[PATCH bpf-next v14 1/4] bpf: Add update_socket_protocol hook
Yonghong Song
yonghong.song at linux.dev
Fri Aug 18 15:26:06 UTC 2023
On 8/18/23 1:24 AM, Geliang Tang wrote:
> 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 at tessares.net>
>> Acked-by: Yonghong Song <yonghong.song at linux.dev>
>> Signed-off-by: Geliang Tang <geliang.tang at suse.com>
>> ---
>> 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?
This is a sparse warning. Let us ignore it for now. We already have
__diag_ignore for missing prototypes in the above, but sparse won't
recognize them. Also, 'static' is conflict with '__weak' attribute,
and we cannot remove '__weak' attribute.
>
> 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
>>
>
More information about the Linux-security-module-archive
mailing list