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authorPaolo Abeni <pabeni@redhat.com>2020-03-04 16:51:07 +0100
committerDavid S. Miller <davem@davemloft.net>2020-03-05 21:34:42 -0800
commit2398e3991bda7caa6b112a6f650fbab92f732b91 (patch)
tree57236049c35a02f7a728e5aa499bbd33931c9528
parenta3aefbfe45751bf7b338c181b97608e276b5bb73 (diff)
downloadlinux-2398e3991bda7caa6b112a6f650fbab92f732b91.tar.bz2
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@redhat.com> Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--net/mptcp/options.c19
1 files 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;