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@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?
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
