diff --git a/arp_cache.c b/arp_cache.c
index 829351b..63f0bd8 100644
--- a/arp_cache.c
+++ b/arp_cache.c
@@ -42,6 +42,10 @@ void arpc_free(ArpCache *aprc) {
 }
 
 void arpc_learn(ArpCache *arpc, const ArpEntry *newEntry) {
+    if (newEntry->eth[0] & 0x01) { // don't learn multicast addresses
+        return;
+    }
+
     // TODO: nagyon dummy...
     for (uint16_t i = 0; i < arpc->fill; i++) {
         ArpEntry * entry = arpc->entries + i;
diff --git a/arp_cache.h b/arp_cache.h
index e00ef94..3aefd4e 100644
--- a/arp_cache.h
+++ b/arp_cache.h
@@ -1,5 +1,5 @@
-#ifndef ETHERLIB_TEST_ARP_CACHE_H
-#define ETHERLIB_TEST_ARP_CACHE_H
+#ifndef ETHERLIB_ARP_CACHE_H
+#define ETHERLIB_ARP_CACHE_H
 
 #include "prefab/packet_parsers/ethernet_frame.h"
 #include "prefab/packet_parsers/ipv4_types.h"
@@ -68,4 +68,4 @@ const ArpEntry *arpc_get_ask(ArpCache *arpc, ip4_addr ip);
  */
 void arpc_dump(ArpCache * arpc);
 
-#endif //ETHERLIB_TEST_ARP_CACHE_H
+#endif //ETHERLIB_ARP_CACHE_H
diff --git a/cbd_table.h b/cbd_table.h
index 99712f5..919fb05 100644
--- a/cbd_table.h
+++ b/cbd_table.h
@@ -1,5 +1,5 @@
-#ifndef ETHERLIB_TEST_CBD_TABLE_H
-#define ETHERLIB_TEST_CBD_TABLE_H
+#ifndef ETHERLIB_CBD_TABLE_H
+#define ETHERLIB_CBD_TABLE_H
 
 #include <stdint.h>
 #include "connection_block.h"
@@ -58,4 +58,4 @@ bool cbdt_get_connection_block(CbdTable * cbdt, cbd d, ConnBlock * connBlock);
  */
 void cbdt_report(const CbdTable * cbdt);
 
-#endif //ETHERLIB_TEST_CBD_TABLE_H
+#endif //ETHERLIB_CBD_TABLE_H
diff --git a/docs/customdoxygen.css b/docs/customdoxygen.css
index e19998a..e1a7be0 100644
--- a/docs/customdoxygen.css
+++ b/docs/customdoxygen.css
@@ -62,6 +62,41 @@ p.reference, p.definition {
 	font: 400 14px/22px 'Crimson Text',Roboto,sans-serif;
 }
 
+#nav-tree {
+	background-color: var(--light-green-yellow-crayola);
+	background-image: none;
+}
+
+div#nav-path ul {
+	background-image: none;
+}
+
+#nav-tree .selected {
+	background-image: none;
+	background-color: var(--eggplant);
+}
+
+span.arrow {
+	color: var(--ebony);
+	font-size: 120%;
+}
+
+div.item span.label {
+	font-size: 13px !important;
+	font-family: 'Fira Code', Roboto, sans-serif !important;
+}
+
+.ui-resizable-handle {
+	background-image: none;
+	background-color: var(--ebony);
+}
+
+.ui-resizable-e {
+	width: 3px;
+}
+
+
+
 /* @group Heading Levels */
 
 h1.groupheader {
diff --git a/dynmem.h b/dynmem.h
index 9aca29e..b4b4d79 100644
--- a/dynmem.h
+++ b/dynmem.h
@@ -3,6 +3,10 @@
 
 #include <stdint.h>
 
+#ifdef DYNMEM_DEBUG
+#include <stdio.h>
+#endif
+
 /**
  * Initialize EtherLib dynamic memory management subsystem,
  * based on heap pointer and size given in etherlib_options.h
diff --git a/eth_interface.c b/eth_interface.c
index 5ba8658..b6410ba 100644
--- a/eth_interface.c
+++ b/eth_interface.c
@@ -32,6 +32,8 @@ EthInterface *ethintf_new(EthIODef * io) {
 
     ethIntf->txQ = mq_create(ETHLIB_DEF_MQ_SIZE);
 
+    ethIntf->ipra = ipra_new();
+
     return ethIntf;
 }
 
diff --git a/eth_interface.h b/eth_interface.h
index a905652..43d0f86 100644
--- a/eth_interface.h
+++ b/eth_interface.h
@@ -7,6 +7,7 @@
 #include "arp_cache.h"
 #include "connection_block.h"
 #include "msg_queue.h"
+#include "prefab/conn_blocks/ipv4/ip_assembler.h"
 
 /**
  * Ethernet interface low level definition.
@@ -35,6 +36,7 @@ typedef struct EthInterface_ {
     ArpCache * arpc; ///< ARP cache
     ConnBlock arpCb; ///< ARP connection block
     MsgQueue * txQ; ///< Transmit queue
+    IPv4Assembler * ipra; ///< IPv4 reassembler
 } EthInterface;
 
 /**
diff --git a/msg_queue.h b/msg_queue.h
index dcdc163..fbeb38c 100644
--- a/msg_queue.h
+++ b/msg_queue.h
@@ -1,5 +1,5 @@
-#ifndef ETHERLIB_TEST_MSG_QUEUE_H
-#define ETHERLIB_TEST_MSG_QUEUE_H
+#ifndef ETHERLIB_MSG_QUEUE_H
+#define ETHERLIB_MSG_QUEUE_H
 
 #include <stdint.h>
 #include "packet.h"
@@ -52,4 +52,4 @@ RawPckt mq_top(MsgQueue * mq);
  */
 void mq_pop(MsgQueue * mq);
 
-#endif //ETHERLIB_TEST_MSG_QUEUE_H
+#endif //ETHERLIB_MSG_QUEUE_H
diff --git a/packet_registry.h b/packet_registry.h
index 0255fd1..c337587 100644
--- a/packet_registry.h
+++ b/packet_registry.h
@@ -44,6 +44,17 @@ typedef struct {
     PcktPropsHeader
 } PcktProps;
 
+// special processing function returns
+#define PROC_FN_RET_OK (0) // OK, go ahead!
+#define PROC_FN_RET_ABORT (-1) // abort further processing
+#define PROC_FN_RET_REPRST (-2) // replace packet and restart packet processing
+
+typedef struct {
+    void * p;
+    uint32_t u;
+    bool8_t b;
+} PcktProcFnPassbackData;
+
 /**
  * @typedef int (*PcktProcFn)(const uint8_t *pHdr, uint32_t size, uint8_t *pPcktProps);
  * @brief Pckt processing function template.
@@ -52,11 +63,9 @@ typedef struct {
  * @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)
+ * @return one of the special processing function return values
  */
-typedef int (*PcktProcFn)(const uint8_t *hdr, uint32_t size, struct PcktHeaderElement_ * pcktHdrLe, struct EthInterface_ * intf);
+typedef int (*PcktProcFn)(const uint8_t *hdr, uint32_t size, struct PcktHeaderElement_ * pcktHdrLe, struct EthInterface_ * intf, PcktProcFnPassbackData * pb);
 
 /**
  * @struct PcktClassDesc
diff --git a/packet_sieve.c b/packet_sieve.c
index ea0b74b..f755d39 100644
--- a/packet_sieve.c
+++ b/packet_sieve.c
@@ -24,15 +24,18 @@ PcktSieve *packsieve_new(EthInterface * intf) {
     return sieve;
 }
 
-void packsieve_input(const PcktSieve *sieve, const RawPckt *rawPckt) {
+void packsieve_input(PcktSieve *sieve, const RawPckt *rawPckt) {
     // extract fields
     uint8_t *data = rawPckt->payload;
     uint32_t size = rawPckt->size;
+    bool mrd = false; // 'Must Release Data': at the end of processing not only release headers but data buffer as well
 
+    restart:;
     // process payload, fetch packet class etc.
     uint16_t ownClass = 0, containerClass = 0; // Ethernet...
     uint16_t offset = 0;
     PcktHeaderElement *lastHeader = NULL, *outermostHeader = NULL;
+    int procRet;
 
     do {
         // get packet descriptor
@@ -56,7 +59,22 @@ void packsieve_input(const PcktSieve *sieve, const RawPckt *rawPckt) {
         }
 
         // call parsing function
-        cdesc->procFun(data + offset, size - offset, header, sieve->intf);
+        PcktProcFnPassbackData pb;
+        procRet = cdesc->procFun(data + offset, size - offset, header, sieve->intf, &pb);
+        switch (procRet) {
+            case PROC_FN_RET_REPRST:
+                data = pb.p; // store new packet data
+                size = pb.u;
+                mrd = pb.b;
+                // NO BREAK!
+            case PROC_FN_RET_ABORT:
+                goto header_release; // GOTO :D!
+                break;
+            case PROC_FN_RET_OK:
+            default:
+                break;
+        }
+
         uint16_t containedClass = header->props.containedPacketClass;
         if (containedClass != 0) {
             containerClass = ownClass;
@@ -83,7 +101,7 @@ void packsieve_input(const PcktSieve *sieve, const RawPckt *rawPckt) {
 
     // lookup headers in the sieve
     const PcktHeaderElement *headerIter = outermostHeader;
-    const PcktSieveLayer *layer = &sieve->layer0; // innermost matched sieve layer
+    PcktSieveLayer *layer = &sieve->layer0; // innermost matched sieve layer
     bool found = true; // first structure is always an Ethernet-frame
     while (found && headerIter) {
         const PcktSieveLayer *nodeIter = layer->nodes;
@@ -99,7 +117,16 @@ void packsieve_input(const PcktSieve *sieve, const RawPckt *rawPckt) {
                     packet.payload = data + offset;
                     packet.headerSize = offset;
                     packet.payloadSize = size - offset;
-                    layer->cbFn(&packet, layer->tag);
+                    int action = layer->cbFn(&packet, layer->tag);
+
+                    // execute special return action
+                    switch (action) {
+                        case SIEVE_LAYER_REMOVE_THIS:
+                            packsieve_remove_layer(layer);
+                            break;
+                        default:
+                            break;
+                    }
                 }
                 headerIter = containedHeader;
             } else {
@@ -123,6 +150,13 @@ void packsieve_input(const PcktSieve *sieve, const RawPckt *rawPckt) {
         dynmem_free(iter);
         iter = next;
     }
+    if (procRet == PROC_FN_RET_REPRST) { // if a restart was requested, then run everything again!
+        goto restart;
+    }
+    data_release:;
+    if (mrd) {
+        dynmem_free(data);
+    }
 }
 
 PcktSieveLayer *packsieve_new_layer(PcktSieveLayer *parent, const PcktSieveFilterCondition *filtCond, bool matchAny, SieveFilterFn filtFn, SieveCallBackFn cbFn, PcktSieveLayerTag tag, uint16_t pcktClass) {
@@ -214,7 +248,7 @@ bool packsieve_remove_layer(PcktSieveLayer *layer) {
 void packsieve_report(const PcktSieve * sieve, const PcktSieveLayer *layer, uint32_t indent) {
     if (layer->connBReportFn != NULL) {
         INFO("%*c└─┤", indent, ' ');
-        const ConnBlock connBlock = { sieve->intf, layer, NULL }; // tag not required
+        const ConnBlock connBlock = { sieve, layer, NULL }; // tag not required
         layer->connBReportFn(&connBlock);
         INFO("├───\n");
     } else {
@@ -231,7 +265,7 @@ void packsieve_layer_info(const PcktSieve * sieve, const PcktSieveLayer * layer)
     const PcktSieveLayer *iter = layer;
     while (iter != NULL) { // climb up to the top in the sieve tree
         if (iter->connBReportFn != NULL) {
-            const ConnBlock connBlock = {sieve->intf, iter, NULL}; // tag not required
+            const ConnBlock connBlock = {sieve, iter, NULL}; // tag not required
             iter->connBReportFn(&connBlock);
         } else {
             INFO("[%d]", layer->packetClass);
diff --git a/packet_sieve.h b/packet_sieve.h
index a7c7687..1559c4e 100644
--- a/packet_sieve.h
+++ b/packet_sieve.h
@@ -64,6 +64,9 @@ typedef union {
     uint32_t u;
 } PcktSieveLayerTag;
 
+// actions triggered by callback function returns
+#define SIEVE_LAYER_REMOVE_THIS (-100)
+
 /**
  * Callback function type for packet sieve match.
  */
@@ -114,7 +117,7 @@ PcktSieve * packsieve_new();
  * @param data
  * @param size
  */
-void packsieve_input(const PcktSieve *sieve, const RawPckt *rawPckt);
+void packsieve_input(PcktSieve *sieve, const RawPckt *rawPckt);
 
 /**
  * Create a new sieve filter layer.
diff --git a/pckt_assembler.h b/pckt_assembler.h
index 7d97ea8..0e4711d 100644
--- a/pckt_assembler.h
+++ b/pckt_assembler.h
@@ -1,5 +1,5 @@
-#ifndef ETHERLIB_TEST_PCKT_ASSEMBLER_H
-#define ETHERLIB_TEST_PCKT_ASSEMBLER_H
+#ifndef ETHERLIB_PCKT_ASSEMBLER_H
+#define ETHERLIB_PCKT_ASSEMBLER_H
 
 #include "packet.h"
 
@@ -15,4 +15,4 @@ struct EthInterface_;
  */
 int pckt_assemble(RawPckt *raw, Pckt *cooked);
 
-#endif //ETHERLIB_TEST_PCKT_ASSEMBLER_H
+#endif //ETHERLIB_PCKT_ASSEMBLER_H
diff --git a/prefab/conn_blocks/arp_connblock.c b/prefab/conn_blocks/arp_connblock.c
index 8d995d8..987ffca 100644
--- a/prefab/conn_blocks/arp_connblock.c
+++ b/prefab/conn_blocks/arp_connblock.c
@@ -2,10 +2,8 @@
 
 #include <stddef.h>
 
-#include "../packet_parsers/packet_parsers.h"
 #include "../../utils.h"
 #include "../../dynmem.h"
-#include "../packet_parsers/arp_packet.h"
 
 static bool filtArp(const PcktSieveFilterCondition * filtCond, const PcktProps * contProps, const PcktProps * ownProps, EthInterface * intf) {
     EthernetProps * ethProps = (EthernetProps *) contProps;
diff --git a/prefab/conn_blocks/arp_connblock.h b/prefab/conn_blocks/arp_connblock.h
index 2d06a07..b0b9416 100644
--- a/prefab/conn_blocks/arp_connblock.h
+++ b/prefab/conn_blocks/arp_connblock.h
@@ -1,7 +1,7 @@
-#ifndef ETHERLIB_TEST_ARP_CONNBLOCK_H
-#define ETHERLIB_TEST_ARP_CONNBLOCK_H
+#ifndef ETHERLIB_ARP_CONNBLOCK_H
+#define ETHERLIB_ARP_CONNBLOCK_H
 
-#endif //ETHERLIB_TEST_ARP_CONNBLOCK_H
+#endif //ETHERLIB_ARP_CONNBLOCK_H
 
 #include <stdint.h>
 #include "../../connection_block.h"
diff --git a/prefab/conn_blocks/ethernet_info.h b/prefab/conn_blocks/ethernet_info.h
index ac8117a..7c9b343 100644
--- a/prefab/conn_blocks/ethernet_info.h
+++ b/prefab/conn_blocks/ethernet_info.h
@@ -1,8 +1,8 @@
-#ifndef ETHERLIB_TEST_ETHERNET_INFO_H
-#define ETHERLIB_TEST_ETHERNET_INFO_H
+#ifndef ETHERLIB_ETHERNET_INFO_H
+#define ETHERLIB_ETHERNET_INFO_H
 
 
-#include "etherlib/connection_block.h"
+#include "../../connection_block.h"
 
 /**
  * Print Ethernet sieve layer info.
@@ -10,4 +10,4 @@
  */
 void ethernet_print_report(const ConnBlock* connBlock);
 
-#endif //ETHERLIB_TEST_ETHERNET_INFO_H
+#endif //ETHERLIB_ETHERNET_INFO_H
diff --git a/prefab/conn_blocks/icmp_connblock.h b/prefab/conn_blocks/icmp_connblock.h
index b501a80..c78bca4 100644
--- a/prefab/conn_blocks/icmp_connblock.h
+++ b/prefab/conn_blocks/icmp_connblock.h
@@ -1,5 +1,5 @@
-#ifndef ETHERLIB_TEST_ICMP_CONNBLOCK_H
-#define ETHERLIB_TEST_ICMP_CONNBLOCK_H
+#ifndef ETHERLIB_ICMP_CONNBLOCK_H
+#define ETHERLIB_ICMP_CONNBLOCK_H
 
 #include "../../connection_block.h"
 
@@ -18,4 +18,4 @@ ConnBlock icmp_new_connblock(struct EthInterface_ * intf);
  */
 void icmp_print_report(const ConnBlock* connBlock);
 
-#endif //ETHERLIB_TEST_ICMP_CONNBLOCK_H
+#endif //ETHERLIB_ICMP_CONNBLOCK_H
diff --git a/prefab/conn_blocks/igmp_connblock.h b/prefab/conn_blocks/igmp_connblock.h
index fa06ba6..a8ba178 100644
--- a/prefab/conn_blocks/igmp_connblock.h
+++ b/prefab/conn_blocks/igmp_connblock.h
@@ -1,5 +1,5 @@
-#ifndef ETHERLIB_TEST_IGMP_CONNBLOCK_H
-#define ETHERLIB_TEST_IGMP_CONNBLOCK_H
+#ifndef ETHERLIB_IGMP_CONNBLOCK_H
+#define ETHERLIB_IGMP_CONNBLOCK_H
 
 #include "../../connection_block.h"
 #include "../packet_parsers/ipv4_types.h"
@@ -33,4 +33,4 @@ void igmp_leave_group(ConnBlock * connBlock, ip4_addr ga);
  */
 void igmp_print_report(const ConnBlock* connBlock);
 
-#endif //ETHERLIB_TEST_IGMP_CONNBLOCK_H
+#endif //ETHERLIB_IGMP_CONNBLOCK_H
diff --git a/prefab/conn_blocks/ipv4/ip_assembler.c b/prefab/conn_blocks/ipv4/ip_assembler.c
new file mode 100644
index 0000000..48e8299
--- /dev/null
+++ b/prefab/conn_blocks/ipv4/ip_assembler.c
@@ -0,0 +1,196 @@
+#include <stddef.h>
+#include <memory.h>
+
+#include "ip_assembler.h"
+#include "../../../dynmem.h"
+#include "../../../global_state.h"
+
+IPv4Assembler *ipra_new() {
+    IPv4Assembler *ipra = (IPv4Assembler *) dynmem_alloc(sizeof(IPv4Assembler));
+    ipra->chains = NULL;
+    return ipra;
+}
+
+static IPv4Fragment *ipra_all_frags_recvd(IPv4Assembler *ipra) {
+    IPv4Fragment *fullChain = NULL;
+    FragChainDesc *chainIter = ipra->chains;
+    while ((chainIter != NULL) && (fullChain == NULL)) { // iter over all chains
+        IPv4Fragment *fragIter = chainIter->fragChain;
+        uint16_t expectedOffset = 0; // check that all fragments corresponding to the same IP packet have been received
+        bool continuityOK = true; // we have possessed each fragments contiguously so far
+        while ((fragIter != NULL) && continuityOK) { // iterate over all segments
+            if (fragIter->offset == expectedOffset) {
+                if ((fragIter->next == NULL) && (fragIter->lastFrag)) { // if last stored segment is not the chain's end, then the packet is not full
+                    continuityOK = false;
+                }
+                expectedOffset += fragIter->size;
+            } else {
+                continuityOK = false;
+            }
+            fragIter = fragIter->next;
+        }
+
+        if (continuityOK) { // if we have a full chain, then return with the pointer to it
+            fullChain = chainIter->fragChain;
+        }
+    }
+    return fullChain;
+}
+
+static FragChainDesc *ipra_frag_chain_by_id(IPv4Assembler *ipra, uint16_t id) {
+    FragChainDesc *fragChain = NULL, *iter = ipra->chains;
+    while ((iter != NULL) && (fragChain == NULL)) {
+        if (iter->id == id) {
+            fragChain = iter;
+        }
+        iter = iter->next;
+    }
+    return fragChain;
+}
+
+static void ipra_remove_chain(IPv4Assembler * ipra, uint16_t id) {
+    FragChainDesc * chainDesc = ipra_frag_chain_by_id(ipra, id);
+    if (chainDesc == NULL) {
+        return;
+    }
+
+    timer_unsched(E.tmr, chainDesc->id); // remove timeout schedule
+    IPv4Fragment * iter = chainDesc->fragChain; // unlink and release fragment chain
+    while (iter != NULL) {
+        IPv4Fragment * oldIter = iter;
+        iter = iter->next;
+        dynmem_free(oldIter);
+    }
+
+    FragChainDesc * chainIter = ipra->chains;
+    while (chainIter != NULL) { // unlink chain from chain list
+        if (chainIter->next == chainDesc) { // if element is found
+            chainIter->next = chainDesc->next; // skip by looked up element by setting next properly
+            break; // break the loop
+        }
+        chainIter = chainIter->next;
+    }
+
+    // replace root element with the next one
+    if (ipra->chains == chainDesc) {
+        ipra->chains = chainDesc->next;
+    }
+
+    dynmem_free(chainDesc); // release chain descriptor
+}
+
+#define IP_REASSEMBLY_TIMEOUT_US (1000000)
+
+static void ipra_timeout(Timer * tmr, AlarmUserData user) {
+    IPv4Assembler * ipra = user.ptr;
+    uint16_t id = user.u;
+    ipra_remove_chain(ipra, id);
+}
+
+// insert into chain, without checking ID!
+static void ipra_insert_into_chain(FragChainDesc *chainDesc, const IPv4Props *ipProps, const uint8_t *payload, uint32_t size) {
+    IPv4Fragment *frag = (IPv4Fragment *) dynmem_alloc(sizeof(IPv4Fragment) + size); // allocate fragment
+    frag->size = size;
+    frag->lastFrag = !(ipProps->Flags & IP_FLAG_MF);
+    frag->offset = ipProps->FragmentOffset;
+    memcpy(frag->payload, payload, size);
+    frag->next = NULL;
+
+    IPv4Fragment *iter = chainDesc->fragChain;
+    if (iter != NULL) { // if there are some segments present
+        while (iter != NULL) {
+            if (((iter->offset + iter->size) <= frag->offset) && // normal, sorted insertion
+                ((iter->next == NULL) || (iter->next->offset >= (frag->offset + frag->size)))) {
+                frag->next = iter->next;
+                iter->next = frag;
+            } else if ((iter == chainDesc->fragChain) && (frag->offset < iter->offset)) { // insert before the firstly received segment
+                frag->next = iter;
+                chainDesc->fragChain = frag;
+            }
+            iter = iter->next;
+        }
+    } else {
+        chainDesc->fragChain = frag;
+    }
+    chainDesc->fullSize += size;
+}
+
+void ipra_input(IPv4Assembler *ipra, const IPv4Props *ipProps, const uint8_t *payload, uint32_t size) {
+    uint16_t id = ipProps->Identification;
+    FragChainDesc *chainDesc = ipra_frag_chain_by_id(ipra, id);
+    if (chainDesc == NULL) { // if chain was found, allocate new one
+        chainDesc = (FragChainDesc *) dynmem_alloc(sizeof(FragChainDesc));
+        chainDesc->id = ipProps->Identification;
+        chainDesc->alarmID = 0;
+        chainDesc->fullSize = 0;
+        chainDesc->fragChain = NULL;
+
+        // link-in newly allocated fragment chain (position does not carry meaning, that's why insertion at the beginning is the simplest)
+        chainDesc->next = ipra->chains;
+        ipra->chains = chainDesc;
+    }
+
+    // insert segment into chain
+    ipra_insert_into_chain(chainDesc, ipProps, payload, size);
+
+    // reschedule timeout
+    if (chainDesc->alarmID != 0) {
+        timer_unsched(E.tmr, chainDesc->alarmID);
+    }
+    AlarmUserData aud;
+    aud.ptr = ipra;
+    aud.u = chainDesc->id;
+    timer_sched_rel(E.tmr, IP_REASSEMBLY_TIMEOUT_US, ipra_timeout, aud);
+}
+
+bool ipra_try_reassemble(IPv4Assembler *ipra, uint16_t id, uint8_t **payload, uint16_t *size, PcktHeaderElement *pcktHdrLe) {
+    FragChainDesc *chainDesc = ipra_frag_chain_by_id(ipra, id);
+    if (chainDesc == NULL) { // chain not found
+        return false;
+    }
+
+    // check fragment continuity
+    IPv4Fragment *fragIter = chainDesc->fragChain;
+    uint16_t expectedOffset = 0; // check that all fragments corresponding to the same IP packet have been received
+    bool continuityOK = true; // we have possessed each fragments contiguously so far
+    while ((fragIter != NULL) && continuityOK) { // iterate over all segments
+        if (fragIter->offset == expectedOffset) {
+            if ((fragIter->next == NULL) && !(fragIter->lastFrag)) { // if last stored segment is not the chain's end, then the packet is not full
+                continuityOK = false;
+            }
+            expectedOffset += fragIter->size;
+        } else {
+            continuityOK = false;
+        }
+        fragIter = fragIter->next;
+    }
+
+    if (continuityOK) { // if we have a full chain, then reassemble
+        uint16_t offset = ETH_ETHERNET_HEADER_SIZE + ETH_IPv4_HEADER_SIZE; // offset for Ethernet and IPv4 header
+        *payload = dynmem_alloc(chainDesc->fullSize + offset); // allocate space for the whole packet
+        *size = chainDesc->fullSize;
+
+        uint8_t * p = (*payload);
+        IPv4Fragment * iter = chainDesc->fragChain;
+        while (iter != NULL) { // assemble packet
+            memcpy(p + iter->offset + offset, iter->payload, iter->size);
+            iter = iter->next;
+        }
+
+        // release chain
+        ipra_remove_chain(ipra, id);
+
+        // insert headers and change fields to obfuscate defragmentation
+        IPv4Props * ipProps = HEADER_FETCH_PROPS(IPv4Props, pcktHdrLe);
+        ipProps->Flags = 0;
+        ipProps->FragmentOffset = 0;
+        ipProps->TotalLength = chainDesc->fullSize + ETH_IPv4_HEADER_SIZE;
+
+        insert_ethernet_header(p, pcktHdrLe->prev);
+        insert_ipv4_header(p + ETH_ETHERNET_HEADER_SIZE, pcktHdrLe);
+
+        return true;
+    }
+
+    return false;
+}
\ No newline at end of file
diff --git a/prefab/conn_blocks/ipv4/ip_assembler.h b/prefab/conn_blocks/ipv4/ip_assembler.h
new file mode 100644
index 0000000..8f49965
--- /dev/null
+++ b/prefab/conn_blocks/ipv4/ip_assembler.h
@@ -0,0 +1,54 @@
+#ifndef ETHERLIB_IP_ASSEMBLER_H
+#define ETHERLIB_IP_ASSEMBLER_H
+
+#include <stdint.h>
+#include "../../packet_parsers/ipv4_packet.h"
+
+typedef struct IPv4Fragment_ {
+    uint16_t offset; ///< Address offset of this segment
+    uint16_t size; ///< Size of this segment
+    struct IPv4Fragment_ * next; ///< Pointer to next segment
+    bool8_t lastFrag; ///< It's the last fragment from a packet
+    uint8_t payload[]; ///< Fragment payload
+} IPv4Fragment;
+
+/**
+ * Fragment chain descriptor
+ */
+typedef struct FragChainDesc_ {
+    IPv4Fragment * fragChain; ///< Fragment chain
+    uint32_t alarmID; ///< Alarm ID for reassembly timeout
+    uint16_t id; ///< IP packet identification
+    uint16_t fullSize; ///< Reassembled IP packet size
+    struct FragChainDesc_ * next; ///< Next fragment chain
+} FragChainDesc;
+
+typedef struct {
+    FragChainDesc * chains; ///< Linked list of fragment chains
+} IPv4Assembler;
+
+/**
+ * Create new IPv4 packet reassembler.
+ * @return pointer to newly allocated assembler
+ */
+IPv4Assembler * ipra_new();
+
+/**
+ * Input packet packet fragment.
+ * @param ipra pointer to IP reassembler
+ * @param ipProps pointer to IP properties structure
+ */
+void ipra_input(IPv4Assembler * ipra, const IPv4Props * ipProps, const uint8_t * payload, uint32_t size);
+
+
+/**
+ * Try to reassembly packet.
+ * @param ipra pointer to IPv4 reassembly object
+ * @param id packet sequence identification
+ * @param payload pointer to uint8_t* pointer; filled only on successful reassembly
+ * @param size pointer to uint16_t field; filled only on successful reassembly
+ * @return reassembly was successful
+ */
+bool ipra_try_reassemble(IPv4Assembler *ipra, uint16_t id, uint8_t **payload, uint16_t *size, PcktHeaderElement *pcktHdrLe);
+
+#endif //ETHERLIB_IP_ASSEMBLER_H
diff --git a/prefab/conn_blocks/ipv4_connblock.c b/prefab/conn_blocks/ipv4_connblock.c
index df342c3..a607ab9 100644
--- a/prefab/conn_blocks/ipv4_connblock.c
+++ b/prefab/conn_blocks/ipv4_connblock.c
@@ -4,15 +4,17 @@
 
 #include "ipv4_connblock.h"
 
-#include "../packet_parsers/packet_parsers.h"
 #include "../../utils.h"
+#include "../../global_state.h"
 
 static bool filtIPv4(const PcktSieveFilterCondition *filtCond, const PcktProps *contProps, const PcktProps *ownProps, EthInterface * intf) {
     EthernetProps *etherProps = (EthernetProps *) contProps;
     IPv4Props *ipProps = (IPv4Props *) ownProps;
 
-    return etherProps->length_type == ETH_IPv4_PACKET_CLASS && ((IP_ADDR_FROM_FILTCOND(filtCond) == ipProps->DestIPAddr) ||
+    // check header
+    bool headerOK = (etherProps->length_type == ETH_IPv4_PACKET_CLASS) && ((IP_ADDR_FROM_FILTCOND(filtCond) == ipProps->DestIPAddr) ||
             ((IP_ADDR_FROM_FILTCOND(filtCond) == IPv4_IF_ADDR) && (ipProps->DestIPAddr == intf->ip) && (intf->ip != 0)));
+    return headerOK;
 }
 
 ConnBlock ipv4_new_connblock(EthInterface *intf, ip4_addr ipAddr, SieveCallBackFn cbFn) {
diff --git a/prefab/conn_blocks/tcp/tcp_window.c b/prefab/conn_blocks/tcp/tcp_window.c
index 835a438..cd6735c 100644
--- a/prefab/conn_blocks/tcp/tcp_window.c
+++ b/prefab/conn_blocks/tcp/tcp_window.c
@@ -5,7 +5,7 @@
 #include <memory.h>
 #include <stdbool.h>
 #include "tcp_window.h"
-#include "etherlib/dynmem.h"
+#include "../../../dynmem.h"
 
 TcpWindow *tcpw_create(uint32_t size) {
     uint32_t allocSize = sizeof(TcpWindow) + size; // calculate full allocation size
@@ -41,7 +41,7 @@ TcpWindowSegment * tcpw_store_segment(TcpWindow * tcpw, const uint8_t * data, ui
         tcpw->lastSeg->next = seg;
     }
 
-    mp_report(tcpw->mp);
+    //mp_report(tcpw->mp);
 
     return seg;
 }
@@ -60,7 +60,7 @@ bool tcpw_acknowledge(TcpWindow * tcpw, uint32_t ackNum) {
         }
         mp_free(tcpw->mp, (uint8_t *) oldFirst); // release old first segment
 
-        mp_report(tcpw->mp);
+        //mp_report(tcpw->mp);
 
         return true;
     } else {
diff --git a/prefab/conn_blocks/tcp/tcp_window.h b/prefab/conn_blocks/tcp/tcp_window.h
index dcba1e6..52918c7 100644
--- a/prefab/conn_blocks/tcp/tcp_window.h
+++ b/prefab/conn_blocks/tcp/tcp_window.h
@@ -1,8 +1,8 @@
-#ifndef ETHERLIB_TEST_TCP_WINDOW_H
-#define ETHERLIB_TEST_TCP_WINDOW_H
+#ifndef ETHERLIB_TCP_WINDOW_H
+#define ETHERLIB_TCP_WINDOW_H
 
 #include <stdint.h>
-#include "etherlib/memory_pool.h"
+#include "../../../memory_pool.h"
 
 /**
  * TCP segment descriptor
@@ -57,4 +57,4 @@ TcpWindowSegment * tcpw_store_segment(TcpWindow * tcpw, const uint8_t * data, ui
  */
 bool tcpw_acknowledge(TcpWindow * tcpw, uint32_t ackNum);
 
-#endif //ETHERLIB_TEST_TCP_WINDOW_H
+#endif //ETHERLIB_TCP_WINDOW_H
diff --git a/prefab/conn_blocks/tcp_connblock.c b/prefab/conn_blocks/tcp_connblock.c
index 517c255..3af95e5 100644
--- a/prefab/conn_blocks/tcp_connblock.c
+++ b/prefab/conn_blocks/tcp_connblock.c
@@ -6,14 +6,13 @@
 #include "../packet_parsers/packet_parsers.h"
 #include "../../utils.h"
 #include "../../dynmem.h"
-#include "etherlib/pckt_assembler.h"
-#include "etherlib/eth_interface.h"
+#include "../../pckt_assembler.h"
+#include "../../eth_interface.h"
 #include "ipv4_connblock.h"
-#include "etherlib/prefab/packet_parsers/tcp_segment.h"
-#include "etherlib/gen_queue.h"
+#include "../../gen_queue.h"
 #include "etherlib_options.h"
-#include "etherlib/prefab/conn_blocks/tcp/tcp_window.h"
-#include "etherlib/global_state.h"
+#include "../../prefab/conn_blocks/tcp/tcp_window.h"
+#include "../../global_state.h"
 
 static char *TCP_STATE_NAMES[] = {
         "CLOSED", "LISTEN", "SYN_RCVD", "SYN_SENT", "ESTAB", "FIN_WAIT_1",
@@ -42,13 +41,19 @@ typedef struct {
     uint32_t sequenceNumber; // seq. num of next transmitted octet
     uint32_t ackNumber; // ack. number sent to the remote side (seq. num of next expected octet)
     uint16_t window;
-    TcpWindow * txWin;
+    TcpWindow *txWin;
     ConnBlock connBlock;
-    bool debug;
+    cbd d; // connection block descriptor
+    uint8_t retryLimit;
+    uint8_t retries;
+    uint8_t retryTO; // retry timeout
+    bool8_t debug;
     SieveCallBackFn userCb;
 } TcpState;
 
 #define TCP_DEFAULT_MSS (1200)
+#define TCP_DEFAULT_RETRY_LIMIT (5)
+#define TCP_DEFAULT_RETRY_TO_HS (100)
 
 void tcps_init(TcpState *tcps, uint16_t localPort) {
     tcps->sequenceNumber = (uint32_t) rand();
@@ -60,6 +65,9 @@ void tcps_init(TcpState *tcps, uint16_t localPort) {
     tcps->window = ETHLIB_DEF_TCP_WINDOW_SIZE;
     tcps->txWin = tcpw_create(ETHLIB_DEF_TCP_WINDOW_SIZE);
     //tcps->rxWin = tcpw_create(ETHLIB_DEF_TCP_WINDOW_SIZE);
+    tcps->retryLimit = TCP_DEFAULT_RETRY_LIMIT;
+    tcps->retryTO = TCP_DEFAULT_RETRY_TO_HS;
+    tcps->retries = 0;
     tcps->debug = false;
     tcps->userCb = NULL;
 }
@@ -68,8 +76,8 @@ void tcps_init(TcpState *tcps, uint16_t localPort) {
 
 void tcp_init_connection(ConnBlock *connBlock);
 
-static void retry_to_connect_cb(Timer * timer, AlarmUserData user) {
-    ConnBlock * connBlock = (ConnBlock *) user.ptr;
+static void retry_to_connect_cb(Timer *timer, AlarmUserData user) {
+    ConnBlock *connBlock = (ConnBlock *) user.ptr;
     tcp_init_connection(connBlock);
 }
 
@@ -79,9 +87,12 @@ int tcp_receive_segment_cb(const Pckt *pckt, PcktSieveLayerTag tag) {
 
     TcpConnectionState beginState = tcps->connState;
 
-    IPv4Props * ipProps = HEADER_FETCH_PROPS(IPv4Props, pckt->header->prev);
+    IPv4Props *ipProps = HEADER_FETCH_PROPS(IPv4Props, pckt->header->prev);
     uint16_t dataSize = ipProps->TotalLength - tcpProps->DataOffset - ETH_IPv4_HEADER_SIZE; // extract data size
 
+    int ret = 0;
+    bool willRetry = false; // latest operation is going to be reattempted
+
     // process incoming packet
     switch (tcps->connState) {
         case TCP_STATE_SYN_SENT: {
@@ -95,13 +106,15 @@ int tcp_receive_segment_cb(const Pckt *pckt, PcktSieveLayerTag tag) {
             // get MSS
             TcpOption *mss = tcp_get_option_by_kind(tcpProps->options, TCP_OPT_KIND_MSS);
             if (mss == NULL) {
-                tcps->connState = TCP_STATE_CLOSED; // TODO: not this way...
-                AlarmUserData alarmData;
-                alarmData.ptr = &tcps->connBlock;
-                timer_sched_rel(E.tmr, 1000000, retry_to_connect_cb, alarmData);
+                tcps->connState = TCP_STATE_CLOSED;
+                if (tcps->retries < tcps->retryLimit) {
+                    AlarmUserData alarmData;
+                    alarmData.ptr = &tcps->connBlock;
+                    timer_sched_rel(E.tmr, tcps->retryTO * 10000, retry_to_connect_cb, alarmData);
+                    willRetry = true; // indicate that operation is going to be reattempted
+                }
                 break;
             }
-
             FETCH_WORD_H2N(&tcps->remoteMSS, mss->value);
 
             // send ACK
@@ -130,7 +143,7 @@ int tcp_receive_segment_cb(const Pckt *pckt, PcktSieveLayerTag tag) {
 
                 // process data
                 if (tcps->userCb != NULL) {
-                    PcktSieveLayerTag userTag = { 0 }; // TODO...
+                    PcktSieveLayerTag userTag = {0}; // TODO...
                     tcps->userCb(pckt, userTag);
                 }
             } else if ((dataSize == 0) && (tcps->sequenceNumber == tcpProps->AcknowledgementNumber)) { // outgoing segment was acknowledged by peer
@@ -141,6 +154,7 @@ int tcp_receive_segment_cb(const Pckt *pckt, PcktSieveLayerTag tag) {
         case TCP_STATE_LAST_ACK:
             if (tcpProps->Flags & TCP_FLAG_ACK) {
                 tcps->connState = TCP_STATE_CLOSED;
+                ret = SIEVE_LAYER_REMOVE_THIS; // if peer closed the connection, remove sieve layer
             }
             break;
         case TCP_STATE_CLOSED:
@@ -153,6 +167,14 @@ int tcp_receive_segment_cb(const Pckt *pckt, PcktSieveLayerTag tag) {
         MSG("%s -> %s\n", TCP_STATE_NAMES[beginState], TCP_STATE_NAMES[tcps->connState]);
     }
 
+    // maintain retry counter
+    tcps->retries = willRetry ? (tcps->retries + 1) : 0;
+
+    // release descriptor if not meaningful anymore
+    if (ret == SIEVE_LAYER_REMOVE_THIS) {
+        cbdt_release(E.cbdt, tcps->d); // release descriptor
+    }
+
     return 0; // TODO
 }
 
@@ -235,6 +257,7 @@ cbd tcp_new_connblock(EthInterface *intf, ip4_addr ipAddr, uint16_t port, SieveC
     if (d == CBDT_ERR) { // on error free everything we have allocated before
         packsieve_remove_layer(tcpConnB.sieveLayer);
     }
+    tcpState->d = d; // save descriptor
     return d;
 }
 
@@ -286,6 +309,10 @@ int tcp_send_segment(const struct ConnBlock_ *connBlock, TcpFlag flags, TcpOptio
     if (tcpState->remoteAddr != 0xFFFFFFFF) {
         ArpCache *arpc = connBlock->sieve->intf->arpc;
         const ArpEntry *entry = arpc_get_ask(arpc, tcpState->remoteAddr);
+        if (entry == NULL) {
+            INFO("HW address cannot be ARP-ed, cannot send TCP segment!\n");
+            goto release_resources; // YEAH, goto HERE!
+        }
         memcpy(ethProps->destAddr, entry, ETH_HW_ADDR_LEN);
     }
     memcpy(ethProps->sourceAddr, connBlock->sieve->intf->mac, ETH_HW_ADDR_LEN);
@@ -312,18 +339,19 @@ int tcp_send_segment(const struct ConnBlock_ *connBlock, TcpFlag flags, TcpOptio
 
     ethinf_transmit(connBlock->sieve->intf, &raw);
 
+    // advance TCP sequence number
+    tcpState->sequenceNumber += size;
+
     // free headers
+    release_resources:
     dynmem_free(tcpHeader);
     dynmem_free(ipHeader);
     dynmem_free(ethHeader);
 
-    // advance TCP sequence number
-    tcpState->sequenceNumber += size;
-
     return 0;
 }
 
-uint32_t tcp_send(cbd d, const uint8_t * data, uint32_t size) {
+uint32_t tcp_send(cbd d, const uint8_t *data, uint32_t size) {
     ConnBlock connBlock;
     if (!cbdt_get_connection_block(E.cbdt, d, &connBlock)) {
         ERROR("Invalid CBD descriptor: '%d'!\n", d);
@@ -334,7 +362,7 @@ uint32_t tcp_send(cbd d, const uint8_t * data, uint32_t size) {
     if (tcps->connState == TCP_STATE_ESTAB) { // can send only data if connection is ESTABLISHED
         uint32_t maxWinSize = tcpw_get_max_window_size(tcps->txWin);
         uint32_t txSize = MIN(maxWinSize, size); // limit size to the allocable size of the retransmit buffer
-        TcpWindowSegment * winSeg = tcpw_store_segment(tcps->txWin, data, txSize, tcps->sequenceNumber); // store segment for possible retransmission
+        TcpWindowSegment *winSeg = tcpw_store_segment(tcps->txWin, data, txSize, tcps->sequenceNumber); // store segment for possible retransmission
         tcp_send_segment(&connBlock, TCP_FLAG_ACK, NULL, winSeg->data, winSeg->size);
         return txSize;
     } else {
@@ -342,7 +370,7 @@ uint32_t tcp_send(cbd d, const uint8_t * data, uint32_t size) {
     }
 }
 
-void tcp_print_report(const ConnBlock* connBlock) {
-    const PcktSieveLayer * sl = connBlock->sieveLayer;
+void tcp_print_report(const ConnBlock *connBlock) {
+    const PcktSieveLayer *sl = connBlock->sieveLayer;
     INFO("TCP port: %d", TCP_PORT_FROM_FILTCOND(&sl->filtCond));
 }
\ No newline at end of file
diff --git a/prefab/conn_blocks/tcp_connblock.h b/prefab/conn_blocks/tcp_connblock.h
index 8a3519f..862f254 100644
--- a/prefab/conn_blocks/tcp_connblock.h
+++ b/prefab/conn_blocks/tcp_connblock.h
@@ -1,5 +1,5 @@
-#ifndef ETHERLIB_TEST_TCP_CONNBLOCK_H
-#define ETHERLIB_TEST_TCP_CONNBLOCK_H
+#ifndef ETHERLIB_TCP_CONNBLOCK_H
+#define ETHERLIB_TCP_CONNBLOCK_H
 
 #define TCP_PORT_FROM_FILTCOND(fc) ((fc)->uw[7])
 #define TCP_PORT_TO_FILTCOND(fc,port) (((fc)->uw[7]) = (port))
@@ -8,7 +8,7 @@
 #include "../packet_parsers/ipv4_types.h"
 #include "../../connection_block.h"
 #include "../packet_parsers/tcp_segment.h"
-#include "etherlib/cbd_table.h"
+#include "../../cbd_table.h"
 
 struct EthInterface_;
 
@@ -54,4 +54,4 @@ void tcp_print_report(const ConnBlock* connBlock);
 
 //int tcp_send_segment(const struct ConnBlock_ *connBlock, TcpFlag flags, TcpOption * opts, const uint8_t *data, uint32_t size);
 
-#endif //ETHERLIB_TEST_TCP_CONNBLOCK_H
+#endif //ETHERLIB_TCP_CONNBLOCK_H
diff --git a/prefab/conn_blocks/udp_connblock.c b/prefab/conn_blocks/udp_connblock.c
index 15cb359..306bc36 100644
--- a/prefab/conn_blocks/udp_connblock.c
+++ b/prefab/conn_blocks/udp_connblock.c
@@ -6,11 +6,10 @@
 
 #include <stddef.h>
 
-#include "../packet_parsers/packet_parsers.h"
 #include "../../utils.h"
 #include "../../dynmem.h"
-#include "etherlib/pckt_assembler.h"
-#include "etherlib/global_state.h"
+#include "../../pckt_assembler.h"
+#include "../../global_state.h"
 
 static bool filtUdp(const PcktSieveFilterCondition *filtCond, const PcktProps *contProps, const PcktProps *ownProps, EthInterface *intf) {
     IPv4Props *ipProps = (IPv4Props *) contProps;
@@ -86,6 +85,10 @@ int udp_sendto(cbd d, const uint8_t *data, uint32_t size, ip4_addr addr, uint16_
     if (addr != 0xFFFFFFFF) {
         ArpCache *arpc = connBlock.sieve->intf->arpc;
         const ArpEntry *entry = arpc_get_ask(arpc, addr);
+        if (entry == NULL) {
+            INFO("HW address cannot be ARP-ed, cannot send UDP datagram!\n");
+            goto release_resources; // YEAH, goto HERE!
+        }
         memcpy(ethProps->destAddr, entry, ETH_HW_ADDR_LEN);
     } else {
         memset(ethProps->destAddr, 0xFF, ETH_HW_ADDR_LEN);
@@ -112,6 +115,7 @@ int udp_sendto(cbd d, const uint8_t *data, uint32_t size, ip4_addr addr, uint16_
 
     ethinf_transmit(connBlock.sieve->intf, &raw);
 
+    release_resources:
     // free headers
     dynmem_free(udpHeader);
     dynmem_free(ipHeader);
diff --git a/prefab/conn_blocks/udp_connblock.h b/prefab/conn_blocks/udp_connblock.h
index ae47909..0f8724d 100644
--- a/prefab/conn_blocks/udp_connblock.h
+++ b/prefab/conn_blocks/udp_connblock.h
@@ -5,7 +5,7 @@
 #include "../../connection_block.h"
 #include "../../eth_interface.h"
 #include "ipv4_connblock.h"
-#include "etherlib/cbd_table.h"
+#include "../../cbd_table.h"
 
 #define UDP_PORT_FROM_FILTCOND(fc) ((fc)->uw[0])
 #define UDP_PORT_TO_FILTCOND(fc,port) (((fc)->uw[0]) = (port))
diff --git a/prefab/packet_parsers/arp_packet.c b/prefab/packet_parsers/arp_packet.c
index dc54ade..2a069ea 100644
--- a/prefab/packet_parsers/arp_packet.c
+++ b/prefab/packet_parsers/arp_packet.c
@@ -3,7 +3,6 @@
 //
 
 #include "arp_packet.h"
-#include "../../packet_registry.h"
 #include "ethernet_frame.h"
 #include "../../utils.h"
 #include "../../eth_interface.h"
@@ -24,7 +23,7 @@ static void arp_fetch_mapping(const ArpProps * arpProps, ArpCache * arpc) {
     }
 }
 
-int parse_arp(const uint8_t *hdr, uint32_t size, PcktHeaderElement *pcktHdrLe, struct EthInterface_ *intf) {
+int parse_arp(const uint8_t *hdr, uint32_t size, PcktHeaderElement *pcktHdrLe, struct EthInterface_ *intf, PcktProcFnPassbackData *pb) {
     // parse ARP packet
     ArpProps *arpProps = HEADER_FETCH_PROPS(ArpProps, pcktHdrLe);
     FETCH_WORD_H2N_ADVANCE(&arpProps->HTYPE, hdr); // hardware type
@@ -38,13 +37,14 @@ int parse_arp(const uint8_t *hdr, uint32_t size, PcktHeaderElement *pcktHdrLe, s
     FETCH_ADVANCE(&arpProps->TPA, hdr, sizeof(ip4_addr)); // target protocol address
 
     // fill-in common packet header fields
-    arpProps->validityOK = true;
+    arpProps->validityOK = true; // TODO!
     arpProps->containedPacketClass = 0;
     arpProps->headerSize = ETH_ARP_HEADER_SIZE;
 
     // learn new mapping
     arp_fetch_mapping(arpProps, intf->arpc);
-    return 0;
+
+    return arpProps->validityOK ? PROC_FN_RET_OK : PROC_FN_RET_ABORT;
 }
 
 void insert_arp_header(uint8_t *hdr, const PcktHeaderElement *headers) {
diff --git a/prefab/packet_parsers/arp_packet.h b/prefab/packet_parsers/arp_packet.h
index e108789..74ee4a8 100644
--- a/prefab/packet_parsers/arp_packet.h
+++ b/prefab/packet_parsers/arp_packet.h
@@ -2,8 +2,8 @@
 // Created by epagris on 2022.12.08..
 //
 
-#ifndef ETHERLIB_TEST_ARP_PACKET_H
-#define ETHERLIB_TEST_ARP_PACKET_H
+#ifndef ETHERLIB_ARP_PACKET_H
+#define ETHERLIB_ARP_PACKET_H
 
 #include <stdint.h>
 #include "ipv4_types.h"
@@ -51,7 +51,7 @@ typedef struct {
  * @param intf Ethernet interface
  * @return always 0 OR -1 on failure
  */
-int parse_arp(const uint8_t *hdr, uint32_t size, PcktHeaderElement *pcktHdrLe, struct EthInterface_ *intf);
+int parse_arp(const uint8_t *hdr, uint32_t size, PcktHeaderElement *pcktHdrLe, struct EthInterface_ *intf, PcktProcFnPassbackData *pb);
 
 /**
  * Insert ARP header into packet.
@@ -60,5 +60,5 @@ int parse_arp(const uint8_t *hdr, uint32_t size, PcktHeaderElement *pcktHdrLe, s
  */
 void insert_arp_header(uint8_t *hdr, const PcktHeaderElement *headers);
 
-#endif //ETHERLIB_TEST_ARP_PACKET_H
+#endif //ETHERLIB_ARP_PACKET_H
 
diff --git a/prefab/packet_parsers/dhcp.c b/prefab/packet_parsers/dhcp.c
index 351b5b1..530b76a 100644
--- a/prefab/packet_parsers/dhcp.c
+++ b/prefab/packet_parsers/dhcp.c
@@ -8,7 +8,7 @@
 #include "../../utils.h"
 #include "../../connection_block.h"
 #include "../conn_blocks/udp_connblock.h"
-#include "etherlib/global_state.h"
+#include "../../global_state.h"
 
 static struct {
     DhcpState state;
diff --git a/prefab/packet_parsers/dhcp.h b/prefab/packet_parsers/dhcp.h
index 957b878..388957a 100644
--- a/prefab/packet_parsers/dhcp.h
+++ b/prefab/packet_parsers/dhcp.h
@@ -1,5 +1,5 @@
-#ifndef ETHERLIB_TEST_DHCP_H
-#define ETHERLIB_TEST_DHCP_H
+#ifndef ETHERLIB_DHCP_H
+#define ETHERLIB_DHCP_H
 
 #include <stdint.h>
 #include "../../eth_interface.h"
@@ -58,4 +58,4 @@ void dhcp_initiate(EthInterface * intf);
  */
 void dhcp_start();
 
-#endif //ETHERLIB_TEST_DHCP_H
+#endif //ETHERLIB_DHCP_H
diff --git a/prefab/packet_parsers/ethernet_frame.c b/prefab/packet_parsers/ethernet_frame.c
index fb5a46b..aba9627 100644
--- a/prefab/packet_parsers/ethernet_frame.c
+++ b/prefab/packet_parsers/ethernet_frame.c
@@ -12,7 +12,7 @@
 
 EthernetAddress ETH_ETHERNET_IPMC_HWADDR = { 0x01, 0x00, 0x5E, 0x00, 0x00, 0x00 };
 
-int parse_ethernet(const uint8_t *hdr, uint32_t size, PcktHeaderElement *pcktHdrLe, struct EthInterface_ *intf) {
+int parse_ethernet(const uint8_t *hdr, uint32_t size, PcktHeaderElement *pcktHdrLe, struct EthInterface_ *intf, PcktProcFnPassbackData * pb) {
     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
diff --git a/prefab/packet_parsers/ethernet_frame.h b/prefab/packet_parsers/ethernet_frame.h
index abc7051..17028a5 100644
--- a/prefab/packet_parsers/ethernet_frame.h
+++ b/prefab/packet_parsers/ethernet_frame.h
@@ -42,7 +42,7 @@ struct EthInterface_;
  * @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, PcktHeaderElement *pcktHdrLe, struct EthInterface_ *intf);
+int parse_ethernet(const uint8_t *hdr, uint32_t size, PcktHeaderElement *pcktHdrLe, struct EthInterface_ *intf, PcktProcFnPassbackData * pb);
 
 /**
  * Insert Ethernet header to specified address.
diff --git a/prefab/packet_parsers/icmp_packet.c b/prefab/packet_parsers/icmp_packet.c
index 00a9a35..d81d7dd 100644
--- a/prefab/packet_parsers/icmp_packet.c
+++ b/prefab/packet_parsers/icmp_packet.c
@@ -6,7 +6,7 @@
 #include "../../utils.h"
 #include "ipv4_packet.h"
 
-int parse_icmp(const uint8_t *hdr, uint32_t size, PcktHeaderElement *pcktHdrLe, struct EthInterface_ *intf) {
+int parse_icmp(const uint8_t *hdr, uint32_t size, PcktHeaderElement *pcktHdrLe, struct EthInterface_ *intf, PcktProcFnPassbackData *pb) {
     const uint8_t * hdrStart = hdr;
 
     // parse header
@@ -23,7 +23,7 @@ int parse_icmp(const uint8_t *hdr, uint32_t size, PcktHeaderElement *pcktHdrLe,
     icmpProps->containedPacketClass = 0;
     icmpProps->headerSize = ETH_ICMP_HEADER_SIZE;
 
-    return 0;
+    return icmpProps->validityOK ? PROC_FN_RET_OK : PROC_FN_RET_ABORT;
 }
 
 void insert_icmp_header(uint8_t *hdr, const PcktHeaderElement *headers) {
diff --git a/prefab/packet_parsers/icmp_packet.h b/prefab/packet_parsers/icmp_packet.h
index f1dbc16..4c49d55 100644
--- a/prefab/packet_parsers/icmp_packet.h
+++ b/prefab/packet_parsers/icmp_packet.h
@@ -1,5 +1,5 @@
-#ifndef ETHERLIB_TEST_ICMP_PACKET_H
-#define ETHERLIB_TEST_ICMP_PACKET_H
+#ifndef ETHERLIB_ICMP_PACKET_H
+#define ETHERLIB_ICMP_PACKET_H
 
 #include <stdint.h>
 #include "ipv4_types.h"
@@ -34,7 +34,7 @@ typedef struct {
  * @param intf Ethernet interface through which transmission and reception is carried out
  * @return always 0
  */
-int parse_icmp(const uint8_t *hdr, uint32_t size, PcktHeaderElement *pcktHdrLe, struct EthInterface_ *intf);
+int parse_icmp(const uint8_t *hdr, uint32_t size, PcktHeaderElement *pcktHdrLe, struct EthInterface_ *intf, PcktProcFnPassbackData *pb);
 
 /**
  * Insert ICMP header.
@@ -43,4 +43,4 @@ int parse_icmp(const uint8_t *hdr, uint32_t size, PcktHeaderElement *pcktHdrLe,
  */
 void insert_icmp_header(uint8_t * hdr, const PcktHeaderElement * headers);
 
-#endif //ETHERLIB_TEST_ICMP_PACKET_H
+#endif //ETHERLIB_ICMP_PACKET_H
diff --git a/prefab/packet_parsers/igmp_packet.c b/prefab/packet_parsers/igmp_packet.c
index 0f7c3cb..a6f189d 100644
--- a/prefab/packet_parsers/igmp_packet.c
+++ b/prefab/packet_parsers/igmp_packet.c
@@ -40,7 +40,7 @@ void insert_igmp_header(uint8_t *hdr, const PcktHeaderElement *headers) {
     memcpy(ChkSumPtr, &igmpProps->checksum, 2);
 }
 
-int parse_igmp(const uint8_t * hdr, uint32_t size, PcktHeaderElement * pcktHdrLe, struct EthInterface_ * intf) {
+int parse_igmp(const uint8_t *hdr, uint32_t size, PcktHeaderElement *pcktHdrLe, struct EthInterface_ *intf, PcktProcFnPassbackData *pb) {
     // parse header
     IgmpProps *igmpProps = HEADER_FETCH_PROPS(IgmpProps, pcktHdrLe);
     FETCH_BYTE_ADVANCE(&igmpProps->type, hdr);
@@ -54,5 +54,5 @@ int parse_igmp(const uint8_t * hdr, uint32_t size, PcktHeaderElement * pcktHdrLe
     igmpProps->containedPacketClass = 0;
     igmpProps->headerSize = ETH_IGMP_HEADER_SIZE;
 
-    return 0;
+    return igmpProps->validityOK ? PROC_FN_RET_OK : PROC_FN_RET_ABORT;
 }
diff --git a/prefab/packet_parsers/igmp_packet.h b/prefab/packet_parsers/igmp_packet.h
index 3e9c6ea..562ffe2 100644
--- a/prefab/packet_parsers/igmp_packet.h
+++ b/prefab/packet_parsers/igmp_packet.h
@@ -1,5 +1,5 @@
-#ifndef ETHERLIB_TEST_IGMP_PACKET_H
-#define ETHERLIB_TEST_IGMP_PACKET_H
+#ifndef ETHERLIB_IGMP_PACKET_H
+#define ETHERLIB_IGMP_PACKET_H
 
 #include <stdint.h>
 #include "ipv4_types.h"
@@ -43,6 +43,6 @@ void insert_igmp_header(uint8_t * hdr, const PcktHeaderElement * headers);
  * @param intf Ethernet interface
  * @return always 0
  */
-int parse_igmp(const uint8_t * hdr, uint32_t size, PcktHeaderElement * pcktHdrLe, struct EthInterface_ * intf);
+int parse_igmp(const uint8_t *hdr, uint32_t size, PcktHeaderElement *pcktHdrLe, struct EthInterface_ *intf, PcktProcFnPassbackData *pb);
 
-#endif //ETHERLIB_TEST_IGMP_PACKET_H
+#endif //ETHERLIB_IGMP_PACKET_H
diff --git a/prefab/packet_parsers/ipv4_packet.c b/prefab/packet_parsers/ipv4_packet.c
index 9d24888..96a3fd1 100644
--- a/prefab/packet_parsers/ipv4_packet.c
+++ b/prefab/packet_parsers/ipv4_packet.c
@@ -15,12 +15,12 @@ static bool check_ipv4_validity(const uint8_t *hdr, const IPv4Props *ipProps) {
     bool valid =
             (ipProps->Version == 4) &&
             (ipProps->IHL == (ETH_IP_HEADER_LENGTH / 4)) &&
-            (chksum(hdr, ETH_IPv4_HEADER_SIZE, false) == 0) &&
-            (ipProps->FragmentOffset == 0) && !(ipProps->Flags & 0x02 << 4); // TODO: discard if fragmented
+            (chksum(hdr, ETH_IPv4_HEADER_SIZE, false) == 0); /*&&
+            (ipProps->FragmentOffset == 0) && !(ipProps->Flags & 0x02 << 4); // TODO: discard if fragmented*/
     return valid;
 }
 
-int parse_ipv4(const uint8_t *hdr, uint32_t size, PcktHeaderElement *pcktHdrLe, struct EthInterface_ *intf) {
+int parse_ipv4(const uint8_t *hdr, uint32_t size, PcktHeaderElement *pcktHdrLe, struct EthInterface_ *intf, PcktProcFnPassbackData * pb) {
     const uint8_t *hdrBegin = hdr;
     IPv4Props *ipProps = HEADER_FETCH_PROPS(IPv4Props, pcktHdrLe);
     uint8_t version_length;
@@ -33,7 +33,7 @@ int parse_ipv4(const uint8_t *hdr, uint32_t size, PcktHeaderElement *pcktHdrLe,
     uint16_t flags_fragOffset;
     FETCH_WORD_H2N_ADVANCE(&flags_fragOffset, hdr);
     ipProps->Flags = (flags_fragOffset >> 13) & 0x07;
-    ipProps->FragmentOffset = (flags_fragOffset & ~(0x07 << 13));
+    ipProps->FragmentOffset = (flags_fragOffset & ~(0x07 << 13)) << 3;
     FETCH_ADVANCE(&ipProps->TTL, hdr, 1);
     FETCH_ADVANCE(&ipProps->Protocol, hdr, 1);
     FETCH_WORD_H2N_ADVANCE(&ipProps->HeaderChecksum, hdr);
@@ -54,7 +54,26 @@ int parse_ipv4(const uint8_t *hdr, uint32_t size, PcktHeaderElement *pcktHdrLe,
         arpc_learn(intf->arpc, &entry); // learn new assignment
     }
 
-    return ipProps->validityOK ? ipProps->Protocol : -1;
+    // check whether it is a fragmented packet
+    bool isAFragment = (ipProps->FragmentOffset != 0) || (ipProps->Flags & IP_FLAG_MF);
+    if (isAFragment) {
+        const uint8_t * payloadStart = hdr;
+        ipra_input(intf->ipra, ipProps, payloadStart, size - ETH_IP_HEADER_LENGTH); // input fragment into assembler
+        uint8_t * raPload;
+        uint16_t raSize;
+        bool raOK = ipra_try_reassemble(intf->ipra, ipProps->Identification, &raPload, &raSize, pcktHdrLe);
+        if (raOK) {
+            pb->p = raPload;
+            pb->u = raSize;
+            pb->b = true; // MRD!
+            return PROC_FN_RET_REPRST; // replace buffer and restart processing (with the assembled packet)
+        } else {
+            ipProps->containedPacketClass = 0; // no contained packet if not assembled yet
+            return PROC_FN_RET_ABORT; // stop further processing
+        }
+    }
+
+    return ipProps->validityOK ? PROC_FN_RET_OK : PROC_FN_RET_ABORT;
 }
 
 static uint16_t nextIpIdentification = 0;
diff --git a/prefab/packet_parsers/ipv4_packet.h b/prefab/packet_parsers/ipv4_packet.h
index 986c0bb..7362ed3 100644
--- a/prefab/packet_parsers/ipv4_packet.h
+++ b/prefab/packet_parsers/ipv4_packet.h
@@ -9,6 +9,11 @@
 #define ETH_IPv4_PACKET_CLASS (0x0800)
 #define ETH_IPv4_HEADER_SIZE (20)
 
+typedef enum {
+    IP_FLAG_DNF = 0x02,
+    IP_FLAG_MF = 0x01
+} IPv4Flags;
+
 /**
  * IPv4 header structure
  */
@@ -45,7 +50,7 @@ struct EthInterface_;
  * @param pcktHdrLe pointer to property storage
  * @return Protocol on success or -1 on failure
  */
-int parse_ipv4(const uint8_t *hdr, uint32_t size, PcktHeaderElement *pcktHdrLe, struct EthInterface_ *intf);
+int parse_ipv4(const uint8_t *hdr, uint32_t size, PcktHeaderElement *pcktHdrLe, struct EthInterface_ *intf, PcktProcFnPassbackData * pb);
 
 /**
  * Insert IPv4 header.
diff --git a/prefab/packet_parsers/ipv4_types.h b/prefab/packet_parsers/ipv4_types.h
index 9b8c063..05ecd5b 100644
--- a/prefab/packet_parsers/ipv4_types.h
+++ b/prefab/packet_parsers/ipv4_types.h
@@ -1,5 +1,5 @@
-#ifndef ETHERLIB_TEST_IPV4_TYPES_H
-#define ETHERLIB_TEST_IPV4_TYPES_H
+#ifndef ETHERLIB_IPV4_TYPES_H
+#define ETHERLIB_IPV4_TYPES_H
 
 #include <stdint.h>
 
@@ -8,4 +8,4 @@ typedef uint32_t ip4_addr;
 #define IPv4_ANY_ADDR (0xFFFFFFFF)
 #define IPv4_IF_ADDR  (0x00000000)
 
-#endif //ETHERLIB_TEST_IPV4_TYPES_H
+#endif //ETHERLIB_IPV4_TYPES_H
diff --git a/prefab/packet_parsers/packet_parsers.h b/prefab/packet_parsers/packet_parsers.h
index 942d541..5a0ae3a 100644
--- a/prefab/packet_parsers/packet_parsers.h
+++ b/prefab/packet_parsers/packet_parsers.h
@@ -3,6 +3,11 @@
 
 #include "ethernet_frame.h"
 #include "ipv4_packet.h"
+#include "arp_packet.h"
+#include "icmp_packet.h"
+#include "igmp_packet.h"
+#include "tcp_segment.h"
 #include "udp_packet.h"
+#include "dhcp.h"
 
 #endif //ETHERLIB_PACKET_PARSERS_H
diff --git a/prefab/packet_parsers/tcp_segment.c b/prefab/packet_parsers/tcp_segment.c
index ee6760e..e2f788b 100644
--- a/prefab/packet_parsers/tcp_segment.c
+++ b/prefab/packet_parsers/tcp_segment.c
@@ -3,9 +3,9 @@
 //
 
 #include "tcp_segment.h"
-#include "etherlib/utils.h"
+#include "../../utils.h"
 #include "ethernet_frame.h"
-#include "etherlib/dynmem.h"
+#include "../../dynmem.h"
 
 #include "tcp_udp_common.h"
 #include "ipv4_packet.h"
@@ -112,7 +112,7 @@ TcpOption * tcp_get_option_by_kind(TcpOption * opt, uint16_t kind) {
     return res;
 }
 
-int parse_tcp(const uint8_t *hdr, uint32_t size, PcktHeaderElement *pcktHdrLe, struct EthInterface_ *intf) {
+int parse_tcp(const uint8_t *hdr, uint32_t size, PcktHeaderElement *pcktHdrLe, struct EthInterface_ *intf, PcktProcFnPassbackData *pb) {
     const uint8_t * hdrBegin = hdr;
 
     // fetch fixed portion of the segment header
@@ -150,7 +150,7 @@ int parse_tcp(const uint8_t *hdr, uint32_t size, PcktHeaderElement *pcktHdrLe, s
     tcpProps->validityOK = (chkSum == 0);
     tcpProps->containedPacketClass = 0;
 
-    return tcpProps->validityOK ? 0 : -1;
+    return tcpProps->validityOK ? PROC_FN_RET_OK : PROC_FN_RET_ABORT;
 }
 
 void insert_tcp_header(uint8_t *hdr, const PcktHeaderElement *headers) {
diff --git a/prefab/packet_parsers/tcp_segment.h b/prefab/packet_parsers/tcp_segment.h
index 1071502..ecf853b 100644
--- a/prefab/packet_parsers/tcp_segment.h
+++ b/prefab/packet_parsers/tcp_segment.h
@@ -1,5 +1,5 @@
-#ifndef ETHERLIB_TEST_TCP_SEGMENT_H
-#define ETHERLIB_TEST_TCP_SEGMENT_H
+#ifndef ETHERLIB_TCP_SEGMENT_H
+#define ETHERLIB_TCP_SEGMENT_H
 
 #include <stdint.h>
 #include "../../packet_sieve.h"
@@ -94,7 +94,7 @@ struct EthInterface_;
  * @param pcktHdrLe pointer to property storage
  * @return 0 on success or -1 on failure
  */
-int parse_tcp(const uint8_t *hdr, uint32_t size, PcktHeaderElement *pcktHdrLe, struct EthInterface_ *intf);
+int parse_tcp(const uint8_t *hdr, uint32_t size, PcktHeaderElement *pcktHdrLe, struct EthInterface_ *intf, PcktProcFnPassbackData *pb);
 
 /**
  * Insert TCP header.
@@ -118,4 +118,4 @@ uint32_t tcp_get_options_size(TcpOption * optLe);
  */
 TcpOption * tcp_get_option_by_kind(TcpOption * opt, uint16_t kind);
 
-#endif //ETHERLIB_TEST_TCP_SEGMENT_H
+#endif //ETHERLIB_TCP_SEGMENT_H
diff --git a/prefab/packet_parsers/tcp_udp_common.h b/prefab/packet_parsers/tcp_udp_common.h
index b8d609a..12f7b74 100644
--- a/prefab/packet_parsers/tcp_udp_common.h
+++ b/prefab/packet_parsers/tcp_udp_common.h
@@ -1,5 +1,5 @@
-#ifndef ETHERLIB_TEST_TCP_UDP_COMMON_H
-#define ETHERLIB_TEST_TCP_UDP_COMMON_H
+#ifndef ETHERLIB_TCP_UDP_COMMON_H
+#define ETHERLIB_TCP_UDP_COMMON_H
 
 #include <stdint.h>
 
@@ -20,4 +20,4 @@ typedef struct {
  */
 uint16_t tcp_udp_checksum(const IPv4PseudoHeader *pseudoHeader, const uint8_t * hdr, uint32_t size);
 
-#endif //ETHERLIB_TEST_TCP_UDP_COMMON_H
+#endif //ETHERLIB_TCP_UDP_COMMON_H
diff --git a/prefab/packet_parsers/udp_packet.c b/prefab/packet_parsers/udp_packet.c
index 694764a..fbfd69b 100644
--- a/prefab/packet_parsers/udp_packet.c
+++ b/prefab/packet_parsers/udp_packet.c
@@ -17,7 +17,7 @@ static bool check_udp_validity(const uint8_t * hdr, const PcktHeaderElement *pck
     return valid;
 }
 
-int parse_udp(const uint8_t *hdr, uint32_t size, PcktHeaderElement *pcktHdrLe, struct EthInterface_ *intf) {
+int parse_udp(const uint8_t *hdr, uint32_t size, PcktHeaderElement *pcktHdrLe, struct EthInterface_ *intf, PcktProcFnPassbackData *pb) {
     const uint8_t * hdrBegin = hdr;
     UdpProps *udpProps = HEADER_FETCH_PROPS(UdpProps, pcktHdrLe);
     FETCH_WORD_H2N_ADVANCE(&udpProps->SourcePort, hdr);
@@ -30,7 +30,7 @@ int parse_udp(const uint8_t *hdr, uint32_t size, PcktHeaderElement *pcktHdrLe, s
     udpProps->validityOK = check_udp_validity(hdrBegin, pcktHdrLe);
     udpProps->containedPacketClass = 0;
 
-    return udpProps->validityOK ? 0 : -1;
+    return udpProps->validityOK ? PROC_FN_RET_OK : PROC_FN_RET_ABORT;
 }
 
 void insert_udp_header(uint8_t *hdr, const PcktHeaderElement *headers) {
diff --git a/prefab/packet_parsers/udp_packet.h b/prefab/packet_parsers/udp_packet.h
index ae136d6..c3b863a 100644
--- a/prefab/packet_parsers/udp_packet.h
+++ b/prefab/packet_parsers/udp_packet.h
@@ -30,7 +30,7 @@ struct EthInterface_;
  * @param pcktHdrLe pointer to property storage
  * @return 0 on success or -1 on failure
  */
-int parse_udp(const uint8_t *hdr, uint32_t size, PcktHeaderElement *pcktHdrLe, struct EthInterface_ *intf);
+int parse_udp(const uint8_t *hdr, uint32_t size, PcktHeaderElement *pcktHdrLe, struct EthInterface_ *intf, PcktProcFnPassbackData *pb);
 
 /**
  * Insert UDP header.
diff --git a/timer.h b/timer.h
index 0e3f507..7e25c93 100644
--- a/timer.h
+++ b/timer.h
@@ -1,5 +1,5 @@
-#ifndef ETHERLIB_TEST_TIMER_H
-#define ETHERLIB_TEST_TIMER_H
+#ifndef ETHERLIB_TIMER_H
+#define ETHERLIB_TIMER_H
 
 #include <stdint.h>
 #include <stdbool.h>
@@ -40,7 +40,7 @@ struct Timer_;
 /**
  * Alarm user data.
  */
-typedef union {
+typedef struct {
     void * ptr;
     uint32_t u;
 } AlarmUserData;
@@ -136,4 +136,4 @@ void timer_tick(Timer * tmr, int64_t us);
  */
 void timer_report(const Timer * tmr);
 
-#endif //ETHERLIB_TEST_TIMER_H
+#endif //ETHERLIB_TIMER_H