Commit efaa9990 authored by David S. Miller's avatar David S. Miller

Merge branch 'mptcp-rtx-timer'

Paolo Abeni says:

====================
mptcp: fix 3rd ack rtx timer

Eric noted that the MPTCP code do the wrong thing to schedule
the MPJ 3rd ack timer. He also provided a patch to address the
issues (patch 1/2).

To fix for good the MPJ 3rd ack retransmission timer, we additionally
need to set it after the current ack is transmitted (patch 2/2)

Note that the bug went unnotice so far because all the related
tests required some running data transfer, and that causes
MPTCP-level ack even on the opening MPJ subflow. We now have
explicit packet drill coverage for this code path.
====================
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parents 262ae1f9 bcd97734
......@@ -422,28 +422,6 @@ bool mptcp_syn_options(struct sock *sk, const struct sk_buff *skb,
return false;
}
/* MP_JOIN client subflow must wait for 4th ack before sending any data:
* TCP can't schedule delack timer before the subflow is fully established.
* MPTCP uses the delack timer to do 3rd ack retransmissions
*/
static void schedule_3rdack_retransmission(struct sock *sk)
{
struct inet_connection_sock *icsk = inet_csk(sk);
struct tcp_sock *tp = tcp_sk(sk);
unsigned long timeout;
/* reschedule with a timeout above RTT, as we must look only for drop */
if (tp->srtt_us)
timeout = tp->srtt_us << 1;
else
timeout = TCP_TIMEOUT_INIT;
WARN_ON_ONCE(icsk->icsk_ack.pending & ICSK_ACK_TIMER);
icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
icsk->icsk_ack.timeout = timeout;
sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
}
static void clear_3rdack_retransmission(struct sock *sk)
{
struct inet_connection_sock *icsk = inet_csk(sk);
......@@ -526,7 +504,15 @@ static bool mptcp_established_options_mp(struct sock *sk, struct sk_buff *skb,
*size = TCPOLEN_MPTCP_MPJ_ACK;
pr_debug("subflow=%p", subflow);
schedule_3rdack_retransmission(sk);
/* we can use the full delegate action helper only from BH context
* If we are in process context - sk is flushing the backlog at
* socket lock release time - just set the appropriate flag, will
* be handled by the release callback
*/
if (sock_owned_by_user(sk))
set_bit(MPTCP_DELEGATE_ACK, &subflow->delegated_status);
else
mptcp_subflow_delegate(subflow, MPTCP_DELEGATE_ACK);
return true;
}
return false;
......
......@@ -1596,7 +1596,8 @@ static void __mptcp_subflow_push_pending(struct sock *sk, struct sock *ssk)
if (!xmit_ssk)
goto out;
if (xmit_ssk != ssk) {
mptcp_subflow_delegate(mptcp_subflow_ctx(xmit_ssk));
mptcp_subflow_delegate(mptcp_subflow_ctx(xmit_ssk),
MPTCP_DELEGATE_SEND);
goto out;
}
......@@ -2943,7 +2944,7 @@ void __mptcp_check_push(struct sock *sk, struct sock *ssk)
if (xmit_ssk == ssk)
__mptcp_subflow_push_pending(sk, ssk);
else if (xmit_ssk)
mptcp_subflow_delegate(mptcp_subflow_ctx(xmit_ssk));
mptcp_subflow_delegate(mptcp_subflow_ctx(xmit_ssk), MPTCP_DELEGATE_SEND);
} else {
set_bit(MPTCP_PUSH_PENDING, &mptcp_sk(sk)->flags);
}
......@@ -2993,18 +2994,50 @@ static void mptcp_release_cb(struct sock *sk)
__mptcp_update_rmem(sk);
}
/* MP_JOIN client subflow must wait for 4th ack before sending any data:
* TCP can't schedule delack timer before the subflow is fully established.
* MPTCP uses the delack timer to do 3rd ack retransmissions
*/
static void schedule_3rdack_retransmission(struct sock *ssk)
{
struct inet_connection_sock *icsk = inet_csk(ssk);
struct tcp_sock *tp = tcp_sk(ssk);
unsigned long timeout;
if (mptcp_subflow_ctx(ssk)->fully_established)
return;
/* reschedule with a timeout above RTT, as we must look only for drop */
if (tp->srtt_us)
timeout = usecs_to_jiffies(tp->srtt_us >> (3 - 1));
else
timeout = TCP_TIMEOUT_INIT;
timeout += jiffies;
WARN_ON_ONCE(icsk->icsk_ack.pending & ICSK_ACK_TIMER);
icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
icsk->icsk_ack.timeout = timeout;
sk_reset_timer(ssk, &icsk->icsk_delack_timer, timeout);
}
void mptcp_subflow_process_delegated(struct sock *ssk)
{
struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
struct sock *sk = subflow->conn;
mptcp_data_lock(sk);
if (!sock_owned_by_user(sk))
__mptcp_subflow_push_pending(sk, ssk);
else
set_bit(MPTCP_PUSH_PENDING, &mptcp_sk(sk)->flags);
mptcp_data_unlock(sk);
mptcp_subflow_delegated_done(subflow);
if (test_bit(MPTCP_DELEGATE_SEND, &subflow->delegated_status)) {
mptcp_data_lock(sk);
if (!sock_owned_by_user(sk))
__mptcp_subflow_push_pending(sk, ssk);
else
set_bit(MPTCP_PUSH_PENDING, &mptcp_sk(sk)->flags);
mptcp_data_unlock(sk);
mptcp_subflow_delegated_done(subflow, MPTCP_DELEGATE_SEND);
}
if (test_bit(MPTCP_DELEGATE_ACK, &subflow->delegated_status)) {
schedule_3rdack_retransmission(ssk);
mptcp_subflow_delegated_done(subflow, MPTCP_DELEGATE_ACK);
}
}
static int mptcp_hash(struct sock *sk)
......
......@@ -387,6 +387,7 @@ struct mptcp_delegated_action {
DECLARE_PER_CPU(struct mptcp_delegated_action, mptcp_delegated_actions);
#define MPTCP_DELEGATE_SEND 0
#define MPTCP_DELEGATE_ACK 1
/* MPTCP subflow context */
struct mptcp_subflow_context {
......@@ -492,23 +493,23 @@ static inline void mptcp_add_pending_subflow(struct mptcp_sock *msk,
void mptcp_subflow_process_delegated(struct sock *ssk);
static inline void mptcp_subflow_delegate(struct mptcp_subflow_context *subflow)
static inline void mptcp_subflow_delegate(struct mptcp_subflow_context *subflow, int action)
{
struct mptcp_delegated_action *delegated;
bool schedule;
/* the caller held the subflow bh socket lock */
lockdep_assert_in_softirq();
/* The implied barrier pairs with mptcp_subflow_delegated_done(), and
* ensures the below list check sees list updates done prior to status
* bit changes
*/
if (!test_and_set_bit(MPTCP_DELEGATE_SEND, &subflow->delegated_status)) {
if (!test_and_set_bit(action, &subflow->delegated_status)) {
/* still on delegated list from previous scheduling */
if (!list_empty(&subflow->delegated_node))
return;
/* the caller held the subflow bh socket lock */
lockdep_assert_in_softirq();
delegated = this_cpu_ptr(&mptcp_delegated_actions);
schedule = list_empty(&delegated->head);
list_add_tail(&subflow->delegated_node, &delegated->head);
......@@ -533,16 +534,16 @@ mptcp_subflow_delegated_next(struct mptcp_delegated_action *delegated)
static inline bool mptcp_subflow_has_delegated_action(const struct mptcp_subflow_context *subflow)
{
return test_bit(MPTCP_DELEGATE_SEND, &subflow->delegated_status);
return !!READ_ONCE(subflow->delegated_status);
}
static inline void mptcp_subflow_delegated_done(struct mptcp_subflow_context *subflow)
static inline void mptcp_subflow_delegated_done(struct mptcp_subflow_context *subflow, int action)
{
/* pairs with mptcp_subflow_delegate, ensures delegate_node is updated before
* touching the status bit
*/
smp_wmb();
clear_bit(MPTCP_DELEGATE_SEND, &subflow->delegated_status);
clear_bit(action, &subflow->delegated_status);
}
int mptcp_is_enabled(const struct net *net);
......
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