From: Jianguo Wu <wujianguo106@163.com>
To: mptcp@lists.linux.dev
Subject: [PATCH v2 3/4] mptcp: fix syncookie process if mptcp can not_accept new subflow
Date: Thu, 10 Jun 2021 17:28:47 +0800 [thread overview]
Message-ID: <a8f8ebd3-51eb-b4c2-451b-6646639d0c20@163.com> (raw)
From: Jianguo Wu <wujianguo@chinatelecom.cn>
Lots of "TCP: tcp_fin: Impossible, sk->sk_state=7" in client side
when doing stress testing.
There are at least two cases may trigger this warning:
1.mptcp is in syncookie, and server recv MP_JOIN SYN request,
in subflow_check_req(), the mptcp_can_accept_new_subflow()
return false, so subflow_init_req_cookie_join_save() isn't
called, i.e. not store the data present in the MP_JOIN syn
request and the random nonce in hash table - join_entries[],
but still send synack. When recv 3rd-ack,
mptcp_token_join_cookie_init_state() will return false, and
3rd-ack is dropped, then if mptcp conn is closed by client,
client will send a DATA_FIN and a MPTCP FIN, the DATA_FIN
doesn't have MP_CAPABLE or MP_JOIN,
so mptcp_subflow_init_cookie_req() will return 0, and pass
the cookie check, MP_JOIN request is fallback to normal TCP.
Server will send a TCP FIN if closed, in client side,
when process TCP FIN, it will do reset, the code path is:
tcp_data_queue()->mptcp_incoming_options()
->check_fully_established()->mptcp_subflow_reset().
mptcp_subflow_reset() will set sock state to TCP_CLOSE,
so tcp_fin will hit TCP_CLOSE, and print the warning.
2.mptcp is in syncookie, and server recv 3rd-ack, in
mptcp_subflow_init_cookie_req(), mptcp_can_accept_new_subflow()
return false, and subflow_req->mp_join is not set to 1,
so in subflow_syn_recv_sock() will not reset the MP_JOIN
subflow, but fallback to normal TCP, and then the same thing
happens when server will send a TCP FIN if closed.
For case1, subflow_check_req() return -EPERM,
then tcp_conn_request() will drop MP_JOIN SYN.
For case2, let subflow_syn_recv_sock() call mptcp_can_accept_new_subflow(),
and do fatal fallback, send reset.
Fixes: 9466a1ccebbe("mptcp: enable JOIN requests even if cookies are in use")
Signed-off-by: Jianguo Wu <wujianguo@chinatelecom.cn>
---
net/mptcp/subflow.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index 75ed530..6d98e19 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -224,6 +224,8 @@ static int subflow_check_req(struct request_sock *req,
if (unlikely(req->syncookie)) {
if (mptcp_can_accept_new_subflow(subflow_req->msk))
subflow_init_req_cookie_join_save(subflow_req, skb);
+ else
+ return -EPERM;
}
pr_debug("token=%u, remote_nonce=%u msk=%p", subflow_req->token,
@@ -263,9 +265,7 @@ int mptcp_subflow_init_cookie_req(struct request_sock *req,
if (!mptcp_token_join_cookie_init_state(subflow_req, skb))
return -EINVAL;
- if (mptcp_can_accept_new_subflow(subflow_req->msk))
- subflow_req->mp_join = 1;
-
+ subflow_req->mp_join = 1;
subflow_req->ssn_offset = TCP_SKB_CB(skb)->seq - 1;
}
--
1.8.3.1
next reply other threads:[~2021-06-10 9:28 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-10 9:28 Jianguo Wu [this message]
2021-06-23 7:51 ` [mptcp] aa4272438c: kernel-selftests.net/mptcp.mptcp_join.sh.fail kernel test robot
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