From mboxrd@z Thu Jan 1 00:00:00 1970 From: bugzilla-daemon-590EEB7GvNiWaY/ihj7yzEB+6BGkLq7r@public.gmane.org Subject: [Bug 25322] New: [PATCH] tcp syn cookies will not eat your server anymore Date: Mon, 20 Dec 2010 18:01:10 GMT Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Return-path: Sender: linux-man-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: linux-man-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-man@vger.kernel.org https://bugzilla.kernel.org/show_bug.cgi?id=25322 Summary: [PATCH] tcp syn cookies will not eat your server anymore Product: Documentation Version: unspecified Platform: All OS/Version: Linux Tree: Mainline Status: NEW Severity: normal Priority: P1 Component: man-pages AssignedTo: documentation_man-pages-ztI5WcYan/vQLgFONoPN62D2FQJk+8+b@public.gmane.org ReportedBy: nico-JSaSgPfTjtHYtjvyW6yDsg@public.gmane.org Regression: No Hello Based on a discussion on net-dev (http://article.gmane.org/gmane.linux.network.general/14344), TCP syncookies seem to not be disastrous for performance anymore. Theses improvements happened in 2.6.36, 2.6.33 and 2.6.26. More info in theses commits: - 4dfc28170 Add support for TCP options via timestamps. - c6aefafb7 Add IPv6 support to TCP SYN cookies - 172d69e63 syncookies: add support for ECN What would you think about the following patch about the tcp_syn_cookie entry? diff --git a/man7/tcp.7 b/man7/tcp.7 index 3903c9d..e42bdef 100644 --- a/man7/tcp.7 +++ b/man7/tcp.7 @@ -677,11 +677,10 @@ The kernel must be compiled with Send out syncookies when the syn backlog queue of a socket overflows. The syncookies feature attempts to protect a socket from a SYN flood attack. -This should be used as a last resort, if at all. -This is a violation of the TCP protocol, -and conflicts with other areas of TCP such as TCP extensions. -It can cause problems for clients and relays. -It is not recommended as a tuning mechanism for heavily +Until 2.6.36, it was violating TCP and has to be used as a last +resort, if at all. Since 2.6.36, TCP extensions are preserved and the +impact on performance is minimal. +It is still not recommended as a tuning mechanism for heavily loaded servers to help with overloaded or misconfigured conditions. For recommended alternatives see .IR tcp_max_syn_backlog , By the way, there is no information about tcp_cookie_size, the TCP Cookie Transaction sysctl (this new TCP extension was introduced in 2.6.33), do you want a patch? -- Configure bugmail: https://bugzilla.kernel.org/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are watching the assignee of the bug. -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html