[PATCH v5] net: tftp: Add client support for RFC 7440

[Ramon Fried]

On Sat, Jan 30, 2021 at 10:39 PM Suneel Garapati <suneelglinux at gmail.com> wrote:
>
> Hello Ramon,
>
> With TFTP window size as default 1 and enabling TFTPPUT config option
> results in tftpboot command failure.
>
> Attached the pcap files for with and without TFTPPUT enabled.
> Both captures are the same except that the TFTPPUT option enables ICMP handler
> and for the response from the server triggers a restart of netloop
> operation and eventually fails as below.
>
> > tftpboot 0x30000000 192.168.1.1:Image
> Waiting for RPM0 LMAC0 link status... 10G_R [10G]
> Using rvu_pf#0 device
> TFTP from server 192.168.1.1; our IP address is 192.168.1.16
> Filename 'Image'. Load address: 0x30000000
> Loading: ################################################## 15.8 MiB
> 787.1 KiB/s
> done
> TFTP server died; starting again
> >
>
> I see the code issue as below on net/tftp.c [v2020.10] –
>                 /*
>                  *      Acknowledge the block just received, which will prompt
>                  *      the remote for the next one.
>                  */
>                 if (tftp_cur_block == tftp_next_ack) {
>                         tftp_send();
>                         tftp_next_ack += tftp_windowsize;
>                 }
>
>                 if (len < tftp_block_size) {
>                         //if (tftp_windowsize > 1) [Hack in use for
> now to work around this issue]
>                         tftp_send();                      [ This
> causes extra ACK packet send with same block number and causes server
> to respond with ICMP error]
>                         tftp_complete();
>                 }
>
> I couldn’t try with tftp_windowsize > 1 as the test servers don’t support.
> I tried with all latest commits on net/tftp.c on top of v2020.10 and
> still see the issue.
>
> This change is introduced in
> commit cc6b87ecaa96325577a8fafabc0d5972b816bc6c
> Author: Ramon Fried <rfried.dev at gmail.com>
> Date:   Sat Jul 18 23:31:46 2020 +0300
>
>     net: tftp: Add client support for RFC 7440
>
>     Add support for RFC 7440: "TFTP Windowsize Option".
>
> Reverting this commit on v2020.10 also fixes the issue.
>
> I would like to know if this extra tftp_send is needed at all or only
> for window size > 1
>
> Regards,
> Suneel
Thanks for spotting this, I'll check it out.