Re: [RFC net-next v4 7/9] bridge: mrp: Connect MRP api with the switchev API

From: Horatiu Vultur
Date: Thu Apr 02 2020 - 10:21:37 EST

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The 04/01/2020 19:32, Nikolay Aleksandrov wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>
> On 01/04/2020 19:06, Horatiu Vultur wrote:
> > The 03/30/2020 19:11, Nikolay Aleksandrov wrote:
> >> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> >>
> >> On 27/03/2020 11:21, Horatiu Vultur wrote:
> >>> Implement the MRP api.
> >>>
> >>> In case the HW can't generate MRP Test frames then the SW will try to generate
> >>> the frames. In case that also the SW will fail in generating the frames then a
> >>> error is return to the userspace. The userspace is responsible to generate all
> >>> the other MRP frames regardless if the test frames are generated by HW or SW.
> >>>
> >>> The forwarding/termination of MRP frames is happening in the kernel and is done
> >>> by the MRP instance. The userspace application doesn't do the forwarding.
> >>>
> >>> Signed-off-by: Horatiu Vultur <horatiu.vultur@xxxxxxxxxxxxx>
> >>> ---
> >>> net/bridge/br_mrp.c | 514 ++++++++++++++++++++++++++++++++++++++++++++
> >>> 1 file changed, 514 insertions(+)
> >>> create mode 100644 net/bridge/br_mrp.c
> >>>
> >>
> >> Hi,
> >
> > Hi Nik,
> >
> >> In general the RCU usage needs more work.
> >
> > Thanks for the detailed review, this is my first time when I use the RCU,
> > so I might need to spend more time on time.
> >
> >> Also I might've missed it, but where do you
> >> handle bridge port delete which is used in mrp ?
> >
> > When a port is deleted, then the userspace application will be notified
> > and then the userspace will remove the MRP instance. Because there is no
> > point to have a MRP instance with only 1 port. And the function that
> > delets the MRP instance is br_mrp_del.
> >
>
> How would you execute br_mrp_del() if the port is already deleted from the bridge ?
> Nothing prevents the port to disappear and then you lose all bridge callbacks.

The br_mrp_del() is called on the bridge interface and not on the port.
The flow as I see it: the port is deleted from the bridge, the userspace
will be notified by this, the userspace will determine the bridge on
which was the port and then the userspace will make netlink call on the
bridge interface. In this way it would not loose the callback when the
port is deleted from the bridge.
The question is when the bridge is deleted, I can see that first it
deletes the ports and then it would delete the bridge. In this case I am
loosing the callbacks.
Should the function br_dev_delete be exteded for this?

>
> >> Also do you actually need the mrp->lock ?
> >
> > I think I should be fine not to use mrp->lock because already the rtnl
> > lock is taken.
> > >>
> >>> diff --git a/net/bridge/br_mrp.c b/net/bridge/br_mrp.c
> >>> new file mode 100644
> >>> index 000000000000..f1de792d7a6e
> >>> --- /dev/null
> >>> +++ b/net/bridge/br_mrp.c
> >>> @@ -0,0 +1,514 @@
> >>> +// SPDX-License-Identifier: GPL-2.0-or-later
> >>> +
> >>> +#include "br_private_mrp.h"
> >>> +
> >>> +static const u8 mrp_test_dmac[ETH_ALEN] = { 0x1, 0x15, 0x4e, 0x0, 0x0, 0x1 };
> >>> +
> >>> +static struct net_bridge_port *br_mrp_get_port(struct net_bridge *br,
> >>> + u32 ifindex)
> >>> +{
> >>> + struct net_bridge_port *res = NULL;
> >>> + struct net_bridge_port *port;
> >>> +
> >>> + spin_lock_bh(&br->lock);
> >>> +
> >>
> >> This is called under RTNL, you don't need the br->lock.
> >
> > Will be fix in the next patch series.
> >>
> >>> + list_for_each_entry(port, &br->port_list, list) {
> >>> + if (port->dev->ifindex == ifindex) {
> >>> + res = port;
> >>> + break;
> >>> + }
> >>> + }
> >>> +
> >>> + spin_unlock_bh(&br->lock);
> >>> +
> >>> + return res;
> >>> +}
> >>> +
> >>> +static struct br_mrp *br_mrp_find_id(struct net_bridge *br, u32 ring_id)
> >>> +{
> >>> + struct br_mrp *res = NULL;
> >>> + struct br_mrp *mrp;
> >>> +
> >>> + rcu_read_lock();
> >>> +
> >>
> >> This is generally a bad pattern because it can hide legitimate bugs and make
> >> it harder to debug.
> >
> > Can you give me a little more details why is a bad pattern?
> > I have tried to read about rcu from here[1][2]. But I couldn't see
> > anything about this.
> >
>
> In general you should know the context the function is used in, you cannot use the
> pointer obtained from this search after the rcu_read_unlock(). If this function is
> ever used in context which doesn't have rcu read lock or the writer lock then you'll
> mask the bug here. If you know it is always called from RCU context then just drop
> these, if not then add the proper lockdep annotations so they can be checked.

Thanks for the details. I will fix it in the next patch series.
>
> >>
> >>> + list_for_each_entry_rcu(mrp, &br->mrp_list, list) {
> >>> + if (mrp->ring_id == ring_id) {
> >>> + res = mrp;
> >>> + break;
> >>> + }
> >>> + }
> >>> +
> >>> + rcu_read_unlock();
> >>> +
> >>> + return res;
> >>> +}
> >>> +
> >>> +static struct br_mrp *br_mrp_find_port(struct net_bridge *br,
> >>> + struct net_bridge_port *p)
> >>> +{
> >>> + struct br_mrp *res = NULL;
> >>> + struct br_mrp *mrp;
> >>> +
> >>> + rcu_read_lock();
> >>> +
> >>> + list_for_each_entry_rcu(mrp, &br->mrp_list, list) {
> >>> + if (rcu_dereference(mrp->p_port) == p ||
> >>> + rcu_dereference(mrp->s_port) == p) {
> >>
> >> rcu_access_pointer() is ok for comparisons
> >
> > Will be fix in the next patch series.
> >>
> >>> + res = mrp;
> >>> + break;
> >>> + }
> >>> + }
> >>> +
> >>> + rcu_read_unlock();
> >>> +
> >>> + return res;
> >>> +}
> >>> +
> >>> +static int br_mrp_next_seq(struct br_mrp *mrp)
> >>> +{
> >>> + mrp->seq_id++;
> >>> + return mrp->seq_id;
> >>> +}
> >>> +
> >>> +static struct sk_buff *br_mrp_skb_alloc(struct net_bridge_port *p,
> >>> + const u8 *src, const u8 *dst)
> >>> +{
> >>> + struct ethhdr *eth_hdr;
> >>> + struct sk_buff *skb;
> >>> + u16 *version;
> >>> +
> >>> + skb = dev_alloc_skb(MRP_MAX_FRAME_LENGTH);
> >>> + if (!skb)
> >>> + return NULL;
> >>> +
> >>> + skb->dev = p->dev;
> >>> + skb->protocol = htons(ETH_P_MRP);
> >>> + skb->priority = MRP_FRAME_PRIO;
> >>> + skb_reserve(skb, sizeof(*eth_hdr));
> >>> +
> >>> + eth_hdr = skb_push(skb, sizeof(*eth_hdr));
> >>> + ether_addr_copy(eth_hdr->h_dest, dst);
> >>> + ether_addr_copy(eth_hdr->h_source, src);
> >>> + eth_hdr->h_proto = htons(ETH_P_MRP);
> >>> +
> >>> + version = skb_put(skb, sizeof(*version));
> >>> + *version = cpu_to_be16(MRP_VERSION);
> >>> +
> >>> + return skb;
> >>> +}
> >>> +
> >>> +static void br_mrp_skb_tlv(struct sk_buff *skb,
> >>> + enum br_mrp_tlv_header_type type,
> >>> + u8 length)
> >>> +{
> >>> + struct br_mrp_tlv_hdr *hdr;
> >>> +
> >>> + hdr = skb_put(skb, sizeof(*hdr));
> >>> + hdr->type = type;
> >>> + hdr->length = length;
> >>> +}
> >>> +
> >>> +static void br_mrp_skb_common(struct sk_buff *skb, struct br_mrp *mrp)
> >>> +{
> >>> + struct br_mrp_common_hdr *hdr;
> >>> +
> >>> + br_mrp_skb_tlv(skb, BR_MRP_TLV_HEADER_COMMON, sizeof(*hdr));
> >>> +
> >>> + hdr = skb_put(skb, sizeof(*hdr));
> >>> + hdr->seq_id = cpu_to_be16(br_mrp_next_seq(mrp));
> >>> + memset(hdr->domain, 0xff, MRP_DOMAIN_UUID_LENGTH);
> >>> +}
> >>> +
> >>> +static struct sk_buff *br_mrp_alloc_test_skb(struct br_mrp *mrp,
> >>> + struct net_device *dev,
> >>> + enum br_mrp_port_role_type port_role)
> >>> +{
> >>> + struct net_bridge_port *p = br_port_get_rtnl(dev);
> >>> + struct br_mrp_ring_test_hdr *hdr = NULL;
> >>> + struct net_bridge *br = p->br;
> >>> + struct sk_buff *skb = NULL;
> >>> +
> >>> + if (!p)
> >>> + return NULL;
> >>> +
> >>> + br = p->br;
> >>> +
> >>> + skb = br_mrp_skb_alloc(p, p->dev->dev_addr, mrp_test_dmac);
> >>> + if (!skb)
> >>> + return NULL;
> >>> +
> >>> + br_mrp_skb_tlv(skb, BR_MRP_TLV_HEADER_RING_TEST, sizeof(*hdr));
> >>> + hdr = skb_put(skb, sizeof(*hdr));
> >>> +
> >>> + hdr->prio = cpu_to_be16(MRP_DEFAULT_PRIO);
> >>> + ether_addr_copy(hdr->sa, p->br->dev->dev_addr);
> >>> + hdr->port_role = cpu_to_be16(port_role);
> >>> + hdr->state = cpu_to_be16(mrp->ring_state);
> >>> + hdr->transitions = cpu_to_be16(mrp->ring_transitions);
> >>> + hdr->timestamp = cpu_to_be32(jiffies_to_msecs(jiffies));
> >>> +
> >>> + br_mrp_skb_common(skb, mrp);
> >>> + br_mrp_skb_tlv(skb, BR_MRP_TLV_HEADER_END, 0x0);
> >>> +
> >>> + return skb;
> >>> +}
> >>> +
> >>> +static void br_mrp_test_work_expired(struct work_struct *work)
> >>> +{
> >>> + struct delayed_work *del_work = to_delayed_work(work);
> >>> + struct br_mrp *mrp = container_of(del_work, struct br_mrp, test_work);
> >>> + bool notify_open = false;
> >>> + struct sk_buff *skb;
> >>> +
> >>
> >> Since this runs asynchronously what happens if the port is deleted ?
> >
> > Later I have checks to see if the port is no NULL. Is not good enough?
> > I have these rcu_access_pointer checks and before that I disable the
> > interrupts and get the rcu lock.
> >
>
> That is not safe because you dereference the pointer again after the check
> and it may become NULL between those. You could do ptr = rcu_dereference();
> if (!ptr) and if non-null then continue accessing that memory through ptr.

I see, I will try to use rcu_dereference as you suggested.

>
> >>
> >>> + if (time_before_eq(mrp->test_end, jiffies))
> >>> + return;
> >>> +
> >>> + if (mrp->test_count_miss < mrp->test_max_miss) {
> >>> + mrp->test_count_miss++;
> >>> + } else {
> >>> + /* Notify that the ring is open only if the ring state is
> >>> + * closed, otherwise it would continue to notify at every
> >>> + * interval.
> >>> + */
> >>> + if (mrp->ring_state == BR_MRP_RING_STATE_CLOSED)
> >>> + notify_open = true;
> >>> + }
> >>> +
> >>> + local_bh_disable();
> >>> + rcu_read_lock();
> >>> +
> >>> + if (!rcu_access_pointer(mrp->p_port) ||
> >>> + !rcu_access_pointer(mrp->s_port))
> >>> + goto out;
> >>> +
> >>> + /* Is it possible here to get call to delete the bridge port? If yes
> >>> + * I need to protect it
> >>> + */
> >>> + dev_hold(rcu_dereference(mrp->p_port)->dev);
> >>> +
> >>
> >> This looks all wrong, p_port can become NULL here and you'll deref it.
> >
> > By disabling the interrupts and taking the rcu read lock, will I not be
> > sure that no one can access the p_port?
>
> No. You should read more about how RCU operates.

Yes, I should definetly do that.

>
> > If is not true, how the p_port can become NULL?
> >
>
> Readers and writer run concurrently.
>
> >>
> >>> + skb = br_mrp_alloc_test_skb(mrp, rcu_dereference(mrp->p_port)->dev,
> >>> + BR_MRP_PORT_ROLE_PRIMARY);
> >>> + if (!skb)
> >>> + goto out;
> >>> +
> >>> + skb_reset_network_header(skb);
> >>> + dev_queue_xmit(skb);
> >>> +
> >>> + if (notify_open && !mrp->ring_role_offloaded)
> >>> + br_mrp_port_open(rcu_dereference(mrp->p_port)->dev, true);
> >>> +
> >>> + dev_put(rcu_dereference(mrp->p_port)->dev);
> >>> +
> >>> + dev_hold(rcu_dereference(mrp->s_port)->dev);
> >>> +
> >>
> >> same here
> >>
> >>> + skb = br_mrp_alloc_test_skb(mrp, rcu_dereference(mrp->s_port)->dev,
> >>> + BR_MRP_PORT_ROLE_SECONDARY);
> >>> + if (!skb)
> >>> + goto out;
> >>> +
> >>> + skb_reset_network_header(skb);
> >>> + dev_queue_xmit(skb);
> >>> +
> >>> + if (notify_open && !mrp->ring_role_offloaded)
> >>> + br_mrp_port_open(rcu_dereference(mrp->s_port)->dev, true);
> >>> +
> >>> + dev_put(rcu_dereference(mrp->s_port)->dev);
> >>> +
> >>> +out:
> >>> + rcu_read_unlock();
> >>> + local_bh_enable();
> >>> +
> >>> + queue_delayed_work(system_wq, &mrp->test_work,
> >>> + usecs_to_jiffies(mrp->test_interval));
> >>> +}
> >>> +
> >>> +/* Adds a new MRP instance.
> >>> + * note: called under rtnl_lock
> >>> + */
> >>> +int br_mrp_add(struct net_bridge *br, struct br_mrp_instance *instance)
> >>> +{
> >>> + struct net_bridge_port *p;
> >>> + struct br_mrp *mrp;
> >>> +
> >>> + /* If the ring exists, it is not possible to create another one with the
> >>> + * same ring_id
> >>> + */
> >>> + mrp = br_mrp_find_id(br, instance->ring_id);
> >>> + if (mrp)
> >>> + return -EINVAL;
> >>> +
> >>> + if (!br_mrp_get_port(br, instance->p_ifindex) ||
> >>> + !br_mrp_get_port(br, instance->s_ifindex))
> >>> + return -EINVAL;
> >>> +
> >>> + mrp = devm_kzalloc(&br->dev->dev, sizeof(struct br_mrp), GFP_KERNEL);
> >>> + if (!mrp)
> >>> + return -ENOMEM;
> >>> +
> >>> + /* I think is not needed because this can be replaced with rtnl lock*/
> >>> + spin_lock_init(&mrp->lock);
> >>> + spin_lock(&mrp->lock);
> >>> +
> >>> + mrp->br = br;
> >>
> >> Is this field (mrp->br) used anywhere ?
> >
> > Not anymore. I can remove it in the next patch series.
> >
> >>
> >>> + mrp->ring_id = instance->ring_id;
> >>> +
> >>> + p = br_mrp_get_port(br, instance->p_ifindex);
> >>> + p->state = BR_STATE_FORWARDING;
> >>> + p->flags |= BR_MRP_AWARE;
> >>> + rcu_assign_pointer(mrp->p_port, p);
> >>> +
> >>> + p = br_mrp_get_port(br, instance->s_ifindex);
> >>> + p->state = BR_STATE_FORWARDING;
> >>> + p->flags |= BR_MRP_AWARE;
> >>> + rcu_assign_pointer(mrp->s_port, p);
> >>> +
> >>> + br_mrp_switchdev_add(mrp);
> >>> +
> >>> + spin_unlock(&mrp->lock);
> >>> + synchronize_rcu();
> >>
> >> Why do you need the synchronize here?
> >
> > Actually this shouldn't be after the list_add_tail_rcu? Because I am
> > thinking that some can read the list at the same time I am change it.
>
> That doesn't help, rcu primitives are already safe to run concurrently with readers.
>
> >
> >>
> >>> +
> >>> + list_add_tail_rcu(&mrp->list, &br->mrp_list);
> >>> + INIT_DELAYED_WORK(&mrp->test_work, br_mrp_test_work_expired);
> >>> +
> >>> + return 0;
> >>> +}
> >>> +
> >>> +/* Deletes existing MRP instance.
> >>> + * note: called under rtnl_lock
> >>> + */
> >>> +int br_mrp_del(struct net_bridge *br, struct br_mrp_instance *instance)
> >>> +{
> >>> + struct br_mrp *mrp = br_mrp_find_id(br, instance->ring_id);
> >>> + struct net_bridge_port *p;
> >>> +
> >>> + if (!mrp)
> >>> + return -EINVAL;
> >>> +
> >>> + /* Stop sending MRP_Test frames */
> >>> + cancel_delayed_work(&mrp->test_work);
> >>
> >> cancel_delayed_work_sync() if you'd like to make sure it's stopped and finished (if it was running
> >> during this)
> >
> > Will be fixed in the next patch series.
> >>
> >>> + br_mrp_switchdev_send_ring_test(mrp, 0, 0, 0);
> >>> +
> >>> + spin_lock(&mrp->lock);
> >>> +
> >>> + br_mrp_switchdev_del(mrp);
> >>> +
> >>> + /* Reset the ports */
> >>> + p = rcu_dereference_protected(mrp->p_port, lockdep_is_held(&mrp->lock));
> >>> + if (p) {
> >>> + spin_lock(&br->lock);
> >>> + p->state = BR_STATE_FORWARDING;
> >>> + p->flags &= ~BR_MRP_AWARE;
> >>> + br_mrp_port_switchdev_set_state(p, BR_STATE_FORWARDING);
> >>> + rcu_assign_pointer(mrp->p_port, NULL);
> >>> + spin_unlock(&br->lock);
> >>> + }
> >>> +
> >>> + p = rcu_dereference_protected(mrp->s_port, lockdep_is_held(&mrp->lock));
> >>> + if (p) {
> >>> + spin_lock(&br->lock);
> >>> + p->state = BR_STATE_FORWARDING;
> >>> + p->flags &= ~BR_MRP_AWARE;
> >>> + br_mrp_port_switchdev_set_state(p, BR_STATE_FORWARDING);
> >>> + rcu_assign_pointer(mrp->s_port, NULL);
> >>> + spin_unlock(&br->lock);
> >>> + }
> >>> +
> >>> + /* Destroy the ring */
> >>> + mrp->br = NULL;
> >>> +
> >>> + spin_unlock(&mrp->lock);
> >>> + synchronize_rcu();
> >>> +
> >>> + list_del_rcu(&mrp->list);
> >>> + devm_kfree(&br->dev->dev, mrp);
> >>> +
> >>> + return 0;
> >>> +}
> >>> +
> >>> +int br_mrp_set_port_state(struct net_bridge_port *p,
> >>> + enum br_mrp_port_state_type state)
> >>> +{
> >>> + spin_lock(&p->br->lock);
> >>> +
> >>> + if (state == BR_MRP_PORT_STATE_FORWARDING)
> >>> + p->state = BR_STATE_FORWARDING;
> >>> + else
> >>> + p->state = BR_STATE_BLOCKING;
> >>> +
> >>> + br_mrp_port_switchdev_set_state(p, state);
> >>> +
> >>> + spin_unlock(&p->br->lock);
> >>> +
> >>> + return 0;
> >>> +}
> >>> +
> >>> +int br_mrp_set_port_role(struct net_bridge_port *p,
> >>> + u32 ring_id, enum br_mrp_port_role_type role)
> >>> +{
> >>> + struct br_mrp *mrp = br_mrp_find_id(p->br, ring_id);
> >>> +
> >>> + if (!mrp)
> >>> + return -EINVAL;
> >>> +
> >>> + spin_lock(&mrp->lock);
> >>> +
> >>> + if (role == BR_MRP_PORT_ROLE_PRIMARY)
> >>> + rcu_assign_pointer(mrp->p_port, p);
> >>> + if (role == BR_MRP_PORT_ROLE_SECONDARY)
> >>> + rcu_assign_pointer(mrp->s_port, p);
> >>> +
> >>> + br_mrp_port_switchdev_set_role(p, role);
> >>> +
> >>> + spin_unlock(&mrp->lock);
> >>> + synchronize_rcu();
> >>
> >> Why do you need to synchronize here?
> >
> > Actually this is not needed.
> >>
> >>> +
> >>> + return 0;
> >>> +}
> >>> +
> >>> +int br_mrp_set_ring_state(struct net_bridge *br, u32 ring_id,
> >>> + enum br_mrp_ring_state_type state)
> >>> +{
> >>> + struct br_mrp *mrp = br_mrp_find_id(br, ring_id);
> >>> +
> >>> + if (!mrp)
> >>> + return -EINVAL;
> >>> +
> >>> + if (mrp->ring_state == BR_MRP_RING_STATE_CLOSED &&
> >>> + state != BR_MRP_RING_STATE_CLOSED)
> >>> + mrp->ring_transitions++;
> >>> +
> >>> + mrp->ring_state = state;
> >>> +
> >>> + br_mrp_switchdev_set_ring_state(mrp, state);
> >>> +
> >>> + return 0;
> >>> +}
> >>> +
> >>> +int br_mrp_set_ring_role(struct net_bridge *br, u32 ring_id,
> >>> + enum br_mrp_ring_role_type role)
> >>> +{
> >>> + struct br_mrp *mrp = br_mrp_find_id(br, ring_id);
> >>> + int err;
> >>> +
> >>> + if (!mrp)
> >>> + return -EINVAL;
> >>> +
> >>> + mrp->ring_role = role;
> >>> +
> >>> + /* If there is an error just bailed out */
> >>> + err = br_mrp_switchdev_set_ring_role(mrp, role);
> >>> + if (err && err != -EOPNOTSUPP)
> >>> + return err;
> >>> +
> >>> + /* Now detect if the HW actually applied the role or not. If the HW
> >>> + * applied the role it means that the SW will not to do those operations
> >>> + * anymore. For example if the role ir MRM then the HW will notify the
> >>> + * SW when ring is open, but if the is not pushed to the HW the SW will
> >>> + * need to detect when the ring is open
> >>> + */
> >>> + mrp->ring_role_offloaded = err == -EOPNOTSUPP ? 0 : 1;
> >>> +
> >>> + return 0;
> >>> +}
> >>> +
> >>> +int br_mrp_start_test(struct net_bridge *br, u32 ring_id, u32 interval,
> >>> + u8 max_miss, u32 period)
> >>> +{
> >>> + struct br_mrp *mrp = br_mrp_find_id(br, ring_id);
> >>> +
> >>> + if (!mrp)
> >>> + return -EINVAL;
> >>> +
> >>> + /* Try to push is to the HW and if it fails then continue to generate in
> >>> + * SW and if that also fails then return error
> >>> + */
> >>> + if (!br_mrp_switchdev_send_ring_test(mrp, interval, max_miss, period))
> >>> + return 0;
> >>> +
> >>> + mrp->test_interval = interval;
> >>> + mrp->test_end = jiffies + usecs_to_jiffies(period);
> >>> + mrp->test_max_miss = max_miss;
> >>> + mrp->test_count_miss = 0;
> >>> + queue_delayed_work(system_wq, &mrp->test_work,
> >>> + usecs_to_jiffies(interval));
> >>> +
> >>> + return 0;
> >>> +}
> >>> +
> >>> +/* Process only MRP Test frame. All the other MRP frames are processed by
> >>> + * userspace application
> >>> + * note: already called with rcu_read_lock
> >>> + */
> >>> +static void br_mrp_mrm_process(struct br_mrp *mrp, struct sk_buff *skb)
> >>> +{
> >>> + struct br_mrp_tlv_hdr *hdr;
> >>> +
> >>> + hdr = (struct br_mrp_tlv_hdr *)(skb->data + sizeof(uint16_t));
> >>> +
> >>> + if (hdr->type != BR_MRP_TLV_HEADER_RING_TEST)
> >>> + return;
> >>> +
> >>> + mrp->test_count_miss = 0;
> >>> +
> >>> + br_mrp_port_open(rcu_dereference(mrp->p_port)->dev, false);
> >>> + br_mrp_port_open(rcu_dereference(mrp->s_port)->dev, false);
> >>> +}
> >>> +
> >>> +/* This will just forward the frame to the other mrp ring port(MRC role) or will
> >>> + * not do anything.
> >>> + * note: already called with rcu_read_lock
> >>> + */
> >>> +static int br_mrp_rcv(struct net_bridge_port *p,
> >>> + struct sk_buff *skb, struct net_device *dev)
> >>> +{
> >>> + struct net_device *s_dev, *p_dev, *d_dev;
> >>> + struct net_bridge *br;
> >>> + struct sk_buff *nskb;
> >>> + struct br_mrp *mrp;
> >>> +
> >>> + /* If port is disable don't accept any frames */
> >>> + if (p->state == BR_STATE_DISABLED)
> >>> + return 0;
> >>> +
> >>> + br = p->br;
> >>> + mrp = br_mrp_find_port(br, p);
> >>> + if (unlikely(!mrp))
> >>> + return 0;
> >>> +
> >>> + /* If the role is MRM then don't forward the frames */
> >>> + if (mrp->ring_role == BR_MRP_RING_ROLE_MRM) {
> >>> + br_mrp_mrm_process(mrp, skb);
> >>> + return 1;
> >>> + }
> >>> +
> >>> + nskb = skb_clone(skb, GFP_ATOMIC);
> >>> + if (!nskb)
> >>> + return 0;
> >>> +
> >>> + p_dev = rcu_dereference(mrp->p_port)->dev;
> >>> + s_dev = rcu_dereference(mrp->s_port)->dev;
> >>> +
> >>
> >> Not safe, could deref null.
> >
> > Will be fixed in the next patch series.
> >
> >>
> >>> + if (p_dev == dev)
> >>> + d_dev = s_dev;
> >>> + else
> >>> + d_dev = p_dev;
> >>> +
> >>> + nskb->dev = d_dev;
> >>> + skb_push(nskb, ETH_HLEN);
> >>> + dev_queue_xmit(nskb);
> >>> +
> >>> + return 1;
> >>> +}
> >>> +
> >>> +int br_mrp_process(struct net_bridge_port *p, struct sk_buff *skb)
> >>> +{
> >>> + /* If there is no MRP instance do normal forwarding */
> >>> + if (unlikely(!(p->flags & BR_MRP_AWARE)))
> >>
> >> Shouldn't this one be likely() ?
> >
> > Yes, this should be likely.
> >>
> >>> + goto out;
> >>> +
> >>> + if (unlikely(skb->protocol == htons(ETH_P_MRP)))
> >>> + return br_mrp_rcv(p, skb, p->dev);
> >>> +
> >>> +out:
> >>> + return 0;
> >>> +}
> >>>
> >>
> >
> > [1] https://lwn.net/Articles/262464/
> > [2] https://www.kernel.org/doc/html/latest/RCU/listRCU.html
> >
>

--
/Horatiu

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