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Message-ID: <fbe1a1b0-3d6a-3336-44f8-7d2004ba961f@linux.dev> Date: Fri, 4 Aug 2023 17:00:39 -0700 From: Martin KaFai Lau <martin.lau@...ux.dev> To: Geliang Tang <geliang.tang@...e.com>, Paolo Abeni <pabeni@...hat.com> Cc: bpf@...r.kernel.org, netdev@...r.kernel.org, mptcp@...ts.linux.dev, apparmor@...ts.ubuntu.com, linux-security-module@...r.kernel.org, selinux@...r.kernel.org, linux-kselftest@...r.kernel.org, Yonghong Song <yonghong.song@...ux.dev>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>, 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>, Florent Revest <revest@...omium.org>, Brendan Jackman <jackmanb@...omium.org>, Matthieu Baerts <matthieu.baerts@...sares.net>, Mat Martineau <martineau@...nel.org>, "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, John Johansen <john.johansen@...onical.com>, Paul Moore <paul@...l-moore.com>, James Morris <jmorris@...ei.org>, "Serge E. Hallyn" <serge@...lyn.com>, Stephen Smalley <stephen.smalley.work@...il.com>, Eric Paris <eparis@...isplace.org>, Mykola Lysenko <mykolal@...com>, Shuah Khan <shuah@...nel.org>, Simon Horman <horms@...nel.org> Subject: Re: [PATCH bpf-next v11 1/5] bpf: Add update_socket_protocol hook On 8/3/23 10:07 PM, Geliang Tang wrote: > Add a hook named update_socket_protocol in __sys_socket(), for bpf > progs to attach to and update socket protocol. One user case is to > force legacy TCP apps to create and use MPTCP sockets instead of > TCP ones. > > Define a mod_ret set named bpf_mptcp_fmodret_ids, add the hook > update_socket_protocol into this set, and register it in > bpf_mptcp_kfunc_init(). > > Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/79 > Acked-by: Matthieu Baerts <matthieu.baerts@...sares.net> > Acked-by: Yonghong Song <yonghong.song@...ux.dev> > Signed-off-by: Geliang Tang <geliang.tang@...e.com> > --- > net/mptcp/bpf.c | 15 +++++++++++++++ > net/socket.c | 24 ++++++++++++++++++++++++ > 2 files changed, 39 insertions(+) > > diff --git a/net/mptcp/bpf.c b/net/mptcp/bpf.c > index 5a0a84ad94af..8a16672b94e2 100644 > --- a/net/mptcp/bpf.c > +++ b/net/mptcp/bpf.c > @@ -19,3 +19,18 @@ struct mptcp_sock *bpf_mptcp_sock_from_subflow(struct sock *sk) > > return NULL; > } > + > +BTF_SET8_START(bpf_mptcp_fmodret_ids) > +BTF_ID_FLAGS(func, update_socket_protocol) > +BTF_SET8_END(bpf_mptcp_fmodret_ids) > + > +static const struct btf_kfunc_id_set bpf_mptcp_fmodret_set = { > + .owner = THIS_MODULE, > + .set = &bpf_mptcp_fmodret_ids, > +}; > + > +static int __init bpf_mptcp_kfunc_init(void) > +{ > + return register_btf_fmodret_id_set(&bpf_mptcp_fmodret_set); > +} > +late_initcall(bpf_mptcp_kfunc_init); > diff --git a/net/socket.c b/net/socket.c > index 2b0e54b2405c..9f98ced88ac5 100644 > --- a/net/socket.c > +++ b/net/socket.c > @@ -1644,11 +1644,35 @@ struct file *__sys_socket_file(int family, int type, int protocol) > return sock_alloc_file(sock, flags, NULL); > } > > +/* A hook for bpf progs to attach to and update socket protocol. > + * > + * A static noinline declaration here could cause the compiler to > + * optimize away the function. A global noinline declaration will > + * keep the definition, but may optimize away the callsite. > + * Therefore, __weak is needed to ensure that the call is still > + * emitted, by telling the compiler that we don't know what the > + * function might eventually be. > + * > + * __diag_* below are needed to dismiss the missing prototype warning. > + */ > + > +__diag_push(); > +__diag_ignore_all("-Wmissing-prototypes", > + "kfuncs which will be used in BPF programs"); This "kfuns which will be used in BPF programs" piece is not accurate. It is a fmod_ret entry point for bpf prog. > + > +__weak noinline int update_socket_protocol(int family, int type, int protocol) > +{ > + return protocol; > +} > + > +__diag_pop(); > + > int __sys_socket(int family, int type, int protocol) > { > struct socket *sock; > int flags; > > + protocol = update_socket_protocol(family, type, protocol); Paolo, could you help to take another look and ack this patch if it has addressed your earlier comment ? > sock = __sys_socket_create(family, type, protocol); > if (IS_ERR(sock)) > return PTR_ERR(sock);
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