diff mbox series

[net,2/2] mptcp: drop MP_JOIN request sock on syn cookies

Message ID 3aff0acec0b89a55fdae02194036f34be56b545c.1592388398.git.pabeni@redhat.com
State Deferred, archived
Delegated to: Mat Martineau
Headers show
Series mptcp: cope with syncookie on MP_JOINs | expand

Commit Message

Paolo Abeni June 17, 2020, 10:08 a.m. UTC 
Currently any MPTCP socket using syn cookies will fallback to
TCP at 3rd ack time. In case of MP_JOIN requests, the RFC mandate
closing the child and sockets, but the existing error paths
do not handle the syncookie scenario correctly.

Address the issue always forcing the child shutdown in case of
MP_JOIN fallback.

Fixes: ae2dd7164943 ("mptcp: handle tcp fallback when using syn cookies")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
 net/mptcp/subflow.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

Comments

Mat Martineau June 17, 2020, 6:14 p.m. UTC | #1 
On Wed, 17 Jun 2020, Paolo Abeni wrote:

> Currently any MPTCP socket using syn cookies will fallback to
> TCP at 3rd ack time. In case of MP_JOIN requests, the RFC mandate
> closing the child and sockets, but the existing error paths
> do not handle the syncookie scenario correctly.
>
> Address the issue always forcing the child shutdown in case of
> MP_JOIN fallback.
>
> Fixes: ae2dd7164943 ("mptcp: handle tcp fallback when using syn cookies")
> Signed-off-by: Paolo Abeni <pabeni@redhat.com>
> ---
> net/mptcp/subflow.c | 18 ++++++++++--------
> 1 file changed, 10 insertions(+), 8 deletions(-)

Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com>

--
Mat Martineau
Intel
diff mbox series

Patch

diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index 4068bdb2523b..3838a0b3a21f 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -431,22 +431,25 @@  static struct sock *subflow_syn_recv_sock(const struct sock *sk,
 	struct mptcp_subflow_context *listener = mptcp_subflow_ctx(sk);
 	struct mptcp_subflow_request_sock *subflow_req;
 	struct mptcp_options_received mp_opt;
-	bool fallback_is_fatal = false;
+	bool fallback, fallback_is_fatal;
 	struct sock *new_msk = NULL;
-	bool fallback = false;
 	struct sock *child;
 
 	pr_debug("listener=%p, req=%p, conn=%p", listener, req, listener->conn);
 
-	/* we need later a valid 'mp_capable' value even when options are not
-	 * parsed
+	/* After child creation we must look for 'mp_capable' even when options
+	 * are not parsed
 	 */
 	mp_opt.mp_capable = 0;
-	if (tcp_rsk(req)->is_mptcp == 0)
+
+	/* hopefully temporary handling for MP_JOIN+syncookie */
+	subflow_req = mptcp_subflow_rsk(req);
+	fallback_is_fatal = subflow_req->mp_join;
+	fallback = !tcp_rsk(req)->is_mptcp;
+	if (fallback)
 		goto create_child;
 
 	/* if the sk is MP_CAPABLE, we try to fetch the client key */
-	subflow_req = mptcp_subflow_rsk(req);
 	if (subflow_req->mp_capable) {
 		if (TCP_SKB_CB(skb)->seq != subflow_req->ssn_offset + 1) {
 			/* here we can receive and accept an in-window,
@@ -467,12 +470,11 @@  static struct sock *subflow_syn_recv_sock(const struct sock *sk,
 		if (!new_msk)
 			fallback = true;
 	} else if (subflow_req->mp_join) {
-		fallback_is_fatal = true;
 		mptcp_get_options(skb, &mp_opt);
 		if (!mp_opt.mp_join ||
 		    !subflow_hmac_valid(req, &mp_opt)) {
 			SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINACKMAC);
-			return NULL;
+			fallback = true;
 		}
 	}