On Wednesday 18 March 2026 09:59:29 Qingfang Deng wrote:

On Sat, 14 Mar 2026 02:14:29 +0100, Martin Olivier wrote:

quoted

Currently, the PPP rtnetlink API allows creating a new network interface
with a custom ifname, but it lacks the ability to specify a custom PPP
unit id.

Setting a specific unit id is currently only possible with the
PPPIOCNEWUNIT ioctl. If a user-space program also requires a custom
interface name, it must create the interface first with PPPIOCNEWUNIT
and then rename it.

Resolve this by introducing the IFLA_PPP_UNIT netlink attribute. This
allows user-space programs to atomically request both a custom ifname
and a specific PPP unit id during the RTM_NEWLINK creation process,
eliminating the post-creation renaming for this use case.

Signed-off-by: Martin Olivier <redacted>
---
Changes in v2:
- use nl policy to set IFLA_PPP_UNIT min allowed value instead of a manual check in ppp_nl_validate()
- use of nla_get_s32_default() to collect IFLA_PPP_UNIT value
Link to v1: https://lore.kernel.org/netdev/PAWP192MB2411A5E7D3BE1B55E155A92F9747A@PAWP192MB2411.EURP192.PROD.OUTLOOK.COM/ (local)

The patch itself looks good to me, but I would like to check the
userspace changes too. Please create a pull request at
https://github.com/ppp-project/ppp/pulls

+Cc: Paul Mackerras, Guillaume Nault, Pali Rohár

Regards,
Qingfang

Hello Martin, in past I have sent similar change:
https://lore.kernel.org/linux-ppp/20210807163749.18316-1-pali@kernel.org/T/#u (local)
Look at the discussion, it can be useful to understand why the change
was not accepted.