kernel: Support listening sockets in poll()

kernel/src/net/Socket.h

@@ -65,6 +65,10 @@ class Socket : public VFS::FileInode
         m_metadata.nlinks--;
     }
 
+    virtual bool can_accept_connections() const = 0;
+
+    virtual bool can_read_data() const = 0;
+
     virtual ~Socket() = default;
 
   protected:

kernel/src/net/UnixSocket.h

@@ -17,6 +17,16 @@ class UnixSocket : public Socket
         return (m_state == Connected || m_state == Reset) && !m_data.size();
     }
 
+    bool can_read_data() const override
+    {
+        return (m_state == Connected || m_state == Reset) && m_data.size();
+    }
+
+    bool can_accept_connections() const override
+    {
+        return !m_listen_queue.is_empty();
+    }
+
     Result<usize> send(const u8*, usize, int) override;
     Result<usize> recv(u8*, usize, int) const override;
 

kernel/src/sys/poll.cpp

@@ -2,6 +2,7 @@
 #include "Pledge.h"
 #include "fs/VFS.h"
 #include "memory/MemoryManager.h"
+#include "net/Socket.h"
 #include "sys/Syscall.h"
 #include "thread/Scheduler.h"
 #include <bits/poll.h>
@@ -47,12 +48,27 @@ Result<u64> sys_poll(Registers*, SyscallArgs args)
             auto& inode = inodes[i];
             if (!inode) continue;
 
-            if (kfds[i].events & POLLIN && !inode->will_block_if_read())
+            if (kfds[i].events & POLLIN)
+            {
+                if (inode->type() == VFS::InodeType::Socket)
+                {
+                    auto socket = (Socket*)inode.ptr();
+                    if (socket->can_read_data() || socket->can_accept_connections())
                     {
                         fds_with_events++;
                         kfds[i].revents |= POLLIN;
                     }
                 }
+                else
+                {
+                    if (!inode->will_block_if_read())
+                    {
+                        fds_with_events++;
+                        kfds[i].revents |= POLLIN;
+                    }
+                }
+            }
+        }
 
         if (!fds_with_events && (timeout > 0 || infinite))
         {

libluna/include/luna/CircularQueue.h

@@ -37,7 +37,7 @@ template <typename T, usize Size> class CircularQueue
      * @return true The queue is empty.
      * @return false The queue is not empty.
      */
-    bool is_empty()
+    bool is_empty() const
     {
         return m_tail.load() == m_head.load();
     }
@@ -124,7 +124,7 @@ template <typename T> class DynamicCircularQueue
      * @return true The queue is empty.
      * @return false The queue is not empty.
      */
-    bool is_empty()
+    bool is_empty() const
     {
         return m_tail.load() == m_head.load();
     }