Re: [PATCH mptcp-next 4/5] mptcp: add MPJoinRejected MIB counter

[Matthieu Baerts <matttbe@kernel.org>]

Hi Geliang,

On 31/03/2025 03:59, Geliang Tang wrote:
> Hi Matt,
> 
> On Sat, 2025-03-29 at 17:26 +0100, Matthieu Baerts (NGI0) wrote:
>> This counter is useful to understand why some paths are rejected, and
>> not created as expected.
>>
>> It is incremented when receiving a connection request, if the PM
>> didn't
>> allow the creation of new subflows.
>>
>> Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
>> ---
>>  net/mptcp/mib.c      | 1 +
>>  net/mptcp/mib.h      | 1 +
>>  net/mptcp/protocol.c | 4 +++-
>>  net/mptcp/subflow.c  | 2 ++
>>  4 files changed, 7 insertions(+), 1 deletion(-)
>>
>> diff --git a/net/mptcp/mib.c b/net/mptcp/mib.c
>> index
>> 19eb9292bd6093a760b41f98c1774fd2490c48e3..0c24545f0e8df95b3475bfccc7a
>> 2f2ce440f7ad2 100644
>> --- a/net/mptcp/mib.c
>> +++ b/net/mptcp/mib.c
>> @@ -28,6 +28,7 @@ static const struct snmp_mib mptcp_snmp_list[] = {
>>  	SNMP_MIB_ITEM("MPJoinSynAckHMacFailure",
>> MPTCP_MIB_JOINSYNACKMAC),
>>  	SNMP_MIB_ITEM("MPJoinAckRx", MPTCP_MIB_JOINACKRX),
>>  	SNMP_MIB_ITEM("MPJoinAckHMacFailure", MPTCP_MIB_JOINACKMAC),
>> +	SNMP_MIB_ITEM("MPJoinRejected", MPTCP_MIB_JOINREJECTED),
>>  	SNMP_MIB_ITEM("MPJoinSynTx", MPTCP_MIB_JOINSYNTX),
>>  	SNMP_MIB_ITEM("MPJoinSynTxCreatSkErr",
>> MPTCP_MIB_JOINSYNTXCREATSKERR),
>>  	SNMP_MIB_ITEM("MPJoinSynTxBindErr",
>> MPTCP_MIB_JOINSYNTXBINDERR),
>> diff --git a/net/mptcp/mib.h b/net/mptcp/mib.h
>> index
>> 128282982843a07614a46f9b2c2f7c708306c769..250c6b77977e8f846b5741304f7
>> 841a922f51967 100644
>> --- a/net/mptcp/mib.h
>> +++ b/net/mptcp/mib.h
>> @@ -23,6 +23,7 @@ enum linux_mptcp_mib_field {
>>  	MPTCP_MIB_JOINSYNACKMAC,	/* HMAC was wrong on SYN/ACK
>> + MP_JOIN */
>>  	MPTCP_MIB_JOINACKRX,		/* Received an ACK + MP_JOIN
>> */
>>  	MPTCP_MIB_JOINACKMAC,		/* HMAC was wrong on ACK +
>> MP_JOIN */
>> +	MPTCP_MIB_JOINREJECTED,		/* The PM rejected
>> the JOIN request */
>>  	MPTCP_MIB_JOINSYNTX,		/* Sending a SYN + MP_JOIN
>> */
>>  	MPTCP_MIB_JOINSYNTXCREATSKERR,	/* Not able to create a
>> socket when sending a SYN + MP_JOIN */
>>  	MPTCP_MIB_JOINSYNTXBINDERR,	/* Not able to bind() the
>> address when sending a SYN + MP_JOIN */
>> diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
>> index
>> 9042a86e003036f8eb9680bc6c520fb57d92dbd0..8ba1a4f225bd2014ebdc973e752
>> 702028ee5f31a 100644
>> --- a/net/mptcp/protocol.c
>> +++ b/net/mptcp/protocol.c
>> @@ -3527,8 +3527,10 @@ bool mptcp_finish_join(struct sock *ssk)
>>  		return true;
>>  	}
>>  
>> -	if (!mptcp_pm_allow_new_subflow(msk))
>> +	if (!mptcp_pm_allow_new_subflow(msk)) {
>> +		MPTCP_INC_STATS(sock_net(ssk),
>> MPTCP_MIB_JOINREJECTED);
> 
> nit:
> 
> Although the result is the same as sock_net(ssk), what do you think of
> using sock_net(parent) here?

We could, but why would you prefer using 'parent' instead of 'ssk'? Ii
picked 'ssk' because that's the one passed in argument of this function.
'parent' is obtained from 'ssk'.

I hope you don't mind if I apply the patch as it is because I already
applied the parent patches. I can always change that later of course.

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