Re: [PATCH mptcp-next v10 09/12] mptcp: sysctl: map path_manager to pm_type

[Matthieu Baerts <matttbe@kernel.org>]

Hi Geliang,

On 06/03/2025 12:01, Geliang Tang wrote:
> From: Geliang Tang <tanggeliang@kylinos.cn>
> 
> This patch maps the newly added path manager sysctl "path_manager"
> to the old one "pm_type".
> 
> 	path_manager   pm_type
> 
> 	"kernel"    -> MPTCP_PM_TYPE_KERNEL
> 	"userspace" -> MPTCP_PM_TYPE_USERSPACE
> 	others      -> __MPTCP_PM_TYPE_NR
> 
> Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
> ---
>  net/mptcp/ctrl.c | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/net/mptcp/ctrl.c b/net/mptcp/ctrl.c
> index 1f405be6bc00..6a35e6bb0a63 100644
> --- a/net/mptcp/ctrl.c
> +++ b/net/mptcp/ctrl.c
> @@ -200,6 +200,9 @@ static int mptcp_set_path_manager(char *path_manager, const char *name)
>  static int proc_path_manager(const struct ctl_table *ctl, int write,
>  			     void *buffer, size_t *lenp, loff_t *ppos)
>  {
> +	struct mptcp_pernet *pernet = container_of(ctl->data,
> +						   struct mptcp_pernet,
> +						   path_manager);
>  	char (*path_manager)[MPTCP_PM_NAME_MAX] = ctl->data;
>  	char pm_name[MPTCP_PM_NAME_MAX];
>  	const struct ctl_table tbl = {
> @@ -211,8 +214,16 @@ static int proc_path_manager(const struct ctl_table *ctl, int write,
>  	strscpy(pm_name, *path_manager, MPTCP_PM_NAME_MAX);
>  
>  	ret = proc_dostring(&tbl, write, buffer, lenp, ppos);
> -	if (write && ret == 0)
> +	if (write && ret == 0) {
> +		u8 pm_type = __MPTCP_PM_TYPE_NR;
> +
> +		if (strncmp(pm_name, "kernel", MPTCP_PM_NAME_MAX) == 0)
> +			pm_type = MPTCP_PM_TYPE_KERNEL;
> +		else if (strncmp(pm_name, "userspace", MPTCP_PM_NAME_MAX) == 0)
> +			pm_type = MPTCP_PM_TYPE_USERSPACE;
> +		pernet->pm_type = pm_type;

This should be done after mptcp_set_path_manager(), and if there were no
errors (ret == 0), because if the name is not valid, the path-manager
will not be modified, so pm_type should not be modified as well.

BTW, did you check that setting "pm_type = __MPTCP_PM_TYPE_NR" is OK?
Can we display 2, but not allow to set 2 for pm_type here? In other
words, please check that this is OK with your modifications:

  # sysctl net.mptcp.pm_type=2
  sysctl: setting key "net.mptcp.pm_type": Invalid argument
  # sysctl -q net.mptcp.path_manager = "$BPF_PM"
  # sysctl -n net.mptcp.pm_type
  2

>  		ret = mptcp_set_path_manager(*path_manager, pm_name);
> +	}
>  
>  	return ret;
>  }
Cheers,
Matt
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