[PATCH v5 mptcp-next 14/21] mptcp: validate the data checksum

[Paolo Abeni <pabeni@redhat.com>]

From: Geliang Tang <geliangtang@gmail.com>

This patch added three new members named data_csum, csum_len and map_csum
in struct mptcp_subflow_context, implemented a new function named
mptcp_validate_data_checksum(). Validate the data checksum in the function
__mptcp_move_skbs_from_subflow.

Signed-off-by: Geliang Tang <geliangtang@gmail.com>
---
 net/mptcp/protocol.c | 35 +++++++++++++++++++++++++++++++++++
 net/mptcp/protocol.h |  3 +++
 net/mptcp/subflow.c  |  7 +++++--
 3 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 4c79b0518e81..ba488a36dca0 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -528,6 +528,35 @@ static bool mptcp_check_data_fin(struct sock *sk)
 	return ret;
 }
 
+static bool mptcp_validate_data_checksum(struct sock *ssk)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
+	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
+	struct csum_pseudo_header header;
+	__wsum csum;
+
+	if (__mptcp_check_fallback(msk))
+		goto out;
+
+	if (subflow->csum_len < subflow->map_data_len)
+		goto out;
+
+	header.data_seq = subflow->map_seq;
+	header.subflow_seq = subflow->map_subflow_seq;
+	header.data_len = subflow->map_data_len;
+	header.csum = subflow->map_csum;
+
+	csum = csum_partial(&header, sizeof(header), subflow->data_csum);
+
+	if (csum_fold(csum))
+		return false;
+	subflow->data_csum = 0;
+	subflow->csum_len = 0;
+
+out:
+	return true;
+}
+
 static bool __mptcp_move_skbs_from_subflow(struct mptcp_sock *msk,
 					   struct sock *ssk,
 					   unsigned int *bytes)
@@ -596,6 +625,12 @@ static bool __mptcp_move_skbs_from_subflow(struct mptcp_sock *msk,
 			if (tp->urg_data)
 				done = true;
 
+			if (READ_ONCE(msk->csum_enabled)) {
+				subflow->data_csum = skb_checksum(skb, offset, len,
+								  subflow->data_csum);
+				subflow->csum_len += len;
+				mptcp_validate_data_checksum(ssk);
+			}
 			if (__mptcp_move_skb(msk, ssk, skb, offset, len))
 				moved += len;
 			seq += len;
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index c7cc9382bf77..f1d9657eb6ce 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -399,6 +399,9 @@ struct mptcp_subflow_context {
 	u32	map_subflow_seq;
 	u32	ssn_offset;
 	u32	map_data_len;
+	__wsum	data_csum;
+	u32	csum_len;
+	__sum16	map_csum;
 	u32	request_mptcp : 1,  /* send MP_CAPABLE */
 		request_join : 1,   /* send MP_JOIN */
 		request_bkup : 1,
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index f8732e11a392..8648d25190e1 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -948,9 +948,12 @@ static enum mapping_status get_mapping_status(struct sock *ssk,
 	subflow->map_data_len = data_len;
 	subflow->map_valid = 1;
 	subflow->mpc_map = mpext->mpc_map;
-	pr_debug("new map seq=%llu subflow_seq=%u data_len=%u",
+	subflow->data_csum = 0;
+	subflow->csum_len = 0;
+	subflow->map_csum = mpext->csum;
+	pr_debug("new map seq=%llu subflow_seq=%u data_len=%u csum=%u",
 		 subflow->map_seq, subflow->map_subflow_seq,
-		 subflow->map_data_len);
+		 subflow->map_data_len, subflow->map_csum);
 
 validate_seq:
 	/* we revalidate valid mapping on new skb, because we must ensure
-- 
2.26.2