Skip to content

network: Increase maximum MTU value from 10000 to 65536

Simon Arlott requested to merge sa/gnome-control-center:max-mtu into main

The maximum MTU value of 10000 is too low for USB Ethernet, which has a maximum (for Linux USB gadgets) of 15412 bytes (although the upper limit is the USB wMaxPacketSize which goes up to 4294967295 bytes):

  linux/drivers/usb/gadget/function/u_ether.c:#define GETHER_MAX_MTU_SIZE 15412

Multiple Intel NICs can use an MTU of 16110 bytes:

  linux/drivers/net/ethernet/intel/e1000/e1000_hw.h:#define MAX_JUMBO_FRAME_SIZE         0x3F00
  linux/drivers/net/ethernet/intel/e1000e/defines.h:#define MAX_JUMBO_FRAME_SIZE    0x3F00
  linux/drivers/net/ethernet/intel/igbvf/defines.h:#define MAX_JUMBO_FRAME_SIZE         0x3F00

The NetworkManager limit is 4294967295 bytes but this is unreasonable in a typical enivornment because of the memory required for packets of that size.

The maximum IPv4 and IPv6 (without using Jumbograms) packet size is 65535 bytes so increase the maximum MTU value to 65536 allow full size IP packets to be used.

There is a corresponding change in network-manager-applet.

Edited by Simon Arlott

Merge request reports