netdev - [PATCH net-next 2/5] mptcp: implement MSG

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Date:   Fri, 23 Apr 2021 11:17:06 -0700
From:   Mat Martineau <mathew.j.martineau@...ux.intel.com>
To:     netdev@...r.kernel.org
Cc:     Paolo Abeni <pabeni@...hat.com>, davem@...emloft.net,
        kuba@...nel.org, matthieu.baerts@...sares.net,
        mptcp@...ts.linux.dev,
        Mat Martineau <mathew.j.martineau@...ux.intel.com>
Subject: [PATCH net-next 2/5] mptcp: implement MSG_TRUNC support

From: Paolo Abeni <pabeni@...hat.com>

The mentioned flag is currently silenlty ignored. This
change implements the TCP-like behaviour, dropping the
pending data up to the specified length.

Signed-off-by: Paolo Abeni <pabeni@...hat.com>
Sigend-off-by: Mat Martineau <mathew.j.martineau@...ux.intel.com>
---
 net/mptcp/protocol.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 1d5f23bd640c..ae08c563c712 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1739,7 +1739,7 @@ static void mptcp_wait_data(struct sock *sk, long *timeo)
 
 static int __mptcp_recvmsg_mskq(struct mptcp_sock *msk,
 				struct msghdr *msg,
-				size_t len)
+				size_t len, int flags)
 {
 	struct sk_buff *skb;
 	int copied = 0;
@@ -1750,11 +1750,13 @@ static int __mptcp_recvmsg_mskq(struct mptcp_sock *msk,
 		u32 count = min_t(size_t, len - copied, data_len);
 		int err;
 
-		err = skb_copy_datagram_msg(skb, offset, msg, count);
-		if (unlikely(err < 0)) {
-			if (!copied)
-				return err;
-			break;
+		if (!(flags & MSG_TRUNC)) {
+			err = skb_copy_datagram_msg(skb, offset, msg, count);
+			if (unlikely(err < 0)) {
+				if (!copied)
+					return err;
+				break;
+			}
 		}
 
 		copied += count;
@@ -1966,7 +1968,7 @@ static int mptcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
 	while (copied < len) {
 		int bytes_read;
 
-		bytes_read = __mptcp_recvmsg_mskq(msk, msg, len - copied);
+		bytes_read = __mptcp_recvmsg_mskq(msk, msg, len - copied, flags);
 		if (unlikely(bytes_read < 0)) {
 			if (!copied)
 				copied = bytes_read;
-- 
2.31.1