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Wed, 22 Apr 2026 06:52:07 -0700 (PDT) Received: from [192.168.88.32] ([150.228.93.216]) by smtp.gmail.com with ESMTPSA id 46e09a7af769-7dcd5408b5asm4919147a34.11.2026.04.22.06.51.58 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 22 Apr 2026 06:52:07 -0700 (PDT) Message-ID: Date: Wed, 22 Apr 2026 15:51:54 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mptcp: do not drop partial packets To: Shardul Bankar , matttbe@kernel.org, martineau@kernel.org Cc: geliang@kernel.org, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, horms@kernel.org, netdev@vger.kernel.org, mptcp@lists.linux.dev, linux-kernel@vger.kernel.org, janak@mpiric.us, kalpan.jani@mpiricsoftware.com, Shardul Bankar References: <20260422120954.8877-1-shardul.b@mpiricsoftware.com> Content-Language: en-US From: Paolo Abeni In-Reply-To: <20260422120954.8877-1-shardul.b@mpiricsoftware.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 4/22/26 2:09 PM, Shardul Bankar wrote: > diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c > index 614c3f583ca0..6858e6e283e3 100644 > --- a/net/mptcp/protocol.c > +++ b/net/mptcp/protocol.c > @@ -397,12 +397,27 @@ static bool __mptcp_move_skb(struct sock *sk, struct sk_buff *skb) > return false; > } > > - /* old data, keep it simple and drop the whole pkt, sender > - * will retransmit as needed, if needed. > + /* Completely old data? */ > + if (!after64(MPTCP_SKB_CB(skb)->end_seq, msk->ack_seq)) { > + MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_DUPDATA); > + mptcp_drop(sk, skb); > + return false; > + } > + > + /* Partial packet: map_seq < ack_seq < end_seq. > + * Skip the already-acked bytes and enqueue the new data. > */ > - MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_DUPDATA); > - mptcp_drop(sk, skb); > - return false; > + copy_len = MPTCP_SKB_CB(skb)->end_seq - msk->ack_seq; > + MPTCP_SKB_CB(skb)->offset += msk->ack_seq - MPTCP_SKB_CB(skb)->map_seq; here MPTCP_SKB_CB(skb)->offset is always != 0 ... > + msk->bytes_received += copy_len; > + WRITE_ONCE(msk->ack_seq, msk->ack_seq + copy_len); > + tail = skb_peek_tail(&sk->sk_receive_queue); > + if (tail && mptcp_try_coalesce(sk, tail, skb)) ... so mptcp_try_coalesce() will always fail. /P