| Message ID | 1715245883-3467-1-git-send-email-shradhagupta@linux.microsoft.com (mailing list archive) |
|---|---|
| State | Rejected |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net-next,v3] net: Add sysfs atttribute for max_mtu | expand |
On 2024-05-09 at 14:41:23, Shradha Gupta (shradhagupta@linux.microsoft.com) wrote: > For drivers like MANA, max_mtu value is populated with the value of > maximum MTU that the underlying hardware can support. IIUC, this reads dev->mtu. you can read the same using ifconfig, or any thing that uses SIOCGIFMTU. why do you need to add a new sysfs ? > Exposing this attribute as sysfs param, would be helpful in debugging > and customization of config issues with such drivers. > > --- a/net/core/net-sysfs.c > +++ b/net/core/net-sysfs.c > @@ -114,6 +114,7 @@ NETDEVICE_SHOW_RO(addr_len, fmt_dec); > NETDEVICE_SHOW_RO(ifindex, fmt_dec); > NETDEVICE_SHOW_RO(type, fmt_dec); > NETDEVICE_SHOW_RO(link_mode, fmt_dec); > +NETDEVICE_SHOW_RO(max_mtu, fmt_dec); > > static ssize_t iflink_show(struct device *dev, struct device_attribute *attr, > char *buf) > @@ -660,6 +661,7 @@ static struct attribute *net_class_attrs[] __ro_after_init = { > &dev_attr_ifalias.attr, > &dev_attr_carrier.attr, > &dev_attr_mtu.attr, > + &dev_attr_max_mtu.attr, > &dev_attr_flags.attr, > &dev_attr_tx_queue_len.attr, > &dev_attr_gro_flush_timeout.attr, > -- > 2.34.1 >
On Thu, May 9, 2024 at 11:11 AM Shradha Gupta <shradhagupta@linux.microsoft.com> wrote: > > For drivers like MANA, max_mtu value is populated with the value of > maximum MTU that the underlying hardware can support. > Exposing this attribute as sysfs param, would be helpful in debugging > and customization of config issues with such drivers. > > Signed-off-by: Shradha Gupta <shradhagupta@linux.microsoft.com> > Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com> > --- > Changes in v3: > * Removed the min_mtu sysfs attribute as it was not needed > * Improved the commit message to explain the need for the changes > * Seperated this patch from other mana attributes requirements. > --- > Documentation/ABI/testing/sysfs-class-net | 8 ++++++++ > net/core/net-sysfs.c | 2 ++ > 2 files changed, 10 insertions(+) Sorry, this is a NACK from my side. Adding sysfs attributes is costly for setups adding/deleting many netns/devices per second. RTNL already provides this value. net/core/rtnetlink.c:1850: nla_put_u32(skb, IFLA_MAX_MTU, READ_ONCE(dev->max_mtu)) ||
On Thu, May 09, 2024 at 03:12:25PM +0530, Ratheesh Kannoth wrote: > On 2024-05-09 at 14:41:23, Shradha Gupta (shradhagupta@linux.microsoft.com) wrote: > > For drivers like MANA, max_mtu value is populated with the value of > > maximum MTU that the underlying hardware can support. > IIUC, this reads dev->mtu. I think you are misunderstanding the code. > > +NETDEVICE_SHOW_RO(max_mtu, fmt_dec); /* generate a show function for simple field */ #define NETDEVICE_SHOW(field, format_string) \ static ssize_t format_##field(const struct net_device *dev, char *buf) \ { \ return sysfs_emit(buf, format_string, dev->field); \ } \ static ssize_t field##_show(struct device *dev, \ struct device_attribute *attr, char *buf) \ { \ return netdev_show(dev, attr, buf, format_##field); \ } \ #define NETDEVICE_SHOW_RO(field, format_string) \ NETDEVICE_SHOW(field, format_string); \ static DEVICE_ATTR_RO(field) So field is max_mtu, so that dev->field gets expanded to dev->max_mtu. > you can read the same using ifconfig We stopped using ifconfig years ago. You actually mean "ip link show" > or any thing that uses SIOCGIFMTU. why do you need to add a new sysfs ? SIOCGIFMTU is still implemented, but obsolete, replaced by netlink, as Eric pointed out. Andrew
diff --git a/Documentation/ABI/testing/sysfs-class-net b/Documentation/ABI/testing/sysfs-class-net index ebf21beba846..5dcab8648283 100644 --- a/Documentation/ABI/testing/sysfs-class-net +++ b/Documentation/ABI/testing/sysfs-class-net @@ -352,3 +352,11 @@ Description: 0 threaded mode disabled for this dev 1 threaded mode enabled for this dev == ================================== + +What: /sys/class/net/<iface>/max_mtu +Date: April 2024 +KernelVersion: 6.10 +Contact: netdev@vger.kernel.org +Description: + Indicates the interface's maximum supported MTU value, in + bytes, and in decimal format. diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c index e3d7a8cfa20b..381becdd73a8 100644 --- a/net/core/net-sysfs.c +++ b/net/core/net-sysfs.c @@ -114,6 +114,7 @@ NETDEVICE_SHOW_RO(addr_len, fmt_dec); NETDEVICE_SHOW_RO(ifindex, fmt_dec); NETDEVICE_SHOW_RO(type, fmt_dec); NETDEVICE_SHOW_RO(link_mode, fmt_dec); +NETDEVICE_SHOW_RO(max_mtu, fmt_dec); static ssize_t iflink_show(struct device *dev, struct device_attribute *attr, char *buf) @@ -660,6 +661,7 @@ static struct attribute *net_class_attrs[] __ro_after_init = { &dev_attr_ifalias.attr, &dev_attr_carrier.attr, &dev_attr_mtu.attr, + &dev_attr_max_mtu.attr, &dev_attr_flags.attr, &dev_attr_tx_queue_len.attr, &dev_attr_gro_flush_timeout.attr,