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Mon, 17 Mar 2025 05:03:22 -0700 (PDT) Received: from KERNELXING-MB0.tencent.com ([43.132.141.24]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-225c6bd4e02sm73045835ad.226.2025.03.17.05.03.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 17 Mar 2025 05:03:22 -0700 (PDT) From: Jason Xing To: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, ncardwell@google.com, kuniyu@amazon.com, dsahern@kernel.org Cc: netdev@vger.kernel.org, Jason Xing Subject: [PATCH net-next v4 1/2] tcp: support TCP_RTO_MIN_US for set/getsockopt use Date: Mon, 17 Mar 2025 20:03:13 +0800 Message-Id: <20250317120314.41404-2-kerneljasonxing@gmail.com> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20250317120314.41404-1-kerneljasonxing@gmail.com> References: <20250317120314.41404-1-kerneljasonxing@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: kuba@kernel.org Support adjusting/reading RTO MIN for socket level by using set/getsockopt(). This new option has the same effect as TCP_BPF_RTO_MIN, which means it doesn't affect RTAX_RTO_MIN usage (by using ip route...). Considering that bpf option was implemented before this patch, so we need to use a standalone new option for pure tcp set/getsockopt() use. When the socket is created, its icsk_rto_min is set to the default value that is controlled by sysctl_tcp_rto_min_us. Then if application calls setsockopt() with TCP_RTO_MIN_US flag to pass a valid value, then icsk_rto_min will be overridden in jiffies unit. This patch adds WRITE_ONCE/READ_ONCE to avoid data-race around icsk_rto_min. Signed-off-by: Jason Xing --- Documentation/networking/ip-sysctl.rst | 4 ++-- include/net/tcp.h | 2 +- include/uapi/linux/tcp.h | 1 + net/ipv4/tcp.c | 13 ++++++++++++- 4 files changed, 16 insertions(+), 4 deletions(-) diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst index 054561f8dcae..5c63ab928b97 100644 --- a/Documentation/networking/ip-sysctl.rst +++ b/Documentation/networking/ip-sysctl.rst @@ -1229,8 +1229,8 @@ tcp_pingpong_thresh - INTEGER tcp_rto_min_us - INTEGER Minimal TCP retransmission timeout (in microseconds). Note that the rto_min route option has the highest precedence for configuring this - setting, followed by the TCP_BPF_RTO_MIN socket option, followed by - this tcp_rto_min_us sysctl. + setting, followed by the TCP_BPF_RTO_MIN and TCP_RTO_MIN_US socket + options, followed by this tcp_rto_min_us sysctl. The recommended practice is to use a value less or equal to 200000 microseconds. diff --git a/include/net/tcp.h b/include/net/tcp.h index 7207c52b1fc9..6a7aab854b86 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -806,7 +806,7 @@ u32 tcp_delack_max(const struct sock *sk); static inline u32 tcp_rto_min(const struct sock *sk) { const struct dst_entry *dst = __sk_dst_get(sk); - u32 rto_min = inet_csk(sk)->icsk_rto_min; + u32 rto_min = READ_ONCE(inet_csk(sk)->icsk_rto_min); if (dst && dst_metric_locked(dst, RTAX_RTO_MIN)) rto_min = dst_metric_rtt(dst, RTAX_RTO_MIN); diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h index 32a27b4a5020..b2476cf7058e 100644 --- a/include/uapi/linux/tcp.h +++ b/include/uapi/linux/tcp.h @@ -137,6 +137,7 @@ enum { #define TCP_IS_MPTCP 43 /* Is MPTCP being used? */ #define TCP_RTO_MAX_MS 44 /* max rto time in ms */ +#define TCP_RTO_MIN_US 45 /* min rto time in us */ #define TCP_REPAIR_ON 1 #define TCP_REPAIR_OFF 0 diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 46951e749308..b89c1b676b8e 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -3352,7 +3352,7 @@ int tcp_disconnect(struct sock *sk, int flags) icsk->icsk_probes_out = 0; icsk->icsk_probes_tstamp = 0; icsk->icsk_rto = TCP_TIMEOUT_INIT; - icsk->icsk_rto_min = TCP_RTO_MIN; + WRITE_ONCE(icsk->icsk_rto_min, TCP_RTO_MIN); icsk->icsk_delack_max = TCP_DELACK_MAX; tp->snd_ssthresh = TCP_INFINITE_SSTHRESH; tcp_snd_cwnd_set(tp, TCP_INIT_CWND); @@ -3833,6 +3833,14 @@ int do_tcp_setsockopt(struct sock *sk, int level, int optname, return -EINVAL; WRITE_ONCE(inet_csk(sk)->icsk_rto_max, msecs_to_jiffies(val)); return 0; + case TCP_RTO_MIN_US: { + int rto_min = usecs_to_jiffies(val); + + if (rto_min > TCP_RTO_MIN || rto_min < TCP_TIMEOUT_MIN) + return -EINVAL; + WRITE_ONCE(inet_csk(sk)->icsk_rto_min, rto_min); + return 0; + } } sockopt_lock_sock(sk); @@ -4672,6 +4680,9 @@ int do_tcp_getsockopt(struct sock *sk, int level, case TCP_RTO_MAX_MS: val = jiffies_to_msecs(tcp_rto_max(sk)); break; + case TCP_RTO_MIN_US: + val = jiffies_to_usecs(READ_ONCE(inet_csk(sk)->icsk_rto_min)); + break; default: return -ENOPROTOOPT; }