How TCP backlog works in Linux
When an application puts a socket into LISTEN state using the listen syscall, it needs to specify a backlog for that socket. The backlog is usually described as the limit for the queue of incoming connections. Because of the 3-way handshake used by TCP, an incoming connection goes through an intermediate state SYN RECEIVED before it reaches the ESTABLISHED state and can be returned by the accept s
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ä»¥å‰ (2.6.31 ã¾ã§?) ã¯ä»¥ä¸‹ã®æŒ™å‹•*1。 最åˆã®ãƒšã‚¤ãƒãƒ¼ãƒ‰ã‚’å—ä¿¡ã™ã‚‹ã¾ã§ SYN_RECV ステート クライアント㮠ACK (TCP ãƒãƒ³ãƒ‰ã‚·ã‚§ã‚¤ã‚¯ã®æœ€å¾Œã®ãƒ‘ケット) ã‚’å—ä¿¡ã—ã¦ã„ãŸã¨ã—ã¦ã‚‚ã€SYN-ACK ã‚’é€ã‚Šç¶šã‘ã‚‹ 190 秒ãŸã£ãŸã‚‰ã€ã‚µãƒ¼ãƒå´ã¯ TCP 接続確立失敗ã¨èªè˜ クライアント㯠SYN-ACK ã‚’é€ã£ã¦ã‚‹ã‹ã‚‰æŽ¥ç¶šã§ãã¦ã‚‹ã¤ã‚‚ã‚Š TCP ã®ä»•æ§˜çš„ã«ã©ã†ãªã®ã€ã£ã¦è©±ã¯ã‚ã‹ã‚‹ã€‚ãŸã ã€IP 層ã¯ãƒ‘ケットãƒã‚¹ã®å¯èƒ½æ€§ãŒã‚ã‚‹ã‚ã‘ã§ã€ã‚¤ãƒ³ã‚¿ãƒ¼ãƒãƒƒãƒˆã‚’使ã£ã¦ã„ã¦ã€ã“ã®æŒ™å‹•ã§å•é¡ŒãŒã‚ã‚‹ã¨ã—ãŸã‚‰ã€ãã‚Œã¯ã‚¢ãƒ—リケーションã®ãƒã‚°ã ã¨æ€ã†ã‘ã©ã€‚一方ã§ã€ LAN 上ã§ãƒ‘ケットãƒã‚¹ãŒ (ã»ã¼) èµ·ã“らãªã„å‰æã§ä½œã£ã¦ãŸã‚‰å›°ã‚‹ã“ã¨ãŒã‚ã‚‹ã®ã‹ãªãƒ¼ã€‚Ubuntu ã® BTS ã§è©±ãŒå‡ºã¦ã‚‹ã®ã¯ã€ãã†ã„ã†ã‚±ãƒ¼ã‚¹ (特定ã®ãƒãƒ¼ãƒ‰ã‚¦ã‚§ã‚¢ãƒãƒ¼ãƒ‰ãƒãƒ©ãƒ³ã‚µã¨ TCP_DEFER_ACCEPT を使ㆠApac
SYN cookies - Wikipedia
SYN cookies (スィン・クッã‚ーズ) ã¨ã¯ã€TCP SYN flood攻撃を防ããŸã‚ã«é–‹ç™ºã•ã‚ŒãŸæ‰‹æ³•ã®ã²ã¨ã¤ã€‚1996å¹´ã€ãƒ€ãƒ‹ã‚¨ãƒ«ãƒ»J・ãƒãƒ¼ãƒ³ã‚¹ã‚¿ã‚¤ãƒ³ã‚‰ã«ã‚ˆã‚Šè€ƒæ¡ˆã•ã‚ŒãŸã€‚ SYN flood 攻撃ã®å•é¡Œç‚¹ã¯ã€TCP 接続ãŒé–‹å§‹ã™ã‚‹å‰ã‹ã‚‰ã‚µãƒ¼ãƒãŒã‚¯ãƒ©ã‚¤ã‚¢ãƒ³ãƒˆã® SYN パケットã«ã‚ˆã£ã¦è¨˜æ†¶é ˜åŸŸã‚’消費ã—ã¦ã—ã¾ã†ç‚¹ã«ã‚ã£ãŸã€‚通常ã“ã®è¨˜æ†¶é ˜åŸŸã«ã¯ã€ã‚¯ãƒ©ã‚¤ã‚¢ãƒ³ãƒˆå´ã®IPアドレスã¨ãƒãƒ¼ãƒˆç•ªå·ã€æŽ¥ç¶šã«ä½¿ã†ã‚·ãƒ¼ã‚±ãƒ³ã‚¹ç•ªå·ã€ãŠã‚ˆã³ã‚¯ãƒ©ã‚¤ã‚¢ãƒ³ãƒˆãŒæŒ‡å®šã—ã¦ã㟠TCP接続ã«é–¢ã™ã‚‹æ§˜ã€…ãªè¨å®š (TCPウィンドウã®å¤§ãã•ãªã©) ãŒæ ¼ç´ã•ã‚Œã‚‹ã€‚ã¾ãŸã€ã‚µãƒ¼ãƒã¯ SYN パケットをå—ã‘ã¨ã£ãŸå¾Œã€ã‚¯ãƒ©ã‚¤ã‚¢ãƒ³ãƒˆã«å¯¾ã—㦠SYN ACK パケットを返ã™ã€‚ã“ã“ã«ã¯ãã® TCP 接続ã«é–¢é€£ã¥ã‘られãŸTCPシーケンス番å·ãŒå«ã¾ã‚Œã¦ã„る。TCPシーケンス番å·ã¯ã“れ以é™ã® TCP通信ã®ä¸ã§ã€ã‚¯ãƒ©ã‚¤ã‚¢ãƒ³ãƒˆãŠã‚ˆã³ã‚µãƒ¼ãƒãŒå…±é€šã—ã¦ä½¿
Take advantage of TCP/IP options to optimize data transmission | TechRepublic
Streamlining data transmission is a critical challenge for any enterprise. Thankfully, the TCP/IP protocol provides many ways to optimize data transfer. This article examines several options and shows how they can boost performance. By Alex Kuznetsov, Alex Plant, and Alexander Tormasov Last time, we explained how the TCP_CORK option can decrease the number of packets transferred over a network. Wh
TCP 3-way handshakeã®ãƒ¬ã‚¤ãƒ†ãƒ³ã‚·è»½æ¸›ã®ãŸã‚ã®TCP_DEFER_ACCEPTソケットオプション - ゆã†ã†ãブãƒã‚°
2013/10/22 追記ã—ãŸï¼Ž Starletã®ã‚³ãƒ¼ãƒ‰èªã‚“ã§ã¦listening socketã«TCP_DEFER_ACCEPTã¨ã‹ã„ã†ã‚ªãƒ—ション渡ã—ã¦ãŸã®ã§ã€ã“れ何ã ã£ã¦æ€ã£ã¦èª¿ã¹ãŸï¼Ž TCPã«ç‰¹ã«è©³ã—ã„ã‚ã‘ã§ã¯ãªã„ã®ã§ç†è§£ã«èª¤ã‚ŠãŒã‚ã‚‹ã‹ã‚‚ã—ã‚Œãªã„． package Starlet::Server; ... # set defer accept if ($^O eq 'linux') { setsockopt($self->{listen_sock}, IPPROTO_TCP, 9, 1) # 9ãŒTCP_DEFER_ACCEPTを表㙠and $self->{_using_defer_accept} = 1; } ... TCP_DEFER_ACCEPTã¯Linux 2.4ã‹ã‚‰å°Žå…¥ã•ã‚Œã¦ã„る． Linux 2.6.32ã‹ã‚‰æŒ™å‹•ãŒè‹¥å¹²å¤‰ã‚ã£ã¦ã„るらã—ã„． (linux ã® TCP_DE
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