diff --git a/blockcheck.sh b/blockcheck.sh
index f0c2a0c..3dbdd7e 100755
--- a/blockcheck.sh
+++ b/blockcheck.sh
@@ -143,6 +143,10 @@ IPT_DEL()
 {
 	$IPTABLES -C "$@" >/dev/null 2>/dev/null && $IPTABLES -D "$@"
 }
+IPT_ADD_DEL()
+{
+	on_off_function IPT IPT_DEL "$@"
+}
 IPFW_ADD()
 {
 	ipfw -qf add $IPFW_RULE_NUM "$@"
@@ -199,7 +203,6 @@ check_system()
 		Linux)
 			PKTWS="$NFQWS"
 			PKTWSD=nfqws
-			LO_IFACE=lo
 			linux_fwtype
 			[ "$FWTYPE" = iptables -o "$FWTYPE" = nftables ] || {
 				echo firewall type $FWTYPE not supported in $UNAME
@@ -210,20 +213,17 @@ check_system()
 			PKTWS="$DVTWS"
 			PKTWSD=dvtws
 			FWTYPE=ipfw
-			LO_IFACE=lo0
 			[ -f /etc/platform ] && read SUBSYS </etc/platform
 			;;
 		OpenBSD)
 			PKTWS="$DVTWS"
 			PKTWSD=dvtws
 			FWTYPE=opf
-			LO_IFACE=lo0
 			;;
 		Darwin)
 			PKTWS="$DVTWS"
 			PKTWSD=dvtws
 			FWTYPE=mpf
-			LO_IFACE=lo0
 			;;
 		*)
 			echo $UNAME not supported
@@ -497,130 +497,128 @@ curl_test_http3()
 	curl_with_dig $1 $2 -ISs -A "$USER_AGENT" --max-time $CURL_MAX_TIME --http3-only $CURL_OPT "https://$2" -o /dev/null 2>&1 
 }
 
-pktws_ipt_prepare_tcp()
+ipt_scheme()
 {
-	# $1 - port
+	# $1 - 1 - add , 0 - del
+	# $2 - tcp/udp
+	# $3 - port
+
+	IPT_ADD_DEL $1 OUTPUT -t mangle -p $2 --dport $3 -m mark ! --mark $DESYNC_MARK/$DESYNC_MARK -j NFQUEUE --queue-num $QNUM
+	# to avoid possible INVALID state drop
+	[ "$2" = tcp ] && IPT_ADD_DEL $1 INPUT -p $2 --sport $3 ! --syn -j ACCEPT
+	# for strategies with incoming packets involved (autottl)
+	IPT_ADD_DEL $1 OUTPUT -p $2 --dport $3 -m conntrack --ctstate INVALID -j ACCEPT
+	if [ "$IPV" = 6 -a -n "$IP6_DEFRAG_DISABLE" ]; then
+		# the only way to reliable disable ipv6 defrag. works only in 4.16+ kernels
+		IPT_ADD_DEL $1 OUTPUT -t raw -p $2 -m frag -j CT --notrack
+	elif [ "$IPV" = 4 ]; then
+		# enable fragments
+		IPT_ADD_DEL $1 OUTPUT -f -j ACCEPT
+	fi
+	# enable everything generated by nfqws (works only in OUTPUT, not in FORWARD)
+	# raw table may not be present
+	IPT_ADD_DEL $1 OUTPUT -t raw -m mark --mark $DESYNC_MARK/$DESYNC_MARK -j CT --notrack
+}
+nft_scheme()
+{
+	# $1 - tcp/udp
+	# $2 - port
+	nft add table inet $NFT_TABLE
+	nft "add chain inet $NFT_TABLE postnat { type filter hook output priority 102; }"
+	nft "add rule inet $NFT_TABLE postnat meta nfproto ipv${IPV} $1 dport $2 mark and $DESYNC_MARK != $DESYNC_MARK queue num $QNUM"
+	# for strategies with incoming packets involved (autottl)
+	nft "add chain inet $NFT_TABLE prenat { type filter hook prerouting priority -102; }"
+	# enable everything generated by nfqws (works only in OUTPUT, not in FORWARD)
+	nft "add chain inet $NFT_TABLE predefrag { type filter hook output priority -402; }"
+	nft "add rule inet $NFT_TABLE predefrag meta nfproto ipv${IPV} mark and $DESYNC_MARK !=0 notrack"
+}
+
+pktws_ipt_prepare()
+{
+	# $1 - tcp/udp
+	# $2 - port
 	case "$FWTYPE" in
 		iptables)
-			# to avoid possible INVALID state drop
-			IPT INPUT -p tcp --sport $1 ! --syn -j ACCEPT
-			IPT OUTPUT -p tcp --dport $1 -m conntrack --ctstate INVALID -j ACCEPT
-			if [ "$IPV" = 6 -a -n "$IP6_DEFRAG_DISABLE" ]; then
-				# the only way to reliable disable ipv6 defrag. works only in 4.16+ kernels
-				IPT OUTPUT -t raw -p tcp -m frag -j CT --notrack
-			elif [ "$IPV" = 4 ]; then
-				# enable fragments
-				IPT OUTPUT -f -j ACCEPT
-			fi
-			IPT OUTPUT -t mangle -p tcp --dport $1 -m mark ! --mark $DESYNC_MARK/$DESYNC_MARK -j NFQUEUE --queue-num $QNUM
-			IPT INPUT -t mangle -p tcp --sport $1 -m connbytes --connbytes-dir=original --connbytes-mode=packets --connbytes 1:1 -j NFQUEUE --queue-num $QNUM
-			# enable everything generated by nfqws (works only in OUTPUT, not in FORWARD)
-			# raw table may not be present
-			IPT OUTPUT -t raw -m mark --mark $DESYNC_MARK/$DESYNC_MARK -j CT --notrack
+			ipt_scheme 1 $1 $2
 			;;
 		nftables)
-			nft add table inet $NFT_TABLE
-# prenat
-#			[ "$IPV" = 6 -a -n "$IP6_DEFRAG_DISABLE" ] && {
-#				nft "add chain inet $NFT_TABLE predefrag { type filter hook output priority -402; }"
-#				nft "add rule inet $NFT_TABLE predefrag meta nfproto ipv${IPV} exthdr frag exists notrack"
-#			}
-#			nft "add chain inet $NFT_TABLE premangle { type filter hook output priority -152; }"
-#			nft "add rule inet $NFT_TABLE premangle meta nfproto ipv${IPV} tcp dport $1 mark and 0x40000000 != 0x40000000 queue num $QNUM"
-# postnat. this is good because we need only output traffic
-			nft "add chain inet $NFT_TABLE postnat { type filter hook output priority 102; }"
-			nft "add rule inet $NFT_TABLE postnat meta nfproto ipv${IPV} tcp dport $1 mark and 0x40000000 != 0x40000000 queue num $QNUM"
-			# for strategies with incoming packets involved (autottl)
-			nft "add chain inet $NFT_TABLE prenat { type filter hook prerouting priority -102; }"
-			nft "add rule inet $NFT_TABLE prenat meta nfproto ipv${IPV} tcp sport $1 ct original packets 1 queue num $QNUM"
-			# enable everything generated by nfqws (works only in OUTPUT, not in FORWARD)
-			nft "add chain inet $NFT_TABLE predefrag { type filter hook output priority -402; }"
-			nft "add rule inet $NFT_TABLE predefrag meta nfproto ipv${IPV} mark and $DESYNC_MARK !=0 notrack"
+			nft_scheme $1 $2
 			;;
 		ipfw)
 			# disable PF to avoid interferences
 			pf_is_avail && pfctl -qd
-
-			IPFW_ADD divert $IPFW_DIVERT_PORT tcp from me to any $1 proto ip${IPV} out not diverted not sockarg
-			# for autottl mode
-			IPFW_ADD divert $IPFW_DIVERT_PORT tcp from any $1 to me proto ip${IPV} tcpflags syn,ack in not diverted not sockarg
+			IPFW_ADD divert $IPFW_DIVERT_PORT $1 from me to any $2 proto ip${IPV} out not diverted not sockarg
 			;;
 		opf)
-			opf_prepare_dvtws tcp $1
+			opf_prepare_dvtws $1 $2
+			;;
+	esac
+}
+pktws_ipt_unprepare()
+{
+	# $1 - tcp/udp
+	# $2 - port
+	case "$FWTYPE" in
+		iptables)
+			ipt_scheme 0 $1 $2
+			;;
+		nftables)
+			nft delete table inet $NFT_TABLE 2>/dev/null
+			;;
+		ipfw)
+			IPFW_DEL
+			pf_is_avail && pf_restore
+			;;
+		opf)
+			pf_restore
+			;;
+	esac
+}
+
+pktws_ipt_prepare_tcp()
+{
+	# $1 - port
+
+	pktws_ipt_prepare tcp $1
+
+	case "$FWTYPE" in
+		iptables)
+			# for autottl
+			IPT INPUT -t mangle -p tcp --sport $1 -m connbytes --connbytes-dir=original --connbytes-mode=packets --connbytes 1:1 -j NFQUEUE --queue-num $QNUM
+			;;
+		nftables)
+			# for autottl
+			nft "add rule inet $NFT_TABLE prenat meta nfproto ipv${IPV} tcp sport $1 ct original packets 1 queue num $QNUM"
+			;;
+		ipfw)
+			# for autottl mode
+			IPFW_ADD divert $IPFW_DIVERT_PORT tcp from any $1 to me proto ip${IPV} tcpflags syn,ack in not diverted not sockarg
 			;;
 	esac
 }
 pktws_ipt_unprepare_tcp()
 {
 	# $1 - port
+	
+	pktws_ipt_unprepare tcp $1
+
 	case "$FWTYPE" in
 		iptables)
-			IPT_DEL OUTPUT -t mangle -p tcp --dport $1 -m mark ! --mark $DESYNC_MARK/$DESYNC_MARK -j NFQUEUE --queue-num $QNUM
 			IPT_DEL INPUT -t mangle -p tcp --sport $1 -m connbytes --connbytes-dir=original --connbytes-mode=packets --connbytes 1:1 -j NFQUEUE --queue-num $QNUM
-
-			IPT_DEL INPUT -p tcp --sport $1 ! --syn -j ACCEPT
-			IPT_DEL OUTPUT -p tcp --dport $1 -m conntrack --ctstate INVALID -j ACCEPT
-			if [ "$IPV" = 6 -a -n "$IP6_DEFRAG_DISABLE" ]; then
-				IPT_DEL OUTPUT -t raw -p tcp -m frag -j CT --notrack
-			elif [ "$IPV" = 4 ]; then
-				IPT_DEL OUTPUT -f -j ACCEPT
-			fi
-			# raw table may not be present
-			IPT_DEL OUTPUT -t raw -m mark --mark $DESYNC_MARK/$DESYNC_MARK -j CT --notrack
-			;;
-		nftables)
-			nft delete table inet $NFT_TABLE 2>/dev/null
-			;;
-		ipfw)
-			IPFW_DEL
-			pf_is_avail && pf_restore
-			;;
-		opf)
-			pf_restore
 			;;
 	esac
 }
 pktws_ipt_prepare_udp()
 {
 	# $1 - port
-	case "$FWTYPE" in
-		iptables)
-			IPT OUTPUT -t mangle -p udp --dport $1 -m mark ! --mark $DESYNC_MARK/$DESYNC_MARK -j NFQUEUE --queue-num $QNUM
-			;;
-		nftables)
-			nft add table inet $NFT_TABLE
-			nft "add chain inet $NFT_TABLE premangle { type filter hook output priority -152; }"
-			nft "add rule inet $NFT_TABLE premangle meta nfproto ipv${IPV} udp dport $1 mark and 0x40000000 != 0x40000000 queue num $QNUM"
-			;;
-		ipfw)
-			# disable PF to avoid interferences
-			pf_is_avail && pfctl -qd
 
-			IPFW_ADD divert $IPFW_DIVERT_PORT udp from me to any $1 proto ip${IPV} out not diverted not sockarg
-			;;
-		opf)
-			opf_prepare_dvtws udp $1
-			;;
-	esac
+	pktws_ipt_prepare udp $1
 }
 pktws_ipt_unprepare_udp()
 {
 	# $1 - port
-	case "$FWTYPE" in
-		iptables)
-			IPT_DEL OUTPUT -t mangle -p udp --dport $1 -m mark ! --mark $DESYNC_MARK/$DESYNC_MARK -j NFQUEUE --queue-num $QNUM
-			;;
-		nftables)
-			nft delete table inet $NFT_TABLE 2>/dev/null
-			;;
-		ipfw)
-			IPFW_DEL
-			pf_is_avail && pf_restore
-			;;
-		opf)
-			pf_restore
-			;;
-	esac
+	
+	pktws_ipt_unprepare udp $1
 }
 
 pktws_start()
@@ -882,13 +880,23 @@ pktws_check_domain_http3_bypass()
 	local f desync frag tests
 
 	pktws_curl_test_update $1 $2 --dpi-desync=fake
-	
+
 	[ "$IPV" = 6 ] && {
 		f="hopbyhop destopt"
+		[ -n "$IP6_DEFRAG_DISABLE" ] && f="$f ipfrag1"
 		for desync in $f; do
 			pktws_curl_test_update $1 $2 --dpi-desync=$desync
 		done
 	}
+	[ "$IPV" = 4 -o -n "$IP6_DEFRAG_DISABLE" ] && {
+		for frag in 8 16 24 32 40 64; do
+			tests="ipfrag2"
+			[ "$IPV" = 6 ] && tests="$tests hopbyhop,ipfrag2 destopt,ipfrag2"
+			for desync in $tests; do
+				pktws_curl_test_update $1 $2 --dpi-desync=$desync --dpi-desync-ipfrag-pos-udp=$frag
+			done
+		done
+	}
 	
 	report_strategy $1 $2 $PKTWSD
 }