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mptcp: Do TCP fallback on early DSS checksum failure 

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2100072
Tested: LNST, Tier1
Conflicts: different context in subflow_check_data_avail() as \
	rhel-9 already has the upstream commit f8d4bcacff3b \
	("mptcp: infinite mapping receiving")

Upstream commit:
commit ae66fb2ba6c3dcaf8b9612b65aa949a1a4bed150
Author: Mat Martineau <mathew.j.martineau@linux.intel.com>
Date:   Tue May 17 11:02:12 2022 -0700

    mptcp: Do TCP fallback on early DSS checksum failure

    RFC 8684 section 3.7 describes several opportunities for a MPTCP
    connection to "fall back" to regular TCP early in the connection
    process, before it has been confirmed that MPTCP options can be
    successfully propagated on all SYN, SYN/ACK, and data packets. If a peer
    acknowledges the first received data packet with a regular TCP header
    (no MPTCP options), fallback is allowed.

    If the recipient of that first data packet finds a MPTCP DSS checksum
    error, this provides an opportunity to fail gracefully with a TCP
    fallback rather than resetting the connection (as might happen if a
    checksum failure were detected later).

    This commit modifies the checksum failure code to attempt fallback on
    the initial subflow of a MPTCP connection, only if it's a failure in the
    first data mapping. In cases where the peer initiates the connection,
    requests checksums, is the first to send data, and the peer is sending
    incorrect checksums (see
    https://github.com/multipath-tcp/mptcp_net-next/issues/275), this allows
    the connection to proceed as TCP rather than reset.

    Fixes: dd8bcd1768 ("mptcp: validate the data checksum")
    Acked-by: Paolo Abeni <pabeni@redhat.com>
    Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Paolo Abeni 2022-06-22 17:29:34 +02:00
parent 65330c619e
commit d18f0d700a
2 changed files with 20 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
net/mptcp/protocol.h
View File

@ -466,7 +466,8 @@ struct mptcp_subflow_context {
can_ack : 1, /* only after processing the remote a key */
disposable : 1, /* ctx can be free at ulp release time */
stale : 1, /* unable to snd/rcv data, do not use for xmit */
local_id_valid : 1; /* local_id is correctly initialized */
local_id_valid : 1, /* local_id is correctly initialized */
valid_csum_seen : 1; /* at least one csum validated */
enum mptcp_data_avail data_avail;
bool mp_fail_response_expect;
u32 remote_nonce;

21
net/mptcp/subflow.c
View File

@ -958,11 +958,14 @@ static enum mapping_status validate_data_csum(struct sock *ssk, struct sk_buff *
subflow->map_data_csum);
if (unlikely(csum)) {
MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_DATACSUMERR);
subflow->send_mp_fail = 1;
MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_MPFAILTX);
if (subflow->mp_join || subflow->valid_csum_seen) {
subflow->send_mp_fail = 1;
MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_MPFAILTX);
}
return subflow->mp_join ? MAPPING_INVALID : MAPPING_DUMMY;
}
subflow->valid_csum_seen = 1;
return MAPPING_OK;
}
@ -1153,6 +1156,18 @@ static void subflow_sched_work_if_closed(struct mptcp_sock *msk, struct sock *ss
}
}
static bool subflow_can_fallback(struct mptcp_subflow_context *subflow)
{
struct mptcp_sock *msk = mptcp_sk(subflow->conn);
if (subflow->mp_join)
return false;
else if (READ_ONCE(msk->csum_enabled))
return !subflow->valid_csum_seen;
else
return !subflow->fully_established;
}
static bool subflow_check_data_avail(struct sock *ssk)
{
struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
@ -1238,7 +1253,7 @@ fallback:
return true;
}
if ((subflow->mp_join || subflow->fully_established) && subflow->map_data_len) {
if (!subflow_can_fallback(subflow) && subflow->map_data_len) {
/* fatal protocol error, close the socket.
* subflow_error_report() will introduce the appropriate barriers
*/