From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from m12-12.163.com (m12-12.163.com [220.181.12.12]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 8A67572 for ; Wed, 9 Jun 2021 10:40:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=163.com; s=s110527; h=From:Subject:Message-ID:Date:MIME-Version; bh=gr6UZ O8Kqq6v5bH9aldoGcR6P0c8vdvxDX2WzwHE6+Y=; b=LY+fRUU6uBrsYV0PimLe0 th2W4PeZj6f5CIQ43xweu3yvMPQNFUc0bRKa21gMvEyRgD+ND7RfoUoY/4WtVq6V /PhPuspGuC1aVMgetvUm5mw7ZNg2r/CtF13RccmPmzYRxnbOHtrKTg338Xu9KTUt cHK2YvGxpMpADwR8WD71+Q= Received: from [192.168.16.78] (unknown [110.86.5.93]) by smtp8 (Coremail) with SMTP id DMCowAA3MPx9msBgLj+xIw--.5305S2; Wed, 09 Jun 2021 18:39:58 +0800 (CST) To: mptcp@lists.linux.dev Cc: Florian Westphal , Paolo Abeni From: Jianguo Wu Subject: [PATCH 3/3] mptcp: fix syncookie process if mptcp can not_accept new subflow Message-ID: <1034de3d-5528-ea65-6deb-8a67955f1042@163.com> Date: Wed, 9 Jun 2021 18:39:58 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-CM-TRANSID:DMCowAA3MPx9msBgLj+xIw--.5305S2 X-Coremail-Antispam: 1Uf129KBjvJXoWxAryrJFW3Kr1rCFW5GF45Wrg_yoW5tw1rpF 4UJr4xtrn3AFyfGaySyF4DXr1agrZYyrZxJw4jk347Awn8ursagry8KF1IgFWxCFs3GFy5 tr40qa1qvFnrCaDanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x07b189_UUUUU= X-Originating-IP: [110.86.5.93] X-CM-SenderInfo: 5zxmxt5qjx0iiqw6il2tof0z/xtbB+BaskF2MZMPdtQAAsM From: Jianguo Wu 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() do mptcp_can_accept_new_subflow() check, and do fatal fallback, send reset. And do sanity check in tcp_data_queue(). Fixes: 9466a1ccebbe("mptcp: enable JOIN requests even if cookies are in use") Signed-off-by: Jianguo Wu --- net/ipv4/tcp_input.c | 7 ++++++- net/mptcp/subflow.c | 6 +++--- 2 files changed, 9 insertions(+), 4 deletions(-) diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 7d5e59f..537f24a 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -4941,8 +4941,13 @@ static void tcp_data_queue(struct sock *sk, struct sk_buff *skb) bool fragstolen; int eaten; - if (sk_is_mptcp(sk)) + if (sk_is_mptcp(sk)) { mptcp_incoming_options(sk, skb); + if (sk->sk_state == TCP_CLOSE) { + __kfree_skb(skb); + return; + } + } if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) { __kfree_skb(skb); 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