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Message-ID: <ZXRFkhF0ZxOG30+f@nanopsycho>
Date: Sat, 9 Dec 2023 11:46:42 +0100
From: Jiri Pirko <jiri@...nulli.us>
To: David Wei <dw@...idwei.uk>
Cc: Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>
Subject: Re: [PATCH net-next 1/3] netdevsim: allow two netdevsim ports to be
Fri, Dec 08, 2023 at 10:57:04PM CET, dw@...idwei.uk wrote:
>On 2023-12-08 02:59, Jiri Pirko wrote:
>> Thu, Dec 07, 2023 at 06:21:15PM CET, dw@...idwei.uk wrote:
>>> Add a debugfs file in
>>> /sys/kernel/debug/netdevsim/netdevsimN/ports/B/link
>>
>> "peer" perhaps?
>
>Sounds good.
>
>>
>>>
>>> Writing "M B" to this file will link port A of netdevsim N with port B of
>>> netdevsim M.
>>>
>>> Reading this file will return the linked netdevsim id and port, if any.
>>>
>>> Signed-off-by: David Wei <dw@...idwei.uk>
>>> ---
>>> drivers/net/netdevsim/bus.c | 10 ++++
>>> drivers/net/netdevsim/dev.c | 97 +++++++++++++++++++++++++++++++
>>> drivers/net/netdevsim/netdev.c | 5 ++
>>> drivers/net/netdevsim/netdevsim.h | 3 +
>>> 4 files changed, 115 insertions(+)
>>>
>>> diff --git a/drivers/net/netdevsim/bus.c b/drivers/net/netdevsim/bus.c
>>> index bcbc1e19edde..3e4378e9dbee 100644
>>> --- a/drivers/net/netdevsim/bus.c
>>> +++ b/drivers/net/netdevsim/bus.c
>>> @@ -364,3 +364,13 @@ void nsim_bus_exit(void)
>>> driver_unregister(&nsim_driver);
>>> bus_unregister(&nsim_bus);
>>> }
>>> +
>>> +struct nsim_bus_dev *nsim_bus_dev_get(unsigned int id)
>>> +{
>>> + struct nsim_bus_dev *nsim_bus_dev;
>>> + list_for_each_entry(nsim_bus_dev, &nsim_bus_dev_list, list) {
>>> + if (nsim_bus_dev->dev.id == id)
>>> + return nsim_bus_dev;
>>> + }
>>> + return NULL;
>>> +}
>>> diff --git a/drivers/net/netdevsim/dev.c b/drivers/net/netdevsim/dev.c
>>> index b4d3b9cde8bd..72ad61f141a2 100644
>>> --- a/drivers/net/netdevsim/dev.c
>>> +++ b/drivers/net/netdevsim/dev.c
>>> @@ -25,6 +25,7 @@
>>> #include <linux/mutex.h>
>>> #include <linux/random.h>
>>> #include <linux/rtnetlink.h>
>>> +#include <linux/string.h>
>>> #include <linux/workqueue.h>
>>> #include <net/devlink.h>
>>> #include <net/ip.h>
>>> @@ -388,6 +389,99 @@ static const struct file_operations nsim_dev_rate_parent_fops = {
>>> .owner = THIS_MODULE,
>>> };
>>>
>>> +static ssize_t nsim_dev_link_read(struct file *file, char __user *data,
>>> + size_t count, loff_t *ppos)
>>> +{
>>> + struct nsim_dev_port *nsim_dev_port;
>>> + struct netdevsim *peer;
>>> + unsigned int id, port;
>>> + char buf[11];
>>
>> See below.
>>
>>
>>> + ssize_t len;
>>> +
>>> + nsim_dev_port = file->private_data;
>>> + peer = nsim_dev_port->ns->peer;
>>> + if (!peer) {
>>> + len = scnprintf(buf, sizeof(buf), "\n");
>>> + goto out;
>>> + }
>>> +
>>> + id = peer->nsim_bus_dev->dev.id;
>>> + port = peer->nsim_dev_port->port_index;
>>> + len = scnprintf(buf, sizeof(buf), "%u %u\n", id, port);
>>> +
>>> +out:
>>> + return simple_read_from_buffer(data, count, ppos, buf, len);
>>> +}
>>> +
>>> +static ssize_t nsim_dev_link_write(struct file *file,
>>> + const char __user *data,
>>> + size_t count, loff_t *ppos)
>>> +{
>>> + struct nsim_dev_port *nsim_dev_port, *peer_dev_port;
>>> + struct nsim_bus_dev *peer_bus_dev;
>>> + struct nsim_dev *peer_dev;
>>> + unsigned int id, port;
>>> + char *token, *cur;
>>> + char buf[10];
>>
>> # echo "889879797" >/sys/bus/netdevsim/new_device
>> # devlink dev
>> netdevsim/netdevsim889879797
>>
>> I don't think that 10/11 is enough.
>
>I took char[10] from nsim_bus_dev_max_vfs_write() which seemed like a
>reasonable amount for 4 digit id and ports. How much space is okay to
>allocate on the stack for this? Can you please point me to where
>new_device_store() is called from? I couldn't find it so I don't know
>how big its char *buf arg is.
sysfs:
static BUS_ATTR_WO(new_device);
I see no problem in allocate this buffer using count size
>
>>
>>
>>
>>
>>> + ssize_t ret;
>>> +
>>> + if (count >= sizeof(buf))
>>> + return -ENOSPC;
>>> +
>>> + ret = copy_from_user(buf, data, count);
>>> + if (ret)
>>> + return -EFAULT;
>>> + buf[count] = '\0';
>>> +
>>> + cur = buf;
>>> + token = strsep(&cur, " ");
>>
>> Why you implement this differently, comparing to new_device_store()?
>> Just use sscanf(), no?
>
>I went with strstep() instead of sscanf() because sscanf("%u %u", ...)
>does not fail with echo "1 2 3 4". I'm happy to use sscanf() though if
>this is not an issue.
Up to you, but please maintain some consistency with existing code. If
you want to do this differently, please adjust the existing code first.
>
>>
>>
>>> + if (!token)
>>> + return -EINVAL;
>>
>> In general, in case of user putting in invalid input, please hint him
>> the correct format. Again, see new_device_store().
>
>Got it, I'll add an error message.
>
>>
>>
>>> + ret = kstrtouint(token, 10, &id);
>>> + if (ret)
>>> + return ret;
>>> +
>>> + token = strsep(&cur, " ");
>>> + if (!token)
>>> + return -EINVAL;
>>> + ret = kstrtouint(token, 10, &port);
>>> + if (ret)
>>> + return ret;
>>> +
>>> + /* too many args */
>>> + if (strsep(&cur, " "))
>>> + return -E2BIG;
>>> +
>>> + /* cannot link to self */
>>> + nsim_dev_port = file->private_data;
>>> + if (nsim_dev_port->ns->nsim_bus_dev->dev.id == id)
>>
>> Why not? Loopback between 2 ports of same device seems like completely
>> valid scenario.
>
>I'm imagining physical ports which cannot be connected back to itself. When
>would this physical loopback be valid?
I'm talking about 2 ports of the same netdevsim instance. The instance
can have multiple ports.
>
>>
>>
>>> + return -EINVAL;
>>> +
>>> + /* invalid netdevsim id */
>>> + peer_bus_dev = nsim_bus_dev_get(id);
>>> + if (!peer_bus_dev)
>>> + return -EINVAL;
>>> +
>>> + peer_dev = dev_get_drvdata(&peer_bus_dev->dev);
>>> + list_for_each_entry(peer_dev_port, &peer_dev->port_list, list) {
>>> + if (peer_dev_port->port_index == port) {
>>> + nsim_dev_port->ns->peer = peer_dev_port->ns;
>>> + peer_dev_port->ns->peer = nsim_dev_port->ns;
>>> + return count;
>>> + }
>>> + }
>>> +
>>> + return -EINVAL;
>>> +}
>>> +
>>> +static const struct file_operations nsim_dev_link_fops = {
>>> + .open = simple_open,
>>> + .read = nsim_dev_link_read,
>>> + .write = nsim_dev_link_write,
>>> + .llseek = generic_file_llseek,
>>> + .owner = THIS_MODULE,
>>> +};
>>> +
>>> static int nsim_dev_port_debugfs_init(struct nsim_dev *nsim_dev,
>>> struct nsim_dev_port *nsim_dev_port)
>>> {
>>> @@ -418,6 +512,9 @@ static int nsim_dev_port_debugfs_init(struct nsim_dev *nsim_dev,
>>> }
>>> debugfs_create_symlink("dev", nsim_dev_port->ddir, dev_link_name);
>>>
>>> + debugfs_create_file("link", 0600, nsim_dev_port->ddir,
>>> + nsim_dev_port, &nsim_dev_link_fops);
>>> +
>>> return 0;
>>> }
>>>
>>> diff --git a/drivers/net/netdevsim/netdev.c b/drivers/net/netdevsim/netdev.c
>>> index aecaf5f44374..1abdcd470f21 100644
>>> --- a/drivers/net/netdevsim/netdev.c
>>> +++ b/drivers/net/netdevsim/netdev.c
>>> @@ -388,6 +388,7 @@ nsim_create(struct nsim_dev *nsim_dev, struct nsim_dev_port *nsim_dev_port)
>>> ns->nsim_dev = nsim_dev;
>>> ns->nsim_dev_port = nsim_dev_port;
>>> ns->nsim_bus_dev = nsim_dev->nsim_bus_dev;
>>> + ns->peer = NULL;
>>> SET_NETDEV_DEV(dev, &ns->nsim_bus_dev->dev);
>>> SET_NETDEV_DEVLINK_PORT(dev, &nsim_dev_port->devlink_port);
>>> nsim_ethtool_init(ns);
>>> @@ -409,6 +410,10 @@ void nsim_destroy(struct netdevsim *ns)
>>> struct net_device *dev = ns->netdev;
>>>
>>> rtnl_lock();
>>> + if (ns->peer) {
>>> + ns->peer->peer = NULL;
>>> + ns->peer = NULL;
>>
>> What is this good for?
>
>I want to make sure when a netdevsim is removed, its peer does not
>forward skbs anymore.
I mean "ns->peer = NULL;"
>
>>
>>
>>> + }
>>> unregister_netdevice(dev);
>>> if (nsim_dev_port_is_pf(ns->nsim_dev_port)) {
>>> nsim_macsec_teardown(ns);
>>> diff --git a/drivers/net/netdevsim/netdevsim.h b/drivers/net/netdevsim/netdevsim.h
>>> index 028c825b86db..ac7b34a83585 100644
>>> --- a/drivers/net/netdevsim/netdevsim.h
>>> +++ b/drivers/net/netdevsim/netdevsim.h
>>> @@ -125,6 +125,7 @@ struct netdevsim {
>>> } udp_ports;
>>>
>>> struct nsim_ethtool ethtool;
>>> + struct netdevsim *peer;
>>> };
>>>
>>> struct netdevsim *
>>> @@ -417,3 +418,5 @@ struct nsim_bus_dev {
>>>
>>> int nsim_bus_init(void);
>>> void nsim_bus_exit(void);
>>> +
>>> +struct nsim_bus_dev *nsim_bus_dev_get(unsigned int id);
>>> --
>>> 2.39.3
>>>
>>>
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