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[144.76.156.219]) by smtp.gmail.com with ESMTPSA id s10-20020a1cf20a000000b003fbca942499sm4565068wmc.14.2023.07.20.11.48.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 20 Jul 2023 11:48:21 -0700 (PDT) From: Matthieu Baerts Date: Thu, 20 Jul 2023 20:47:50 +0200 Subject: [PATCH net-next] mptcp: fix rcv buffer auto-tuning MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20230720-upstream-net-next-20230720-mptcp-fix-rcv-buffer-auto-tuning-v1-1-175ef12b8380@tessares.net> X-B4-Tracking: v=1; b=H4sIAFWBuWQC/z2NSwrDMAxErxK0rsBOP6G9SunCduRUizhGlkMg5 O41hXYxi8cM83YoJEwFHt0OQisXXlIDe+ogvF2aCHlsDL3pz2boDdZcVMjNmEhbNsV/NWcNGSN vKGFFX2MkQVd1Qa2J04TeD9f7eHE3ay00QxZq66/9Cb8/eB3HB0Jg51uXAAAA To: mptcp@lists.linux.dev, Eric Dumazet , "David S. Miller" , Jakub Kicinski , Paolo Abeni , Mat Martineau , Soheil Hassas Yeganeh Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Matthieu Baerts X-Mailer: b4 0.12.3 X-Developer-Signature: v=1; a=openpgp-sha256; l=6565; i=matthieu.baerts@tessares.net; h=from:subject:message-id; bh=ncjsZoWoi6M3nrWIFlU5cH+KQzDb9+7q7B0CssmdtN0=; b=owEBbQKS/ZANAwAIAfa3gk9CaaBzAcsmYgBkuYF0JjkkGxokg7H+uhPv/4xlOB+DfTtCaBPUb 2J/OK4XwuiJAjMEAAEIAB0WIQToy4X3aHcFem4n93r2t4JPQmmgcwUCZLmBdAAKCRD2t4JPQmmg cw0IEADU4QQ8URvSIanWpxgjE18H/wO2HMqbCksC+dYfu6i9KtJC+1eJiJs93XJMWOdr8kOBZha rPzy7rxQ09DLOnOxg/jKl6Vyv2VoCst7oxrVcoy7zpRaZT9nyv7kk5pCnKiZe4RpFAda/9XTi3T TEywzuAc0Q7jqH/uXRom/PM+9k8hC2O9njGH3uqh+iSGribZCPhUYZ+T0X0s9o1m2B+ppZHQ5cg S66DPTWIqU2T8Zdgt+rIxRdl6r8UIprfo4EV5vEVIFHx1AK70DVw4IDVXRrxMoFcSNv2q3XMjFb GmnBj16PhBms78YIcfoJLc3AjRleVhybfeXIq8a2oARd6TdTOy04AdziqSyRkexf3KmCRnuQ21n u7Zq7xL1Pjc4Htb2sIn5k0Mk1vTPwr0EbWc/5gmSIBxjXM/PKq7ZvP4WvJvtdzoqxJVJxjBnhZu p56sUUPYcBUqtV7Gcg67QmH9zY/JUmm4Yp3oZNDSaH2ORGesF7L9/X20WeRgUKLCeGuIqN9kaKO Uf9P1jAldKGigpNHKKTh796XaG647M0r9eUsBb9GWpBOULhlFm8ELOruAq7Kwe5CKCUYdcosI0D hd9bVb7muUcC1SWnQ1NsOA4tadRcrpQnxhuWtY8xiPpdTrgyibt57aVHzwIm5jdi8M0J8TPVbIX c9JS13em+AtQXOw== X-Developer-Key: i=matthieu.baerts@tessares.net; a=openpgp; fpr=E8CB85F76877057A6E27F77AF6B7824F4269A073 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Paolo Abeni The MPTCP code uses the assumption that the tcp_win_from_space() helper does not use any TCP-specific field, and thus works correctly operating on an MPTCP socket. The commit dfa2f0483360 ("tcp: get rid of sysctl_tcp_adv_win_scale") broke such assumption, and as a consequence most MPTCP connections stall on zero-window event due to auto-tuning changing the rcv buffer size quite randomly. Address the issue syncing again the MPTCP auto-tuning code with the TCP one. To achieve that, factor out the windows size logic in socket independent helpers, and reuse them in mptcp_rcv_space_adjust(). The MPTCP level scaling_ratio is selected as the minimum one from the all the subflows, as a worst-case estimate. Fixes: dfa2f0483360 ("tcp: get rid of sysctl_tcp_adv_win_scale") Signed-off-by: Paolo Abeni Co-developed-by: Matthieu Baerts Signed-off-by: Matthieu Baerts Acked-by: Soheil Hassas Yeganeh Reviewed-by: Eric Dumazet --- include/net/tcp.h | 20 +++++++++++++++----- net/mptcp/protocol.c | 15 +++++++-------- net/mptcp/protocol.h | 8 +++++++- net/mptcp/subflow.c | 2 +- 4 files changed, 30 insertions(+), 15 deletions(-) diff --git a/include/net/tcp.h b/include/net/tcp.h index c5fb90079920..794642fbd724 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -1430,22 +1430,32 @@ void tcp_select_initial_window(const struct sock *s= k, int __space, __u32 *window_clamp, int wscale_ok, __u8 *rcv_wscale, __u32 init_rcv_wnd); =20 -static inline int tcp_win_from_space(const struct sock *sk, int space) +static inline int __tcp_win_from_space(u8 scaling_ratio, int space) { - s64 scaled_space =3D (s64)space * tcp_sk(sk)->scaling_ratio; + s64 scaled_space =3D (s64)space * scaling_ratio; =20 return scaled_space >> TCP_RMEM_TO_WIN_SCALE; } =20 -/* inverse of tcp_win_from_space() */ -static inline int tcp_space_from_win(const struct sock *sk, int win) +static inline int tcp_win_from_space(const struct sock *sk, int space) +{ + return __tcp_win_from_space(tcp_sk(sk)->scaling_ratio, space); +} + +/* inverse of __tcp_win_from_space() */ +static inline int __tcp_space_from_win(u8 scaling_ratio, int win) { u64 val =3D (u64)win << TCP_RMEM_TO_WIN_SCALE; =20 - do_div(val, tcp_sk(sk)->scaling_ratio); + do_div(val, scaling_ratio); return val; } =20 +static inline int tcp_space_from_win(const struct sock *sk, int win) +{ + return __tcp_space_from_win(tcp_sk(sk)->scaling_ratio, win); +} + static inline void tcp_scaling_ratio_init(struct sock *sk) { /* Assume a conservative default of 1200 bytes of payload per 4K page. diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 3613489eb6e3..553828ef62df 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -90,6 +90,7 @@ static int __mptcp_socket_create(struct mptcp_sock *msk) if (err) return err; =20 + msk->scaling_ratio =3D tcp_sk(ssock->sk)->scaling_ratio; WRITE_ONCE(msk->first, ssock->sk); WRITE_ONCE(msk->subflow, ssock); subflow =3D mptcp_subflow_ctx(ssock->sk); @@ -1881,6 +1882,7 @@ static void mptcp_rcv_space_adjust(struct mptcp_sock = *msk, int copied) { struct mptcp_subflow_context *subflow; struct sock *sk =3D (struct sock *)msk; + u8 scaling_ratio =3D U8_MAX; u32 time, advmss =3D 1; u64 rtt_us, mstamp; =20 @@ -1911,9 +1913,11 @@ static void mptcp_rcv_space_adjust(struct mptcp_sock= *msk, int copied) =20 rtt_us =3D max(sf_rtt_us, rtt_us); advmss =3D max(sf_advmss, advmss); + scaling_ratio =3D min(tp->scaling_ratio, scaling_ratio); } =20 msk->rcvq_space.rtt_us =3D rtt_us; + msk->scaling_ratio =3D scaling_ratio; if (time < (rtt_us >> 3) || rtt_us =3D=3D 0) return; =20 @@ -1922,8 +1926,8 @@ static void mptcp_rcv_space_adjust(struct mptcp_sock = *msk, int copied) =20 if (READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_moderate_rcvbuf) && !(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) { - int rcvmem, rcvbuf; u64 rcvwin, grow; + int rcvbuf; =20 rcvwin =3D ((u64)msk->rcvq_space.copied << 1) + 16 * advmss; =20 @@ -1932,18 +1936,13 @@ static void mptcp_rcv_space_adjust(struct mptcp_soc= k *msk, int copied) do_div(grow, msk->rcvq_space.space); rcvwin +=3D (grow << 1); =20 - rcvmem =3D SKB_TRUESIZE(advmss + MAX_TCP_HEADER); - while (tcp_win_from_space(sk, rcvmem) < advmss) - rcvmem +=3D 128; - - do_div(rcvwin, advmss); - rcvbuf =3D min_t(u64, rcvwin * rcvmem, + rcvbuf =3D min_t(u64, __tcp_space_from_win(scaling_ratio, rcvwin), READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_rmem[2])); =20 if (rcvbuf > sk->sk_rcvbuf) { u32 window_clamp; =20 - window_clamp =3D tcp_win_from_space(sk, rcvbuf); + window_clamp =3D __tcp_win_from_space(scaling_ratio, rcvbuf); WRITE_ONCE(sk->sk_rcvbuf, rcvbuf); =20 /* Make subflows follow along. If we do not do this, we diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index 37fbe22e2433..795f422e8597 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -321,6 +321,7 @@ struct mptcp_sock { u64 time; /* start time of measurement window */ u64 rtt_us; /* last maximum rtt of subflows */ } rcvq_space; + u8 scaling_ratio; =20 u32 subflow_id; u32 setsockopt_seq; @@ -351,9 +352,14 @@ static inline int __mptcp_rmem(const struct sock *sk) return atomic_read(&sk->sk_rmem_alloc) - READ_ONCE(mptcp_sk(sk)->rmem_rel= eased); } =20 +static inline int mptcp_win_from_space(const struct sock *sk, int space) +{ + return __tcp_win_from_space(mptcp_sk(sk)->scaling_ratio, space); +} + static inline int __mptcp_space(const struct sock *sk) { - return tcp_win_from_space(sk, READ_ONCE(sk->sk_rcvbuf) - __mptcp_rmem(sk)= ); + return mptcp_win_from_space(sk, READ_ONCE(sk->sk_rcvbuf) - __mptcp_rmem(s= k)); } =20 static inline struct mptcp_data_frag *mptcp_send_head(const struct sock *s= k) diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c index 9ee3b7abbaf6..ad7080fabb2f 100644 --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -1359,7 +1359,7 @@ void mptcp_space(const struct sock *ssk, int *space, = int *full_space) const struct sock *sk =3D subflow->conn; =20 *space =3D __mptcp_space(sk); - *full_space =3D tcp_full_space(sk); + *full_space =3D mptcp_win_from_space(sk, READ_ONCE(sk->sk_rcvbuf)); } =20 void __mptcp_error_report(struct sock *sk) --- base-commit: b44693495af8f309b8ddec4b30833085d1c2d0c4 change-id: 20230720-upstream-net-next-20230720-mptcp-fix-rcv-buffer-auto-tu= ning-bb759d4a6111 Best regards, --=20 Matthieu Baerts