FOV: Raise lower limit to avoid zoom-loading of distant world (#7234)

In the client, raise lower limit from 30 to 45 degrees, to avoid server
seeing this as a zoom and loading world beyond the server-set limit.
Add minimum in settingtypes.txt and enforce lower limit when set using
minetest.conf.

In the server, distrust the client-sent FOV if below the heuristic zoom
threshold and use the player object property 'zoom_fov' to check it, to
protect against hacked clients.

1 files changed, 3 insertions, 1 deletions

diff --git a/src/camera.cpp b/src/camera.cpp
index ebb154137..1bbdb56ea 100644
--- a/src/camera.cpp
+++ b/src/camera.cpp
@@ -71,7 +71,9 @@ Camera::Camera(MapDrawControl &draw_control, Client *client):
 	 */
 	m_cache_fall_bobbing_amount = g_settings->getFloat("fall_bobbing_amount");
 	m_cache_view_bobbing_amount = g_settings->getFloat("view_bobbing_amount");
-	m_cache_fov                 = g_settings->getFloat("fov");
+	// 45 degrees is the lowest FOV that doesn't cause the server to treat this
+	// as a zoom FOV and load world beyond the set server limits.
+	m_cache_fov                 = std::fmax(g_settings->getFloat("fov"), 45.0f);
 	m_arm_inertia               = g_settings->getBool("arm_inertia");
 	m_nametags.clear();
 }