[PATCH 5.10 039/145] bareudp: set NETIF_F_LLTX flag

From: Greg Kroah-Hartman
Date: Mon Jan 11 2021 - 08:32:39 EST

From: Taehee Yoo <ap420073@xxxxxxxxx>

[ Upstream commit d9e44981739a96f1a468c13bbbd54ace378caf1c ]

Like other tunneling interfaces, the bareudp doesn't need TXLOCK.
So, It is good to set the NETIF_F_LLTX flag to improve performance and
to avoid lockdep's false-positive warning.

Test commands:
ip netns add A
ip netns add B
ip link add veth0 netns A type veth peer name veth1 netns B
ip netns exec A ip link set veth0 up
ip netns exec A ip a a 10.0.0.1/24 dev veth0
ip netns exec B ip link set veth1 up
ip netns exec B ip a a 10.0.0.2/24 dev veth1

for i in {2..1}
do
let A=$i-1
ip netns exec A ip link add bareudp$i type bareudp \
dstport $i ethertype ip
ip netns exec A ip link set bareudp$i up
ip netns exec A ip a a 10.0.$i.1/24 dev bareudp$i
ip netns exec A ip r a 10.0.$i.2 encap ip src 10.0.$A.1 \
dst 10.0.$A.2 via 10.0.$i.2 dev bareudp$i

ip netns exec B ip link add bareudp$i type bareudp \
dstport $i ethertype ip
ip netns exec B ip link set bareudp$i up
ip netns exec B ip a a 10.0.$i.2/24 dev bareudp$i
ip netns exec B ip r a 10.0.$i.1 encap ip src 10.0.$A.2 \
dst 10.0.$A.1 via 10.0.$i.1 dev bareudp$i
done
ip netns exec A ping 10.0.2.2

Splat looks like:
[ 96.992803][ T822] ============================================
[ 96.993954][ T822] WARNING: possible recursive locking detected
[ 96.995102][ T822] 5.10.0+ #819 Not tainted
[ 96.995927][ T822] --------------------------------------------
[ 96.997091][ T822] ping/822 is trying to acquire lock:
[ 96.998083][ T822] ffff88810f753898 (_xmit_NONE#2){+.-.}-{2:2}, at: __dev_queue_xmit+0x1f52/0x2960
[ 96.999813][ T822]
[ 96.999813][ T822] but task is already holding lock:
[ 97.001192][ T822] ffff88810c385498 (_xmit_NONE#2){+.-.}-{2:2}, at: __dev_queue_xmit+0x1f52/0x2960
[ 97.002908][ T822]
[ 97.002908][ T822] other info that might help us debug this:
[ 97.004401][ T822] Possible unsafe locking scenario:
[ 97.004401][ T822]
[ 97.005784][ T822] CPU0
[ 97.006407][ T822] ----
[ 97.007010][ T822] lock(_xmit_NONE#2);
[ 97.007779][ T822] lock(_xmit_NONE#2);
[ 97.008550][ T822]
[ 97.008550][ T822] *** DEADLOCK ***
[ 97.008550][ T822]
[ 97.010057][ T822] May be due to missing lock nesting notation
[ 97.010057][ T822]
[ 97.011594][ T822] 7 locks held by ping/822:
[ 97.012426][ T822] #0: ffff888109a144f0 (sk_lock-AF_INET){+.+.}-{0:0}, at: raw_sendmsg+0x12f7/0x2b00
[ 97.014191][ T822] #1: ffffffffbce2f5a0 (rcu_read_lock_bh){....}-{1:2}, at: ip_finish_output2+0x249/0x2020
[ 97.016045][ T822] #2: ffffffffbce2f5a0 (rcu_read_lock_bh){....}-{1:2}, at: __dev_queue_xmit+0x1fd/0x2960
[ 97.017897][ T822] #3: ffff88810c385498 (_xmit_NONE#2){+.-.}-{2:2}, at: __dev_queue_xmit+0x1f52/0x2960
[ 97.019684][ T822] #4: ffffffffbce2f600 (rcu_read_lock){....}-{1:2}, at: bareudp_xmit+0x31b/0x3690 [bareudp]
[ 97.021573][ T822] #5: ffffffffbce2f5a0 (rcu_read_lock_bh){....}-{1:2}, at: ip_finish_output2+0x249/0x2020
[ 97.023424][ T822] #6: ffffffffbce2f5a0 (rcu_read_lock_bh){....}-{1:2}, at: __dev_queue_xmit+0x1fd/0x2960
[ 97.025259][ T822]
[ 97.025259][ T822] stack backtrace:
[ 97.026349][ T822] CPU: 3 PID: 822 Comm: ping Not tainted 5.10.0+ #819
[ 97.027609][ T822] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014
[ 97.029407][ T822] Call Trace:
[ 97.030015][ T822] dump_stack+0x99/0xcb
[ 97.030783][ T822] __lock_acquire.cold.77+0x149/0x3a9
[ 97.031773][ T822] ? stack_trace_save+0x81/0xa0
[ 97.032661][ T822] ? register_lock_class+0x1910/0x1910
[ 97.033673][ T822] ? register_lock_class+0x1910/0x1910
[ 97.034679][ T822] ? rcu_read_lock_sched_held+0x91/0xc0
[ 97.035697][ T822] ? rcu_read_lock_bh_held+0xa0/0xa0
[ 97.036690][ T822] lock_acquire+0x1b2/0x730
[ 97.037515][ T822] ? __dev_queue_xmit+0x1f52/0x2960
[ 97.038466][ T822] ? check_flags+0x50/0x50
[ 97.039277][ T822] ? netif_skb_features+0x296/0x9c0
[ 97.040226][ T822] ? validate_xmit_skb+0x29/0xb10
[ 97.041151][ T822] _raw_spin_lock+0x30/0x70
[ 97.041977][ T822] ? __dev_queue_xmit+0x1f52/0x2960
[ 97.042927][ T822] __dev_queue_xmit+0x1f52/0x2960
[ 97.043852][ T822] ? netdev_core_pick_tx+0x290/0x290
[ 97.044824][ T822] ? mark_held_locks+0xb7/0x120
[ 97.045712][ T822] ? lockdep_hardirqs_on_prepare+0x12c/0x3e0
[ 97.046824][ T822] ? __local_bh_enable_ip+0xa5/0xf0
[ 97.047771][ T822] ? ___neigh_create+0x12a8/0x1eb0
[ 97.048710][ T822] ? trace_hardirqs_on+0x41/0x120
[ 97.049626][ T822] ? ___neigh_create+0x12a8/0x1eb0
[ 97.050556][ T822] ? __local_bh_enable_ip+0xa5/0xf0
[ 97.051509][ T822] ? ___neigh_create+0x12a8/0x1eb0
[ 97.052443][ T822] ? check_chain_key+0x244/0x5f0
[ 97.053352][ T822] ? rcu_read_lock_bh_held+0x56/0xa0
[ 97.054317][ T822] ? ip_finish_output2+0x6ea/0x2020
[ 97.055263][ T822] ? pneigh_lookup+0x410/0x410
[ 97.056135][ T822] ip_finish_output2+0x6ea/0x2020
[ ... ]

Acked-by: Guillaume Nault <gnault@xxxxxxxxxx>
Fixes: 571912c69f0e ("net: UDP tunnel encapsulation module for tunnelling different protocols like MPLS, IP, NSH etc.")
Signed-off-by: Taehee Yoo <ap420073@xxxxxxxxx>
Link: https://lore.kernel.org/r/20201228152136.24215-1-ap420073@xxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/net/bareudp.c | 1 +
1 file changed, 1 insertion(+)

--- a/drivers/net/bareudp.c
+++ b/drivers/net/bareudp.c
@@ -534,6 +534,7 @@ static void bareudp_setup(struct net_dev
SET_NETDEV_DEVTYPE(dev, &bareudp_type);
dev->features |= NETIF_F_SG | NETIF_F_HW_CSUM;
dev->features |= NETIF_F_RXCSUM;
+ dev->features |= NETIF_F_LLTX;
dev->features |= NETIF_F_GSO_SOFTWARE;
dev->hw_features |= NETIF_F_SG | NETIF_F_HW_CSUM | NETIF_F_RXCSUM;
dev->hw_features |= NETIF_F_GSO_SOFTWARE;