On Wed, Aug 16, 2023 at 09:11:56AM +0800, 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 fmod_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@xxxxxxxxxxxx> > Acked-by: Yonghong Song <yonghong.song@xxxxxxxxx> > Signed-off-by: Geliang Tang <geliang.tang@xxxxxxxx> > --- > net/mptcp/bpf.c | 15 +++++++++++++++ > net/socket.c | 26 +++++++++++++++++++++++++- > 2 files changed, 40 insertions(+), 1 deletion(-) > > 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 5d4e37595e9a..fdb5233bf560 100644 > --- a/net/socket.c > +++ b/net/socket.c > @@ -1657,12 +1657,36 @@ 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", > + "A fmod_ret entry point for BPF programs"); Hi Martin & Yonghong, I got a sparse warning for this new added 'update_socket_protocol': > touch net/socket.c && make C=1 net/socket.o net/socket.c:1676:21: warning: symbol 'update_socket_protocol' was not declared. Should it be static? What should I do to fix it, or should I just leave it here? Please give me some suggestions. Thanks, -Geliang > + > +__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; > > - sock = __sys_socket_create(family, type, protocol); > + sock = __sys_socket_create(family, type, > + update_socket_protocol(family, type, protocol)); > if (IS_ERR(sock)) > return PTR_ERR(sock); > > -- > 2.35.3 >
