Network overhaul : support for multiple NICs, performance improvement

- Add support for multiple NICs
- Switch from polling to an event loop for the host networking to avoid latency and locking issues

src/network/net_event.c

@@ -0,0 +1,76 @@
+#ifdef _WIN32
+#define WIN32_LEAN_AND_MEAN
+#include <windows.h>
+#else
+#include <unistd.h>
+#include <fcntl.h>
+#endif
+
+#include <86box/net_event.h>
+
+
+#ifndef _WIN32
+static void setup_fd(int fd)
+{
+  fcntl(fd, F_SETFD, FD_CLOEXEC);
+  fcntl(fd, F_SETFL, O_NONBLOCK);
+}
+#endif
+
+void
+net_event_init(net_evt_t *event)
+{
+#ifdef _WIN32
+    event->handle = CreateEvent(NULL, FALSE, FALSE, NULL);
+#else
+    (void)pipe(event->fds);
+    setup_fd(event->fds[0]);
+    setup_fd(event->fds[1]);
+#endif
+}
+
+void
+net_event_set(net_evt_t *event)
+{
+#ifdef _WIN32
+    SetEvent(event->handle);
+#else
+    (void)write(event->fds[1], "a", 1);
+#endif
+}
+
+void
+net_event_clear(net_evt_t *event)
+{
+#ifdef _WIN32
+    /* Do nothing on WIN32 since we use an auto-reset event */
+#else
+    char dummy[1];
+    (void)read(event->fds[0], &dummy, sizeof(dummy));
+#endif
+}
+
+void
+net_event_close(net_evt_t *event)
+{
+#ifdef _WIN32
+    CloseHandle(event->handle);
+#else
+    close(event->fds[0]);
+    close(event->fds[1]);
+#endif
+}
+
+#ifdef _WIN32
+HANDLE
+net_event_get_handle(net_evt_t *event)
+{
+    return event->handle;
+}
+#else
+int
+net_event_get_fd(net_evt_t *event)
+{
+    return event->fds[0];
+}
+#endif