feat(kernel): make DNS resolution work properly

* Add the loopback device
* Create the /etc/resolv.conf file, where the entry is the default SLIRP
  DNS server address.
* Add sock_send() for Unix sockets.
* On socket(), create the inode with name <{type}_socket> instead of
  just <socket> which makes debugging easier.
* Add some assertions that I will deal with later :)

Signed-off-by: Anhad Singh <[email protected]>

Author: Andy-Python-Programmer

CONTRIBUTING.md

@@ -36,4 +36,6 @@ $ lldb
 (lldb)
 ````
 
-Check out the docs for your debugger for information about how to use the debugger.
+Check out the docs for your debugger for information about how to use the debugger.
+
+`./aero.py -- -netdev user,id=spider -device e1000,netdev=spider,id=ck_nic0 -object filter-dump,id=spider,netdev=spider,file=qemulog.log`

base-files/etc/resolv.conf

@@ -0,0 +1 @@
+nameserver 10.0.2.3

src/Cargo.lock

@@ -76,6 +76,10 @@ impl Cache {
     }
 
     fn request(&mut self, ip: Ipv4Addr, packet: RawPacket) {
+        if ip == Ipv4Addr::LOOPBACK {
+            panic!()
+        }
+
         if self.0.get_mut(&ip).is_some() {
             todo!()
         } else {

src/aero_kernel/src/net/arp.rs

@@ -0,0 +1,60 @@
+// Copyright (C) 2021-2023 The Aero Project Developers.
+//
+// This file is part of The Aero Project.
+//
+// Aero is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Aero is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Aero. If not, see <https://www.gnu.org/licenses/>.
+
+//! Loopback device.
+
+use alloc::boxed::Box;
+use alloc::sync::Arc;
+use crabnet::data_link::MacAddr;
+use crabnet::network::Ipv4Addr;
+
+use crate::utils::dma::DmaAllocator;
+
+use super::{NetworkDevice, NetworkDriver, RecvPacket};
+
+pub struct Loopback;
+
+impl NetworkDriver for Loopback {
+    fn send(&self, _packet: Box<[u8], DmaAllocator>) {
+        todo!()
+    }
+
+    fn recv(&self) -> RecvPacket {
+        todo!()
+    }
+
+    fn recv_end(&self, _packet_id: usize) {
+        todo!()
+    }
+
+    #[inline]
+    fn mac(&self) -> MacAddr {
+        // TODO: What should this really be?
+        MacAddr::NULL
+    }
+}
+
+lazy_static::lazy_static! {
+    pub static ref LOOPBACK: Arc<NetworkDevice> = (|| {
+        let device = Arc::new(NetworkDevice::new(Arc::new(Loopback)));
+
+        device.set_ip(Ipv4Addr::LOOPBACK);
+        device.set_subnet_mask(Ipv4Addr::new(255, 0, 0, 0));
+
+        device
+    })();
+}