[PATCH net-next 07/16] mptcp: add csum_reqd in mptcp_options_received

[Mat Martineau <mathew.j.martineau@linux.intel.com>]

From: Geliang Tang <geliangtang@gmail.com>

This patch added a new flag csum_reqd in struct mptcp_options_received, if
the flag MPTCP_CAP_CHECKSUM_REQD is set in the receiving MP_CAPABLE
suboption, set this flag.

In mptcp_sk_clone and subflow_finish_connect, if the csum_reqd flag is set,
enable the msk->csum_enabled flag.

Acked-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Geliang Tang <geliangtang@gmail.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
---
 net/mptcp/options.c  | 7 ++++---
 net/mptcp/protocol.c | 2 ++
 net/mptcp/protocol.h | 1 +
 net/mptcp/subflow.c  | 2 ++
 4 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/net/mptcp/options.c b/net/mptcp/options.c
index ae69059583a7..2e2551590ecd 100644
--- a/net/mptcp/options.c
+++ b/net/mptcp/options.c
@@ -71,11 +71,9 @@ static void mptcp_parse_option(const struct sk_buff *skb,
 		 * "If a checksum is not present when its use has been
 		 * negotiated, the receiver MUST close the subflow with a RST as
 		 * it is considered broken."
-		 *
-		 * We don't implement DSS checksum - fall back to TCP.
 		 */
 		if (flags & MPTCP_CAP_CHECKSUM_REQD)
-			break;
+			mp_opt->csum_reqd = 1;
 
 		mp_opt->mp_capable = 1;
 		if (opsize >= TCPOLEN_MPTCP_MPC_SYNACK) {
@@ -327,6 +325,8 @@ void mptcp_get_options(const struct sock *sk,
 		       const struct sk_buff *skb,
 		       struct mptcp_options_received *mp_opt)
 {
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 	const struct tcphdr *th = tcp_hdr(skb);
 	const unsigned char *ptr;
 	int length;
@@ -342,6 +342,7 @@ void mptcp_get_options(const struct sock *sk,
 	mp_opt->dss = 0;
 	mp_opt->mp_prio = 0;
 	mp_opt->reset = 0;
+	mp_opt->csum_reqd = READ_ONCE(msk->csum_enabled);
 
 	length = (th->doff * 4) - sizeof(struct tcphdr);
 	ptr = (const unsigned char *)(th + 1);
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index f0da067301f6..b6e5c0930533 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -2810,6 +2810,8 @@ struct sock *mptcp_sk_clone(const struct sock *sk,
 	msk->token = subflow_req->token;
 	msk->subflow = NULL;
 	WRITE_ONCE(msk->fully_established, false);
+	if (mp_opt->csum_reqd)
+		WRITE_ONCE(msk->csum_enabled, true);
 
 	msk->write_seq = subflow_req->idsn + 1;
 	msk->snd_nxt = msk->write_seq;
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index a7ed0b8eb9bc..66e5063ac6c9 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -133,6 +133,7 @@ struct mptcp_options_received {
 		rm_addr : 1,
 		mp_prio : 1,
 		echo : 1,
+		csum_reqd : 1,
 		backup : 1;
 	u32	token;
 	u32	nonce;
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index aa6b307b27c8..9b82ce635c6e 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -405,6 +405,8 @@ static void subflow_finish_connect(struct sock *sk, const struct sk_buff *skb)
 			goto fallback;
 		}
 
+		if (mp_opt.csum_reqd)
+			WRITE_ONCE(mptcp_sk(parent)->csum_enabled, true);
 		subflow->mp_capable = 1;
 		subflow->can_ack = 1;
 		subflow->remote_key = mp_opt.sndr_key;
-- 
2.32.0