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[82.132.221.54]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-c15d3859f69sm517493566b.27.2026.07.11.02.22.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 11 Jul 2026 02:22:41 -0700 (PDT) From: Pavel Begunkov To: "David S . Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , netdev@vger.kernel.org Cc: io-uring@vger.kernel.org, asml.silence@gmail.com Subject: [RFC 1/9] net: allow __tcp_read_sock actors to steal skbs Date: Sat, 11 Jul 2026 10:22:11 +0100 Message-ID: <5466eea5fc519674df08dea564da17635a1cd6fc.1783619193.git.asml.silence@gmail.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: io-uring@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Currently __tcp_read_sock() owns skbs and expects them to be present when the actor function returns (modulo collapsing). For zcrx optimisations I want to be able to take ownership of the skb in the callback, add a helper doing that. It's only implemented for tcp, hence keep "tcp" in the helper name. It could be later extended to other protocols but would need some whitelisting mechanism. Signed-off-by: Pavel Begunkov --- include/linux/net.h | 1 + include/net/tcp.h | 13 +++++++++++++ net/ipv4/tcp.c | 11 +++++++++++ 3 files changed, 25 insertions(+) diff --git a/include/linux/net.h b/include/linux/net.h index f268f395ce47..ed882aeac4a5 100644 --- a/include/linux/net.h +++ b/include/linux/net.h @@ -165,6 +165,7 @@ typedef struct { void *data; } arg; int error; + bool stolen; } read_descriptor_t; struct vm_area_struct; diff --git a/include/net/tcp.h b/include/net/tcp.h index ecbadcb3a744..3d25707b73c3 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -3089,6 +3089,19 @@ static inline int tcp_recv_should_stop(struct sock *sk) signal_pending(current); } +static inline bool tcp_read_sock_steal_skb(read_descriptor_t *desc, + struct sk_buff *skb, + struct sock *sk) +{ + if (skb_shared(skb)) + return false; + + desc->stolen = true; + __skb_unlink(skb, &sk->sk_receive_queue); + skb_orphan(skb); + return true; +} + INDIRECT_CALLABLE_DECLARE(union tcp_seq_and_ts_off tcp_v4_init_seq_and_ts_off(const struct net *net, const struct sk_buff *skb)); diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 432fa28e47d4..309a0e6b0173 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -1677,6 +1677,7 @@ static int __tcp_read_sock(struct sock *sk, read_descriptor_t *desc, return -ENOTCONN; while ((skb = tcp_recv_skb(sk, seq, &offset)) != NULL) { if (offset < skb->len) { + u8 tcp_flags = TCP_SKB_CB(skb)->tcp_flags; int used; size_t len; @@ -1689,6 +1690,7 @@ static int __tcp_read_sock(struct sock *sk, read_descriptor_t *desc, if (!len) break; } + desc->stolen = false; used = recv_actor(desc, skb, offset, len); if (used <= 0) { if (!copied) @@ -1701,6 +1703,14 @@ static int __tcp_read_sock(struct sock *sk, read_descriptor_t *desc, copied += used; offset += used; + if (desc->stolen) { + if (tcp_flags & TCPHDR_FIN) { + ++seq; + break; + } + goto next; + } + /* If recv_actor drops the lock (e.g. TCP splice * receive) the skb pointer might be invalid when * getting here: tcp_collapse might have deleted it @@ -1721,6 +1731,7 @@ static int __tcp_read_sock(struct sock *sk, read_descriptor_t *desc, break; } tcp_eat_recv_skb(sk, skb); +next: if (!desc->count) break; WRITE_ONCE(*copied_seq, seq); -- 2.54.0