From owner-svn-src-head@freebsd.org Wed Sep 11 18:48:26 2019 Return-Path: Delivered-To: svn-src-head@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id CF842DC9D8; Wed, 11 Sep 2019 18:48:26 +0000 (UTC) (envelope-from gallatin@FreeBSD.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) server-signature RSA-PSS (4096 bits) client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mxrelay.nyi.freebsd.org", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 46T9s657gFz4HZc; Wed, 11 Sep 2019 18:48:26 +0000 (UTC) (envelope-from gallatin@FreeBSD.org) Received: from repo.freebsd.org (repo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:0]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mxrelay.nyi.freebsd.org (Postfix) with ESMTPS id 8F082AB05; Wed, 11 Sep 2019 18:48:26 +0000 (UTC) (envelope-from gallatin@FreeBSD.org) Received: from repo.freebsd.org ([127.0.1.37]) by repo.freebsd.org (8.15.2/8.15.2) with ESMTP id x8BImQUc056189; Wed, 11 Sep 2019 18:48:26 GMT (envelope-from gallatin@FreeBSD.org) Received: (from gallatin@localhost) by repo.freebsd.org (8.15.2/8.15.2/Submit) id x8BImQnn056188; Wed, 11 Sep 2019 18:48:26 GMT (envelope-from gallatin@FreeBSD.org) Message-Id: <201909111848.x8BImQnn056188@repo.freebsd.org> X-Authentication-Warning: repo.freebsd.org: gallatin set sender to gallatin@FreeBSD.org using -f From: Andrew Gallatin Date: Wed, 11 Sep 2019 18:48:26 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r352228 - head/sys/netinet X-SVN-Group: head X-SVN-Commit-Author: gallatin X-SVN-Commit-Paths: head/sys/netinet X-SVN-Commit-Revision: 352228 X-SVN-Commit-Repository: base MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 11 Sep 2019 18:48:26 -0000 Author: gallatin Date: Wed Sep 11 18:48:26 2019 New Revision: 352228 URL: https://svnweb.freebsd.org/changeset/base/352228 Log: Avoid unneeded call to arc4random() in syncache_add() Don't call arc4random() unconditionally to initialize sc_iss, and then when syncookies are enabled, just overwrite it with the return value from from syncookie_generate(). Instead, only call arc4random() to initialize sc_iss when syncookies are not enabled. Note that on a system under a syn flood attack, arc4random() becomes quite expensive, and the chacha_poly crypto that it calls is one of the more expensive things happening on the system. Removing this unneeded arc4random() call reduces CPU from about 40% to about 35% in my test scenario (Broadwell Xeon, 6Mpps syn flood attack). Reviewed by: rrs, tuxen, bz Sponsored by: Netflix Differential Revision: https://reviews.freebsd.org/D21591 Modified: head/sys/netinet/tcp_syncache.c Modified: head/sys/netinet/tcp_syncache.c ============================================================================== --- head/sys/netinet/tcp_syncache.c Wed Sep 11 18:40:05 2019 (r352227) +++ head/sys/netinet/tcp_syncache.c Wed Sep 11 18:48:26 2019 (r352228) @@ -1543,7 +1543,6 @@ skip_alloc: sc->sc_todctx = todctx; #endif sc->sc_irs = th->th_seq; - sc->sc_iss = arc4random(); sc->sc_flags = 0; sc->sc_flowlabel = 0; @@ -1617,6 +1616,8 @@ skip_alloc: if (V_tcp_syncookies) sc->sc_iss = syncookie_generate(sch, sc); + else + sc->sc_iss = arc4random(); #ifdef INET6 if (autoflowlabel) { if (V_tcp_syncookies)