* [PATCH net 1/2] mptcp: fix checksum byte order
2022-05-17 18:02 [PATCH net 0/2] mptcp: Fix checksum byte order on little-endian Mat Martineau
@ 2022-05-17 18:02 ` Mat Martineau
2022-05-17 18:02 ` [PATCH net 2/2] mptcp: Do TCP fallback on early DSS checksum failure Mat Martineau
2022-05-18 12:30 ` [PATCH net 0/2] mptcp: Fix checksum byte order on little-endian patchwork-bot+netdevbpf
2 siblings, 0 replies; 4+ messages in thread
From: Mat Martineau @ 2022-05-17 18:02 UTC (permalink / raw)
To: netdev
Cc: Paolo Abeni, davem, kuba, edumazet, matthieu.baerts, mptcp,
Mat Martineau
From: Paolo Abeni <pabeni@redhat.com>
The MPTCP code typecasts the checksum value to u16 and
then converts it to big endian while storing the value into
the MPTCP option.
As a result, the wire encoding for little endian host is
wrong, and that causes interoperabilty interoperability
issues with other implementation or host with different endianness.
Address the issue writing in the packet the unmodified __sum16 value.
MPTCP checksum is disabled by default, interoperating with systems
with bad mptcp-level csum encoding should cause fallback to TCP.
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/275
Fixes: c5b39e26d003 ("mptcp: send out checksum for DSS")
Fixes: 390b95a5fb84 ("mptcp: receive checksum for DSS")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
---
net/mptcp/options.c | 36 ++++++++++++++++++++++++------------
net/mptcp/protocol.h | 2 +-
net/mptcp/subflow.c | 2 +-
3 files changed, 26 insertions(+), 14 deletions(-)
diff --git a/net/mptcp/options.c b/net/mptcp/options.c
index 325383646f5c..b548cec86c9d 100644
--- a/net/mptcp/options.c
+++ b/net/mptcp/options.c
@@ -107,7 +107,7 @@ static void mptcp_parse_option(const struct sk_buff *skb,
ptr += 2;
}
if (opsize == TCPOLEN_MPTCP_MPC_ACK_DATA_CSUM) {
- mp_opt->csum = (__force __sum16)get_unaligned_be16(ptr);
+ mp_opt->csum = get_unaligned((__force __sum16 *)ptr);
mp_opt->suboptions |= OPTION_MPTCP_CSUMREQD;
ptr += 2;
}
@@ -221,7 +221,7 @@ static void mptcp_parse_option(const struct sk_buff *skb,
if (opsize == expected_opsize + TCPOLEN_MPTCP_DSS_CHECKSUM) {
mp_opt->suboptions |= OPTION_MPTCP_CSUMREQD;
- mp_opt->csum = (__force __sum16)get_unaligned_be16(ptr);
+ mp_opt->csum = get_unaligned((__force __sum16 *)ptr);
ptr += 2;
}
@@ -1240,7 +1240,7 @@ static void mptcp_set_rwin(const struct tcp_sock *tp)
WRITE_ONCE(msk->rcv_wnd_sent, ack_seq);
}
-u16 __mptcp_make_csum(u64 data_seq, u32 subflow_seq, u16 data_len, __wsum sum)
+__sum16 __mptcp_make_csum(u64 data_seq, u32 subflow_seq, u16 data_len, __wsum sum)
{
struct csum_pseudo_header header;
__wsum csum;
@@ -1256,15 +1256,25 @@ u16 __mptcp_make_csum(u64 data_seq, u32 subflow_seq, u16 data_len, __wsum sum)
header.csum = 0;
csum = csum_partial(&header, sizeof(header), sum);
- return (__force u16)csum_fold(csum);
+ return csum_fold(csum);
}
-static u16 mptcp_make_csum(const struct mptcp_ext *mpext)
+static __sum16 mptcp_make_csum(const struct mptcp_ext *mpext)
{
return __mptcp_make_csum(mpext->data_seq, mpext->subflow_seq, mpext->data_len,
~csum_unfold(mpext->csum));
}
+static void put_len_csum(u16 len, __sum16 csum, void *data)
+{
+ __sum16 *sumptr = data + 2;
+ __be16 *ptr = data;
+
+ put_unaligned_be16(len, ptr);
+
+ put_unaligned(csum, sumptr);
+}
+
void mptcp_write_options(__be32 *ptr, const struct tcp_sock *tp,
struct mptcp_out_options *opts)
{
@@ -1340,8 +1350,9 @@ void mptcp_write_options(__be32 *ptr, const struct tcp_sock *tp,
put_unaligned_be32(mpext->subflow_seq, ptr);
ptr += 1;
if (opts->csum_reqd) {
- put_unaligned_be32(mpext->data_len << 16 |
- mptcp_make_csum(mpext), ptr);
+ put_len_csum(mpext->data_len,
+ mptcp_make_csum(mpext),
+ ptr);
} else {
put_unaligned_be32(mpext->data_len << 16 |
TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
@@ -1392,11 +1403,12 @@ void mptcp_write_options(__be32 *ptr, const struct tcp_sock *tp,
goto mp_capable_done;
if (opts->csum_reqd) {
- put_unaligned_be32(opts->data_len << 16 |
- __mptcp_make_csum(opts->data_seq,
- opts->subflow_seq,
- opts->data_len,
- ~csum_unfold(opts->csum)), ptr);
+ put_len_csum(opts->data_len,
+ __mptcp_make_csum(opts->data_seq,
+ opts->subflow_seq,
+ opts->data_len,
+ ~csum_unfold(opts->csum)),
+ ptr);
} else {
put_unaligned_be32(opts->data_len << 16 |
TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index f4ce28bb0fdc..fb40dd676a26 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -723,7 +723,7 @@ void mptcp_token_destroy(struct mptcp_sock *msk);
void mptcp_crypto_key_sha(u64 key, u32 *token, u64 *idsn);
void mptcp_crypto_hmac_sha(u64 key1, u64 key2, u8 *msg, int len, void *hmac);
-u16 __mptcp_make_csum(u64 data_seq, u32 subflow_seq, u16 data_len, __wsum sum);
+__sum16 __mptcp_make_csum(u64 data_seq, u32 subflow_seq, u16 data_len, __wsum sum);
void __init mptcp_pm_init(void);
void mptcp_pm_data_init(struct mptcp_sock *msk);
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index 8c37087f0d84..e90fe7eec43a 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -888,7 +888,7 @@ static enum mapping_status validate_data_csum(struct sock *ssk, struct sk_buff *
{
struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
u32 offset, seq, delta;
- u16 csum;
+ __sum16 csum;
int len;
if (!csum_reqd)
--
2.36.1
^ permalink raw reply related [flat|nested] 4+ messages in thread* [PATCH net 2/2] mptcp: Do TCP fallback on early DSS checksum failure
2022-05-17 18:02 [PATCH net 0/2] mptcp: Fix checksum byte order on little-endian Mat Martineau
2022-05-17 18:02 ` [PATCH net 1/2] mptcp: fix checksum byte order Mat Martineau
@ 2022-05-17 18:02 ` Mat Martineau
2022-05-18 12:30 ` [PATCH net 0/2] mptcp: Fix checksum byte order on little-endian patchwork-bot+netdevbpf
2 siblings, 0 replies; 4+ messages in thread
From: Mat Martineau @ 2022-05-17 18:02 UTC (permalink / raw)
To: netdev; +Cc: Mat Martineau, davem, kuba, pabeni, edumazet, matthieu.baerts,
mptcp
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: dd8bcd1768ff ("mptcp: validate the data checksum")
Acked-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
---
net/mptcp/protocol.h | 3 ++-
net/mptcp/subflow.c | 21 ++++++++++++++++++---
2 files changed, 20 insertions(+), 4 deletions(-)
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index fb40dd676a26..5655a63aa6a8 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -443,7 +443,8 @@ 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;
u32 remote_nonce;
u64 thmac;
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index e90fe7eec43a..be76ada89d96 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -955,11 +955,14 @@ 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;
}
@@ -1141,6 +1144,18 @@ 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);
@@ -1218,7 +1233,7 @@ static bool subflow_check_data_avail(struct sock *ssk)
return true;
}
- if (subflow->mp_join || subflow->fully_established) {
+ if (!subflow_can_fallback(subflow)) {
/* fatal protocol error, close the socket.
* subflow_error_report() will introduce the appropriate barriers
*/
--
2.36.1
^ permalink raw reply related [flat|nested] 4+ messages in thread