From patchwork Wed Mar 18 09:43:20 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Ilpo_J=C3=A4rvinen?= X-Patchwork-Id: 1257336 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming-netdev@ozlabs.org Delivered-To: patchwork-incoming-netdev@ozlabs.org Authentication-Results: ozlabs.org; spf=none (no SPF record) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=netdev-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=helsinki.fi Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 48j4rM5dqFz9sPk for ; Wed, 18 Mar 2020 20:44:35 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727737AbgCRJoe (ORCPT ); Wed, 18 Mar 2020 05:44:34 -0400 Received: from smtp-rs2-vallila1.fe.helsinki.fi ([128.214.173.73]:51664 "EHLO smtp-rs2-vallila1.fe.helsinki.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727617AbgCRJn6 (ORCPT ); Wed, 18 Mar 2020 05:43:58 -0400 Received: from whs-18.cs.helsinki.fi (whs-18.cs.helsinki.fi [128.214.166.46]) by smtp-rs2.it.helsinki.fi (8.14.7/8.14.7) with ESMTP id 02I9hplx012879; Wed, 18 Mar 2020 11:43:51 +0200 Received: by whs-18.cs.helsinki.fi (Postfix, from userid 1070048) id F33CD360030; Wed, 18 Mar 2020 11:43:50 +0200 (EET) From: =?iso-8859-1?q?Ilpo_J=E4rvinen?= To: netdev@vger.kernel.org Cc: Yuchung Cheng , Neal Cardwell , Eric Dumazet , Olivier Tilmans Subject: [RFC PATCH 16/28] tcp: allow embedding leftover into option padding Date: Wed, 18 Mar 2020 11:43:20 +0200 Message-Id: <1584524612-24470-17-git-send-email-ilpo.jarvinen@helsinki.fi> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1584524612-24470-1-git-send-email-ilpo.jarvinen@helsinki.fi> References: <1584524612-24470-1-git-send-email-ilpo.jarvinen@helsinki.fi> MIME-Version: 1.0 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Ilpo Järvinen There is some waste space in the option usage due to padding of 32-bit fields. AccECN option can take advantage of those few bytes as its tail is often consuming just a few odd bytes. Signed-off-by: Ilpo Järvinen --- net/ipv4/tcp_output.c | 22 +++++++++++++++++----- 1 file changed, 17 insertions(+), 5 deletions(-) diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index adc22d0d75fd..9ff6d14363df 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -504,6 +504,8 @@ static void mptcp_options_write(__be32 *ptr, struct tcp_out_options *opts) #endif } +#define NOP_LEFTOVER ((TCPOPT_NOP << 8) | TCPOPT_NOP) + /* Write previously computed TCP options to the packet. * * Beware: Something in the Internet is very sensitive to the ordering of @@ -521,6 +523,8 @@ static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp, struct tcp_out_options *opts) { u16 options = opts->options; /* mungable copy */ + u16 leftover_bytes = NOP_LEFTOVER; /* replace next NOPs if avail */ + int leftover_size = 2; if (unlikely(OPTION_MD5 & options)) { *ptr++ = htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) | @@ -554,17 +558,22 @@ static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp, } if (unlikely(OPTION_SACK_ADVERTISE & options)) { - *ptr++ = htonl((TCPOPT_NOP << 24) | - (TCPOPT_NOP << 16) | + *ptr++ = htonl((leftover_bytes << 16) | (TCPOPT_SACK_PERM << 8) | TCPOLEN_SACK_PERM); + leftover_bytes = NOP_LEFTOVER; } if (unlikely(OPTION_WSCALE & options)) { - *ptr++ = htonl((TCPOPT_NOP << 24) | + u8 highbyte = TCPOPT_NOP; + + if (unlikely(leftover_size == 1)) + highbyte = leftover_bytes >> 8; + *ptr++ = htonl((highbyte << 24) | (TCPOPT_WINDOW << 16) | (TCPOLEN_WINDOW << 8) | opts->ws); + leftover_bytes = NOP_LEFTOVER; } if (unlikely(opts->num_sack_blocks)) { @@ -572,8 +581,7 @@ static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp, tp->duplicate_sack : tp->selective_acks; int this_sack; - *ptr++ = htonl((TCPOPT_NOP << 24) | - (TCPOPT_NOP << 16) | + *ptr++ = htonl((leftover_bytes << 16) | (TCPOPT_SACK << 8) | (TCPOLEN_SACK_BASE + (opts->num_sack_blocks * TCPOLEN_SACK_PERBLOCK))); @@ -585,6 +593,10 @@ static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp, } tp->rx_opt.dsack = 0; + } else if (unlikely(leftover_bytes != NOP_LEFTOVER)) { + *ptr++ = htonl((leftover_bytes << 16) | + (TCPOPT_NOP << 8) | + TCPOPT_NOP); } if (unlikely(OPTION_FAST_OPEN_COOKIE & options)) {