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[195.231.44.239]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-47ff79b819dsm7681190f8f.16.2026.08.06.09.42.50 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 06 Aug 2026 09:42:50 -0700 (PDT) Message-ID: <80572775-6e76-4c79-83e2-efdedbd3f3b8@redhat.com> Date: Thu, 6 Aug 2026 18:42:50 +0200 Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 mptcp-next 7/7] mptcp: implemented OoO queue pruning From: Paolo Abeni To: mptcp@lists.linux.dev, "Matthieu Baerts (NGI0)" References: In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: edicur8yIjuDB7UlREVexQft0REXT_gJ-gV8gfZQetM_1786034572 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 8/6/26 4:45 PM, Paolo Abeni wrote: > When moving incoming skbs in the msk receive queue and the latter > is above limits, prune it as needed quite alike what TCP is doing > at the subflow level. The main difference relies in the stop condition: > since MPTCP does not perform collapsing, it's better off dropping the > bare minimum to fit the (newer) incoming packet. > > Signed-off-by: Paolo Abeni > Tested-by: Gang Yan > Reviewed-by: Matthieu Baerts (NGI0) > --- > v -> v: > - prune only for new data > - reorganize the code to follow more closely TCP > --- > net/mptcp/mib.c | 1 + > net/mptcp/mib.h | 1 + > net/mptcp/protocol.c | 81 ++++++++++++++++++++++++++++++++++++++------ > 3 files changed, 73 insertions(+), 10 deletions(-) > > diff --git a/net/mptcp/mib.c b/net/mptcp/mib.c > index ef65e2df709f..2569385bab7c 100644 > --- a/net/mptcp/mib.c > +++ b/net/mptcp/mib.c > @@ -87,6 +87,7 @@ static const struct snmp_mib mptcp_snmp_list[] = { > SNMP_MIB_ITEM("WinProbe", MPTCP_MIB_WINPROBE), > SNMP_MIB_ITEM("BacklogDrop", MPTCP_MIB_BACKLOGDROP), > SNMP_MIB_ITEM("RcvPruned", MPTCP_MIB_RCVPRUNED), > + SNMP_MIB_ITEM("OFOPruned", MPTCP_MIB_OFOPRUNED), > }; > > /* mptcp_mib_alloc - allocate percpu mib counters > diff --git a/net/mptcp/mib.h b/net/mptcp/mib.h > index 9271205f682e..3a3425e258a7 100644 > --- a/net/mptcp/mib.h > +++ b/net/mptcp/mib.h > @@ -90,6 +90,7 @@ enum linux_mptcp_mib_field { > MPTCP_MIB_WINPROBE, /* MPTCP-level zero window probe */ > MPTCP_MIB_BACKLOGDROP, /* Backlog over memory limit */ > MPTCP_MIB_RCVPRUNED, /* Dropped due to memory constraints */ > + MPTCP_MIB_OFOPRUNED, /* MPTCP-level OoO queue pruned */ > __MPTCP_MIB_MAX > }; > > diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c > index 63f2c18bc01f..ec874d2ead6a 100644 > --- a/net/mptcp/protocol.c > +++ b/net/mptcp/protocol.c > @@ -242,6 +242,65 @@ static bool mptcp_rcvbuf_grow(struct sock *sk, u32 newval) > return false; > } > > +/* "Inspired" from the TCP version; main difference: stop as soon as the MPTCP > + * socket is under memory limit. > + */ > +static void mptcp_prune_ofo_queue(struct sock *sk, > + const struct sk_buff *in_skb) > +{ > + struct mptcp_sock *msk = mptcp_sk(sk); > + struct rb_node *node, *prev; > + bool pruned = false; > + u64 mem; > + > + if (RB_EMPTY_ROOT(&msk->out_of_order_queue)) > + return; > + > + node = &msk->ooo_last_skb->rbnode; > + > + do { > + struct sk_buff *skb = rb_to_skb(node); > + > + /* Stop pruning if the incoming skb would land in OoO tail. */ > + if (after64(MPTCP_SKB_CB(in_skb)->map_seq, > + MPTCP_SKB_CB(skb)->map_seq)) > + break; > + > + pruned = true; > + prev = rb_prev(node); > + rb_erase(node, &msk->out_of_order_queue); > + mptcp_drop(sk, skb); > + msk->ooo_last_skb = rb_to_skb(prev); > + > + mem = (unsigned int)sk_rmem_alloc_get(sk); > + if (mem <= sk->sk_rcvbuf) > + break; > + > + node = prev; > + } while (node); > + > + if (pruned) > + MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_OFOPRUNED); > +} > + > +/* The stack can't drop packets for fallback socket at the msk level, or the > + * stream will break. > + */ > +static bool mptcp_can_ingest(const struct sock *sk) > +{ > + return unlikely(sk_rmem_alloc_get(sk) <= READ_ONCE(sk->sk_rcvbuf)) || > + __mptcp_check_fallback(mptcp_sk(sk)); The above should obviously be: 'likely(...)' @Matttbe: please LMK if you prefer a repost or you could adjust that while applying to the export branch. /P