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 ยง3.3.2: 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: a0c1d0eafd1e ("mptcp: Use 32-bit DATA_ACK when possible")
Acked-by: Paolo Abeni <[email protected]>
Signed-off-by: Davide Caratti <[email protected]>
---
net/mptcp/options.c | 2 +-
net/mptcp/protocol.h | 2 +-
net/mptcp/subflow.c | 3 +--
3 files changed, 3 insertions(+), 4 deletions(-)
diff --git a/net/mptcp/options.c b/net/mptcp/options.c
index 888bbbbb3e8a..9d7fa93fe0cf 100644
--- a/net/mptcp/options.c
+++ b/net/mptcp/options.c
@@ -516,7 +516,7 @@ static bool mptcp_established_options_dss(struct sock *sk,
struct sk_buff *skb,
return ret;
}
- if (subflow->use_64bit_ack) {
+ if (READ_ONCE(msk->use_64bit_ack)) {
ack_size = TCPOLEN_MPTCP_DSS_ACK64;
opts->ext_copy.data_ack = READ_ONCE(msk->ack_seq);
opts->ext_copy.ack64 = 1;
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 20f04ac85409..285dd8b2b43a 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -202,6 +202,7 @@ struct mptcp_sock {
bool fully_established;
bool rcv_data_fin;
bool snd_data_fin_enable;
+ bool use_64bit_ack; /* Set when we received a 64-bit DSN */
spinlock_t join_list_lock;
struct work_struct work;
struct list_head conn_list;
@@ -294,7 +295,6 @@ struct mptcp_subflow_context {
backup : 1,
data_avail : 1,
rx_eof : 1,
- use_64bit_ack : 1, /* Set when we received a 64-bit DSN */
can_ack : 1; /* only after processing the remote a key */
u32 remote_nonce;
u64 thmac;
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index 6f035af1c9d2..91bef7bfffa6 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -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 */
--
2.26.2
