Hi Jonas,
On 1/14/26 7:29 PM, Jonas Karlman wrote:
Hi Quentin,
On 1/14/2026 6:08 PM, Quentin Schulz wrote:
Hi Jonas,
On 1/14/26 4:37 PM, Jonas Karlman wrote:
Hi Quentin,
On 1/14/2026 4:01 PM, Quentin Schulz wrote:
Hi Jonas,
On 1/6/26 9:34 PM, Jonas Karlman wrote:
With the legacy networking stack, it is possible to use USE_SERVERIP,
SERVERIP and BOOTP_PREFER_SERVERIP Kconfg options to force use of a
specific TFTP server ip.
Using the lwIP networking stack use of the 'tftpserverip' environment
variable provide the closest equivalent functionality.
It does read serverip environment variable if it's set, so this should
match the behavior with the legacy network stack no?
This is what I first thought, however it seem that the lwip stack differ
slightly from the legacy stack, in that the dhcp lookup always seem to
reset the serverip env var.
As for BOOTP_PREFER_SERVERIP, this would need to be implemented in lwip
and isn't covered by this new variable is it?
For the lwip stack it looks like the BOOTP_PREFER_SERVERIP Kconfig
option possible was replaced with use of a 'tftpserverip' env var.
For legacy stack I had something like following in a .config fragment:
CONFIG_BOOTP_PREFER_SERVERIP=y
CONFIG_SERVERIP="192.168.2.50"
CONFIG_USE_SERVERIP=y
And this meant the serverip would not be overwritten by the dhcp command
for example (in the legacy stack)? When doing PXE/TFTP, I always do
setenv autoload no; dhcp; setenv serverip X.Y.Z.A; pxe get; pxe boot
I tried to keep it as simple as possible, as I have not used network
boot before, and used something like following:
env set boot_targets pxe; bootflow scan -lbG
and when I need to use a USB Ethernet dongle I use something like:
env delete -f ethaddr; env set boot_targets usb pxe; bootflow scan -lbG
When I control the DHCP server, I can actually set the TFTP server
directly and can skip setting the serverip as it'll be set by the dhcp
command correctly it seems?
For my homelab I use UniFi and should be able to control DHCP options,
however looking at U-Boot it looks like option 66 or 150 is just ignored,
see [1].
case 66: /* Ignore TFTP server name */
[1]
https://source.denx.de/u-boot/u-boot/-/blob/master/net/bootp.c?ref_type=heads#L952
From my very limited testing it looks like I am forced to set serverip
in env and cannot use a DHCP option to set the TFTP server to use.
Still on my RK3588 Tiger (on a different network, legacy stack):
=> env set boot_targets pxe; bootflow scan -lbG
Scanning for bootflows in all bootdevs
Seq Method State Uclass Part Name Filename
--- ----------- ------ -------- ---- ------------------------
----------------
pcie_dw_rockchip pcie@fe150000: PCIe-0 Link Fail
Scanning bootdev '[email protected]':
ethernet@fe1b0000 Waiting for PHY auto negotiation to complete...... done
BOOTP broadcast 1
DHCP client bound to address 192.168.1.144 (5 ms)
missing environment variable: pxeuuid
Retrieving file: pxelinux.cfg/01-aa-38-40-51-be-af
Using ethernet@fe1b0000 device
TFTP from server 192.168.1.211; our IP address is 192.168.1.144
My DHCP server is on OpenWRT at 192.168.1.1, and my TFTP server is on
192.168.1.211, with the setup steps explained in my first answer. If I
don't boot (remove -b), then I can see serverip is set to 192.168.1.211.
So *something* is working here.
And when I then also tried lwIP, and that seem to result in new or
different issues, e.g.:
- lwIP seem to be configured to allow very few packet fragments, trying
to use a reasonoble tftp blocksize, e.g. TFTP_BLOCKSIZE=4096 or more
seem to cause drop of packets.
- lwIP is very very slow to timeout compared to legacy when serverip
point to an invalid TFTP server and pxelinux.cfg files is looked up.
- sometimes got hit with random SError issues when second file was
loaded from TFTP, this issue was thankfully fixed with [2].
Rough first experience with lwIP :)
Are you planning on new Rockchip board/SoC support to use lwIP?
[2]
https://patchwork.ozlabs.org/project/uboot/patch/[email protected]/
From my notes, for an OpenWRT DHCP server:
Network → DHCP and DNS → PXE/TFTP tab → Add button
Filename: default
Server name: fileserver
Server address: <TFTP server IP address>
Force: checked (may not be necessary)
Save & Apply button
I'm assuming you need this for your labgrid farm so hopefully you have a
way to control the DHCP server :)
Correct, I have been playing around with network boot in my labgrid farm
and hit a few mines along the way :-)
Should result in a few network related patches in next few days.
Adding NET_LWIP=y made pxe booting stop working and 'serverip' always
ended up as the dhpc server regardless if it was set to something else.
Interesting. With tiger-rk3588_defconfig (legacy stack), I get:
=> setenv serverip 192.192.192.192
=> setenv autoload no
=> dhcp
ethernet@fe1b0000 Waiting for PHY auto negotiation to complete........ done
BOOTP broadcast 1
BOOTP broadcast 2
BOOTP broadcast 3
DHCP client bound to address 10.2.162.193 (1394 ms)
=> printenv serverip
serverip=10.2.0.122
Since lwip instead prioritize the 'tftpserverip' env over the 'serverip'
env for tftp use, adding a similar env var Kconfig option was easy but
may be wrong path?
I don't mind the addition but I'm wondering if it's not a band-aid patch
for something else? Maybe lwip missing setting the BOOTP server from a
DHCP lease for example?
Possible, setting tftp from dhcp also seem to be missing from legacy
stack, if I am not mistaken. I do think the separation of tftpserverip
and serverip for lwIP stack at least is a step in right direction, I am
new to network booting from U-Boot so what do I know :-)
I'm not sure the point of lwip is to keep all the quirks from the legacy
stack, but it doesn't hurt to bring this up :)
Cheers,
Quentin
