[PATCH net] mptcp: add missing memory scheduling in the rx path

[Paolo Abeni]

When moving the skbs from the subflow into the msk receive
queue, we must schedule there the required amount of memory.

Try to borrow the required memory from the subflow, if needed,
so that we leverage the existing TCP heuristic.

Fixes: 6771bfd9ee24 ("mptcp: update mptcp ack sequence from work queue")
Signed-off-by: Paolo Abeni <pab...@redhat.com>
---
 net/mptcp/protocol.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 185dacb39781..e7419fd15d84 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -274,6 +274,15 @@ static bool __mptcp_move_skb(struct mptcp_sock *msk, 
struct sock *ssk,
        skb_ext_reset(skb);
        skb_orphan(skb);
 
+       /* try to fetch required memory from subflow */
+       if (!sk_rmem_schedule(sk, skb, skb->truesize)) {
+               if (ssk->sk_forward_alloc < skb->truesize)
+                       goto drop;
+               __sk_mem_reclaim(ssk, skb->truesize);
+               if (!sk_rmem_schedule(sk, skb, skb->truesize))
+                       goto drop;
+       }
+
        /* the skb map_seq accounts for the skb offset:
         * mptcp_subflow_get_mapped_dsn() is based on the current tp->copied_seq
         * value
@@ -301,6 +310,7 @@ static bool __mptcp_move_skb(struct mptcp_sock *msk, struct 
sock *ssk,
         * will retransmit as needed, if needed.
         */
        MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_DUPDATA);
+drop:
        mptcp_drop(sk, skb);
        return false;
 }
-- 
2.26.2