mptcp: implement MSG_TRUNC support

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@redhat.com>
Sigend-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 1d5f23b..ae08c56 100644 (file)
--- 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;