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bpf: Add update_socket_protocol hook

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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@tessares.net>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Signed-off-by: Geliang Tang <geliang.tang@suse.com>
Link: https://lore.kernel.org/r/ac84be00f97072a46f8a72b4e2be46cbb7fa5053.1692147782.git.geliang.tang@suse.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
This commit is contained in:
Geliang Tang 2023-08-16 09:11:56 +08:00 committed by Martin KaFai Lau
parent 053bbf9bff
commit 0dd061a6a1
2 changed files with 40 additions and 1 deletions
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15
net/mptcp/bpf.c
View File

@ -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);

26
net/socket.c
View File

@ -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");
__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);