uint32_t size) {
+int udp_sendto(const struct ConnBlock_ * connBlock, const uint8_t *data, uint32_t size, ip4_addr addr, uint16_t port) {
     // allocate headers
     PcktHeaderElement * udpHeader = ALLOC_HEADER_ELEMENT(UdpProps);
     PcktHeaderElement * ipHeader = ALLOC_HEADER_ELEMENT(IPv4Props);
@@ -46,12 +50,71 @@ int udp_send(const struct ConnBlock_ * connBlock, const uint8_t *data, uint32_t
     ethHeader->next = ipHeader;
     ethHeader->prev = NULL;
 
+    // prepare headers
     UdpProps * udpProps = HEADER_FETCH_PROPS(UdpProps, udpHeader);
     IPv4Props * ipProps = HEADER_FETCH_PROPS(IPv4Props, ipHeader);
     EthernetProps * ethProps = HEADER_FETCH_PROPS(EthernetProps, ethHeader);
 
-    udpProps->Length = size;
+    // fetch sieve layers and fill transmit headers
+    PcktSieveLayer * layer = connBlock->sieveLayer; // UDP layer
+    udpProps->SourcePort = UDP_PORT_FROM_FILTCOND(&layer->filtCond);
+    udpProps->DestinationPort = port;
+    udpProps->Length = ETH_UDP_HEADER_SIZE + size;
+    udpProps->Checksum = 0;
 
+    // IP
+    layer = layer->parent;
+    ipProps->IHL = ETH_IPv4_HEADER_SIZE / 4;
+    ipProps->Version = 4;
+    ipProps->DSF = 0x00;
+    ipProps->TotalLength = ETH_IPv4_HEADER_SIZE + ETH_UDP_HEADER_SIZE + size;
+    // Identification is filled on header insertion
+    ipProps->Flags = 0x00;
+    ipProps->FragmentOffset = 0x00;
+    ipProps->TTL = 255;
+    ipProps->Protocol = ETH_UDP_PACKET_CLASS;
+    // HeaderChecksum is calculated on header insertion
+    ipProps->SourceIPAddr = connBlock->intf->ip;
+    ipProps->DestIPAddr = addr;
+
+    // Ethernet
+    layer = layer->parent;
+    if (addr != 0xFFFFFFFF) {
+        memset(ethProps->destAddr, 0x00, ETH_HW_ADDR_LEN); // TODO...
+    } else {
+        memset(ethProps->destAddr, 0xFF, ETH_HW_ADDR_LEN);
+    }
+    memcpy(ethProps->sourceAddr, connBlock->intf->mac, ETH_HW_ADDR_LEN);
+    ethProps->length_type = ETH_IPv4_PACKET_CLASS;
+
+    // allocate transmit buffer
+    uint32_t txHeaderSize = ETH_ETHERNET_HEADER_SIZE + ETH_IPv4_HEADER_SIZE + ETH_UDP_HEADER_SIZE;
+    uint32_t txBufSize = txHeaderSize + size + 4;
+    uint8_t * txBuf = dynmem_alloc(txBufSize);
+
+    // copy payload
+    memcpy(txBuf + txHeaderSize, data, size);
+
+    // insert UDP header
+    insert_udp_header(txBuf + ETH_ETHERNET_HEADER_SIZE + ETH_IPv4_HEADER_SIZE, udpHeader);
+
+    // insert IPv4 header
+    insert_ipv4_header(txBuf + ETH_ETHERNET_HEADER_SIZE, ipHeader);
+
+    // insert Ethernet header
+    insert_ethernet_header(txBuf, ethHeader);
+
+    // append CRC at the end
+    uint32_t crc = crc32(txBuf, txBufSize - 4);
+    memcpy(txBuf + txBufSize - 4, &crc, 4);
+
+    // send packet
+    RawPckt rpckt;
+    rpckt.size = txBufSize;
+    rpckt.payload = txBuf;
+    rpckt.time_s = 0;
+    rpckt.time_ns = 0;
+    ethinf_transmit(connBlock->intf, &rpckt);
 
     return 0;
 }
diff --git a/prefab/conn_blocks/udp_connblock.h b/prefab/conn_blocks/udp_connblock.h
index a88d9b2..a6c627e 100644
--- a/prefab/conn_blocks/udp_connblock.h
+++ b/prefab/conn_blocks/udp_connblock.h
@@ -6,6 +6,9 @@
 #include "../../eth_interface.h"
 #include "ipv4_connblock.h"
 
+#define UDP_PORT_FROM_FILTCOND(fc) ((fc)->uw[0])
+#define UDP_PORT_TO_FILTCOND(fc,port) (((fc)->uw[0]) = (port))
+
 /**
  * Create new IPv4 connection block.
  * @param intf interface to the connection block will be associated
@@ -18,7 +21,12 @@ ConnBlock udp_new_connblock(EthInterface * intf, ip4_addr ipAddr, uint16_t port,
 
 /**
  * UDP transmit callback.
+ * @param connBlock UDP connection block
+ * @param data pointer to data buffer
+ * @param size data size
+ * @param addr remote address to send datagram to
+ * @param addr remote port
  */
-int udp_send(const struct ConnBlock_ * connBlock, const uint8_t * data, uint32_t size);
+int udp_sendto(const struct ConnBlock_ * connBlock, const uint8_t * data, uint32_t size, ip4_addr addr, uint16_t port);
 
 #endif //ETHERLIB_UDP_CONNBLOCK_H
diff --git a/prefab/packet_parsers/arp_packet.c b/prefab/packet_parsers/arp_packet.c
index 895a943..74873b9 100644
--- a/prefab/packet_parsers/arp_packet.c
+++ b/prefab/packet_parsers/arp_packet.c
@@ -3,18 +3,10 @@
 //
 
 #include "arp_packet.h"
+#include "../../packet_registry.h"
+#include "ethernet_frame.h"
+#include "../../utils.h"
 
 int parse_arp_packet(const uint8_t *hdr, uint32_t size, PcktProps * props) {
-    EthernetProps * frameProps = (EthernetProps *)props;
-    FETCH_ADVANCE(frameProps->destAddr, hdr, ETH_HW_ADDR_LEN); // copy destination address
-    FETCH_ADVANCE(frameProps->sourceAddr, hdr, ETH_HW_ADDR_LEN); // copy destination address
-    FETCH_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;
+    return 0;
 }
\ No newline at end of file
diff --git a/prefab/packet_parsers/dhcp.c b/prefab/packet_parsers/dhcp.c
new file mode 100644
index 0000000..d796667
--- /dev/null
+++ b/prefab/packet_parsers/dhcp.c
@@ -0,0 +1,113 @@
+//
+// Created by epagris on 2022.12.09..
+//
+
+#include <stdlib.h>
+#include "dhcp.h"
+#include "../../dynmem.h"
+#include "../../utils.h"
+#include "../../connection_block.h"
+#include "../conn_blocks/udp_connblock.h"
+
+static struct {
+   DhcpState state;
+   void * buf;
+   ConnBlock connb;
+   uint32_t tranId;
+} s;
+
+static const uint8_t DHCP_MAGIC_COOKIE[] = { 99, 130, 83, 99 };
+
+#define SNAME_LEN (64)
+#define FILE_LEN (128)
+
+// (Exact copy of the standard.)
+typedef enum {
+    DHCPDISCOVER = 1,
+    DHCPOFFER = 2,
+    DHCPREQUEST = 3,
+    DHCPDECLINE = 4,
+    DHCPACK = 5,
+    DHCPNAK = 6,
+    DHCPRELEASE = 7
+} DhcpMsgType;
+
+static void dhcp_option_insert_msg_type(uint8_t ** bufPtr, int msgType) {
+    (*bufPtr)[0] = 0x35;
+    (*bufPtr)[1] = 1;
+    (*bufPtr)[2] = msgType;
+    (*bufPtr) += 3;
+}
+
+static void dhcp_option_insert_max_msg_size(uint8_t ** bufPtr, uint16_t maxSize) {
+    (*bufPtr)[0] = 0x39;
+    (*bufPtr)[1] = 2;
+    (*bufPtr)[2] = (maxSize >> 8) & 0xFF;
+    (*bufPtr)[3] = maxSize & 0xFF;
+    (*bufPtr) += 4;
+}
+
+static void dhcp_option_insert_end(uint8_t ** bufPtr) {
+    (*bufPtr)[0] = 0xFF;
+    (*bufPtr) += 1;
+}
+
+static void dhcp_send(EthInterface * intf, DhcpOps * ops) {
+    // construct message
+    uint8_t * buf = (uint8_t *)s.buf;
+    memset(buf, 0, DHCP_MIN_PACKET_SIZE);
+    FILL_BYTE_ADVANCE(buf, &(ops->op));
+    FILL_BYTE_ADVANCE(buf, &(ops->htype));
+    FILL_BYTE_ADVANCE(buf, &(ops->hlen));
+    FILL_BYTE_ADVANCE(buf, &(ops->hops));
+    FILL_DWORD_H2N_ADVANCE(buf, ops->xid);
+    FILL_WORD_H2N_ADVANCE(buf, ops->secs);
+    FILL_WORD_H2N_ADVANCE(buf, ops->flags);
+    FILL_DWORD_H2N_ADVANCE(buf, ops->ciaddr);
+    FILL_DWORD_H2N_ADVANCE(buf, ops->yiaddr);
+    FILL_DWORD_H2N_ADVANCE(buf, ops->siaddr);
+    FILL_DWORD_H2N_ADVANCE(buf, ops->giaddr);
+    FILL_ADVANCE(buf, ops->chaddr, 16);
+    buf += SNAME_LEN + FILE_LEN;
+    FILL_ADVANCE(buf, DHCP_MAGIC_COOKIE, 4); // DHCP magic cookie
+
+    // insert options
+    dhcp_option_insert_msg_type(&buf, DHCPDISCOVER);
+    dhcp_option_insert_max_msg_size(&buf, 1500);
+    dhcp_option_insert_end(&buf);
+
+    udp_sendto(&s.connb, s.buf, DHCP_MIN_PACKET_SIZE, IPv4_ANY_ADDR, DHCP_SERVER_PORT);
+}
+
+static void dhcp_discover(EthInterface * intf) {
+    s.tranId = rand();
+    DhcpOps ops = { 0 };
+
+    ops.op = DHCP_BOOTREQUEST;
+    ops.htype = 1;
+    ops.hlen = 6;
+    ops.hops = 0;
+    ops.xid = s.tranId;
+    ops.secs = 0;
+    ops.flags = 0;
+    ops.ciaddr = 0;
+    ops.yiaddr = 0;
+    ops.siaddr = 0;
+    ops.giaddr = 0;
+
+    memcpy(ops.chaddr, intf->mac, ETH_HW_ADDR_LEN);
+
+    dhcp_send(intf, &ops);
+}
+
+static int dhcp_resp_cb(const Pckt * pckt) {
+    return 0;
+}
+
+void dhcp_initiate(EthInterface *intf) {
+    s.state = DHCP_INIT_REBOOT;
+    s.buf = dynmem_alloc(DHCP_MIN_PACKET_SIZE);
+    s.connb = udp_new_connblock(intf, IPv4_ANY_ADDR, DHCP_CLIENT_PORT, dhcp_resp_cb);
+
+    dhcp_discover(intf);
+}
diff --git a/prefab/packet_parsers/dhcp.h b/prefab/packet_parsers/dhcp.h
new file mode 100644
index 0000000..ca9e144
--- /dev/null
+++ b/prefab/packet_parsers/dhcp.h
@@ -0,0 +1,56 @@
+#ifndef ETHERLIB_TEST_DHCP_H
+#define ETHERLIB_TEST_DHCP_H
+
+#include <stdint.h>
+#include "../../eth_interface.h"
+
+typedef struct {
+    uint8_t op; ///< Operations
+    uint8_t htype; ///< Hardware type
+    uint8_t hlen; ///< Hardware address length
+    uint8_t hops; ///< Number of network hops
+    uint32_t xid; ///< Transaction ID
+    uint16_t secs; ///< Seconds elapsed since client started trying to boot
+    uint16_t flags; ///< Flags
+    uint32_t ciaddr; ///< Client IP address (filled in DHCPREQUEST)
+    uint32_t yiaddr; ///< 'Your' client IP address
+    uint32_t siaddr; ///< ...
+    uint32_t giaddr; ///< ...
+    uint8_t chaddr[16]; ///< Client hardware address
+    char * sname; ///< Optional server host name
+    char * file; ///< Boot file name
+} DhcpOps;
+
+/**
+ * DHCP state.
+ */
+typedef enum {
+    DHCP_INIT_REBOOT,
+    DHCP_REBOOTING,
+    DHCP_INIT,
+    DHCP_REQUESTING,
+    DHCP_SELECTING,
+    DHCP_REBINDING,
+    DHCP_BOUND,
+    DHCP_RENEWING
+} DhcpState;
+
+/**
+ * DHCP op codes.
+ */
+typedef enum {
+    DHCP_BOOTREQUEST = 1,
+    DHCP_BOOTREPLY = 0
+} DhcpOpCode;
+
+#define DHCP_MIN_PACKET_SIZE (312)
+#define DHCP_CLIENT_PORT (68)
+#define DHCP_SERVER_PORT (67)
+
+/**
+ * Initiate DHCP on interface
+ * @param intf interface
+ */
+void dhcp_initiate(EthInterface * intf);
+
+#endif //ETHERLIB_TEST_DHCP_H
diff --git a/prefab/packet_parsers/ethernet_frame.c b/prefab/packet_parsers/ethernet_frame.c
index 959621a..0bb23bf 100644
--- a/prefab/packet_parsers/ethernet_frame.c
+++ b/prefab/packet_parsers/ethernet_frame.c
@@ -10,8 +10,8 @@
 #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;
+int parse_ethernet(const uint8_t *hdr, uint32_t size, PcktHeaderElement *pcktHdrLe, struct EthInterface_ *intf) {
+    EthernetProps * frameProps = (EthernetProps *) &pcktHdrLe->props;
     FETCH_ADVANCE(frameProps->destAddr, hdr, ETH_HW_ADDR_LEN); // copy destination address
     FETCH_ADVANCE(frameProps->sourceAddr, hdr, ETH_HW_ADDR_LEN); // copy destination address
     FETCH_WORD_H2N_ADVANCE(&frameProps->length_type, hdr); // copy length/type field
diff --git a/prefab/packet_parsers/ethernet_frame.h b/prefab/packet_parsers/ethernet_frame.h
index ef07732..daecbb9 100644
--- a/prefab/packet_parsers/ethernet_frame.h
+++ b/prefab/packet_parsers/ethernet_frame.h
@@ -12,6 +12,8 @@
 #define ETH_HW_ADDR_LEN (6)
 #define ETH_ETHERNET_HEADER_SIZE (14)
 
+#define HEADER_FETCH_PROPS(T,h) (T *)(&((h)->props))
+
 typedef uint8_t EthernetAddress[ETH_HW_ADDR_LEN];
 
 /**
@@ -25,14 +27,16 @@ typedef struct {
     uint16_t length_type; ///< frame length_type
 } EthernetProps;
 
+struct EthInterface_;
+
 /**
  * Parse raw Ethernet frames.
  * @param hdr pointer to the Ethernet packet header
  * @param size total frame size
- * @param props pointer to property storage
+ * @param pcktHdrLe 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);
+int parse_ethernet(const uint8_t *hdr, uint32_t size, PcktHeaderElement *pcktHdrLe, struct EthInterface_ *intf);
 
 /**
  * Insert Ethernet header to specified address.
diff --git a/prefab/packet_parsers/ipv4_packet.c b/prefab/packet_parsers/ipv4_packet.c
index ab76d68..7c196d9 100644
--- a/prefab/packet_parsers/ipv4_packet.c
+++ b/prefab/packet_parsers/ipv4_packet.c
@@ -3,28 +3,26 @@
 //
 
 #include <stdbool.h>
+#include "ethernet_frame.h"
 #include "ipv4_packet.h"
 #include "../../utils.h"
 
-static uint16_t ip_checksum(const IPv4Props * ipProps) {
+#include "../../eth_interface.h"
+
+static uint16_t ip_checksum(const uint8_t * hdr) {
     // 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];
+    const uint16_t *pField = (const uint16_t *) hdr;
+    for (uint8_t i = 0; i < (ETH_IPv4_HEADER_SIZE / sizeof(uint16_t)); i++) {
+        uint16_t field = pField[i];
+        if (i != 5) { // 6. 16-bit long field is the checksum itself, do not count in
+            sum += field;
         }
     }
 
-    // 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);
+    while (sum >> 16) {
+        sum = (sum & 0xFFFF) + (sum >> 16);
+    }
 
     // invert result
     uint16_t sum16 = sum ^ 0xFFFF;
@@ -33,16 +31,17 @@ static uint16_t ip_checksum(const IPv4Props * ipProps) {
 
 #define ETH_IP_HEADER_LENGTH (20)
 
-static bool check_ipv4_validity(const IPv4Props * ipProps) {
+static bool check_ipv4_validity(const uint8_t * hdr, const IPv4Props *ipProps) {
     bool valid =
-            ipProps->Version != 4 &&
-            ipProps->IHL == ETH_IP_HEADER_LENGTH &&
-            ipProps->HeaderChecksum == ip_checksum(ipProps);
+            (ipProps->Version == 4) &&
+            (ipProps->IHL == (ETH_IP_HEADER_LENGTH / 4)) &&
+            (ntohs(ipProps->HeaderChecksum) == ip_checksum(hdr));
     return valid;
 }
 
-int parse_ipv4(const uint8_t *hdr, uint32_t size, PcktProps * props) {
-    IPv4Props * ipProps = (IPv4Props *)props;
+int parse_ipv4(const uint8_t *hdr, uint32_t size, PcktHeaderElement *pcktHdrLe, struct EthInterface_ *intf) {
+    const uint8_t * hdrBegin = hdr;
+    IPv4Props *ipProps = HEADER_FETCH_PROPS(IPv4Props, pcktHdrLe);
     uint8_t version_length;
     FETCH_ADVANCE(&version_length, hdr, 1);
     ipProps->Version = (version_length) >> 4;
@@ -57,31 +56,47 @@ int parse_ipv4(const uint8_t *hdr, uint32_t size, PcktProps * props) {
     FETCH_ADVANCE(&ipProps->TTL, hdr, 1);
     FETCH_ADVANCE(&ipProps->Protocol, hdr, 1);
     FETCH_WORD_H2N_ADVANCE(&ipProps->HeaderChecksum, hdr);
-    //FETCH_DWORD_H2N_ADVANCE(&ipProps->SourceIPAddr, hdr);
-    //FETCH_DWORD_H2N_ADVANCE(&ipProps->DestIPAddr, hdr);
-    FETCH_ADVANCE(&ipProps->SourceIPAddr, hdr, 4);
+    FETCH_ADVANCE(&ipProps->SourceIPAddr, hdr, 4); // NO network -> host byte order conversion!
     FETCH_ADVANCE(&ipProps->DestIPAddr, hdr, 4);
 
     // fill-in common packet header fields
-    ipProps->validityOK = check_ipv4_validity(ipProps);
+    ipProps->validityOK = check_ipv4_validity(hdrBegin, ipProps);
     ipProps->containedPacketClass = ipProps->Protocol;
     ipProps->headerSize = ETH_IP_HEADER_LENGTH;
 
+    // if packet is valid, learn MAC-IP mapping
+    if (ipProps->validityOK) {
+        EthernetProps * ethProps = HEADER_FETCH_PROPS(EthernetProps, pcktHdrLe->prev); // fetch Ethernet header
+        ArpEntry entry; // fill entry
+        memcpy(&entry.eth, ethProps->sourceAddr, ETH_HW_ADDR_LEN);
+        entry.ip = ipProps->SourceIPAddr;
+        arpc_learn(intf->arpc, &entry); // learn new assignment
+    }
+
     return ipProps->validityOK ? ipProps->Protocol : -1;
 }
 
+static uint16_t nextIpIdentification = 0;
+
 void insert_ipv4_header(uint8_t *hdr, const PcktHeaderElement *headers) {
-    IPv4Props * ipProps = (IPv4Props *)&headers->props;
+    uint8_t * hdrOrig = hdr;
+    IPv4Props *ipProps = (IPv4Props *) &headers->props;
+    ipProps->Identification = nextIpIdentification++; // auto-insert identification
     uint8_t version_length = (ipProps->Version << 4) | (ipProps->IHL & 0x0F);
     FILL_ADVANCE(hdr, &version_length, 1);
     FILL_ADVANCE(hdr, &ipProps->DSF, 1);
     FILL_WORD_H2N_ADVANCE(hdr, ipProps->TotalLength);
     FILL_WORD_H2N_ADVANCE(hdr, ipProps->Identification);
     uint16_t flags_fragOffset = ((ipProps->Flags & 0x07) << 13) | (ipProps->FragmentOffset & ~(0x07 << 13));
+    FILL_WORD_H2N_ADVANCE(hdr, flags_fragOffset); // TODO...
     FILL_ADVANCE(hdr, &ipProps->TTL, 1);
     FILL_ADVANCE(hdr, &ipProps->Protocol, 1);
-    uint16_t checksum = ip_checksum(ipProps);
-    FILL_WORD_H2N_ADVANCE(hdr, checksum);
+    uint8_t * ChkSumPtr = hdr;
+    FILL_WORD_H2N_ADVANCE(hdr, 0x0000);
     FILL_ADVANCE(hdr, &ipProps->SourceIPAddr, 4);
     FILL_ADVANCE(hdr, &ipProps->DestIPAddr, 4);
+
+    // calculate checksum after filling header
+    uint16_t checksum = ip_checksum(hdrOrig);
+    memcpy(ChkSumPtr, &checksum, 2);
 }
diff --git a/prefab/packet_parsers/ipv4_packet.h b/prefab/packet_parsers/ipv4_packet.h
index c30eca4..4523c0a 100644
--- a/prefab/packet_parsers/ipv4_packet.h
+++ b/prefab/packet_parsers/ipv4_packet.h
@@ -6,6 +6,7 @@
 #include "../../packet_sieve.h"
 
 #define ETH_IPv4_PACKET_CLASS (0x0800)
+#define ETH_IPv4_HEADER_SIZE (20)
 
 /**
  * IPv4 header structure
@@ -34,14 +35,16 @@ typedef struct {
     uint32_t DestIPAddr; ///< destination IP-address
 } IPv4Props;
 
+struct EthInterface_;
+
 /**
  * Parse raw IPv4 packets.
  * @param hdr pointer to the IPv4 packet header
  * @param size total packet size
- * @param props pointer to property storage
+ * @param pcktHdrLe pointer to property storage
  * @return Protocol on success or -1 on failure
  */
-int parse_ipv4(const uint8_t *hdr, uint32_t size, PcktProps * props);
+int parse_ipv4(const uint8_t *hdr, uint32_t size, PcktHeaderElement *pcktHdrLe, struct EthInterface_ *intf);
 
 /**
  * Insert IPv4 header.
diff --git a/prefab/packet_parsers/ipv4_types.h b/prefab/packet_parsers/ipv4_types.h
new file mode 100644
index 0000000..a639a6a
--- /dev/null
+++ b/prefab/packet_parsers/ipv4_types.h
@@ -0,0 +1,10 @@
+#ifndef ETHERLIB_TEST_IPV4_TYPES_H
+#define ETHERLIB_TEST_IPV4_TYPES_H
+
+#include <stdint.h>
+
+typedef uint32_t ip4_addr;
+
+#define IPv4_ANY_ADDR (0xFFFFFFFF)
+
+#endif //ETHERLIB_TEST_IPV4_TYPES_H
diff --git a/prefab/packet_parsers/udp_packet.c b/prefab/packet_parsers/udp_packet.c
index 35715d9..31cb876 100644
--- a/prefab/packet_parsers/udp_packet.c
+++ b/prefab/packet_parsers/udp_packet.c
@@ -2,6 +2,7 @@
 #include "udp_packet.h"
 #include "../../utils.h"
 #include "ipv4_packet.h"
+#include "ethernet_frame.h"
 
 #define ETH_UDP_HEADER_SIZE (8)
 
@@ -13,30 +14,40 @@ typedef struct {
     uint16_t udpLength;
 } UdpPseudoHeader;
 
-static uint16_t udp_checksum(const UdpPseudoHeader * pseudoHeader, const uint8_t * headerPayload, uint32_t headerPayloadSize) {
-    uint16_t chksum = 0;
-    uint16_t i;
+static uint16_t udp_checksum(const UdpPseudoHeader *pseudoHeader, const uint8_t * hdr, uint32_t size) {
+    uint32_t chksum = 0;
 
     // pseudoheader
-    for (i = 0; i < sizeof(UdpPseudoHeader) / 2; i++) {
-        chksum += ~((uint16_t *)pseudoHeader)[i];
+    for (uint16_t i = 0; i < sizeof(UdpPseudoHeader) / 2; i++) {
+        uint16_t field = ((uint16_t *) pseudoHeader)[i];
+        field = htons(field);
+        chksum += field;
     }
 
-    // UDP header and payload
-    for (i = 0; i < headerPayloadSize / 2; i++) {
+    // UDP header and hdr
+    for (uint16_t i = 0; i < size / 2; i++) {
         if (i != 3) { // skip Checksum field
-            chksum += ~((uint16_t *) headerPayload)[i];
+            uint16_t field = ((uint16_t *) hdr)[i];
+            field = htons(field);
+            chksum += field;
         }
     }
 
     // pad if packet size is odd
-    chksum += ~((uint16_t)headerPayload[headerPayloadSize - 1] << 8);
+    if (size % 2) {
+        chksum += ((uint16_t) (hdr[size - 1] << 8));
+    }
 
-    return chksum;
+    while (chksum >> 16) {
+        chksum = (chksum & 0xFFFF) + (chksum >> 16);
+    }
+
+    uint16_t sum16 = ~(chksum & 0xFFFF);
+    return sum16;
 }
 
-int parse_udp(const uint8_t *hdr, uint32_t size, PcktProps * props) {
-    UdpProps * udpProps = (UdpProps *)props;
+int parse_udp(const uint8_t *hdr, uint32_t size, PcktHeaderElement *pcktHdrLe, struct EthInterface_ *intf) {
+    UdpProps *udpProps = HEADER_FETCH_PROPS(UdpProps, pcktHdrLe);
     FETCH_WORD_H2N_ADVANCE(&udpProps->SourcePort, hdr);
     FETCH_WORD_H2N_ADVANCE(&udpProps->DestinationPort, hdr);
     FETCH_WORD_H2N_ADVANCE(&udpProps->Length, hdr);
@@ -44,22 +55,23 @@ int parse_udp(const uint8_t *hdr, uint32_t size, PcktProps * props) {
 
     // common fields...
     udpProps->headerSize = ETH_UDP_HEADER_SIZE;
-    udpProps->validityOK = size == udpProps->Length; // TODO UDP checksum validation!
+    udpProps->validityOK = (size == udpProps->Length); // TODO UDP checksum validation!
     udpProps->containedPacketClass = 0;
 
     return udpProps->validityOK ? 0 : -1;
 }
 
 void insert_udp_header(uint8_t *hdr, const PcktHeaderElement *headers) {
-    UdpProps * udpProps = (UdpProps *) &headers->props;
+    uint8_t *hdrBegin = hdr;
+    UdpProps *udpProps = (UdpProps *) &headers->props;
     FILL_WORD_H2N_ADVANCE(hdr, udpProps->SourcePort);
     FILL_WORD_H2N_ADVANCE(hdr, udpProps->DestinationPort);
     FILL_WORD_H2N_ADVANCE(hdr, udpProps->Length);
 
     // calculate checksum
-    const IPv4Props * ipProps = (IPv4Props *)&headers->prev->props;
-    UdpPseudoHeader ph = { ipProps->SourceIPAddr, ipProps->DestIPAddr, 0, ETH_UDP_PACKET_CLASS, udpProps->Length };
-    udpProps->Checksum = udp_checksum(&ph, hdr, udpProps->Length);
+    const IPv4Props *ipProps = (IPv4Props *) &headers->prev->props;
+    UdpPseudoHeader ph = {ipProps->SourceIPAddr, ipProps->DestIPAddr, 0, ETH_UDP_PACKET_CLASS, htons(udpProps->Length)};
+    udpProps->Checksum = udp_checksum(&ph, hdrBegin, udpProps->Length);
     FILL_WORD_H2N_ADVANCE(hdr, udpProps->Checksum);
 }
 
diff --git a/prefab/packet_parsers/udp_packet.h b/prefab/packet_parsers/udp_packet.h
index f230bb8..ae136d6 100644
--- a/prefab/packet_parsers/udp_packet.h
+++ b/prefab/packet_parsers/udp_packet.h
@@ -6,6 +6,7 @@
 #include "../../packet_sieve.h"
 
 #define ETH_UDP_PACKET_CLASS (17)
+#define ETH_UDP_HEADER_SIZE (8)
 
 /**
  * @struct UdpProps
@@ -20,14 +21,16 @@ typedef struct {
     uint16_t Checksum; ///> UDP checksum
 } UdpProps;
 
+struct EthInterface_;
+
 /**
  * Parse raw UDP packets.
  * @param hdr pointer to the UDP packet header
  * @param size total packet size
- * @param props pointer to property storage
+ * @param pcktHdrLe pointer to property storage
  * @return 0 on success or -1 on failure
  */
-int parse_udp(const uint8_t *hdr, uint32_t size, PcktProps * props);
+int parse_udp(const uint8_t *hdr, uint32_t size, PcktHeaderElement *pcktHdrLe, struct EthInterface_ *intf);
 
 /**
  * Insert UDP header.
diff --git a/utils.c b/utils.c
index 402b911..72ace8d 100644
--- a/utils.c
+++ b/utils.c
@@ -54,7 +54,7 @@ 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 >> 8) ^ crc32table[(checksum ^ data[i]) & 0xFF];
     }
     checksum = ~checksum;
     return checksum;
diff --git a/utils.h b/utils.h
index 88381aa..d150cd0 100644
--- a/utils.h
+++ b/utils.h
@@ -34,6 +34,8 @@
 #define ERROR(...) MSG(__VA_ARGS__)
 #define INFO(...) MSG(__VA_ARGS__)
 
+#define SNPRINTF(s,n,...) snprintf(s,n,__VA_ARGS__)
+
 #define IPv4(a,b,c,d) ((a) | (b << 8) | (c << 16) | (d << 24))
 #define PRINT_IPv4(ip) MSG("%u.%u.%u.%u", (ip & 0xFF), ((ip >> 8) & 0xFF), ((ip >> 16) & 0xFF), ((ip >> 24) & 0xFF))
 
@@ -44,10 +46,12 @@
 
 #define FETCH_ADVANCE(dst,src,n) memcpy((dst), (src), n), (src) += n
 #define FILL_ADVANCE(dst,src,n) memcpy((dst), (src), n), (dst) += n
+#define FETCH_BYTE_ADVANCE(dst,src) FETCH_ADVANCE(dst,src,1)
+#define FILL_BYTE_ADVANCE(dst,src) FILL_ADVANCE(dst,src,1)
 #define FETCH_WORD_H2N_ADVANCE(dst,w) { uint16_t u; memcpy(&u, w, 2); u = htons(u); memcpy((dst), &u, 2); (w) += 2; }
 #define FILL_WORD_H2N_ADVANCE(dst,w) { uint16_t u = htons(w); memcpy((dst), &u, 2); (dst) += 2; }
 #define FETCH_DWORD_H2N_ADVANCE(dst,dw) { uint32_t du; memcpy(&du, dw, 4); du = htonl(du); memcpy((dst), &du, 4); (dw) += 4; }
-#define FILL_DWORD_H2N_ADVANCE(dst,w) { uint32_t du = htonl(dw); memcpy(dst, &du, 4); (dst) += 4; }
+#define FILL_DWORD_H2N_ADVANCE(dst,dw) { uint32_t du = htonl(dw); memcpy(dst, &du, 4); (dst) += 4; }
 
 
 // ------------------