Commit 37198e93 authored by Davide Caratti's avatar Davide Caratti Committed by Jakub Kicinski
Browse files

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: default avatarPaolo Abeni <pabeni@redhat.com>
Signed-off-by: default avatarDavide Caratti <dcaratti@redhat.com>
Reviewed-by: default avatarMat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: default avatarJakub 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 */

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