From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 E927C35BDBF; Thu, 19 Mar 2026 23:45:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773963949; cv=none; b=pTRe0WSz0Yvr+Qz2s6aHZoQyoz/QrmRE64b3GVAuTpdfMD3sextx65Pk4IpbKRF6Ru81d+VJyJWyrwehiA42V3Pl2ChHly7Ko9YaywwkAXKHvyE1xnPfb7JMmWzF0x0R0zt/tUswbQT4sVw2Bh1I2SPwWgdB0pEAmSZncwKfqhE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773963949; c=relaxed/simple; bh=RQmJSTgeYlHzTm6YHQv+LZXZKDSGYerO9dS13cpXStY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=hi/NZSuq1DNiMijqYYLGO+B3J22z1PPTgbPSCA1QqG3RTiCmy0nlGcgXYpyT9UIlC/WaVn1PKqCcc+IwZjizNsslzTIidsRa3/41dx3IiAm+GJ8U+TEdqv234GHcv45MQ/1I878luYGECGTXBM6jaeRUxNYDbwmhHCn+uPEQIZw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=TxhQIg6t; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="TxhQIg6t" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 24A03C2BCB3; Thu, 19 Mar 2026 23:45:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773963948; bh=RQmJSTgeYlHzTm6YHQv+LZXZKDSGYerO9dS13cpXStY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=TxhQIg6tNKmhiL1B9/Gw+ixDRVPUVJvBzrsCA0z/wEZ8og1rWWNXJYbG5x4/bmDIv qPalhPBdimNQShZO4GV2UHW0eSor13TkO1KMNpl+J6uBqPAxAghqEL0X9xLSg4bfCb DIBmt/BZzVddToXDikdUCHlS/20+1DCpbkbA+eyCh1M+agBztfWNJX6A8qsOpqfIWP J+XJ+GG9knObVor0YphOpkTExnSPtgF9fuDq5Q3t4XwOLy9Rn2XVJCSd5RvIzc0ntR u6mFyym3X/lpoBppCc1Fp4Fg0Mx5cE1NnMIoOBQIhukNgYBcFUYISH6mhsprgACk9B d1F12jQATSQug== From: Jakub Kicinski To: bpf@vger.kernel.org Cc: Jakub Kicinski , andrii@kernel.org, eddyz87@gmail.com, ast@kernel.org, daniel@iogearbox.net, martin.lau@linux.dev, song@kernel.org, yonghong.song@linux.dev, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, jolsa@kernel.org, shuah@kernel.org, linux-kselftest@vger.kernel.org Subject: [PATCH bpf-next 2/2] selftests/bpf: test that dst is cleared on same-protocol encap Date: Thu, 19 Mar 2026 16:45:31 -0700 Message-ID: <20260319234531.3022634-2-kuba@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260319234531.3022634-1-kuba@kernel.org> References: <20260319234531.3022634-1-kuba@kernel.org> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Verify that bpf_skb_adjust_room() clears the routing dst even when the encap L3 protocol matches the original packet (e.g. IPIP). The dst selected for the inner packet is not valid for the encapsulated result; a stale dst could lead to misrouting. Signed-off-by: Jakub Kicinski --- CC: andrii@kernel.org CC: eddyz87@gmail.com CC: ast@kernel.org CC: daniel@iogearbox.net CC: martin.lau@linux.dev CC: song@kernel.org CC: yonghong.song@linux.dev CC: john.fastabend@gmail.com CC: kpsingh@kernel.org CC: sdf@fomichev.me CC: haoluo@google.com CC: jolsa@kernel.org CC: shuah@kernel.org CC: bpf@vger.kernel.org CC: linux-kselftest@vger.kernel.org --- .../selftests/bpf/prog_tests/test_dst_clear.c | 75 +++++++++++++++++++ .../selftests/bpf/progs/test_dst_clear.c | 57 ++++++++++++++ 2 files changed, 132 insertions(+) create mode 100644 tools/testing/selftests/bpf/prog_tests/test_dst_clear.c create mode 100644 tools/testing/selftests/bpf/progs/test_dst_clear.c diff --git a/tools/testing/selftests/bpf/prog_tests/test_dst_clear.c b/tools/testing/selftests/bpf/prog_tests/test_dst_clear.c new file mode 100644 index 000000000000..8190c56556fb --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/test_dst_clear.c @@ -0,0 +1,75 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2026 Meta Platforms, Inc. and affiliates. */ + +#include +#include +#include + +#include "test_progs.h" +#include "network_helpers.h" +#include "test_dst_clear.skel.h" + +#define NS_TEST "dst_clear_ns" +#define IPV4_IFACE_ADDR "1.0.0.1" +#define UDP_TEST_PORT 7777 + +void test_dst_clear(void) +{ + LIBBPF_OPTS(bpf_tc_hook, qdisc_hook, .attach_point = BPF_TC_EGRESS); + LIBBPF_OPTS(bpf_tc_opts, tc_attach); + struct nstoken *nstoken = NULL; + struct test_dst_clear *skel; + struct sockaddr_in addr; + socklen_t addrlen; + char buf[128] = {}; + int sockfd, err; + + skel = test_dst_clear__open_and_load(); + if (!ASSERT_OK_PTR(skel, "skel open_and_load")) + return; + + SYS(fail, "ip netns add %s", NS_TEST); + SYS(fail, "ip -net %s addr add %s/8 dev lo", NS_TEST, IPV4_IFACE_ADDR); + SYS(fail, "ip -net %s link set dev lo up", NS_TEST); + + nstoken = open_netns(NS_TEST); + if (!ASSERT_OK_PTR(nstoken, "open_netns")) + goto fail; + + qdisc_hook.ifindex = if_nametoindex("lo"); + if (!ASSERT_GT(qdisc_hook.ifindex, 0, "if_nametoindex lo")) + goto fail; + + err = bpf_tc_hook_create(&qdisc_hook); + if (!ASSERT_OK(err, "create qdisc hook")) + goto fail; + + tc_attach.prog_fd = bpf_program__fd(skel->progs.dst_clear); + err = bpf_tc_attach(&qdisc_hook, &tc_attach); + if (!ASSERT_OK(err, "attach filter")) + goto fail; + + addrlen = sizeof(addr); + err = make_sockaddr(AF_INET, IPV4_IFACE_ADDR, UDP_TEST_PORT, + (void *)&addr, &addrlen); + if (!ASSERT_OK(err, "make_sockaddr")) + goto fail; + sockfd = socket(AF_INET, SOCK_DGRAM, 0); + if (!ASSERT_NEQ(sockfd, -1, "socket")) + goto fail; + err = sendto(sockfd, buf, sizeof(buf), 0, (void *)&addr, addrlen); + close(sockfd); + if (!ASSERT_EQ(err, sizeof(buf), "send")) + goto fail; + + ASSERT_TRUE(skel->bss->had_dst, "had_dst"); + ASSERT_TRUE(skel->bss->dst_cleared, "dst_cleared"); + +fail: + if (nstoken) { + bpf_tc_hook_destroy(&qdisc_hook); + close_netns(nstoken); + } + SYS_NOFAIL("ip netns del " NS_TEST); + test_dst_clear__destroy(skel); +} diff --git a/tools/testing/selftests/bpf/progs/test_dst_clear.c b/tools/testing/selftests/bpf/progs/test_dst_clear.c new file mode 100644 index 000000000000..7ac9604fd99c --- /dev/null +++ b/tools/testing/selftests/bpf/progs/test_dst_clear.c @@ -0,0 +1,57 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2026 Meta Platforms, Inc. and affiliates. */ + +#include "vmlinux.h" +#include "bpf_tracing_net.h" +#include +#include + +#define UDP_TEST_PORT 7777 + +void *bpf_cast_to_kern_ctx(void *) __ksym; + +bool had_dst = false; +bool dst_cleared = false; + +SEC("tc") +int dst_clear(struct __sk_buff *skb) +{ + struct sk_buff *kskb; + struct iphdr iph; + struct udphdr udph; + int err; + + if (skb->protocol != __bpf_constant_htons(ETH_P_IP)) + return TC_ACT_OK; + + if (bpf_skb_load_bytes(skb, ETH_HLEN, &iph, sizeof(iph))) + return TC_ACT_OK; + + if (iph.protocol != IPPROTO_UDP) + return TC_ACT_OK; + + if (bpf_skb_load_bytes(skb, ETH_HLEN + sizeof(iph), &udph, sizeof(udph))) + return TC_ACT_OK; + + if (udph.dest != __bpf_constant_htons(UDP_TEST_PORT)) + return TC_ACT_OK; + + kskb = bpf_cast_to_kern_ctx(skb); + had_dst = (kskb->_skb_refdst != 0); + + /* Same-protocol encap (IPIP): protocol stays IPv4, but the dst + * from the original routing is no longer valid for the outer hdr. + */ + err = bpf_skb_adjust_room(skb, (s32)sizeof(struct iphdr), + BPF_ADJ_ROOM_MAC, + BPF_F_ADJ_ROOM_FIXED_GSO | + BPF_F_ADJ_ROOM_ENCAP_L3_IPV4); + if (err) + return TC_ACT_SHOT; + + dst_cleared = (kskb->_skb_refdst == 0); + + return TC_ACT_SHOT; +} + +char __license[] SEC("license") = "GPL"; -- 2.53.0