From nobody Sat Nov 23 19:34:48 2024 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass(p=none dis=none) header.from=linaro.org ARC-Seal: i=1; a=rsa-sha256; t=1730997191; cv=none; d=zohomail.com; s=zohoarc; b=eOGWljOz8cAjF6EobyKExDnnbPIAQCBSXT1iGrdfvOAlDu25Dd8AROEKgXpShBclZNLvOL9xEBBvtttaa01bVxltKLOIjj/1nt+ClsvRZvp9Z8RhNIkAVSG0bZfG5MxRS2KwHaKi+VKPFQun/Wvv+UzpMSNWwTsTIfqACZ5v9bk= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1730997191; h=Content-Transfer-Encoding:Cc:Cc:Date:Date:From:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:Subject:To:To:Message-Id:Reply-To; bh=1WMn0gaL6wgiSUyaLJnx1vDmLwUkpAicF45c17E4Yr8=; b=Q3emXms+Kth9wGJTXrpminU+hhtRNH1Tr/NCj1kV7gogSfj7geJjt9tYTJ+GU98fcYlPUaL7DiE5WibFjrariQz17IZrBlnAVlmjv4GJptVRMCUEcE1ogWmHpofWEcfEUu7EgnxxcQ7NWXPV8lIQWrGx+NjzXaT2jx5sH6wLoRA= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass header.from= (p=none dis=none) Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 173099719168659.52918133502578; Thu, 7 Nov 2024 08:33:11 -0800 (PST) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1t95Qj-0007z1-Ff; Thu, 07 Nov 2024 11:32:21 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1t95Qf-0007xg-UQ for qemu-devel@nongnu.org; Thu, 07 Nov 2024 11:32:17 -0500 Received: from mail-wm1-x334.google.com ([2a00:1450:4864:20::334]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1t95Qc-00049A-9w for qemu-devel@nongnu.org; Thu, 07 Nov 2024 11:32:17 -0500 Received: by mail-wm1-x334.google.com with SMTP id 5b1f17b1804b1-4315df7b43fso9905195e9.0 for ; Thu, 07 Nov 2024 08:32:13 -0800 (PST) Received: from orth.archaic.org.uk (orth.archaic.org.uk. [2001:8b0:1d0::2]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-381ed9ea587sm2185161f8f.78.2024.11.07.08.32.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 07 Nov 2024 08:32:12 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; t=1730997132; x=1731601932; darn=nongnu.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=1WMn0gaL6wgiSUyaLJnx1vDmLwUkpAicF45c17E4Yr8=; b=OPQLQaPE6OvhLw/xhCv8puflQ5mxywR1+3LnApsO6r3duRmoh6MNmSN7GdSLhwbZUQ wiBUHMEIbkjPFzl2aC2nGOZKGJeF8/UQUm/fU59Wx4SRrJkIOhguOdNjEkCE6FrIRuPE rqDrA0GpBtXR1DnZZbTW6etCWbBOuB+zkFDHBo2at6309bJVqpwIn7xine1wdklccNs6 F2i3iFG/56oDeCOptGxQtFFAf05mNWP58uUlHxmfKtiRcNKGLBijrREX5/JowwN2ZS4q BGxkKuIkWOXSiv3DUn7lF050GHEPYSubdozs4DKoVObcd1aKY+ETZmD/IyTHgw1femV6 BIMg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1730997132; x=1731601932; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=1WMn0gaL6wgiSUyaLJnx1vDmLwUkpAicF45c17E4Yr8=; b=Q8GzOZydVGI4qntVDe1yrrO62Rp4UtXq5N+oHvSbn3h/FvCt40rymrKUZZdfmkLSdI OopKpqDIF0YxOOa6Q07tTooipu+HRi0fXZCbketu5XZg13bHnKdRbjuSVwHGaBqPbN1j cAm9tGfSXQoTOjJtRJl1taKcEKh/dAwB1+MqLpLW0s3jiSmi+224Ckjv0HdFYeZsPGX9 KqA+CIRoL76EPh4uLZw2xp6A43cf/5jrN6ch6IVvgM1utlCe45fR0B+EMJ94qVpjkdFr +eMz8QI63DenSdZQES/gMCWvBtF/DB8yOHrLPYB3XADNYTtuvUwLQHqDSI06inrAZWRB xP5Q== X-Gm-Message-State: AOJu0Yw15HKzquGj8RjztOswt9U5m37m5IhwN3prtf840DeC6aV8VHH4 lcHA4wkEtLoOUmgcHkFmw2MMUNeI4VDtA+nnP2EigwBfgkZ26tJVLjiRpBUd7PLea6Q2kATFwgg r X-Google-Smtp-Source: AGHT+IH4oIePH81+EzzXucdNZidk5sBsfDPXspJVpqIOwT0Apq6CtsLWJd49iLNraCW0Xng6Q6ZTew== X-Received: by 2002:a05:600c:281:b0:431:3933:1d30 with SMTP id 5b1f17b1804b1-431a0c3b8f4mr374746315e9.5.1730997132619; Thu, 07 Nov 2024 08:32:12 -0800 (PST) From: Peter Maydell To: qemu-devel@nongnu.org Cc: "Michael S. Tsirkin" , Jason Wang , Dmitry Fleytman , Akihiko Odaki Subject: [PATCH 1/2] hw/net/virtio-net.c: Don't assume IP length field is aligned Date: Thu, 7 Nov 2024 16:32:09 +0000 Message-Id: <20241107163210.3620697-2-peter.maydell@linaro.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20241107163210.3620697-1-peter.maydell@linaro.org> References: <20241107163210.3620697-1-peter.maydell@linaro.org> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=2a00:1450:4864:20::334; envelope-from=peter.maydell@linaro.org; helo=mail-wm1-x334.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @linaro.org) X-ZM-MESSAGEID: 1730997194423116600 Content-Type: text/plain; charset="utf-8" In virtio-net.c we assume that the IP length field in the packet is aligned, and we copy its address into a uint16_t* in the VirtioNetRscUnit struct which we then dereference later. This isn't a safe assumption; it will also result in compilation failures if we mark the ip_header struct as QEMU_PACKED because the compiler will not let you take the address of an unaligned struct field. Make the ip_plen field in VirtioNetRscUnit a void*, and make all the places where we read or write through that pointer instead use some new accessor functions read_unit_ip_len() and write_unit_ip_len() which account for the pointer being potentially unaligned and also do the network-byte-order conversion we were previously using htons() to perform. Signed-off-by: Peter Maydell --- include/hw/virtio/virtio-net.h | 2 +- hw/net/virtio-net.c | 23 +++++++++++++++++++---- 2 files changed, 20 insertions(+), 5 deletions(-) diff --git a/include/hw/virtio/virtio-net.h b/include/hw/virtio/virtio-net.h index 060c23c04d2..b9ea9e824e3 100644 --- a/include/hw/virtio/virtio-net.h +++ b/include/hw/virtio/virtio-net.h @@ -102,7 +102,7 @@ typedef struct VirtioNetRscStat { /* Rsc unit general info used to checking if can coalescing */ typedef struct VirtioNetRscUnit { void *ip; /* ip header */ - uint16_t *ip_plen; /* data len pointer in ip header field */ + void *ip_plen; /* pointer to unaligned uint16_t data len in ip header = */ struct tcp_header *tcp; /* tcp header */ uint16_t tcp_hdrlen; /* tcp header len */ uint16_t payload; /* pure payload without virtio/eth/ip/tcp */ diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c index f2104ed364a..11cf462180d 100644 --- a/hw/net/virtio-net.c +++ b/hw/net/virtio-net.c @@ -2049,6 +2049,21 @@ static ssize_t virtio_net_do_receive(NetClientState = *nc, const uint8_t *buf, return virtio_net_receive_rcu(nc, buf, size, false); } =20 +/* + * Accessors to read and write the IP packet data length field. This + * is a potentially unaligned network-byte-order 16 bit unsigned integer + * pointed to by unit->ip_len. + */ +static uint16_t read_unit_ip_len(VirtioNetRscUnit *unit) +{ + return ldl_be_p(unit->ip_plen); +} + +static void write_unit_ip_len(VirtioNetRscUnit *unit, uint16_t l) +{ + stl_be_p(unit->ip_plen, l); +} + static void virtio_net_rsc_extract_unit4(VirtioNetRscChain *chain, const uint8_t *buf, VirtioNetRscUnit *unit) @@ -2063,7 +2078,7 @@ static void virtio_net_rsc_extract_unit4(VirtioNetRsc= Chain *chain, unit->ip_plen =3D &ip->ip_len; unit->tcp =3D (struct tcp_header *)(((uint8_t *)unit->ip) + ip_hdrlen); unit->tcp_hdrlen =3D (htons(unit->tcp->th_offset_flags) & 0xF000) >> 1= 0; - unit->payload =3D htons(*unit->ip_plen) - ip_hdrlen - unit->tcp_hdrlen; + unit->payload =3D read_unit_ip_len(unit) - ip_hdrlen - unit->tcp_hdrle= n; } =20 static void virtio_net_rsc_extract_unit6(VirtioNetRscChain *chain, @@ -2082,7 +2097,7 @@ static void virtio_net_rsc_extract_unit6(VirtioNetRsc= Chain *chain, =20 /* There is a difference between payload length in ipv4 and v6, ip header is excluded in ipv6 */ - unit->payload =3D htons(*unit->ip_plen) - unit->tcp_hdrlen; + unit->payload =3D read_unit_ip_len(unit) - unit->tcp_hdrlen; } =20 static size_t virtio_net_rsc_drain_seg(VirtioNetRscChain *chain, @@ -2231,7 +2246,7 @@ static int32_t virtio_net_rsc_coalesce_data(VirtioNet= RscChain *chain, VirtioNetRscUnit *o_unit; =20 o_unit =3D &seg->unit; - o_ip_len =3D htons(*o_unit->ip_plen); + o_ip_len =3D read_unit_ip_len(o_unit); nseq =3D htonl(n_unit->tcp->th_seq); oseq =3D htonl(o_unit->tcp->th_seq); =20 @@ -2267,7 +2282,7 @@ coalesce: o_unit->payload +=3D n_unit->payload; /* update new data len */ =20 /* update field in ip header */ - *o_unit->ip_plen =3D htons(o_ip_len + n_unit->payload); + write_unit_ip_len(o_unit, o_ip_len + n_unit->payload); =20 /* Bring 'PUSH' big, the whql test guide says 'PUSH' can be coales= ced for windows guest, while this may change the behavior for linux --=20 2.34.1 From nobody Sat Nov 23 19:34:48 2024 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass(p=none dis=none) header.from=linaro.org ARC-Seal: i=1; a=rsa-sha256; t=1730997179; cv=none; d=zohomail.com; s=zohoarc; b=K0pVbCXETKtPiViPUnRCbqgcCVWpqIzaZbU3Wn6DiZh1EIv9K4LEOxA17aIeg3B7Xn7JicOHoLgiD1mOtxN9gd+B4EWyWvwHTJX/QSfPPCBPB3xjNTlEZSUi9eJrWUGIvmIpO5tTLU73WtYPcvcAgccocYD80/2Gq0resi1DsbM= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1730997179; h=Content-Transfer-Encoding:Cc:Cc:Date:Date:From:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:Subject:To:To:Message-Id:Reply-To; bh=3cl4ZO8ew2BAiajP9BAvW5+7ZXDojU8B2khh55fONv8=; b=BdiNx5R2w+fP7cVL/nMvB4DxpwVDflQxrf0pgvWJp8Qitf1yAFyFlubr93lrtCDVcrr4ascmVzseEwwzw8N1l00jYRvMH88+mNs5iqiy1ZK1OfW/7f3J0TtY+ezS1n1mz9QhNpe2VHc79eShcAwZbHdnUA/tdUJe2LD3Etb/R2I= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass header.from= (p=none dis=none) Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1730997179735652.4877407961408; Thu, 7 Nov 2024 08:32:59 -0800 (PST) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1t95Qi-0007yO-Td; Thu, 07 Nov 2024 11:32:20 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1t95Qf-0007xf-U9 for qemu-devel@nongnu.org; Thu, 07 Nov 2024 11:32:17 -0500 Received: from mail-wr1-x435.google.com ([2a00:1450:4864:20::435]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1t95Qc-00049u-Lr for qemu-devel@nongnu.org; Thu, 07 Nov 2024 11:32:17 -0500 Received: by mail-wr1-x435.google.com with SMTP id ffacd0b85a97d-37d4ac91d97so1022625f8f.2 for ; Thu, 07 Nov 2024 08:32:14 -0800 (PST) Received: from orth.archaic.org.uk (orth.archaic.org.uk. [2001:8b0:1d0::2]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-381ed9ea587sm2185161f8f.78.2024.11.07.08.32.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 07 Nov 2024 08:32:12 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; t=1730997133; x=1731601933; darn=nongnu.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=3cl4ZO8ew2BAiajP9BAvW5+7ZXDojU8B2khh55fONv8=; b=GMvTBYoTiQsHNdUppdQAN9QAjzU6z9jGRYXckHjUFaTPHfT6qmgLI2xXc31w9f9JOF xcwQtlxhSpruEv02Ptv7/hY098OjneYCvQlSyIu1fTehlz7Zq97+bI3KkbRXm57/QfTQ zi+Rw0JUhinIFh1kiXlY3FLlk7oMMnv91CZMCDnf+RoB6u5iIPphJAL+9qog0u1WemcG GD9JI27Z2W8fFCyZnaGqcLN4lFSxx3GhmGlPhkSzAOuytUksrUg/40qKfXB2s9LZLpA2 pWh6osGskyiNq6lDnqpt2wvT0y96dzJ5W326B+9Bio1CI2AZdfqCgGH9egOWJt8zuQyZ Az9w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1730997133; x=1731601933; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=3cl4ZO8ew2BAiajP9BAvW5+7ZXDojU8B2khh55fONv8=; b=Na6xWXMjrL4tPKsLcJhCaDlOOmPrnTRima+E6cZd6Y+1K4KC/9+vN8/1oDn8QGT6k/ T8ztfVGq3m8jn1Jb4LVOrE4WyAMUs0Zo7alpJTSE6lFg8o1llKimCjGBaGsMfkd8Y9on 1Uwl8Sc3t/VBBVMercEMDVtxizFT8Eld88mlY1BNSjml+uZKnYGp9vSorBi0OdB3pqUP WaX0BsAc4e1ut2QMarPFqdhi4BAexkhrekoVxLr4Qw4VNfBFbr0heMHp6llfISdVIhLR KY/c6oYnkCCaMBCEj0t6igKNZlcy/MdtjAaN2DqG1OuZK4+HYfvhdchAPcMIsrm4bRqy 72zg== X-Gm-Message-State: AOJu0Yy6pF0X6FJQbtxNgtqiGhTyfN4LuNsGz9SvkG7YWSsMpqJygLUY SzYeTf6X10tXKOIDVrhl3f4UjHvSIZOL81TzzGuEa3nfV1f88gRnz9rGcWMm3qnQ8VS9aa4/kj1 3 X-Google-Smtp-Source: AGHT+IFHQb4h2VI2jURzQ9uJmqNRbDVdHLyLxU8jg32m/b7eZU8mA6Gr+f03Obdvq1b/hzcyDKE2DA== X-Received: by 2002:a5d:59a7:0:b0:37d:4376:6e1d with SMTP id ffacd0b85a97d-381c7ac45b8mr24204658f8f.41.1730997133200; Thu, 07 Nov 2024 08:32:13 -0800 (PST) From: Peter Maydell To: qemu-devel@nongnu.org Cc: "Michael S. Tsirkin" , Jason Wang , Dmitry Fleytman , Akihiko Odaki Subject: [PATCH 2/2] net: mark struct ip_header as QEMU_PACKED Date: Thu, 7 Nov 2024 16:32:10 +0000 Message-Id: <20241107163210.3620697-3-peter.maydell@linaro.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20241107163210.3620697-1-peter.maydell@linaro.org> References: <20241107163210.3620697-1-peter.maydell@linaro.org> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=2a00:1450:4864:20::435; envelope-from=peter.maydell@linaro.org; helo=mail-wr1-x435.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @linaro.org) X-ZM-MESSAGEID: 1730997182007116600 Content-Type: text/plain; charset="utf-8" The ip_header is not actually guaranteed to be aligned. We attempt to deal with this in some places such as net_checksum_calculate() by using stw_be_p and so on to access the fields, but this is not sufficient to be correct, because even accessing a byte member within an unaligned struct is undefined behaviour. The clang sanitizer will emit warnings like these if net_checksum_calculate() is called: Stopping network: ../../net/checksum.c:106:9: runtime error: member ac= cess within misaligned address 0x556aad9b502e for type 'struct ip_header', = which requires 4 byte alignment 0x556aad9b502e: note: pointer points here 34 56 08 00 45 00 01 48 a5 09 40 00 40 11 7c 8b 0a 00 02 0f 0a 00 0= 2 02 00 44 00 43 01 34 19 56 ^ SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior ../../net/check= sum.c:106:9 in ../../net/checksum.c:106:9: runtime error: load of misaligned address 0= x556aad9b502e for type 'uint8_t' (aka 'unsigned char'), which requires 4 by= te alignment 0x556aad9b502e: note: pointer points here 34 56 08 00 45 00 01 48 a5 09 40 00 40 11 7c 8b 0a 00 02 0f 0a 00 0= 2 02 00 44 00 43 01 34 19 56 ^ Fix this by marking the ip_header struct as QEMU_PACKED, so that the compiler knows that it might be unaligned and will generate the right code for accessing fields. Signed-off-by: Peter Maydell --- include/net/eth.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/net/eth.h b/include/net/eth.h index 3b80b6e07f3..14c34f530fe 100644 --- a/include/net/eth.h +++ b/include/net/eth.h @@ -56,7 +56,7 @@ struct ip_header { uint8_t ip_p; /* protocol */ uint16_t ip_sum; /* checksum */ uint32_t ip_src, ip_dst; /* source and destination address */ -}; +} QEMU_PACKED; =20 typedef struct tcp_header { uint16_t th_sport; /* source port */ --=20 2.34.1