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net: mptcp: make DACK4/DACK8 usage consistent among all subflows

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using packetdrill it's possible to observe the same MPTCP DSN being acked
by different subflows with DACK4 and DACK8. This is in contrast with what
specified in RFC8684 §3.3.2: if an MPTCP endpoint transmits a 64-bit wide
DSN, it MUST be acknowledged with a 64-bit wide DACK. Fix 'use_64bit_ack'
variable to make it a property of MPTCP sockets, not TCP subflows.

Fixes: a0c1d0eafd ("mptcp: Use 32-bit DATA_ACK when possible")
Acked-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Davide Caratti
2020-10-06 18:26:17 +02:00
committed by Jakub Kicinski
parent 0da1ccbbef
commit 37198e93ce
3 changed files with 3 additions and 4 deletions
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3
net/mptcp/subflow.c
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@@ -769,12 +769,11 @@ static enum mapping_status get_mapping_status(struct sock *ssk,
if (!mpext->dsn64) {
map_seq = expand_seq(subflow->map_seq, subflow->map_data_len,
mpext->data_seq);
subflow->use_64bit_ack = 0;
pr_debug("expanded seq=%llu", subflow->map_seq);
} else {
map_seq = mpext->data_seq;
subflow->use_64bit_ack = 1;
}
WRITE_ONCE(mptcp_sk(subflow->conn)->use_64bit_ack, !!mpext->dsn64);
if (subflow->map_valid) {
/* Allow replacing only with an identical map */