vhost/vsock: support MSG_EOR bit processing

'MSG_EOR' handling has similar logic as 'MSG_EOM' - if bit present
in packet's header, reset it to 0. Then restore it back if packet
processing wasn't completed. Instead of bool variable for each
flag, bit mask variable was added: it has logical OR of 'MSG_EOR'
and 'MSG_EOM' if needed, to restore flags, this variable is ORed
with flags field of packet.

Signed-off-by: Arseny Krasnov <arseny.krasnov@kaspersky.com>

drivers/vhost/vsock.c

@@ -114,7 +114,7 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
 		size_t nbytes;
 		size_t iov_len, payload_len;
 		int head;
-		bool restore_flag = false;
+		u32 flags_to_restore = 0;
 
 		spin_lock_bh(&vsock->send_pkt_list_lock);
 		if (list_empty(&vsock->send_pkt_list)) {
@@ -179,15 +179,20 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
 			 * created dynamically and are initialized with header
 			 * of current packet(except length). But in case of
 			 * SOCK_SEQPACKET, we also must clear message delimeter
-			 * bit(VIRTIO_VSOCK_SEQ_EOM). Otherwise, instead of one
-			 * packet with delimeter(which marks end of message),
-			 * there will be sequence of packets with delimeter
-			 * bit set. After initialized header will be copied to
-			 * rx buffer, this bit will be restored.
+			 * bit (VIRTIO_VSOCK_SEQ_EOM) and MSG_EOR bit
+			 * (VIRTIO_VSOCK_SEQ_EOR) if set. Otherwise,
+			 * there will be sequence of packets with these
+			 * bits set. After initialized header will be copied to
+			 * rx buffer, these required bits will be restored.
 			 */
 			if (le32_to_cpu(pkt->hdr.flags) & VIRTIO_VSOCK_SEQ_EOM) {
 				pkt->hdr.flags &= ~cpu_to_le32(VIRTIO_VSOCK_SEQ_EOM);
-				restore_flag = true;
+				flags_to_restore |= VIRTIO_VSOCK_SEQ_EOM;
+
+				if (le32_to_cpu(pkt->hdr.flags & VIRTIO_VSOCK_SEQ_EOR)) {
+					pkt->hdr.flags &= ~cpu_to_le32(VIRTIO_VSOCK_SEQ_EOR);
+					flags_to_restore |= VIRTIO_VSOCK_SEQ_EOR;
+				}
 			}
 		}
 
@@ -224,8 +229,7 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
 		 * to send it with the next available buffer.
 		 */
 		if (pkt->off < pkt->len) {
-			if (restore_flag)
-				pkt->hdr.flags |= cpu_to_le32(VIRTIO_VSOCK_SEQ_EOM);
+			pkt->hdr.flags |= cpu_to_le32(flags_to_restore);
 
 			/* We are queueing the same virtio_vsock_pkt to handle
 			 * the remaining bytes, and we want to deliver it