Commit 37198e93 authored Oct 06, 2020 by Davide Caratti Committed by Jakub Kicinski Oct 09, 2020

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

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: a0c1d0ea ("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>

parent 0da1ccbb

net/mptcp/options.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -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;

net/mptcp/protocol.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -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;

net/mptcp/subflow.c

+1 −2

Original line number	Diff line number	Diff line
		@@ -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 */