From patchwork Thu Jul 27 12:51:23 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Menglong Dong X-Patchwork-Id: 13330084 X-Patchwork-Delegate: kuba@kernel.org Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (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 03632171A0 for ; Thu, 27 Jul 2023 12:51:51 +0000 (UTC) Received: from mail-oi1-x243.google.com (mail-oi1-x243.google.com [IPv6:2607:f8b0:4864:20::243]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B04DF1BC1; Thu, 27 Jul 2023 05:51:50 -0700 (PDT) Received: by mail-oi1-x243.google.com with SMTP id 5614622812f47-3a3c78ede4bso760178b6e.2; Thu, 27 Jul 2023 05:51:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1690462310; x=1691067110; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=/1M9X9cFhRpVGts4/6dZs2oXMtLocqBd/PjGY4NYMgE=; b=I9eJSV426qImFidD8Ebfo6fX+GXG4523bJDNxkEit+0Jw2KPB30aL3zQJda2cLHSUL X4jAVkwILnOBwkkhkT8JBhmr3pbLfR11cTE2FNyaVhgCWsPQmboy+ySiD4l7TdPyu3on TO7PB34zf+DrG8ITeUU8rMME2pIRTsQNGx9khnmSbRazAiUdngsASFL37+VIxS41X5cx RSmivjBMsmYTi2muveCrTHGEMlWu8UnzECrvbOgUCIjs6FOh+VHgaItghZkkW6T+/CQ7 m+Eeiu8lGkgNs9TUAE/jg1K03KFJRDB8EbnTxFepkejJt6/gBPWk3YhAl5ksXNofHzES iFcA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1690462310; x=1691067110; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=/1M9X9cFhRpVGts4/6dZs2oXMtLocqBd/PjGY4NYMgE=; b=F+No8HYoYxgiE7W8ICFiif5thY75oAqcHWlNUM0Zf0CBKDVtdJIjlgg5wEZ6hGFBQA 1Pny3D5vR7QbF594CxkC+erIuKNqkN5TlC5zN5qQrRC3kgBEPtMkKwHwg1+4RCZG6zgL NiDIfMUy/1LUodiaJjdZPt54VAjpaHv37tJQXdjiSyHI7Gztwv9YhEtnY5wHh2yqrcwo lBiU4SBl7tLhkcN/h23QiwIoBNIwG4fNpZGOz8fcgmPMuEAv5MwwSCptQPY7VKx7ej5A W1FeF49e0BV+92Xmx9K5QYPlWOG8w8nRpx3VOvj08wvyJqsd9a/y1AmdFQc6dm6kWWyQ pBDQ== X-Gm-Message-State: ABy/qLaEYokv07QXnvizjlOCD2CP34YMBaofFi0RmiBnieHHBo0a9hYf O22I04si0huvA6AwKaDlFTs= X-Google-Smtp-Source: APBJJlFgSvwYdtnkiqvDYoA0Wj1j+2pza/e2UDGV2p8H8od6WPeyjYLOJiRBIrk8OdrMtnpfyPCbFg== X-Received: by 2002:a05:6808:1b12:b0:3a3:7612:28c7 with SMTP id bx18-20020a0568081b1200b003a3761228c7mr3678694oib.23.1690462309938; Thu, 27 Jul 2023 05:51:49 -0700 (PDT) Received: from localhost.localdomain ([43.132.98.115]) by smtp.gmail.com with ESMTPSA id l4-20020a63be04000000b0055386b1415dsm1315048pgf.51.2023.07.27.05.51.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 27 Jul 2023 05:51:48 -0700 (PDT) From: menglong8.dong@gmail.com X-Google-Original-From: imagedong@tencent.com To: edumazet@google.com Cc: davem@davemloft.net, kuba@kernel.org, pabeni@redhat.com, dsahern@kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Menglong Dong Subject: [PATCH net-next 1/3] net: tcp: send zero-window ACK when no memory Date: Thu, 27 Jul 2023 20:51:23 +0800 Message-Id: <20230727125125.1194376-2-imagedong@tencent.com> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20230727125125.1194376-1-imagedong@tencent.com> References: <20230727125125.1194376-1-imagedong@tencent.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_FROM, RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net X-Patchwork-Delegate: kuba@kernel.org From: Menglong Dong For now, skb will be dropped when no memory, which makes client keep retrans util timeout and it's not friendly to the users. In this patch, we reply an ACK with zero-window in this case to update the snd_wnd of the sender to 0. Therefore, the sender won't timeout the connection and will probe the zero-window with the retransmits. Signed-off-by: Menglong Dong --- include/net/inet_connection_sock.h | 3 ++- net/ipv4/tcp_input.c | 4 ++-- net/ipv4/tcp_output.c | 14 +++++++++++--- 3 files changed, 15 insertions(+), 6 deletions(-) diff --git a/include/net/inet_connection_sock.h b/include/net/inet_connection_sock.h index c2b15f7e5516..be3c858a2ebb 100644 --- a/include/net/inet_connection_sock.h +++ b/include/net/inet_connection_sock.h @@ -164,7 +164,8 @@ enum inet_csk_ack_state_t { ICSK_ACK_TIMER = 2, ICSK_ACK_PUSHED = 4, ICSK_ACK_PUSHED2 = 8, - ICSK_ACK_NOW = 16 /* Send the next ACK immediately (once) */ + ICSK_ACK_NOW = 16, /* Send the next ACK immediately (once) */ + ICSK_ACK_NOMEM = 32, }; void inet_csk_init_xmit_timers(struct sock *sk, diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 3cd92035e090..03111af6115d 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -5061,7 +5061,8 @@ static void tcp_data_queue(struct sock *sk, struct sk_buff *skb) reason = SKB_DROP_REASON_PROTO_MEM; NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRCVQDROP); sk->sk_data_ready(sk); - goto drop; + inet_csk(sk)->icsk_ack.pending |= ICSK_ACK_NOMEM; + goto out_of_window; } eaten = tcp_queue_rcv(sk, skb, &fragstolen); @@ -5102,7 +5103,6 @@ static void tcp_data_queue(struct sock *sk, struct sk_buff *skb) out_of_window: tcp_enter_quickack_mode(sk, TCP_MAX_QUICKACKS); inet_csk_schedule_ack(sk); -drop: tcp_drop_reason(sk, skb, reason); return; } diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 2cb39b6dad02..81aa2c615924 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -257,11 +257,19 @@ EXPORT_SYMBOL(tcp_select_initial_window); static u16 tcp_select_window(struct sock *sk) { struct tcp_sock *tp = tcp_sk(sk); - u32 old_win = tp->rcv_wnd; - u32 cur_win = tcp_receive_window(tp); - u32 new_win = __tcp_select_window(sk); struct net *net = sock_net(sk); + u32 old_win = tp->rcv_wnd; + u32 cur_win, new_win; + + /* Make the window 0 if we failed to queue the data because we + * are out of memory. The window is temporary, so we don't store + * it on the socket. + */ + if (unlikely(inet_csk(sk)->icsk_ack.pending & ICSK_ACK_NOMEM)) + return 0; + cur_win = tcp_receive_window(tp); + new_win = __tcp_select_window(sk); if (new_win < cur_win) { /* Danger Will Robinson! * Don't update rcv_wup/rcv_wnd here or else From patchwork Thu Jul 27 12:51:24 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Menglong Dong X-Patchwork-Id: 13330085 X-Patchwork-Delegate: kuba@kernel.org Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (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 58051171A0 for ; Thu, 27 Jul 2023 12:51:54 +0000 (UTC) Received: from mail-pf1-x441.google.com (mail-pf1-x441.google.com [IPv6:2607:f8b0:4864:20::441]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7AAD81BC1; Thu, 27 Jul 2023 05:51:53 -0700 (PDT) Received: by mail-pf1-x441.google.com with SMTP id d2e1a72fcca58-686b91c2744so728845b3a.0; Thu, 27 Jul 2023 05:51:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1690462313; x=1691067113; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=+xv0faR8qn1Zj+OjUn+kfjlxGEdmNSeFnyT9mw1cYmU=; b=XxuM3J9vD9/FwSGMeuln3H92KmlfmkZ/SdpBGsMO31FUAQhD1OipNCu5wf6CU+AAN3 YJaNAsRqqQijQ9b18NMNwMj05Y9RQnrLY50iZFZJq6kqosPfZhIJzzm00FaNHOpuP89j /tgNmzpeOFqQyRXBdP6a1hu85Oa7RCW+bs1SmkPXem5liVcx8DbEpSJIwztO9+Ax3OUA 71IJ/SlhTbUVbtLc4v4gT5SW2GzXGIAdNQQDPu8ywhmOaxTtjgyGBwTY27ybDKEV+leO ctbGxjwTEhoCkPbwF3Y4jHr+0JzWD5A6FZXWGWBxaJheMcaJkpmOINCUD1Zb6w2xXOPI puXA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1690462313; x=1691067113; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=+xv0faR8qn1Zj+OjUn+kfjlxGEdmNSeFnyT9mw1cYmU=; b=jR+GAq8SsRfbQ450A9EVcLM21IJnIbASNnLUUiQ9WY03UP9eNrmo1acZfvA+WDTxql uMAtCseMjrE6UhMbBrgerhjWo0HkwTlIjAV5hcmDmq95H0t0w/cGCDnPmHZeZzGMVI69 XzE8PMSSCl2oA5yBR3NH7TwCR4Gxn4h9tAZEOQ5hlaAJOMySScEYfmdqr9nWt/YjD4fz /WE5sEltHa6mQhzU0uLkG6Aar5MzNAEDwhht541QM8fxWprRId+HqtyWtPsVwImr02B4 mwZaSx+XIb4BjK9PmZIOKXZuXW5gl0S0c4aCpX2VrlvmQ4Is08mlq4oTghpP35zxLXBa NX+A== X-Gm-Message-State: ABy/qLaithrqg01wegpRvIn2OAMF2nDL3RQUp0EE0czc+eDi/8ZiTiKw nXQd/TrsGT3kN9VZx+1PlbM= X-Google-Smtp-Source: APBJJlG3tK3earJosgCNZih7eD+7O3/4mh8se6jIgdNLuIfAFvARP4j3OueUINSQd9JM8+ovEbyBdA== X-Received: by 2002:a05:6a21:3298:b0:13a:52ce:13cc with SMTP id yt24-20020a056a21329800b0013a52ce13ccmr5111694pzb.51.1690462312932; Thu, 27 Jul 2023 05:51:52 -0700 (PDT) Received: from localhost.localdomain ([43.132.98.115]) by smtp.gmail.com with ESMTPSA id l4-20020a63be04000000b0055386b1415dsm1315048pgf.51.2023.07.27.05.51.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 27 Jul 2023 05:51:52 -0700 (PDT) From: menglong8.dong@gmail.com X-Google-Original-From: imagedong@tencent.com To: edumazet@google.com Cc: davem@davemloft.net, kuba@kernel.org, pabeni@redhat.com, dsahern@kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Menglong Dong Subject: [PATCH net-next 2/3] net: tcp: allow zero-window ACK update the window Date: Thu, 27 Jul 2023 20:51:24 +0800 Message-Id: <20230727125125.1194376-3-imagedong@tencent.com> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20230727125125.1194376-1-imagedong@tencent.com> References: <20230727125125.1194376-1-imagedong@tencent.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_FROM, RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net X-Patchwork-Delegate: kuba@kernel.org From: Menglong Dong Fow now, an ACK can update the window in following case, according to the tcp_may_update_window(): 1. the ACK acknowledged new data 2. the ACK has new data 3. the ACK expand the window and the seq of it is valid Now, we allow the ACK update the window if the window is 0, and the seq/ack of it is valid. This is for the case that the receiver replies an zero-window ACK when it is under memory stress and can't queue the new data. Signed-off-by: Menglong Dong --- net/ipv4/tcp_input.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 03111af6115d..d13b89370f76 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -3526,7 +3526,7 @@ static inline bool tcp_may_update_window(const struct tcp_sock *tp, { return after(ack, tp->snd_una) || after(ack_seq, tp->snd_wl1) || - (ack_seq == tp->snd_wl1 && nwin > tp->snd_wnd); + (ack_seq == tp->snd_wl1 && (nwin > tp->snd_wnd || !nwin)); } /* If we update tp->snd_una, also update tp->bytes_acked */ From patchwork Thu Jul 27 12:51:25 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Menglong Dong X-Patchwork-Id: 13330086 X-Patchwork-Delegate: kuba@kernel.org Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (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 27DB0171C9 for ; Thu, 27 Jul 2023 12:51:59 +0000 (UTC) Received: from mail-pf1-x444.google.com (mail-pf1-x444.google.com [IPv6:2607:f8b0:4864:20::444]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 20F151FFC; Thu, 27 Jul 2023 05:51:57 -0700 (PDT) Received: by mail-pf1-x444.google.com with SMTP id d2e1a72fcca58-6862842a028so703424b3a.0; Thu, 27 Jul 2023 05:51:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1690462316; x=1691067116; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=GQgiv4sJ/sPXZQ43kqJjA4dVyOkNO7+7aA6t8NxmmyQ=; b=eeAxrZ9WGMH+9s61002Q5SSLdR+MJFvTd8G6/NopLVnL0r1bII1ps7l8+oMzhkp+kL kZaAYdAfe3mtCx+d1slojmacDu+nxXnWfw583PDuZuLw1Od8BHkdudH6qSY0Q7+ECbOH YEWhahHNGq9D6sOmmzi/hB6RccvolWbHXR446NXVtmg5DidBUjIFxB4rX6AdSGthSdZk YSIxJib58yoVjAaqciB5yPuSJ/fztyiGTT8tEM2TIlYmVfoydbwQbwU2kMzPye2FtwTD YSQ5vlTKfanGOKjqkvIGsLVwxKseitHw6wNRb0LlUL1NsfQ2aT/vCU014i8LKaD8irMI AJ4A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1690462316; x=1691067116; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=GQgiv4sJ/sPXZQ43kqJjA4dVyOkNO7+7aA6t8NxmmyQ=; b=EuBbfjPZQ8/czO7SJS4QsPlkOJ2XhJ9sdvzv5X1cY/0Z5qctRYUbwMX6qC3uonpJ/U 9Mye3nX4FK3TrdiwQP+NHXpEc+4gJ9lAni61QjIfmV5F5v0U+2ROkDPtpmotYPPocWwm sACAhrlV0n9p8iqNjtw1jCUZot15nVSApZi/AHps70L9AplYOMM2JNL8CrAPEsBYBv6I YwXpt04hBNdxYGDUouNl3n2XpWnQw51nFlP8Sr6HvuvkeEZCfM0/VCd8PqQYdSdR+yK+ RnI+Um7vHX6qSOudBneNiafrf3KWfSaTBbRVvchQ863Zf+mo4f303sIUwSR+FaAaFAqb Pviw== X-Gm-Message-State: ABy/qLYR1fdAbsh0bU8iDUmH27h/vytUgFa2FqkWF7eQB/oDuTxu9E+R gmRodj8/q6oSGBr1mMprqOE= X-Google-Smtp-Source: APBJJlHllk/EfWReDH/gTBZwq8drWBpvIcz+juGTJqtySXhf8ugKpuJXBtt6QmLu8Ama9Un2i/xakA== X-Received: by 2002:a05:6a20:a109:b0:133:e3e3:dc07 with SMTP id q9-20020a056a20a10900b00133e3e3dc07mr5363445pzk.49.1690462316347; Thu, 27 Jul 2023 05:51:56 -0700 (PDT) Received: from localhost.localdomain ([43.132.98.115]) by smtp.gmail.com with ESMTPSA id l4-20020a63be04000000b0055386b1415dsm1315048pgf.51.2023.07.27.05.51.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 27 Jul 2023 05:51:55 -0700 (PDT) From: menglong8.dong@gmail.com X-Google-Original-From: imagedong@tencent.com To: edumazet@google.com Cc: davem@davemloft.net, kuba@kernel.org, pabeni@redhat.com, dsahern@kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Menglong Dong Subject: [PATCH net-next 3/3] net: tcp: check timeout by icsk->icsk_timeout in tcp_retransmit_timer() Date: Thu, 27 Jul 2023 20:51:25 +0800 Message-Id: <20230727125125.1194376-4-imagedong@tencent.com> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20230727125125.1194376-1-imagedong@tencent.com> References: <20230727125125.1194376-1-imagedong@tencent.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_FROM, RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net X-Patchwork-Delegate: kuba@kernel.org From: Menglong Dong In tcp_retransmit_timer(), a window shrunk connection will be regarded as timeout if 'tcp_jiffies32 - tp->rcv_tstamp > TCP_RTO_MAX'. This is not right all the time. The retransmits will become zero-window probes in tcp_retransmit_timer() if the 'snd_wnd==0'. Therefore, the icsk->icsk_rto will come up to TCP_RTO_MAX sooner or later. However, the timer is not precise enough, as it base on timer wheel. Sorry that I am not good at timer, but I know the concept of time-wheel. The longer of the timer, the rougher it will be. So the timeout is not triggered after TCP_RTO_MAX, but 122877ms as I tested. Therefore, 'tcp_jiffies32 - tp->rcv_tstamp > TCP_RTO_MAX' is always true once the RTO come up to TCP_RTO_MAX. Fix this by replacing the 'tcp_jiffies32' with '(u32)icsk->icsk_timeout', which is exact the timestamp of the timeout. Signed-off-by: Menglong Dong --- net/ipv4/tcp_timer.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c index 470f581eedd4..3a20db15a186 100644 --- a/net/ipv4/tcp_timer.c +++ b/net/ipv4/tcp_timer.c @@ -511,7 +511,11 @@ void tcp_retransmit_timer(struct sock *sk) tp->snd_una, tp->snd_nxt); } #endif - if (tcp_jiffies32 - tp->rcv_tstamp > TCP_RTO_MAX) { + /* It's a little rough here, we regard any valid packet that + * update tp->rcv_tstamp as the reply of the retransmitted + * packet. + */ + if ((u32)icsk->icsk_timeout - tp->rcv_tstamp > TCP_RTO_MAX) { tcp_write_err(sk); goto out; }