lwip tftp not working on imx8mm

[Tim Harvey]

On Mon, May 26, 2025 at 6:25 AM Peter Robinson <pbrobinson at gmail.com> wrote:
>
> Hi Tim,
>
> > I've enabled LWIP on imx8mm_venice to see how it's doing and while
> > dhcp/dns/ping/wget appear to work great, tftp is broken.
> >
> > Enabling LWIP_DEBUG shows the following:
> > ip4_input: packet accepted on interface et
> > IP packet dropped since it was fragmented (0x2000) (while IP_REASSEMBLY == 0).
> >
> > I tried enabling IP_REASSEMBLY in lwip but that seems to change the issue to:
> > ip4_input: packet accepted on interface et
> > ip4_input:
> > IP header:
> > +-------------------------------+
> > | 4 | 5 |  0xc0 |       108     | (v, hl, tos, len)
> > +-------------------------------+
> > |    10568      |000|       0   | (id, flags, offset)
> > +-------------------------------+
> > |   64  |    1  |    0xe25b     | (ttl, proto, chksum)
> > +-------------------------------+
> > |  172  |   24  |    0  |    2  | (src)
> > +-------------------------------+
> > |  172  |   24  |   21  |  251  | (dest)
> > +-------------------------------+
> > ip4_input: p->len 108 p->tot_len 108
> > Unsupported transport protocol 1
> >
> > Any ideas what the issue is here?
>
> You reported the same issue some time ago [1] and while I could fine
> the original thread in my inbox, I thought we had got to the bottom of
> the issue and it had been fixed I couldn't find a follow up thread.
> Maybe Fabio can remember as I seem to recall he was the one that got
> to the bottom of the issue.
>
> Peter
>
> [1] https://lists.denx.de/pipermail/u-boot/2023-November/538832.html

Hi Peter,

At that time (before lwip was merged) none of the network apps worked
on imx fec and it was found that the root cause was that LwIP uses
malloc() to allocate the outgoing packets and didn't enforce any
alignment. This was later resolved. At one time lwip
dhcp/ping/tftp/wget worked fine for me on imx fec but its very likely
at the time I may have been using a default or smaller
CONFIG_TFTP_BLOCKSIZE.

Best Regards,

Tim