Re: [PATCH net-next v2 05/14] tcp: grow rcvbuf to back scaled-window quantization slack
From: Paolo Abeni <pabeni@redhat.com>
Date: 2026-03-16 11:24:19
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On 3/14/26 9:13 PM, atwellwea@gmail.com wrote:
quoted hunk ↗ jump to hunk
From: Wesley Atwell <redacted> Teach TCP to grow sk_rcvbuf when scale rounding would otherwise expose more sender-visible window than the current hard receive-memory backing can cover. The new helper keeps backlog and memory-pressure limits in the same units as the rest of the receive path, while __tcp_select_window() backs any rounding slack before advertising it. Signed-off-by: Wesley Atwell <redacted> --- include/net/tcp.h | 12 ++++++++++++ net/ipv4/tcp_input.c | 36 ++++++++++++++++++++++++++++++++++-- net/ipv4/tcp_output.c | 15 +++++++++++++-- 3 files changed, 59 insertions(+), 4 deletions(-)diff --git a/include/net/tcp.h b/include/net/tcp.h index fc22ab6b80d5..5b479ad44f89 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h@@ -397,6 +397,7 @@ 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, u32 newval); +bool tcp_try_grow_rcvbuf(struct sock *sk, int needed); 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);@@ -1844,6 +1845,17 @@ static inline int tcp_rwnd_avail(const struct sock *sk) return tcp_rmem_avail(sk) - READ_ONCE(sk->sk_backlog.len); } +/* Passive children clone the listener's sk_socket until accept() grafts + * their own struct socket,
AFAICS, the above statement is false, see sk_set_socket() in sk_clone()
so only sockets that point back to themselves
+ * should autotune receive-buffer backing.
+ */
+static inline bool tcp_rcvbuf_grow_allowed(const struct sock *sk)
+{
+ struct socket *sock = READ_ONCE(sk->sk_socket);You can just check `sk->sk_socket`. Also you could re-use this helper in tcp_data_queue_ofo(). /P