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

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

[Davide Caratti]

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

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

[Mat Martineau]

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

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

[Matthieu Baerts]

Hi Davide, Mat,

On 22/09/2021 15:56, 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>

Thank you for the patch and the review!

Now in our tree (fix for -net)!

- 060daf584b27: mptcp: allow changing the 'backup' bit when no sockets
are open
- Results: eb5a9ba15e16..b84c295b0ad7

Builds and tests are now in progress:

https://cirrus-ci.com/github/multipath-tcp/mptcp_net-next/export/20210923T163816
https://github.com/multipath-tcp/mptcp_net-next/actions/workflows/build-validation.yml?query=branch:export/20210923T163816

Cheers,
Matt
-- 
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www.tessares.net