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.
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