From: Nicolas Rybowski <nicolas.rybowski@tessares.net>
To: Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>, Andrii Nakryiko <andriin@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@chromium.org>,
"David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>
Cc: Nicolas Rybowski <nicolas.rybowski@tessares.net>,
Matthieu Baerts <matthieu.baerts@tessares.net>,
Mat Martineau <mathew.j.martineau@linux.intel.com>,
netdev@vger.kernel.org, bpf@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: [PATCH bpf-next 1/3] bpf: expose is_mptcp flag to bpf_tcp_sock
Date: Fri, 21 Aug 2020 17:15:39 +0200 [thread overview]
Message-ID: <20200821151544.1211989-2-nicolas.rybowski@tessares.net> (raw)
In-Reply-To: <20200821151544.1211989-1-nicolas.rybowski@tessares.net>
is_mptcp is a field from struct tcp_sock used to indicate that the
current tcp_sock is part of the MPTCP protocol.
In this protocol, a first socket (mptcp_sock) is created with
sk_protocol set to IPPROTO_MPTCP (=262) for control purpose but it
isn't directly on the wire. This is the role of the subflow (kernel)
sockets which are classical tcp_sock with sk_protocol set to
IPPROTO_TCP. The only way to differentiate such sockets from plain TCP
sockets is the is_mptcp field from tcp_sock.
Such an exposure in BPF is thus required to be able to differentiate
plain TCP sockets from MPTCP subflow sockets in BPF_PROG_TYPE_SOCK_OPS
programs.
The choice has been made to silently pass the case when CONFIG_MPTCP is
unset by defaulting is_mptcp to 0 in order to make BPF independent of
the MPTCP configuration. Another solution is to make the verifier fail
in 'bpf_tcp_sock_is_valid_ctx_access' but this will add an additional
'#ifdef CONFIG_MPTCP' in the BPF code and a same injected BPF program
will not run if MPTCP is not set.
An example use-case is provided in
https://github.com/multipath-tcp/mptcp_net-next/tree/scripts/bpf/examples
Suggested-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Acked-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Acked-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Nicolas Rybowski <nicolas.rybowski@tessares.net>
---
include/uapi/linux/bpf.h | 1 +
net/core/filter.c | 9 ++++++++-
tools/include/uapi/linux/bpf.h | 1 +
3 files changed, 10 insertions(+), 1 deletion(-)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 0480f893facd..a9fccfdb3a62 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -3865,6 +3865,7 @@ struct bpf_tcp_sock {
__u32 delivered; /* Total data packets delivered incl. rexmits */
__u32 delivered_ce; /* Like the above but only ECE marked packets */
__u32 icsk_retransmits; /* Number of unrecovered [RTO] timeouts */
+ __u32 is_mptcp; /* Is MPTCP subflow? */
};
struct bpf_sock_tuple {
diff --git a/net/core/filter.c b/net/core/filter.c
index b2df52086445..eb400aeea282 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -5742,7 +5742,7 @@ bool bpf_tcp_sock_is_valid_access(int off, int size, enum bpf_access_type type,
struct bpf_insn_access_aux *info)
{
if (off < 0 || off >= offsetofend(struct bpf_tcp_sock,
- icsk_retransmits))
+ is_mptcp))
return false;
if (off % size != 0)
@@ -5876,6 +5876,13 @@ u32 bpf_tcp_sock_convert_ctx_access(enum bpf_access_type type,
case offsetof(struct bpf_tcp_sock, icsk_retransmits):
BPF_INET_SOCK_GET_COMMON(icsk_retransmits);
break;
+ case offsetof(struct bpf_tcp_sock, is_mptcp):
+#ifdef CONFIG_MPTCP
+ BPF_TCP_SOCK_GET_COMMON(is_mptcp);
+#else
+ *insn++ = BPF_MOV32_IMM(si->dst_reg, 0);
+#endif
+ break;
}
return insn - insn_buf;
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 0480f893facd..a9fccfdb3a62 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -3865,6 +3865,7 @@ struct bpf_tcp_sock {
__u32 delivered; /* Total data packets delivered incl. rexmits */
__u32 delivered_ce; /* Like the above but only ECE marked packets */
__u32 icsk_retransmits; /* Number of unrecovered [RTO] timeouts */
+ __u32 is_mptcp; /* Is MPTCP subflow? */
};
struct bpf_sock_tuple {
--
2.28.0
next prev parent reply other threads:[~2020-08-21 15:19 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-21 15:15 [PATCH bpf-next 0/3] bpf: add MPTCP subflow support Nicolas Rybowski
2020-08-21 15:15 ` Nicolas Rybowski [this message]
2020-08-21 15:15 ` [PATCH bpf-next 2/3] mptcp: attach subflow socket to parent cgroup Nicolas Rybowski
2020-08-21 15:15 ` [PATCH bpf-next 3/3] bpf: add 'bpf_mptcp_sock' structure and helper Nicolas Rybowski
2020-08-24 22:01 ` [PATCH bpf-next 0/3] bpf: add MPTCP subflow support Alexei Starovoitov
2020-08-25 18:55 ` Nicolas Rybowski
2020-08-26 19:12 ` Alexei Starovoitov
2020-08-27 11:54 ` Nicolas Rybowski
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