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mptcp: use "middlebox interference" RST when no DSS
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RFC8684 suggests use of "Middlebox interference (code 0x06)" in case of
fully established subflow that carries data at TCP level with no DSS
sub-option.

This is generally the case when mpext is NULL or mpext->use_map is 0:
use a dedicated value of 'mapping_status' and use it before closing the
socket in subflow_check_data_avail().

Link: multipath-tcp/mptcp_net-next#518
Signed-off-by: Davide Caratti <[email protected]>
Signed-off-by: Matthieu Baerts (NGI0) <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>
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dcaratti authored and kuba-moo committed Oct 28, 2024
1 parent 5add80b commit 46a3282
Showing 1 changed file with 8 additions and 4 deletions.
12 changes: 8 additions & 4 deletions net/mptcp/subflow.c
Original file line number Diff line number Diff line change
Expand Up @@ -971,7 +971,8 @@ enum mapping_status {
MAPPING_EMPTY,
MAPPING_DATA_FIN,
MAPPING_DUMMY,
MAPPING_BAD_CSUM
MAPPING_BAD_CSUM,
MAPPING_NODSS
};

static void dbg_bad_map(struct mptcp_subflow_context *subflow, u32 ssn)
Expand Down Expand Up @@ -1128,8 +1129,9 @@ static enum mapping_status get_mapping_status(struct sock *ssk,
return MAPPING_EMPTY;
}

/* If the required DSS has likely been dropped by a middlebox */
if (!subflow->map_valid)
return MAPPING_INVALID;
return MAPPING_NODSS;

goto validate_seq;
}
Expand Down Expand Up @@ -1343,7 +1345,7 @@ static bool subflow_check_data_avail(struct sock *ssk)
status = get_mapping_status(ssk, msk);
trace_subflow_check_data_avail(status, skb_peek(&ssk->sk_receive_queue));
if (unlikely(status == MAPPING_INVALID || status == MAPPING_DUMMY ||
status == MAPPING_BAD_CSUM))
status == MAPPING_BAD_CSUM || status == MAPPING_NODSS))
goto fallback;

if (status != MAPPING_OK)
Expand Down Expand Up @@ -1396,7 +1398,9 @@ static bool subflow_check_data_avail(struct sock *ssk)
* subflow_error_report() will introduce the appropriate barriers
*/
subflow->reset_transient = 0;
subflow->reset_reason = MPTCP_RST_EMPTCP;
subflow->reset_reason = status == MAPPING_NODSS ?
MPTCP_RST_EMIDDLEBOX :
MPTCP_RST_EMPTCP;

reset:
WRITE_ONCE(ssk->sk_err, EBADMSG);
Expand Down

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