From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5ADE6479882 for ; Thu, 1 Oct 2026 19:11:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790881916; cv=none; b=qbWuin2W/3QvYGpmwM/FnAu+2FiDxMPcGVLCJuQYe70W9UFFWSwYqsFmFhlOy9rwX82gWYMYatIqbr3kdF51xkLlRrhFfpd4rJiMc1Zwi8PpsH6HOrdNtzeghuXi0vDvZGbUwGFz0djrOyBBe8Ct/MJq9xmlFhJpLv6xPcrbVvg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790881916; c=relaxed/simple; bh=2kQ5HyGCqIYXmwehYvuH4lBXZGqsljvo2J6EHtZr31I=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=oGrcQm7D0b9kT1BC4y07KJ1p2kPcQTMq/dCzX0M4BCj0pM//HGZN5ZN/v9+JndfusL3kj+ECqfxGFDzWVaj6nHiCeYGpN5YHct1FrQQPSEexR0Wm6KcAMjMs3Ei3UDULZLegQf9gxacS1FzNOSUH2YimlKf8wQgJ01Sa6mKr2ng= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=MsE+Fbca; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="MsE+Fbca" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 302A71F000FF; Thu, 1 Oct 2026 19:11:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790881911; bh=5A9+ICU2a47qU3a3ecQUGkAkvb1goP7YtH5Yta52Gt8=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=MsE+FbcaUWhfxee8oskfcvrmCQcajBOl0Tt+t22pvGZIhztejRH50RxlL1RJYghld e3qrCEuQSt7OVSRajAVLl6tuSIZf7Ubu269NvnPgfLj/THSzFYLfBf3TZi+xYCu7fn D0iMtIDE8liQs2Lq+Bfeqm6JWE6B6DlE+vJLBqMq4yPIG26Ru9bEDxHb5db9pRBluB vFJEVsB2viytua2XKkY/twljuNxToD94XUrONvmxTJIlZzQs8OfN6dFzgs7mVbXy8j gqY+h8Y8jVHRlY8L6VzmHszodoKCjeIvEi3Pw6r0RBgo79Y/tgdNHekaknoHT0BlD7 i6WIcIOnxyXCw== From: Eric Dumazet To: "David S . Miller" , Jakub Kicinski , Paolo Abeni , Willem de Bruijn Cc: "Michael S . Tsirkin" , Simon Horman , netdev@vger.kernel.org, edumazet@google.com, Eric Dumazet Subject: [PATCH v3 net 3/3] selftests: net: tun: add test for VLAN-tagged GSO without NEEDS_CSUM Date: Thu, 1 Oct 2026 19:11:40 +0000 Message-ID: <20261001191140.2818991-4-edumazet@kernel.org> X-Mailer: git-send-email 2.56.0.rc1.315.gc6ed9934b7-goog In-Reply-To: <20261001191140.2818991-1-edumazet@kernel.org> References: <20261001191140.2818991-1-edumazet@kernel.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Add selftests in tun.c verifying that a VLAN-tagged (802.1Q) TCPv4 GSO packet without VIRTIO_NET_HDR_F_NEEDS_CSUM (both flags = 0 and flags = VIRTIO_NET_HDR_F_DATA_VALID) is accepted when written to a TAP device (/dev/net/tun with IFF_TAP | IFF_NO_PI | IFF_VNET_HDR). Also verify that the following are rejected with -EINVAL: - a mismatched GSO type (VIRTIO_NET_HDR_GSO_TCPV6 on a VLAN-tagged IPv4 packet). - a frame whose TCP header is truncated after 10 bytes. Pulling only sizeof(struct iphdr) + sizeof(struct tcphdr) bytes would accept it, so this requires the transport offset found by flow dissection. Finally, verify that a 65540-byte frame is accepted. Its skb->len is above U16_MAX while it is flow-dissected, before eth_type_trans() pulls the Ethernet header. Based on a reproducer by Michael S. Tsirkin . Assisted-by: LLM Signed-off-by: Eric Dumazet --- tools/testing/selftests/net/tun.c | 136 ++++++++++++++++++++++++++++++ 1 file changed, 136 insertions(+) diff --git a/tools/testing/selftests/net/tun.c b/tools/testing/selftests/net/tun.c index abe488bac50bb3b05df5c446836c1c3dfa9ea604..afaa81c9bac5311944c9a70a20de05bffb683f26 100644 --- a/tools/testing/selftests/net/tun.c +++ b/tools/testing/selftests/net/tun.c @@ -9,6 +9,7 @@ #include #include #include +#include #include #include @@ -542,6 +543,141 @@ TEST_F(tun, reattach_close_delete) EXPECT_EQ(tun_delete(self->ifname), 0); } +FIXTURE(tun_vnet_gso) +{ + char ifname[IFNAMSIZ]; + int fd; +}; + +FIXTURE_SETUP(tun_vnet_gso) +{ + int flags = IFF_TAP | IFF_NO_PI | IFF_VNET_HDR; + + memset(self->ifname, 0, sizeof(self->ifname)); + self->fd = tun_open(self->ifname, flags, 0, 0, NULL); + ASSERT_GE(self->fd, 0); +} + +FIXTURE_TEARDOWN(tun_vnet_gso) +{ + if (self->fd >= 0) + close(self->fd); +} + +static int build_vlan_tcpv4_gso_packet(uint8_t *buf, int payload_len) +{ + uint16_t vlan_tag[2] = { htons(100), htons(ETH_P_IP) }; + uint8_t *cur = buf + sizeof(struct virtio_net_hdr); + struct virtio_net_hdr vh = { 0 }; + struct tcphdr tcph = { 0 }; + uint32_t sum; + + cur += build_eth(cur, ETH_P_8021Q, param_hwaddr_outer_src, + param_hwaddr_outer_dst); + + /* 802.1Q tag: VID=100, inner protocol=ETH_P_IP */ + memcpy(cur, vlan_tag, sizeof(vlan_tag)); + cur += sizeof(vlan_tag); + + cur += build_ipv4_header(cur, IPPROTO_TCP, + sizeof(tcph) + payload_len, + ¶m_ipaddr4_outer_src, + ¶m_ipaddr4_outer_dst); + + tcph.source = htons(12345); + tcph.dest = htons(80); + tcph.seq = htonl(1); + tcph.doff = sizeof(tcph) / 4; + tcph.ack = 1; + tcph.window = htons(65535); + memcpy(cur, &tcph, sizeof(tcph)); + memset(cur + sizeof(tcph), PKT_DATA, payload_len); + + sum = add_csum((const uint8_t *)¶m_ipaddr4_outer_src, + sizeof(param_ipaddr4_outer_src)); + sum += add_csum((const uint8_t *)¶m_ipaddr4_outer_dst, + sizeof(param_ipaddr4_outer_dst)); + sum += htons(IPPROTO_TCP) + htons(sizeof(tcph) + payload_len); + sum += add_csum(cur, sizeof(tcph) + payload_len); + tcph.check = finish_ip_csum(sum); + memcpy(cur, &tcph, sizeof(tcph)); + cur += sizeof(tcph) + payload_len; + + vh.gso_type = VIRTIO_NET_HDR_GSO_TCPV4; + vh.gso_size = 1400; + vh.hdr_len = (cur - buf) - sizeof(vh) - payload_len; + memcpy(buf, &vh, sizeof(vh)); + + return cur - buf; +} + +TEST_F(tun_vnet_gso, vlan_tcpv4_gso_no_csum) +{ + struct virtio_net_hdr vh; + uint8_t pkt[4096] = { 0 }; + int len, ret; + + len = build_vlan_tcpv4_gso_packet(pkt, 2800); + memcpy(&vh, pkt, sizeof(vh)); + + /* Valid VLAN-tagged TCPv4 GSO with flags = 0 (no NEEDS_CSUM) */ + vh.flags = 0; + memcpy(pkt, &vh, sizeof(vh)); + ret = write(self->fd, pkt, len); + ASSERT_EQ(ret, len); + + /* Valid VLAN-tagged TCPv4 GSO with flags = DATA_VALID */ + vh.flags = VIRTIO_NET_HDR_F_DATA_VALID; + memcpy(pkt, &vh, sizeof(vh)); + ret = write(self->fd, pkt, len); + ASSERT_EQ(ret, len); + + /* Mismatched GSO type (TCPV6 on VLAN-tagged IPv4 packet) */ + vh.flags = 0; + vh.gso_type = VIRTIO_NET_HDR_GSO_TCPV6; + memcpy(pkt, &vh, sizeof(vh)); + ret = write(self->fd, pkt, len); + ASSERT_EQ(ret, -1); + ASSERT_EQ(errno, EINVAL); + + /* TCP header truncated after 10 bytes, without NEEDS_CSUM. + * Requires the transport header offset found by flow dissection: + * pulling only sizeof(struct iphdr) + sizeof(struct tcphdr) bytes + * from the mac header would accept this frame. + */ + vh.gso_type = VIRTIO_NET_HDR_GSO_TCPV4; + vh.hdr_len = ETH_HLEN + 4 + sizeof(struct iphdr) + 10; + memcpy(pkt, &vh, sizeof(vh)); + ret = write(self->fd, pkt, sizeof(vh) + vh.hdr_len); + ASSERT_EQ(ret, -1); + ASSERT_EQ(errno, EINVAL); +} + +TEST_F(tun_vnet_gso, vlan_tcpv4_gso_no_csum_64k) +{ + /* Ethernet frame of 65540 bytes: skb->len is above U16_MAX when the + * frame is flow-dissected, before eth_type_trans() pulls ETH_HLEN. + */ + const int payload_len = 65540 - ETH_HLEN - 4 - + sizeof(struct iphdr) - sizeof(struct tcphdr); + struct virtio_net_hdr vh; + uint8_t *pkt; + int len, ret; + + pkt = calloc(1, sizeof(vh) + 65540); + ASSERT_NE(pkt, NULL); + + len = build_vlan_tcpv4_gso_packet(pkt, payload_len); + ASSERT_EQ(len, sizeof(vh) + 65540); + memcpy(&vh, pkt, sizeof(vh)); + + vh.flags = 0; + memcpy(pkt, &vh, sizeof(vh)); + ret = write(self->fd, pkt, len); + free(pkt); + ASSERT_EQ(ret, len); +} + FIXTURE(tun_vnet_udptnl) { char ifname[IFNAMSIZ]; -- 2.56.0.rc1.315.gc6ed9934b7-goog