Re: [PATCH mptcp-net v2] mptcp: allow changing the 'backup' bit when no sockets are open

[Mat Martineau <mathew.j.martineau@linux.intel.com>]

On Wed, 22 Sep 2021, Davide Caratti wrote:

> current Linux refuses to change the 'backup' bit of MPTCP endpoints, i.e.
> using MPTCP_PM_CMD_SET_FLAGS, unless it finds (at least) one subflow that
> matches the endpoint address. There is no reason for that, so we can just
> ignore the return value of mptcp_nl_addr_backup(). In this way, endpoints
> can reconfigure their 'backup' flag even if no MPTCP sockets are open (or
> more generally, in case the MP_PRIO message is not sent out).
>
> Fixes: 0f9f696a502e ("mptcp: add set_flags command in PM netlink")
> Signed-off-by: Davide Caratti <dcaratti@redhat.com>
> ---
>
> Notes:
>    v2:
>     - ignore the return value of mptcp_nl_addr_backup() rather than just
>       gixing the case of 0 open sockets, from Mat Martineau
>
> net/mptcp/pm_netlink.c | 5 +----
> 1 file changed, 1 insertion(+), 4 deletions(-)
>
> diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
> index c4f9a5ce3815..c3722eedc671 100644
> --- a/net/mptcp/pm_netlink.c
> +++ b/net/mptcp/pm_netlink.c
> @@ -1718,10 +1718,7 @@ static int mptcp_nl_cmd_set_flags(struct sk_buff *skb, struct genl_info *info)
>
> 	list_for_each_entry(entry, &pernet->local_addr_list, list) {
> 		if (addresses_equal(&entry->addr, &addr.addr, true)) {
> -			ret = mptcp_nl_addr_backup(net, &entry->addr, bkup);
> -			if (ret)
> -				return ret;
> -
> +			mptcp_nl_addr_backup(net, &entry->addr, bkup);

Strictly speaking, should leave a blank line before this 'if' statement, 
but other than that it looks good. I can fix it up before sending to 
netdev.

Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com>

> 			if (bkup)
> 				entry->flags |= MPTCP_PM_ADDR_FLAG_BACKUP;
> 			else
> -- 
> 2.31.1
>
>

--
Mat Martineau
Intel