On 25. 04. 24, 20:01, Dianne Skoll wrote:
Hi,
I have (somewhat) narrowed down when the kernel bug appeared by installing
Debian 10, 11 and 12 in KVM virtual machines.
The bug is NOT present in Debian 10, kernel version 4.19.67.
The bug IS present in Debian 11, kernel version 5.10.209
The bug IS present in Debian 12, kernel version 6.1.85
So I guess it was introduced sometime between 4.19.67 and 5.10.209. I'll
take a look to see if I can do a git bisect.
[To recap, the bug is that the N_HDLC line discipline sometimes
coalesces two write()s so you get them both back in a single read()
which is contrary to what it's supposed to do... preserve the write
boundaries as individual frames.]
I believe it is a correct behavior after all. As you use pty for
testing, the "framing" is lost during the pty-to-pty pass on the flush
to ldisc path (receive_buf()).
[ T1056] n_hdlc_send_frames: ptm2 sending frame 0000000081e69927, count=6
[ T1056] frame 0000000081e69927 completed
[ T1056] n_hdlc_send_frames: ptm2 sending frame 00000000576db119, count=5
[ T1056] frame 00000000576db119 completed
[ T123] n_hdlc_tty_receive: pts2 buf=00000000a616a2be count=11
[ T1056] n_hdlc_tty_read: pts2 rbuf=00000000a616a2be
kbuf=000000004abc3c35 offset=0 ret=11
thanks,
--
js
suse labs
