That's the behaviour with the default packet scheduler.

In some early design, the default scheduler was supposed to take into
account only the received backup flags, but it ended up not being the
case, and setting the flag would also affect outgoing data.

Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 man/man8/ip-mptcp.8 | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/man/man8/ip-mptcp.8 b/man/man8/ip-mptcp.8
index 11df43ce..4d4c879b 100644
--- a/man/man8/ip-mptcp.8
+++ b/man/man8/ip-mptcp.8
@@ -172,8 +172,9 @@ If this is a
 endpoint, the subflows created using this endpoint will have the backup
 flag set during the connection process. This flag instructs the peer to
 only send data on a given subflow when all non-backup subflows are
-unavailable. This does not affect outgoing data, where subflow priority
-is determined by the backup/non-backup flag received from the peer
+unavailable. This does also affect outgoing data when the default packets
+scheduler is used. With it, the subflow priority is determined by the
+backup/non-backup flag sent to or received from the peer.
 
 .TP
 .BR fullmesh

-- 
2.45.2

On Tue, 23 Jul 2024, Matthieu Baerts (NGI0) wrote:

> That's the behaviour with the default packet scheduler.
>
> In some early design, the default scheduler was supposed to take into
> account only the received backup flags, but it ended up not being the
> case, and setting the flag would also affect outgoing data.
>
> Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
> ---
> man/man8/ip-mptcp.8 | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/man/man8/ip-mptcp.8 b/man/man8/ip-mptcp.8
> index 11df43ce..4d4c879b 100644
> --- a/man/man8/ip-mptcp.8
> +++ b/man/man8/ip-mptcp.8
> @@ -172,8 +172,9 @@ If this is a
> endpoint, the subflows created using this endpoint will have the backup

Hi Matthieu -

I think we should clarify this text some more.

> flag set during the connection process. This flag instructs the peer to

Changing it to "remote peer" on the above line will help clarify the part 
about the packet scheduler below.

> only send data on a given subflow when all non-backup subflows are
> -unavailable. This does not affect outgoing data, where subflow priority
> -is determined by the backup/non-backup flag received from the peer
> +unavailable. This does also affect outgoing data when the default packets
> +scheduler is used. With it, the subflow priority is determined by the
> +backup/non-backup flag sent to or received from the peer.
>

How about: "When using the default packet scheduler with a 'backup' 
endpoint, outgoing data from the local peer is also affected: packets will 
only be sent from this endpoint when all non-backup subflows are 
unavailable."

The other patches all look good to me.

- Mat

Hi Mat,

On 25/07/2024 00:25, Mat Martineau wrote:
> On Tue, 23 Jul 2024, Matthieu Baerts (NGI0) wrote:
> 
>> That's the behaviour with the default packet scheduler.
>>
>> In some early design, the default scheduler was supposed to take into
>> account only the received backup flags, but it ended up not being the
>> case, and setting the flag would also affect outgoing data.
>>
>> Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
>> ---
>> man/man8/ip-mptcp.8 | 5 +++--
>> 1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/man/man8/ip-mptcp.8 b/man/man8/ip-mptcp.8
>> index 11df43ce..4d4c879b 100644
>> --- a/man/man8/ip-mptcp.8
>> +++ b/man/man8/ip-mptcp.8
>> @@ -172,8 +172,9 @@ If this is a
>> endpoint, the subflows created using this endpoint will have the backup
> 
> Hi Matthieu -
> 
> I think we should clarify this text some more.

Good idea!

>> flag set during the connection process. This flag instructs the peer to
> 
> Changing it to "remote peer" on the above line will help clarify the
> part about the packet scheduler below.

Indeed!

>> only send data on a given subflow when all non-backup subflows are
>> -unavailable. This does not affect outgoing data, where subflow priority
>> -is determined by the backup/non-backup flag received from the peer
>> +unavailable. This does also affect outgoing data when the default
>> packets
>> +scheduler is used. With it, the subflow priority is determined by the
>> +backup/non-backup flag sent to or received from the peer.
>>
> 
> How about: "When using the default packet scheduler with a 'backup'
> endpoint, outgoing data from the local peer is also affected: packets
> will only be sent from this endpoint when all non-backup subflows are
> unavailable."

Clearer indeed, thanks!

> The other patches all look good to me.

I just send a v3. I guess that's OK for you if I add your Acked-by, and
send it to netdev?

Cheers,
Matt
-- 
Sponsored by the NGI0 Core fund.