tcp-repair: Handle zero-length data put in rcv queue

tcp-repair: Handle zero-length data put in rcv queue

When sending data into a tcp socket in repair state we should check
for the amount of data being 0 explicitly. Otherwise we'll have an skb
with seq == end_seq in rcv queue, but tcp doesn't expect this to happen
(in particular a warn_on in tcp_recvmsg shoots).

Signed-off-by: Pavel Emelyanov <[email protected]>
Reported-by: Giorgos Mavrikas <[email protected]>
Signed-off-by: David S. Miller <[email protected]>