netdev - [PATCH v4 bpf 0/2] bpf: return proper error codes for lwt redirect

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Date: Tue, 25 Jul 2023 18:07:04 -0700
From: Yan Zhai <yan@...udflare.com>
To: bpf@...r.kernel.org
Cc: Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Andrii Nakryiko <andrii@...nel.org>,
	Martin KaFai Lau <martin.lau@...ux.dev>, Song Liu <song@...nel.org>,
	Yonghong Song <yhs@...com>,
	John Fastabend <john.fastabend@...il.com>,
	KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...gle.com>,
	Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Mykola Lysenko <mykolal@...com>, Shuah Khan <shuah@...nel.org>,
	Yan Zhai <yan@...udflare.com>, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, linux-kselftest@...r.kernel.org,
	kernel-team@...udflare.com, Jordan Griege <jgriege@...udflare.com>,
	Markus Elfring <Markus.Elfring@....de>,
	Jakub Sitnicki <jakub@...udflare.com>
Subject: [PATCH v4 bpf 0/2] bpf: return proper error codes for lwt redirect

lwt xmit hook does not expect positive return values in function
ip_finish_output2 and ip6_finish_output2. However, BPF redirect programs
can return positive values such like NET_XMIT_DROP, NET_RX_DROP, and etc
as errors. Such return values can panic the kernel unexpectedly:

https://gist.github.com/zhaiyan920/8fbac245b261fe316a7ef04c9b1eba48

This patch fixes the return values from BPF redirect, so the error
handling would be consistent at xmit hook. It also adds a few test cases
to prevent future regressions.

v3: https://lore.kernel.org/bpf/cover.1690255889.git.yan@cloudflare.com/ 
v2: https://lore.kernel.org/netdev/ZLdY6JkWRccunvu0@debian.debian/ 
v1: https://lore.kernel.org/bpf/ZLbYdpWC8zt9EJtq@debian.debian/

changes since v3:
  * minor change in commit message and changelogs
  * tested by Jakub Sitnicki

changes since v2:
  * subject name changed
  * also covered redirect to ingress case
  * added selftests

changes since v1:
  * minor code style changes

Yan Zhai (2):
  bpf: fix skb_do_redirect return values
  bpf: selftests: add lwt redirect regression test cases

 include/linux/netdevice.h                     |   2 +
 net/core/filter.c                             |   9 +-
 tools/testing/selftests/bpf/Makefile          |   1 +
 .../selftests/bpf/progs/test_lwt_redirect.c   |  66 +++++++
 .../selftests/bpf/test_lwt_redirect.sh        | 174 ++++++++++++++++++
 5 files changed, 250 insertions(+), 2 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/progs/test_lwt_redirect.c
 create mode 100755 tools/testing/selftests/bpf/test_lwt_redirect.sh

-- 
2.30.2