From patchwork Fri Aug 10 09:16:50 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Samuel Thibault X-Patchwork-Id: 956159 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=nongnu.org (client-ip=2001:4830:134:3::11; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=ens-lyon.org Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 41mzzR56S5z9s7Q for ; Fri, 10 Aug 2018 19:17:23 +1000 (AEST) Received: from localhost ([::1]:55089 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fo3Xt-00009X-6P for incoming@patchwork.ozlabs.org; Fri, 10 Aug 2018 05:17:21 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:56368) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fo3XZ-00009O-1o for qemu-devel@nongnu.org; Fri, 10 Aug 2018 05:17:02 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fo3XV-0002c5-QM for qemu-devel@nongnu.org; Fri, 10 Aug 2018 05:17:00 -0400 Received: from mail3-relais-sop.national.inria.fr ([192.134.164.104]:4892) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fo3XV-0002Zh-Dy for qemu-devel@nongnu.org; Fri, 10 Aug 2018 05:16:57 -0400 X-IronPort-AV: E=Sophos;i="5.53,219,1531778400"; d="scan'208";a="275483872" Received: from unknown (HELO var.youpi.perso.aquilenet.fr) ([193.50.110.215]) by mail3-relais-sop.national.inria.fr with ESMTP/TLS/AES256-GCM-SHA384; 10 Aug 2018 11:16:55 +0200 Received: from samy by var.youpi.perso.aquilenet.fr with local (Exim 4.91) (envelope-from ) id 1fo3XT-0003sx-9T; Fri, 10 Aug 2018 11:16:55 +0200 From: Samuel Thibault To: qemu-devel@nongnu.org Date: Fri, 10 Aug 2018 11:16:50 +0200 Message-Id: <20180810091650.14194-1-samuel.thibault@ens-lyon.org> X-Mailer: git-send-email 2.18.0 X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 192.134.164.104 Subject: [Qemu-devel] [PATCH] slirp: document mbuf pointers and sizes X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Peter Maydell , Samuel Thibault , stefanha@redhat.com, jan.kiszka@siemens.com Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" From: Peter Maydell and fix confusing datasize name into gapsize in m_inc. Signed-off-by: Peter Maydell Signed-off-by: Samuel Thibault --- slirp/mbuf.c | 14 +++++++------- slirp/mbuf.h | 13 +++++++++++++ 2 files changed, 20 insertions(+), 7 deletions(-) diff --git a/slirp/mbuf.c b/slirp/mbuf.c index 1b7868355a..aa1f28afb1 100644 --- a/slirp/mbuf.c +++ b/slirp/mbuf.c @@ -151,7 +151,7 @@ m_cat(struct mbuf *m, struct mbuf *n) void m_inc(struct mbuf *m, int size) { - int datasize; + int gapsize; /* some compilers throw up on gotos. This one we can fake. */ if (M_ROOM(m) > size) { @@ -159,17 +159,17 @@ m_inc(struct mbuf *m, int size) } if (m->m_flags & M_EXT) { - datasize = m->m_data - m->m_ext; - m->m_ext = g_realloc(m->m_ext, size + datasize); + gapsize = m->m_data - m->m_ext; + m->m_ext = g_realloc(m->m_ext, size + gapsize); } else { - datasize = m->m_data - m->m_dat; - m->m_ext = g_malloc(size + datasize); + gapsize = m->m_data - m->m_dat; + m->m_ext = g_malloc(size + gapsize); memcpy(m->m_ext, m->m_dat, m->m_size); m->m_flags |= M_EXT; } - m->m_data = m->m_ext + datasize; - m->m_size = size + datasize; + m->m_data = m->m_ext + gapsize; + m->m_size = size + gapsize; } diff --git a/slirp/mbuf.h b/slirp/mbuf.h index 33b84485d6..bfdf8c4577 100644 --- a/slirp/mbuf.h +++ b/slirp/mbuf.h @@ -47,6 +47,19 @@ * free the m_ext. This is inefficient memory-wise, but who cares. */ +/* + * mbufs allow to have a gap between the start of the allocated buffer (m_ext if + * M_EXT is set, m_dat otherwise) and the in-use data: + * + * |--gapsize----->|---m_len-------> + * |----------m_size------------------------------> + * |----M_ROOM--------------------> + * |-M_FREEROOM--> + * + * ^ ^ ^ + * m_dat/m_ext m_data end of buffer + */ + /* * How much room is in the mbuf, from m_data to the end of the mbuf */