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Message-Id: <d4f2f87c56fa1662bbc39baaee74b26bc646e141.1583337038.git.pabeni@redhat.com>
Date: Wed, 4 Mar 2020 16:51:07 +0100
From: Paolo Abeni <pabeni@...hat.com>
To: netdev@...r.kernel.org
Cc: Mat Martineau <mathew.j.martineau@...ux.intel.com>,
Matthieu Baerts <matthieu.baerts@...sares.net>,
"David S. Miller" <davem@...emloft.net>,
Christoph Paasch <cpaasch@...le.com>
Subject: [PATCH net v2] mptcp: always include dack if possible.
Currently passive MPTCP socket can skip including the DACK
option - if the peer sends data before accept() completes.
The above happens because the msk 'can_ack' flag is set
only after the accept() call.
Such missing DACK option may cause - as per RFC spec -
unwanted fallback to TCP.
This change addresses the issue using the key material
available in the current subflow, if any, to create a suitable
dack option when msk ack seq is not yet available.
v1 -> v2:
- adavance the generated ack after the initial MPC packet
Fixes: d22f4988ffec ("mptcp: process MP_CAPABLE data option")
Signed-off-by: Paolo Abeni <pabeni@...hat.com>
---
net/mptcp/options.c | 19 +++++++++++++++++--
1 file changed, 17 insertions(+), 2 deletions(-)
diff --git a/net/mptcp/options.c b/net/mptcp/options.c
index 45acd877bef3..fd2c3150e591 100644
--- a/net/mptcp/options.c
+++ b/net/mptcp/options.c
@@ -334,6 +334,8 @@ static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb,
struct mptcp_sock *msk;
unsigned int ack_size;
bool ret = false;
+ bool can_ack;
+ u64 ack_seq;
u8 tcp_fin;
if (skb) {
@@ -360,9 +362,22 @@ static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb,
ret = true;
}
+ /* passive sockets msk will set the 'can_ack' after accept(), even
+ * if the first subflow may have the already the remote key handy
+ */
+ can_ack = true;
opts->ext_copy.use_ack = 0;
msk = mptcp_sk(subflow->conn);
- if (!msk || !READ_ONCE(msk->can_ack)) {
+ if (likely(msk && READ_ONCE(msk->can_ack))) {
+ ack_seq = msk->ack_seq;
+ } else if (subflow->can_ack) {
+ mptcp_crypto_key_sha(subflow->remote_key, NULL, &ack_seq);
+ ack_seq++;
+ } else {
+ can_ack = false;
+ }
+
+ if (unlikely(!can_ack)) {
*size = ALIGN(dss_size, 4);
return ret;
}
@@ -375,7 +390,7 @@ static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb,
dss_size += ack_size;
- opts->ext_copy.data_ack = msk->ack_seq;
+ opts->ext_copy.data_ack = ack_seq;
opts->ext_copy.ack64 = 1;
opts->ext_copy.use_ack = 1;
--
2.21.1
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