[MPTCP][PATCH v2 mptcp-next 02/16] mptcp: generate the data checksum

[Geliang Tang <geliangtang@gmail.com>]

This patch add a new member named csum in struct mptcp_ext, implemented a
new function named mptcp_generate_data_checksum().

Generate the data checksum in mptcp_sendmsg_frag, save it in mpext->csum.

Signed-off-by: Geliang Tang <geliangtang@gmail.com>
---
 include/net/mptcp.h  |  1 +
 net/mptcp/protocol.c | 21 +++++++++++++++++++++
 net/mptcp/protocol.h |  7 +++++++
 3 files changed, 29 insertions(+)

diff --git a/include/net/mptcp.h b/include/net/mptcp.h
index 83f23774b908..23bbd439e115 100644
--- a/include/net/mptcp.h
+++ b/include/net/mptcp.h
@@ -23,6 +23,7 @@ struct mptcp_ext {
 	u64		data_seq;
 	u32		subflow_seq;
 	u16		data_len;
+	__sum16		csum;
 	u8		use_map:1,
 			dsn64:1,
 			data_fin:1,
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 56103814afed..b053f92a8ee1 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1254,6 +1254,25 @@ static bool mptcp_alloc_tx_skb(struct sock *sk, struct sock *ssk)
 	return __mptcp_alloc_tx_skb(sk, ssk, sk->sk_allocation);
 }
 
+static __sum16 mptcp_generate_data_checksum(struct sk_buff *skb)
+{
+	struct csum_pseudo_header header;
+	struct mptcp_ext *mpext;
+	__wsum csum;
+
+	mpext = mptcp_get_ext(skb);
+
+	header.data_seq = mpext->data_seq;
+	header.subflow_seq = mpext->subflow_seq;
+	header.data_len = mpext->data_len;
+	header.csum = 0;
+
+	csum = skb_checksum(skb, 0, skb->len, 0);
+	csum = csum_partial(&header, sizeof(header), csum);
+
+	return csum_fold(csum);
+}
+
 static int mptcp_sendmsg_frag(struct sock *sk, struct sock *ssk,
 			      struct mptcp_data_frag *dfrag,
 			      struct mptcp_sendmsg_info *info)
@@ -1352,6 +1371,8 @@ static int mptcp_sendmsg_frag(struct sock *sk, struct sock *ssk,
 		tcp_push_pending_frames(ssk);
 	}
 out:
+	if (READ_ONCE(msk->csum_enabled))
+		mpext->csum = mptcp_generate_data_checksum(tail);
 	mptcp_subflow_ctx(ssk)->rel_write_seq += ret;
 	return ret;
 }
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 826019bb2093..b13b95cedb5e 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -332,6 +332,13 @@ static inline struct mptcp_data_frag *mptcp_rtx_head(const struct sock *sk)
 	return list_first_entry_or_null(&msk->rtx_queue, struct mptcp_data_frag, list);
 }
 
+struct csum_pseudo_header {
+	u64 data_seq;
+	u32 subflow_seq;
+	u16 data_len;
+	__sum16 csum;
+};
+
 struct mptcp_subflow_request_sock {
 	struct	tcp_request_sock sk;
 	u16	mp_capable : 1,
-- 
2.30.2