net: Add MSG_WAITFORONE flag to recvmmsg

net: Add MSG_WAITFORONE flag to recvmmsg

Add new flag MSG_WAITFORONE for the recvmmsg() syscall.
When this flag is specified for a blocking socket, recvmmsg()
will only block until at least 1 packet is available.  The
default behavior is to block until all vlen packets are
available.  This flag has no effect on non-blocking sockets
or when used in combination with MSG_DONTWAIT.

Signed-off-by: Brandon L Black <[email protected]>
Acked-by: Ulrich Drepper <[email protected]>
Acked-by: Eric Dumazet <[email protected]>
Acked-by: Arnaldo Carvalho de Melo <[email protected]>
Signed-off-by: David S. Miller <[email protected]>