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mptcp: cleanup fallback dummy mapping generation 

MPTCP currently access ack_seq outside the msk socket log scope to
generate the dummy mapping for fallback socket. Soon we are going
to introduce backlog usage and even for fallback socket the ack_seq
value will be significantly off outside of the msk socket lock scope.

Avoid relying on ack_seq for dummy mapping generation, using instead
the subflow sequence number. Note that in case of disconnect() and
(re)connect() we must ensure that any previous state is re-set.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Geliang Tang <geliang@kernel.org>
Tested-by: Geliang Tang <geliang@kernel.org>
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20251121-net-next-mptcp-memcg-backlog-imp-v1-6-1f34b6c1e0b1@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
pull/1354/merge
Paolo Abeni 2025-11-21 18:02:05 +01:00 committed by Jakub Kicinski
parent 85f22b8e1e
commit 2834f8edd7
2 changed files with 10 additions and 1 deletions
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3
net/mptcp/protocol.c
View File

@ -3274,6 +3274,9 @@ static int mptcp_disconnect(struct sock *sk, int flags)
msk->bytes_retrans = 0;
msk->rcvspace_init = 0;
/* for fallback's sake */
WRITE_ONCE(msk->ack_seq, 0);
WRITE_ONCE(sk->sk_shutdown, 0);
sk_error_report(sk);
return 0;

8
net/mptcp/subflow.c
View File

@ -491,6 +491,9 @@ static void subflow_set_remote_key(struct mptcp_sock *msk,
mptcp_crypto_key_sha(subflow->remote_key, NULL, &subflow->iasn);
subflow->iasn++;
/* for fallback's sake */
subflow->map_seq = subflow->iasn;
WRITE_ONCE(msk->remote_key, subflow->remote_key);
WRITE_ONCE(msk->ack_seq, subflow->iasn);
WRITE_ONCE(msk->can_ack, true);
@ -1435,9 +1438,12 @@ reset:
skb = skb_peek(&ssk->sk_receive_queue);
subflow->map_valid = 1;
subflow->map_seq = READ_ONCE(msk->ack_seq);
subflow->map_data_len = skb->len;
subflow->map_subflow_seq = tcp_sk(ssk)->copied_seq - subflow->ssn_offset;
subflow->map_seq = __mptcp_expand_seq(subflow->map_seq,
subflow->iasn +
TCP_SKB_CB(skb)->seq -
subflow->ssn_offset - 1);
WRITE_ONCE(subflow->data_avail, true);
return true;
}