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net/sched: act_police: more accurate MTU policing 

in current Linux, MTU policing does not take into account that packets at
the TC ingress have the L2 header pulled. Thus, the same TC police action
(with the same value of tcfp_mtu) behaves differently for ingress/egress.
In addition, the full GSO size is compared to tcfp_mtu: as a consequence,
the policer drops GSO packets even when individual segments have the L2 +
L3 + L4 + payload length below the configured valued of tcfp_mtu.

Improve the accuracy of MTU policing as follows:
 - account for mac_len for non-GSO packets at TC ingress.
 - compare MTU threshold with the segmented size for GSO packets.
Also, add a kselftest that verifies the correct behavior.

Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Reviewed-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Davide Caratti 2022-02-10 18:56:08 +01:00 committed by David S. Miller
parent 2618a0dae0
commit 4ddc844eb8
2 changed files with 67 additions and 1 deletions
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16
net/sched/act_police.c
View File

@ -239,6 +239,20 @@ release_idr:
return err;
}
static bool tcf_police_mtu_check(struct sk_buff *skb, u32 limit)
{
u32 len;
if (skb_is_gso(skb))
return skb_gso_validate_mac_len(skb, limit);
len = qdisc_pkt_len(skb);
if (skb_at_tc_ingress(skb))
len += skb->mac_len;
return len <= limit;
}
static int tcf_police_act(struct sk_buff *skb, const struct tc_action *a,
struct tcf_result *res)
{
@ -261,7 +275,7 @@ static int tcf_police_act(struct sk_buff *skb, const struct tc_action *a,
goto inc_overlimits;
}
if (qdisc_pkt_len(skb) <= p->tcfp_mtu) {
if (tcf_police_mtu_check(skb, p->tcfp_mtu)) {
if (!p->rate_present && !p->pps_present) {
ret = p->tcfp_result;
goto end;

52
tools/testing/selftests/net/forwarding/tc_police.sh
View File

@ -37,6 +37,8 @@ ALL_TESTS="
police_tx_mirror_test
police_pps_rx_test
police_pps_tx_test
police_mtu_rx_test
police_mtu_tx_test
"
NUM_NETIFS=6
source tc_common.sh
@ -346,6 +348,56 @@ police_pps_tx_test()
tc filter del dev $rp2 egress protocol ip pref 1 handle 101 flower
}
police_mtu_common_test() {
RET=0
local test_name=$1; shift
local dev=$1; shift
local direction=$1; shift
tc filter add dev $dev $direction protocol ip pref 1 handle 101 flower \
dst_ip 198.51.100.1 ip_proto udp dst_port 54321 \
action police mtu 1042 conform-exceed drop/ok
# to count "conform" packets
tc filter add dev $h2 ingress protocol ip pref 1 handle 101 flower \
dst_ip 198.51.100.1 ip_proto udp dst_port 54321 \
action drop
mausezahn $h1 -a own -b $(mac_get $rp1) -A 192.0.2.1 -B 198.51.100.1 \
-t udp sp=12345,dp=54321 -p 1001 -c 10 -q
mausezahn $h1 -a own -b $(mac_get $rp1) -A 192.0.2.1 -B 198.51.100.1 \
-t udp sp=12345,dp=54321 -p 1000 -c 3 -q
tc_check_packets "dev $dev $direction" 101 13
check_err $? "wrong packet counter"
# "exceed" packets
local overlimits_t0=$(tc_rule_stats_get ${dev} 1 ${direction} .overlimits)
test ${overlimits_t0} = 10
check_err $? "wrong overlimits, expected 10 got ${overlimits_t0}"
# "conform" packets
tc_check_packets "dev $h2 ingress" 101 3
check_err $? "forwarding error"
tc filter del dev $h2 ingress protocol ip pref 1 handle 101 flower
tc filter del dev $dev $direction protocol ip pref 1 handle 101 flower
log_test "$test_name"
}
police_mtu_rx_test()
{
police_mtu_common_test "police mtu (rx)" $rp1 ingress
}
police_mtu_tx_test()
{
police_mtu_common_test "police mtu (tx)" $rp2 egress
}
setup_prepare()
{
h1=${NETIFS[p1]}