From 2469baa1c302df7575f86c717e55684ea0d8dc7d Mon Sep 17 00:00:00 2001
From: Jayant <jayantmishra632@gmail.com>
Date: Sun, 11 Sep 2022 19:53:48 +0530
Subject: [PATCH] new code

---
 docs/Devices.md | 105 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 105 insertions(+)
 create mode 100644 docs/Devices.md

diff --git a/docs/Devices.md b/docs/Devices.md
new file mode 100644
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--- /dev/null
+++ b/docs/Devices.md
@@ -0,0 +1,105 @@
+#Description of devices:
+</br>
+
+###Use Of Convoluted Bounds And Queues :
+
+- Here in the method below, we are using a bound which is more convoluted so that it'll become easy for us to pass both references and smart pointers, such as mutex guards here.
+
+- Along with this, we are also maintaining a pair of queue rx/tx.These queues are being  used to transfer packets bw VM and net devices. it is actually used along with MIMO between the guest and the devices.
+
+- Then we'll need to explicitly set MAC address. So to make this happen We'll need a minimal config space to support setting an explicit MAC addr,on the guest interface at least. We use an empty one for now.
+
+    
+
+
+
+```
+impl<M> Net<M>
+
+    M: GuestAddressSpace + Clone + Send + 'static,
+{
+    pub fn new<B>(env: &mut Env<M, B>, args: &NetArgs) -> Result<Arc<Mutex<Self>>>
+    
+        
+        B: DerefMut,
+        B::Target: MmioManager<D = Arc<dyn DeviceMmio + Send + Sync>>,
+    {
+        let device_features = (1 << VIRTIO_F_VERSION_1)
+            | (1 << VIRTIO_F_RING_EVENT_IDX)
+            | (1 << VIRTIO_F_IN_ORDER)
+            | (1 << VIRTIO_NET_F_CSUM)
+            | (1 << VIRTIO_NET_F_GUEST_CSUM)
+            | (1 << VIRTIO_NET_F_GUEST_TSO4)
+            | (1 << VIRTIO_NET_F_GUEST_TSO6)
+            | (1 << VIRTIO_NET_F_GUEST_UFO)
+            | (1 << VIRTIO_NET_F_HOST_TSO4)
+            | (1 << VIRTIO_NET_F_HOST_TSO6)
+            | (1 << VIRTIO_NET_F_HOST_UFO);
+
+      
+        let queues = vec![
+            Queue::new(env.mem.clone(), QUEUE_MAX_SIZE),
+            Queue::new(env.mem.clone(), QUEUE_MAX_SIZE),
+        ];
+
+        
+        let config_space = Vec::new();
+        let virtio_cfg = VirtioConfig::new(device_features, queues, config_space);
+
+        let common_cfg = CommonConfig::new(virtio_cfg, env).map_err(Error::Virtio)?;
+
+        let net = Arc::new(Mutex::new(Net {
+            cfg: common_cfg,
+            tap_name: args.tap_name.clone(),
+        }));
+
+        env.register_mmio_device(net.clone())
+            .map_err(Error::Virtio)?;
+
+        Ok(net)
+    }
+}
+```
+
+
+
+</br>
+</br>
+</br>
+
+###Set offload flags:
+- Then we are using Set offload flags to match the relevent virtio features of the device .
+- For now statically set in the constructor 
+
+
+        
+       
+        tap.set_offload(
+            bindings::TUN_F_CSUM
+                | bindings::TUN_F_UFO
+                | bindings::TUN_F_TSO4
+                | bindings::TUN_F_TSO6,
+        )
+        .map_err(Error::Tap)?;
+       
+       
+</br>
+</br>
+</br>
+
+
+###Defining Layout Of Header :
+- Here we are defining the layout of the header.
+- The layout of the header is specified in the standard and is 12 bytes in size. We should define this somewhere.
+       
+        tap.set_vnet_hdr_size(VIRTIO_NET_HDR_SIZE as i32)
+            .map_err(Error::Tap)?;
+
+        let driver_notify = SingleFdSignalQueue {
+            irqfd: self.cfg.irqfd.clone(),
+            interrupt_status: self.cfg.virtio.interrupt_status.clone(),
+        };
+        
+
+
+      
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