Re: [PATCH net 1/2] rtnetlink: count IFLA_PARENT_DEV_{NAME,BUS_NAME} in if_nlmsg_size

[Sergey Ryazanov <ryazanov.s.a@gmail.com>]

On March 18, 2026 12:45:52 PM, Sabrina Dubroca <sd@queasysnail.net> wrote:
>Commit 00e77ed8e64d ("rtnetlink: add IFLA_PARENT_[DEV|DEV_BUS]_NAME")
>added those attributes to rtnl_fill_ifinfo, but forgot to extend
>if_nlmsg_size.

Nice catch! Please find an implementation question below.

>Fixes: 00e77ed8e64d ("rtnetlink: add IFLA_PARENT_[DEV|DEV_BUS]_NAME")
>Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
>---
> net/core/rtnetlink.c | 16 ++++++++++++++++
> 1 file changed, 16 insertions(+)
>
>diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
>index dad4b1054955..a116362f5f32 100644
>--- a/net/core/rtnetlink.c
>+++ b/net/core/rtnetlink.c
>@@ -1267,6 +1267,21 @@ static size_t rtnl_dpll_pin_size(const struct net_device *dev)
> 	return size;
> }
> 
>+static size_t rtnl_dev_parent_size(const struct net_device *dev)
>+{
>+	size_t size = 0;
>+
>+	/* IFLA_PARENT_DEV_NAME */
>+	if (dev->dev.parent)
>+		size += strlen(dev_name(dev->dev.parent)) + 1;

Shall we use nla_total_size() to account alignment?

>+	/* IFLA_PARENT_DEV_BUS_NAME */
>+	if (dev->dev.parent && dev->dev.parent->bus)
>+		size += strlen(dev->dev.parent->bus->name) + 1;
>+
>+	return size;
>+}
>+
> static noinline size_t if_nlmsg_size(const struct net_device *dev,
> 				     u32 ext_filter_mask)
> {
>@@ -1328,6 +1343,7 @@ static noinline size_t if_nlmsg_size(const struct net_device *dev,
> 	       + nla_total_size(8)  /* IFLA_MAX_PACING_OFFLOAD_HORIZON */
> 	       + nla_total_size(2)  /* IFLA_HEADROOM */
> 	       + nla_total_size(2)  /* IFLA_TAILROOM */
>+	       + rtnl_dev_parent_size(dev)
> 	       + 0;
> 
> 	if (!(ext_filter_mask & RTEXT_FILTER_SKIP_STATS))

--
Sergey
Hi Sabrina,