[Linuxptp-users] bad message due to padding of FOLLOW_UP and DELAY_REQ

[Peter B. <pe...@be...>]

Hi,

I have a setup with TI processor using the cpsw driver from Linux 
mainline, kernel version 5.4. I'm using IEEE 802.3 network transport and 
sending PTP frames on Ethernet. When sending SYNC, FOLLOW_UP and 
DELAY_REQ that has a length of 58 bytes they get padded up to 64 bytes. 
When receiving FOLLOW_UP and DELAY_REQ in linuxptp they are dropped with 
message "bad message" because the stack treats the padding as a TLV 
entry (suffix_post_recv in msg.c returns 4) and the pdulen and 
messageLength mismatch.

IEEE 802.3 minimum PDU size is 64 bytes. PTP messages SYNC, FOLLOW_UP 
and DELAY_REQ is smaller than that, 58 bytes. Are there any spec telling 
how to send PTP messages smaller than 64 bytes on Ethernet?

On the other side in my setup I have a PC with e1000e driver. On that 
side when sending SYNC, FOLLOW_UP and DELAY_REQ over Ethernet the PDUs 
are padded to 60 bytes. Also tested a NXP processor (i.Mx8mp) and that 
one also padded to 60 bytes. A slightly different approach that is 
working with linuxptp. Is my issue with the TI processor a driver issue 
with the cpsw driver in Linux?

Thanks,
/Peter