Syslinux - Dec 2025 - tftp-hpa fails to netboot raspberry pi 4

Hello,

the current Version of tftp-hpa 5.3+20251116-1 in Debian testing fails
to netboot a raspberry pi 4. It times out with a last message of
firmware not found after ~3 minutes.

tftp-hpa version 5.2+20240610-3 works fine.

I have pcap file of both a working and a non-working version
(~25kB) that I can share.

I'd also be happy to do further testing if you do not have a
raspi to reproduce.

Best regards,

Joerg

On Sun, Dec 07, 2025 at 12:09:57AM +0100, Joerg Dorchain via Syslinux
wrote:
> 
> I'd also be happy to do further testing if you do not have a
> raspi to reproduce.
Well, I did meanwhile.

After staring at pcaps for a while and comparing bits, I ended
up at commit 340d4b66512ae57a44e28bdcf15b1c051c3d35e0 Fix remap,
add remap test mode that introduced this regression.

From looking at it, I would guess that it affects all situations
where a tftp client requests a non-existant file in the normal
course of requests, i.e. it not only affects raspberries.

Please consider including the attached patch.

Bye,

Joerg



diff --git a/tftpd/tftpd.c b/tftpd/tftpd.c
index e2a52ad..b8ba8a4 100644
--- a/tftpd/tftpd.c
+++ b/tftpd/tftpd.c
@@ -1910,6 +1910,7 @@ static void nak(int error, const char *msg)
         msg = "Request failed";
 
     tp = (struct tftphdr *)buf;
+    tp->th_opcode = htons((u_short) ERROR);
     tp->th_code = htons((u_short) error);
 
     length = strlen(msg) + 1;
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