From patchwork Tue Apr 23 13:05:48 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Florian Westphal X-Patchwork-Id: 13639882 X-Patchwork-Delegate: kuba@kernel.org Received: from Chamillionaire.breakpoint.cc (Chamillionaire.breakpoint.cc [91.216.245.30]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1CE5C81722; Tue, 23 Apr 2024 11:11:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.216.245.30 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713870680; cv=none; b=M/nc0Kt/Xkb9IT4+hHsl3nRshRsOUZBouNNFR1nHdDh4JqNI0AIa2wh71aiqugToBgxlRIxDWOb48sHhkynZJY49hC4GqbmvE0JGlo+tBRCxUEn47c2U9Fnt7thsZ6KXYB+T/ahJ/NDGSLr6IlP3+o+l0xQsXawbI6OVtG4ZmvI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713870680; c=relaxed/simple; bh=kKtn93TwIuA2Vm0dDPR3fJH1nZR/lqp1S+yjVh8ZQAY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=MP58N2g8lo1DkTXvPmmrswmwCq32zwjOdAzhXIAKxCbBxgJT3ZK2EMkJx+7JtDaT4L1FM9wMwPrWuwg8kn3/oVMZqsOvOQGTVp1p1eXgsGS1k5AbAZY9CqJPHzprDJ90kxhEp4s1Qij0FGM+Zs86C3Y2PCovQhLP8dJylBaLcBc= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=strlen.de; spf=pass smtp.mailfrom=breakpoint.cc; arc=none smtp.client-ip=91.216.245.30 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=strlen.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=breakpoint.cc Received: from fw by Chamillionaire.breakpoint.cc with local (Exim 4.92) (envelope-from ) id 1rzE3O-0006wO-2M; Tue, 23 Apr 2024 13:11:14 +0200 From: Florian Westphal To: Cc: Paolo Abeni , "David S. Miller" , Eric Dumazet , Jakub Kicinski , , pablo@netfilter.org Subject: [PATCH net-next 5/7] selftests: netfilter: nft_flowtable.sh: shellcheck cleanups Date: Tue, 23 Apr 2024 15:05:48 +0200 Message-ID: <20240423130604.7013-6-fw@strlen.de> X-Mailer: git-send-email 2.43.2 In-Reply-To: <20240423130604.7013-1-fw@strlen.de> References: <20240423130604.7013-1-fw@strlen.de> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: kuba@kernel.org no functional changes intended except that test will now SKIP in case kernel lacks bridge support and initial rule load failure provides nft version information. Signed-off-by: Florian Westphal --- .../selftests/net/netfilter/nft_flowtable.sh | 257 +++++++++--------- 1 file changed, 136 insertions(+), 121 deletions(-) diff --git a/tools/testing/selftests/net/netfilter/nft_flowtable.sh b/tools/testing/selftests/net/netfilter/nft_flowtable.sh index 8b5a3a7e22f0..86d516e8acd6 100755 --- a/tools/testing/selftests/net/netfilter/nft_flowtable.sh +++ b/tools/testing/selftests/net/netfilter/nft_flowtable.sh @@ -37,17 +37,17 @@ cleanup() { rm -f "$nsin" "$ns1out" "$ns2out" - [ $log_netns -eq 0 ] && sysctl -q net.netfilter.nf_log_all_netns=$log_netns + [ "$log_netns" -eq 0 ] && sysctl -q net.netfilter.nf_log_all_netns="$log_netns" } trap cleanup EXIT sysctl -q net.netfilter.nf_log_all_netns=1 -ip link add veth0 netns $nsr1 type veth peer name eth0 netns $ns1 -ip link add veth1 netns $nsr1 type veth peer name veth0 netns $nsr2 +ip link add veth0 netns "$nsr1" type veth peer name eth0 netns "$ns1" +ip link add veth1 netns "$nsr1" type veth peer name veth0 netns "$nsr2" -ip link add veth1 netns $nsr2 type veth peer name eth0 netns $ns2 +ip link add veth1 netns "$nsr2" type veth peer name eth0 netns "$ns2" for dev in veth0 veth1; do ip -net "$nsr1" link set "$dev" up @@ -90,13 +90,13 @@ do esac done -if ! ip -net $nsr1 link set veth0 mtu $omtu; then +if ! ip -net "$nsr1" link set veth0 mtu "$omtu"; then exit 1 fi -ip -net $ns1 link set eth0 mtu $omtu +ip -net "$ns1" link set eth0 mtu "$omtu" -if ! ip -net $nsr2 link set veth1 mtu $rmtu; then +if ! ip -net "$nsr2" link set veth1 mtu "$rmtu"; then exit 1 fi @@ -108,7 +108,7 @@ if ! ip -net "$nsr2" link set veth0 mtu "$lmtu"; then exit 1 fi -ip -net $ns2 link set eth0 mtu $rmtu +ip -net "$ns2" link set eth0 mtu "$rmtu" # transfer-net between nsr1 and nsr2. # these addresses are not used for connections. @@ -119,35 +119,34 @@ ip -net "$nsr2" addr add 192.168.10.2/24 dev veth0 ip -net "$nsr2" addr add fee1:2::2/64 dev veth0 nodad for i in 0 1; do - ip netns exec $nsr1 sysctl net.ipv4.conf.veth$i.forwarding=1 > /dev/null - ip netns exec $nsr2 sysctl net.ipv4.conf.veth$i.forwarding=1 > /dev/null + ip netns exec "$nsr1" sysctl net.ipv4.conf.veth$i.forwarding=1 > /dev/null + ip netns exec "$nsr2" sysctl net.ipv4.conf.veth$i.forwarding=1 > /dev/null done -for ns in $ns1 $ns2;do - ip -net $ns link set lo up - ip -net $ns link set eth0 up +for ns in "$ns1" "$ns2";do + ip -net "$ns" link set eth0 up - if ! ip netns exec $ns sysctl net.ipv4.tcp_no_metrics_save=1 > /dev/null; then + if ! ip netns exec "$ns" sysctl net.ipv4.tcp_no_metrics_save=1 > /dev/null; then echo "ERROR: Check Originator/Responder values (problem during address addition)" exit 1 fi # don't set ip DF bit for first two tests - ip netns exec $ns sysctl net.ipv4.ip_no_pmtu_disc=1 > /dev/null + ip netns exec "$ns" sysctl net.ipv4.ip_no_pmtu_disc=1 > /dev/null done -ip -net $ns1 addr add 10.0.1.99/24 dev eth0 -ip -net $ns2 addr add 10.0.2.99/24 dev eth0 -ip -net $ns1 route add default via 10.0.1.1 -ip -net $ns2 route add default via 10.0.2.1 -ip -net $ns1 addr add dead:1::99/64 dev eth0 nodad -ip -net $ns2 addr add dead:2::99/64 dev eth0 nodad -ip -net $ns1 route add default via dead:1::1 -ip -net $ns2 route add default via dead:2::1 +ip -net "$ns1" addr add 10.0.1.99/24 dev eth0 +ip -net "$ns2" addr add 10.0.2.99/24 dev eth0 +ip -net "$ns1" route add default via 10.0.1.1 +ip -net "$ns2" route add default via 10.0.2.1 +ip -net "$ns1" addr add dead:1::99/64 dev eth0 nodad +ip -net "$ns2" addr add dead:2::99/64 dev eth0 nodad +ip -net "$ns1" route add default via dead:1::1 +ip -net "$ns2" route add default via dead:2::1 -ip -net $nsr1 route add default via 192.168.10.2 -ip -net $nsr2 route add default via 192.168.10.1 +ip -net "$nsr1" route add default via 192.168.10.2 +ip -net "$nsr2" route add default via 192.168.10.1 -ip netns exec $nsr1 nft -f - < /dev/null; then +if ! ip netns exec "$ns1" ping -c 1 -q 10.0.2.99 > /dev/null; then echo "ERROR: $ns1 cannot reach ns2" 1>&2 exit 1 fi -if ! ip netns exec $ns2 ping -c 1 -q 10.0.1.99 > /dev/null; then +if ! ip netns exec "$ns2" ping -c 1 -q 10.0.1.99 > /dev/null; then echo "ERROR: $ns2 cannot reach $ns1" 1>&2 exit 1 fi @@ -235,23 +235,27 @@ check_counters() local what=$1 local ok=1 - local orig=$(ip netns exec $nsr1 nft reset counter inet filter routed_orig | grep packets) - local repl=$(ip netns exec $nsr1 nft reset counter inet filter routed_repl | grep packets) + local orig repl + orig=$(ip netns exec "$nsr1" nft reset counter inet filter routed_orig | grep packets) + repl=$(ip netns exec "$nsr1" nft reset counter inet filter routed_repl | grep packets) local orig_cnt=${orig#*bytes} local repl_cnt=${repl#*bytes} - local fs=$(du -sb $nsin) + local fs + fs=$(du -sb "$nsin") local max_orig=${fs%%/*} local max_repl=$((max_orig/4)) - if [ $orig_cnt -gt $max_orig ];then + # flowtable fastpath should bypass normal routing one, i.e. the counters in forward hook + # should always be lower than the size of the transmitted file (max_orig). + if [ "$orig_cnt" -gt "$max_orig" ];then echo "FAIL: $what: original counter $orig_cnt exceeds expected value $max_orig" 1>&2 ret=1 ok=0 fi - if [ $repl_cnt -gt $max_repl ];then + if [ "$repl_cnt" -gt $max_repl ];then echo "FAIL: $what: reply counter $repl_cnt exceeds expected value $max_repl" 1>&2 ret=1 ok=0 @@ -267,39 +271,40 @@ check_dscp() local what=$1 local ok=1 - local counter=$(ip netns exec $ns2 nft reset counter inet filter ip4dscp3 | grep packets) + local counter + counter=$(ip netns exec "$ns2" nft reset counter inet filter ip4dscp3 | grep packets) local pc4=${counter%*bytes*} local pc4=${pc4#*packets} - local counter=$(ip netns exec $ns2 nft reset counter inet filter ip4dscp0 | grep packets) + counter=$(ip netns exec "$ns2" nft reset counter inet filter ip4dscp0 | grep packets) local pc4z=${counter%*bytes*} local pc4z=${pc4z#*packets} case "$what" in "dscp_none") - if [ $pc4 -gt 0 ] || [ $pc4z -eq 0 ]; then + if [ "$pc4" -gt 0 ] || [ "$pc4z" -eq 0 ]; then echo "FAIL: dscp counters do not match, expected dscp3 == 0, dscp0 > 0, but got $pc4,$pc4z" 1>&2 ret=1 ok=0 fi ;; "dscp_fwd") - if [ $pc4 -eq 0 ] || [ $pc4z -eq 0 ]; then + if [ "$pc4" -eq 0 ] || [ "$pc4z" -eq 0 ]; then echo "FAIL: dscp counters do not match, expected dscp3 and dscp0 > 0 but got $pc4,$pc4z" 1>&2 ret=1 ok=0 fi ;; "dscp_ingress") - if [ $pc4 -eq 0 ] || [ $pc4z -gt 0 ]; then + if [ "$pc4" -eq 0 ] || [ "$pc4z" -gt 0 ]; then echo "FAIL: dscp counters do not match, expected dscp3 > 0, dscp0 == 0 but got $pc4,$pc4z" 1>&2 ret=1 ok=0 fi ;; "dscp_egress") - if [ $pc4 -eq 0 ] || [ $pc4z -gt 0 ]; then + if [ "$pc4" -eq 0 ] || [ "$pc4z" -gt 0 ]; then echo "FAIL: dscp counters do not match, expected dscp3 > 0, dscp0 == 0 but got $pc4,$pc4z" 1>&2 ret=1 ok=0 @@ -311,7 +316,7 @@ check_dscp() ok=0 esac - if [ $ok -eq 1 ] ;then + if [ "$ok" -eq 1 ] ;then echo "PASS: $what: dscp packet counters match" fi } @@ -356,10 +361,12 @@ test_tcp_forwarding_ip() if ! check_transfer "$nsin" "$ns2out" "ns1 -> ns2"; then lret=1 + ret=1 fi if ! check_transfer "$nsin" "$ns1out" "ns1 <- ns2"; then lret=1 + ret=1 fi return $lret @@ -376,7 +383,7 @@ test_tcp_forwarding_set_dscp() { check_dscp "dscp_none" -ip netns exec $nsr1 nft -f - <&2 - ip netns exec $nsr1 nft list ruleset + ip netns exec "$nsr1" nft list ruleset ret=1 fi # delete default route, i.e. ns2 won't be able to reach ns1 and # will depend on ns1 being masqueraded in nsr1. # expect ns1 has nsr1 address. -ip -net $ns2 route del default via 10.0.2.1 -ip -net $ns2 route del default via dead:2::1 -ip -net $ns2 route add 192.168.10.1 via 10.0.2.1 +ip -net "$ns2" route del default via 10.0.2.1 +ip -net "$ns2" route del default via dead:2::1 +ip -net "$ns2" route add 192.168.10.1 via 10.0.2.1 # Second test: # Same, but with NAT enabled. Same as in first test: we expect normal forward path # to handle most packets. -ip netns exec $nsr1 nft -f - <&2 exit 0 fi -if ! test_tcp_forwarding_nat $ns1 $ns2 0 ""; then +if ! test_tcp_forwarding_nat "$ns1" "$ns2" 0 ""; then echo "FAIL: flow offload for ns1/ns2 with NAT" 1>&2 - ip netns exec $nsr1 nft list ruleset + ip netns exec "$nsr1" nft list ruleset ret=1 fi @@ -501,35 +508,40 @@ fi # Same as second test, but with PMTU discovery enabled. This # means that we expect the fastpath to handle packets as soon # as the endpoints adjust the packet size. -ip netns exec $ns1 sysctl net.ipv4.ip_no_pmtu_disc=0 > /dev/null -ip netns exec $ns2 sysctl net.ipv4.ip_no_pmtu_disc=0 > /dev/null +ip netns exec "$ns1" sysctl net.ipv4.ip_no_pmtu_disc=0 > /dev/null +ip netns exec "$ns2" sysctl net.ipv4.ip_no_pmtu_disc=0 > /dev/null # reset counters. # With pmtu in-place we'll also check that nft counters # are lower than file size and packets were forwarded via flowtable layer. # For earlier tests (large mtus), packets cannot be handled via flowtable # (except pure acks and other small packets). -ip netns exec $nsr1 nft reset counters table inet filter >/dev/null +ip netns exec "$nsr1" nft reset counters table inet filter >/dev/null -if ! test_tcp_forwarding_nat $ns1 $ns2 1 ""; then +if ! test_tcp_forwarding_nat "$ns1" "$ns2" 1 ""; then echo "FAIL: flow offload for ns1/ns2 with NAT and pmtu discovery" 1>&2 - ip netns exec $nsr1 nft list ruleset + ip netns exec "$nsr1" nft list ruleset fi # Another test: # Add bridge interface br0 to Router1, with NAT enabled. -ip -net $nsr1 link add name br0 type bridge -ip -net $nsr1 addr flush dev veth0 -ip -net $nsr1 link set up dev veth0 -ip -net $nsr1 link set veth0 master br0 -ip -net $nsr1 addr add 10.0.1.1/24 dev br0 -ip -net $nsr1 addr add dead:1::1/64 dev br0 nodad -ip -net $nsr1 link set up dev br0 +test_bridge() { +if ! ip -net "$nsr1" link add name br0 type bridge 2>/dev/null;then + echo "SKIP: could not add bridge br0" + [ "$ret" -eq 0 ] && ret=$ksft_skip + return +fi +ip -net "$nsr1" addr flush dev veth0 +ip -net "$nsr1" link set up dev veth0 +ip -net "$nsr1" link set veth0 master br0 +ip -net "$nsr1" addr add 10.0.1.1/24 dev br0 +ip -net "$nsr1" addr add dead:1::1/64 dev br0 nodad +ip -net "$nsr1" link set up dev br0 -ip netns exec $nsr1 sysctl net.ipv4.conf.br0.forwarding=1 > /dev/null +ip netns exec "$nsr1" sysctl net.ipv4.conf.br0.forwarding=1 > /dev/null # br0 with NAT enabled. -ip netns exec $nsr1 nft -f - <&2 - ip netns exec $nsr1 nft list ruleset + ip netns exec "$nsr1" nft list ruleset ret=1 fi # Another test: # Add bridge interface br0 to Router1, with NAT and VLAN. -ip -net $nsr1 link set veth0 nomaster -ip -net $nsr1 link set down dev veth0 -ip -net $nsr1 link add link veth0 name veth0.10 type vlan id 10 -ip -net $nsr1 link set up dev veth0 -ip -net $nsr1 link set up dev veth0.10 -ip -net $nsr1 link set veth0.10 master br0 - -ip -net $ns1 addr flush dev eth0 -ip -net $ns1 link add link eth0 name eth0.10 type vlan id 10 -ip -net $ns1 link set eth0 up -ip -net $ns1 link set eth0.10 up -ip -net $ns1 addr add 10.0.1.99/24 dev eth0.10 -ip -net $ns1 route add default via 10.0.1.1 -ip -net $ns1 addr add dead:1::99/64 dev eth0.10 nodad - -if ! test_tcp_forwarding_nat $ns1 $ns2 1 "bridge and VLAN"; then +ip -net "$nsr1" link set veth0 nomaster +ip -net "$nsr1" link set down dev veth0 +ip -net "$nsr1" link add link veth0 name veth0.10 type vlan id 10 +ip -net "$nsr1" link set up dev veth0 +ip -net "$nsr1" link set up dev veth0.10 +ip -net "$nsr1" link set veth0.10 master br0 + +ip -net "$ns1" addr flush dev eth0 +ip -net "$ns1" link add link eth0 name eth0.10 type vlan id 10 +ip -net "$ns1" link set eth0 up +ip -net "$ns1" link set eth0.10 up +ip -net "$ns1" addr add 10.0.1.99/24 dev eth0.10 +ip -net "$ns1" route add default via 10.0.1.1 +ip -net "$ns1" addr add dead:1::99/64 dev eth0.10 nodad + +if ! test_tcp_forwarding_nat "$ns1" "$ns2" 1 "bridge and VLAN"; then echo "FAIL: flow offload for ns1/ns2 with bridge NAT and VLAN" 1>&2 - ip netns exec $nsr1 nft list ruleset + ip netns exec "$nsr1" nft list ruleset ret=1 fi # restore test topology (remove bridge and VLAN) -ip -net $nsr1 link set veth0 nomaster -ip -net $nsr1 link set veth0 down -ip -net $nsr1 link set veth0.10 down -ip -net $nsr1 link delete veth0.10 type vlan -ip -net $nsr1 link delete br0 type bridge -ip -net $ns1 addr flush dev eth0.10 -ip -net $ns1 link set eth0.10 down -ip -net $ns1 link set eth0 down -ip -net $ns1 link delete eth0.10 type vlan +ip -net "$nsr1" link set veth0 nomaster +ip -net "$nsr1" link set veth0 down +ip -net "$nsr1" link set veth0.10 down +ip -net "$nsr1" link delete veth0.10 type vlan +ip -net "$nsr1" link delete br0 type bridge +ip -net "$ns1" addr flush dev eth0.10 +ip -net "$ns1" link set eth0.10 down +ip -net "$ns1" link set eth0 down +ip -net "$ns1" link delete eth0.10 type vlan # restore address in ns1 and nsr1 -ip -net $ns1 link set eth0 up -ip -net $ns1 addr add 10.0.1.99/24 dev eth0 -ip -net $ns1 route add default via 10.0.1.1 -ip -net $ns1 addr add dead:1::99/64 dev eth0 nodad -ip -net $ns1 route add default via dead:1::1 -ip -net $nsr1 addr add 10.0.1.1/24 dev veth0 -ip -net $nsr1 addr add dead:1::1/64 dev veth0 nodad -ip -net $nsr1 link set up dev veth0 +ip -net "$ns1" link set eth0 up +ip -net "$ns1" addr add 10.0.1.99/24 dev eth0 +ip -net "$ns1" route add default via 10.0.1.1 +ip -net "$ns1" addr add dead:1::99/64 dev eth0 nodad +ip -net "$ns1" route add default via dead:1::1 +ip -net "$nsr1" addr add 10.0.1.1/24 dev veth0 +ip -net "$nsr1" addr add dead:1::1/64 dev veth0 nodad +ip -net "$nsr1" link set up dev veth0 +} + +test_bridge KEY_SHA="0x"$(ps -af | sha1sum | cut -d " " -f 1) KEY_AES="0x"$(ps -af | md5sum | cut -d " " -f 1) @@ -613,25 +628,25 @@ do_esp() { local spi_out=$6 local spi_in=$7 - ip -net $ns xfrm state add src $remote dst $me proto esp spi $spi_in enc aes $KEY_AES auth sha1 $KEY_SHA mode tunnel sel src $rnet dst $lnet - ip -net $ns xfrm state add src $me dst $remote proto esp spi $spi_out enc aes $KEY_AES auth sha1 $KEY_SHA mode tunnel sel src $lnet dst $rnet + ip -net "$ns" xfrm state add src "$remote" dst "$me" proto esp spi "$spi_in" enc aes "$KEY_AES" auth sha1 "$KEY_SHA" mode tunnel sel src "$rnet" dst "$lnet" + ip -net "$ns" xfrm state add src "$me" dst "$remote" proto esp spi "$spi_out" enc aes "$KEY_AES" auth sha1 "$KEY_SHA" mode tunnel sel src "$lnet" dst "$rnet" # to encrypt packets as they go out (includes forwarded packets that need encapsulation) - ip -net $ns xfrm policy add src $lnet dst $rnet dir out tmpl src $me dst $remote proto esp mode tunnel priority 1 action allow + ip -net "$ns" xfrm policy add src "$lnet" dst "$rnet" dir out tmpl src "$me" dst "$remote" proto esp mode tunnel priority 1 action allow # to fwd decrypted packets after esp processing: - ip -net $ns xfrm policy add src $rnet dst $lnet dir fwd tmpl src $remote dst $me proto esp mode tunnel priority 1 action allow + ip -net "$ns" xfrm policy add src "$rnet" dst "$lnet" dir fwd tmpl src "$remote" dst "$me" proto esp mode tunnel priority 1 action allow } -do_esp $nsr1 192.168.10.1 192.168.10.2 10.0.1.0/24 10.0.2.0/24 $SPI1 $SPI2 +do_esp "$nsr1" 192.168.10.1 192.168.10.2 10.0.1.0/24 10.0.2.0/24 "$SPI1" "$SPI2" -do_esp $nsr2 192.168.10.2 192.168.10.1 10.0.2.0/24 10.0.1.0/24 $SPI2 $SPI1 +do_esp "$nsr2" 192.168.10.2 192.168.10.1 10.0.2.0/24 10.0.1.0/24 "$SPI2" "$SPI1" -ip netns exec $nsr1 nft delete table ip nat +ip netns exec "$nsr1" nft delete table ip nat # restore default routes -ip -net $ns2 route del 192.168.10.1 via 10.0.2.1 -ip -net $ns2 route add default via 10.0.2.1 -ip -net $ns2 route add default via dead:2::1 +ip -net "$ns2" route del 192.168.10.1 via 10.0.2.1 +ip -net "$ns2" route add default via 10.0.2.1 +ip -net "$ns2" route add default via dead:2::1 if test_tcp_forwarding "$ns1" "$ns2"; then check_counters "ipsec tunnel mode for ns1/ns2" @@ -641,7 +656,7 @@ else ip netns exec "$nsr1" cat /proc/net/xfrm_stat 1>&2 fi -if [ x"$1" = x ]; then +if [ "$1" = "" ]; then low=1280 mtu=$((65536 - low)) o=$(((RANDOM%mtu) + low))