From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C17F0C8C8; Mon, 11 Dec 2023 18:46:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="bgkAxEqQ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 47853C433CA; Mon, 11 Dec 2023 18:46:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1702320381; bh=TGzXTfEICl/VoO7YSi5M/+zHWoYDYxCKb4aPeBAGL/E=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=bgkAxEqQKzrtFavhsHFEVVF5O84tufq1V/0kB7uPjv/ik5NYX86V8FYmv6mPeUBXa hl20zN2WwF6W4X8XT4/Z0gJUaewT2Ck7vE4pwynFkHN7dkQD9wgqpibZGOZynl0DxH CiHMg925XZFXBEIUPtSbsjNLVIcq66r/mhKyNaGo= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, David Gibson , Stefano Brivio , Paolo Abeni , Eric Dumazet , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.1 040/194] tcp: fix mid stream window clamp. Date: Mon, 11 Dec 2023 19:20:30 +0100 Message-ID: <20231211182038.374626631@linuxfoundation.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20231211182036.606660304@linuxfoundation.org> References: <20231211182036.606660304@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Paolo Abeni [ Upstream commit 58d3aade20cdddbac6c9707ac0f3f5f8c1278b74 ] After the blamed commit below, if the user-space application performs window clamping when tp->rcv_wnd is 0, the TCP socket will never be able to announce a non 0 receive window, even after completely emptying the receive buffer and re-setting the window clamp to higher values. Refactor tcp_set_window_clamp() to address the issue: when the user decreases the current clamp value, set rcv_ssthresh according to the same logic used at buffer initialization, but ensuring reserved mem provisioning. To avoid code duplication factor-out the relevant bits from tcp_adjust_rcv_ssthresh() in a new helper and reuse it in the above scenario. When increasing the clamp value, give the rcv_ssthresh a chance to grow according to previously implemented heuristic. Fixes: 3aa7857fe1d7 ("tcp: enable mid stream window clamp") Reported-by: David Gibson Reported-by: Stefano Brivio Signed-off-by: Paolo Abeni Reviewed-by: Eric Dumazet Link: https://lore.kernel.org/r/705dad54e6e6e9a010e571bf58e0b35a8ae70503.1701706073.git.pabeni@redhat.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- include/net/tcp.h | 9 +++++++-- net/ipv4/tcp.c | 22 +++++++++++++++++++--- 2 files changed, 26 insertions(+), 5 deletions(-) diff --git a/include/net/tcp.h b/include/net/tcp.h index 19646fdec23dc..c3d56b337f358 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -1460,17 +1460,22 @@ static inline int tcp_full_space(const struct sock *sk) return tcp_win_from_space(sk, READ_ONCE(sk->sk_rcvbuf)); } -static inline void tcp_adjust_rcv_ssthresh(struct sock *sk) +static inline void __tcp_adjust_rcv_ssthresh(struct sock *sk, u32 new_ssthresh) { int unused_mem = sk_unused_reserved_mem(sk); struct tcp_sock *tp = tcp_sk(sk); - tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U * tp->advmss); + tp->rcv_ssthresh = min(tp->rcv_ssthresh, new_ssthresh); if (unused_mem) tp->rcv_ssthresh = max_t(u32, tp->rcv_ssthresh, tcp_win_from_space(sk, unused_mem)); } +static inline void tcp_adjust_rcv_ssthresh(struct sock *sk) +{ + __tcp_adjust_rcv_ssthresh(sk, 4U * tcp_sk(sk)->advmss); +} + void tcp_cleanup_rbuf(struct sock *sk, int copied); void __tcp_cleanup_rbuf(struct sock *sk, int copied); diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 288678f17ccaf..58409ea2da0af 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -3473,9 +3473,25 @@ int tcp_set_window_clamp(struct sock *sk, int val) return -EINVAL; tp->window_clamp = 0; } else { - tp->window_clamp = val < SOCK_MIN_RCVBUF / 2 ? - SOCK_MIN_RCVBUF / 2 : val; - tp->rcv_ssthresh = min(tp->rcv_wnd, tp->window_clamp); + u32 new_rcv_ssthresh, old_window_clamp = tp->window_clamp; + u32 new_window_clamp = val < SOCK_MIN_RCVBUF / 2 ? + SOCK_MIN_RCVBUF / 2 : val; + + if (new_window_clamp == old_window_clamp) + return 0; + + tp->window_clamp = new_window_clamp; + if (new_window_clamp < old_window_clamp) { + /* need to apply the reserved mem provisioning only + * when shrinking the window clamp + */ + __tcp_adjust_rcv_ssthresh(sk, tp->window_clamp); + + } else { + new_rcv_ssthresh = min(tp->rcv_wnd, tp->window_clamp); + tp->rcv_ssthresh = max(new_rcv_ssthresh, + tp->rcv_ssthresh); + } } return 0; } -- 2.42.0