netdev - Re: [PATCH v2 net 2/3] tcp: add newval parameter to tcp_rcvbuf

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Message-ID: <89c7bbd1-c9d7-4ef1-94fb-48a424e03594@kernel.org>
Date: Mon, 27 Oct 2025 18:22:19 +0100
From: Matthieu Baerts <matttbe@...nel.org>
To: Eric Dumazet <edumazet@...gle.com>
Cc: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski
 <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Simon Horman <horms@...nel.org>, Neal Cardwell <ncardwell@...gle.com>,
 Willem de Bruijn <willemb@...gle.com>, Kuniyuki Iwashima
 <kuniyu@...gle.com>, Mat Martineau <martineau@...nel.org>,
 Geliang Tang <geliang@...nel.org>, netdev@...r.kernel.org,
 eric.dumazet@...il.com
Subject: Re: [PATCH v2 net 2/3] tcp: add newval parameter to tcp_rcvbuf_grow()

On 27/10/2025 16:37, Eric Dumazet wrote:
> On Mon, Oct 27, 2025 at 7:50 AM Matthieu Baerts <matttbe@...nel.org> wrote:
>>
>> Hi Eric,
>>
>> On 27/10/2025 08:38, Eric Dumazet wrote:
>>> This patch has no functional change, and prepares the following one.
>>>
>>> tcp_rcvbuf_grow() will need to have access to tp->rcvq_space.space
>>> old and new values.
>>>
>>> Change mptcp_rcvbuf_grow() in a similar way.
>>
>> Thank you for the v2, and for having adapted MPTCP as well.
>>
>>> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
>>> ---
>>>  include/net/tcp.h    |  2 +-
>>>  net/ipv4/tcp_input.c | 15 ++++++++-------
>>>  net/mptcp/protocol.c | 16 ++++++++--------
>>>  3 files changed, 17 insertions(+), 16 deletions(-)
>>>
>>> diff --git a/include/net/tcp.h b/include/net/tcp.h
>>> index 5ca230ed526ae02711e8d2a409b91664b73390f2..ab20f549b8f9143671b75ed0a3f87d64b9e73583 100644
>>> --- a/include/net/tcp.h
>>> +++ b/include/net/tcp.h
>>> @@ -370,7 +370,7 @@ void tcp_delack_timer_handler(struct sock *sk);
>>>  int tcp_ioctl(struct sock *sk, int cmd, int *karg);
>>>  enum skb_drop_reason tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb);
>>>  void tcp_rcv_established(struct sock *sk, struct sk_buff *skb);
>>> -void tcp_rcvbuf_grow(struct sock *sk);
>>> +void tcp_rcvbuf_grow(struct sock *sk, u32 newval);
>>>  void tcp_rcv_space_adjust(struct sock *sk);
>>>  int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp);
>>>  void tcp_twsk_destructor(struct sock *sk);
>>> diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
>>> index 31ea5af49f2dc8a6f95f3f8c24065369765b8987..600b733e7fb554c36178e432996ecc7d4439268a 100644
>>> --- a/net/ipv4/tcp_input.c
>>> +++ b/net/ipv4/tcp_input.c
>>> @@ -891,18 +891,21 @@ static inline void tcp_rcv_rtt_measure_ts(struct sock *sk,
>>>       }
>>>  }
>>>
>>> -void tcp_rcvbuf_grow(struct sock *sk)
>>> +void tcp_rcvbuf_grow(struct sock *sk, u32 newval)
>>>  {
>>>       const struct net *net = sock_net(sk);
>>>       struct tcp_sock *tp = tcp_sk(sk);
>>> -     int rcvwin, rcvbuf, cap;
>>> +     u32 rcvwin, rcvbuf, cap, oldval;
>>> +
>>> +     oldval = tp->rcvq_space.space;
>>
>> Even if the series as a whole is OK, NIPA (and the MPTCP CI) are
>> complaining about this line, because in this patch, 'oldval' is set but
>> not used. It is used in the next patch.
>>
>> I guess we want to fix this to prevent issues with 'git bisect'. If yes,
>> do you mind moving the declaration to the next patch please?
> 
> This is quite annoying.
> 
> Whole point was to have separate patches to help review, not to add more work.

Indeed, I'm sorry about that.

Because the build tests didn't pass, this series has not been queued to
be validated with the selftests, etc. on NIPA.

> I will not have time to send a V3 soon, I am OOO.

Tomorrow, I can send a v3 including the small fix if that can help, and
if there are no objections.

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