Don't set socket as blocking in recvmmsg for non Linux targets (#2611)

* Don't set socket as blocking in recvmmsg for non Linux targets

- The user of the function is controling this flag

* added a test

src/recvmmsg.rs

@@ -10,7 +10,6 @@ pub const NUM_RCVMMSGS: usize = 16;
 #[cfg(not(target_os = "linux"))]
 pub fn recv_mmsg(socket: &UdpSocket, packets: &mut [Packet]) -> io::Result<usize> {
     let mut i = 0;
-    socket.set_nonblocking(false)?;
     let count = cmp::min(NUM_RCVMMSGS, packets.len());
     for p in packets.iter_mut().take(count) {
         p.meta.size = 0;
@@ -87,6 +86,7 @@ pub fn recv_mmsg(sock: &UdpSocket, packets: &mut [Packet]) -> io::Result<usize>
 mod tests {
     use crate::packet::PACKET_DATA_SIZE;
     use crate::recvmmsg::*;
+    use std::time::{Duration, Instant};
 
     #[test]
     pub fn test_recv_mmsg_one_iter() {
@@ -137,6 +137,38 @@ mod tests {
         }
     }
 
+    #[test]
+    pub fn test_recv_mmsg_multi_iter_timeout() {
+        let reader = UdpSocket::bind("127.0.0.1:0").expect("bind");
+        let addr = reader.local_addr().unwrap();
+        reader.set_read_timeout(Some(Duration::new(5, 0))).unwrap();
+        reader.set_nonblocking(false).unwrap();
+        let sender = UdpSocket::bind("127.0.0.1:0").expect("bind");
+        let saddr = sender.local_addr().unwrap();
+        let sent = NUM_RCVMMSGS + 10;
+        for _ in 0..sent {
+            let data = [0; PACKET_DATA_SIZE];
+            sender.send_to(&data[..], &addr).unwrap();
+        }
+
+        let start = Instant::now();
+        let mut packets = vec![Packet::default(); NUM_RCVMMSGS * 2];
+        let recv = recv_mmsg(&reader, &mut packets[..]).unwrap();
+        assert_eq!(NUM_RCVMMSGS, recv);
+        for i in 0..recv {
+            assert_eq!(packets[i].meta.size, PACKET_DATA_SIZE);
+            assert_eq!(packets[i].meta.addr(), saddr);
+        }
+
+        let recv = recv_mmsg(&reader, &mut packets[..]).unwrap();
+        assert_eq!(sent - NUM_RCVMMSGS, recv);
+        for i in 0..recv {
+            assert_eq!(packets[i].meta.size, PACKET_DATA_SIZE);
+            assert_eq!(packets[i].meta.addr(), saddr);
+        }
+        assert!(start.elapsed().as_secs() < 5);
+    }
+
     #[test]
     pub fn test_recv_mmsg_multi_addrs() {
         let reader = UdpSocket::bind("127.0.0.1:0").expect("bind");