Commit d961bee4 authored by Paolo Abeni's avatar Paolo Abeni
Browse files

Merge branch 'net-sched-use-the-backlog-for-nested-mirred-ingress' 

Davide Caratti says:

====================
net/sched: use the backlog for nested mirred ingress

TC mirred has a protection against excessive stack growth, but that
protection doesn't really guarantee the absence of recursion, nor
it guards against loops. Patch 1/2 rewords "recursion" to "nesting" to
make this more clear.
We can leverage on this existing mechanism to prevent TCP / SCTP from doing
soft lock-up in some specific scenarios that uses mirred egress->ingress:
patch 2 changes mirred so that the networking backlog is used for nested
mirred ingress actions.
====================

Link: https://lore.kernel.org/r/cover.1674233458.git.dcaratti@redhat.com


Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
parents 5cf6c22b ca22da2f

net/sched/act_mirred.c

+15 −8
Original line number Diff line number Diff line
@@ -29,8 +29,8 @@ 
static LIST_HEAD(mirred_list);

static DEFINE_SPINLOCK(mirred_list_lock);



#define MIRRED_RECURSION_LIMIT    4

static DEFINE_PER_CPU(unsigned int, mirred_rec_level);

#define MIRRED_NEST_LIMIT    4

static DEFINE_PER_CPU(unsigned int, mirred_nest_level);



static bool tcf_mirred_is_act_redirect(int action)

{
@@ -206,12 +206,19 @@ static int tcf_mirred_init(struct net *net, struct nlattr *nla, 
	return err;

}



static bool is_mirred_nested(void)

{

	return unlikely(__this_cpu_read(mirred_nest_level) > 1);

}



static int tcf_mirred_forward(bool want_ingress, struct sk_buff *skb)

{

	int err;



	if (!want_ingress)

		err = tcf_dev_queue_xmit(skb, dev_queue_xmit);

	else if (is_mirred_nested())

		err = netif_rx(skb);

	else

		err = netif_receive_skb(skb);
@@ -226,7 +233,7 @@ TC_INDIRECT_SCOPE int tcf_mirred_act(struct sk_buff *skb, 
	struct sk_buff *skb2 = skb;

	bool m_mac_header_xmit;

	struct net_device *dev;

	unsigned int rec_level;

	unsigned int nest_level;

	int retval, err = 0;

	bool use_reinsert;

	bool want_ingress;
@@ -237,11 +244,11 @@ TC_INDIRECT_SCOPE int tcf_mirred_act(struct sk_buff *skb, 
	int mac_len;

	bool at_nh;



	rec_level = __this_cpu_inc_return(mirred_rec_level);

	if (unlikely(rec_level > MIRRED_RECURSION_LIMIT)) {

	nest_level = __this_cpu_inc_return(mirred_nest_level);

	if (unlikely(nest_level > MIRRED_NEST_LIMIT)) {

		net_warn_ratelimited("Packet exceeded mirred recursion limit on dev %s\n",

				     netdev_name(skb->dev));

		__this_cpu_dec(mirred_rec_level);

		__this_cpu_dec(mirred_nest_level);

		return TC_ACT_SHOT;

	}
@@ -310,7 +317,7 @@ TC_INDIRECT_SCOPE int tcf_mirred_act(struct sk_buff *skb, 
			err = tcf_mirred_forward(want_ingress, skb);

			if (err)

				tcf_action_inc_overlimit_qstats(&m->common);

			__this_cpu_dec(mirred_rec_level);

			__this_cpu_dec(mirred_nest_level);

			return TC_ACT_CONSUMED;

		}

	}
@@ -322,7 +329,7 @@ TC_INDIRECT_SCOPE int tcf_mirred_act(struct sk_buff *skb, 
		if (tcf_mirred_is_act_redirect(m_eaction))

			retval = TC_ACT_SHOT;

	}

	__this_cpu_dec(mirred_rec_level);

	__this_cpu_dec(mirred_nest_level);



	return retval;

}

tools/testing/selftests/net/forwarding/tc_actions.sh

+48 −1
Original line number Diff line number Diff line
@@ -3,7 +3,8 @@ 


ALL_TESTS="gact_drop_and_ok_test mirred_egress_redirect_test \

	mirred_egress_mirror_test matchall_mirred_egress_mirror_test \

	gact_trap_test mirred_egress_to_ingress_test"

	gact_trap_test mirred_egress_to_ingress_test \

	mirred_egress_to_ingress_tcp_test"

NUM_NETIFS=4

source tc_common.sh

source lib.sh
@@ -198,6 +199,52 @@ mirred_egress_to_ingress_test() 
	log_test "mirred_egress_to_ingress ($tcflags)"

}



mirred_egress_to_ingress_tcp_test()

{

	local tmpfile=$(mktemp) tmpfile1=$(mktemp)



	RET=0

	dd conv=sparse status=none if=/dev/zero bs=1M count=2 of=$tmpfile

	tc filter add dev $h1 protocol ip pref 100 handle 100 egress flower \

		$tcflags ip_proto tcp src_ip 192.0.2.1 dst_ip 192.0.2.2 \

			action ct commit nat src addr 192.0.2.2 pipe \

			action ct clear pipe \

			action ct commit nat dst addr 192.0.2.1 pipe \

			action ct clear pipe \

			action skbedit ptype host pipe \

			action mirred ingress redirect dev $h1

	tc filter add dev $h1 protocol ip pref 101 handle 101 egress flower \

		$tcflags ip_proto icmp \

			action mirred ingress redirect dev $h1

	tc filter add dev $h1 protocol ip pref 102 handle 102 ingress flower \

		ip_proto icmp \

			action drop



	ip vrf exec v$h1 nc --recv-only -w10 -l -p 12345 -o $tmpfile1  &

	local rpid=$!

	ip vrf exec v$h1 nc -w1 --send-only 192.0.2.2 12345 <$tmpfile

	wait -n $rpid

	cmp -s $tmpfile $tmpfile1

	check_err $? "server output check failed"



	$MZ $h1 -c 10 -p 64 -a $h1mac -b $h1mac -A 192.0.2.1 -B 192.0.2.1 \

		-t icmp "ping,id=42,seq=5" -q

	tc_check_packets "dev $h1 egress" 101 10

	check_err $? "didn't mirred redirect ICMP"

	tc_check_packets "dev $h1 ingress" 102 10

	check_err $? "didn't drop mirred ICMP"

	local overlimits=$(tc_rule_stats_get ${h1} 101 egress .overlimits)

	test ${overlimits} = 10

	check_err $? "wrong overlimits, expected 10 got ${overlimits}"



	tc filter del dev $h1 egress protocol ip pref 100 handle 100 flower

	tc filter del dev $h1 egress protocol ip pref 101 handle 101 flower

	tc filter del dev $h1 ingress protocol ip pref 102 handle 102 flower



	rm -f $tmpfile $tmpfile1

	log_test "mirred_egress_to_ingress_tcp ($tcflags)"

}



setup_prepare()

{

	h1=${NETIFS[p1]}