Re: less prints superfluous characters with --no-init

[Reuben mac Saoidhea]

you really ought to use `type', not `which',
in case it is a shell function etc.

Re: less prints superfluous characters with --no-init

[Richard Ulmer]

"Richard Ulmer"  wrote:
> Hi all,
> I find this behaviour unexpected:
> 
> $ printf foo | less --no-init | xxd
> : 666f 6f1b 5b41 1b5b 4b   foo.[A.[K
> 
> less prints ANSI escape codes for 'cursor up' and 'erase in line' at the
> end of my message. Interestingly, when doing the same within tmux, the
> result is different:
> 
> $ printf foo | less --no-init | xxd
> : 666f 6f1b 4d1b 5b4b  foo.M.[K
> 
> Is this intended behaviour? If so, is there any flag to disable this?
> 
> Greetings,
> Richard

Another user mentioned, that he couldn't reproduce the problem, which
made me check 'which less'. I found that I wasn't using /usr/bin/less,
but a script around it, which I forgot about. The script caused the
problem.

Sorry for the unnecessary mail.

Richard

Re: less prints superfluous characters with --no-init

[Christian Weisgerber]

"Richard Ulmer":

> I find this behaviour unexpected:
> 
> $ printf foo | less --no-init | xxd
> : 666f 6f1b 5b41 1b5b 4b   foo.[A.[K
> 
> less prints ANSI escape codes for 'cursor up' and 'erase in line' at the
> end of my message.

I cannot reproduce this.

$ printf foo | less --no-init | hexdump -C
  66 6f 6f  |foo|
0003

-- 
Christian "naddy" Weisgerber  na...@mips.inka.de

Troubleshooting a spinning fork(2)

[Joel Knight]

Hi.

I'm looking for guidance on how to troubleshoot a piece of software
which is spinning after calling fork(2).

I'm working on making the s2n-tls[1] library build on OpenBSD[2]. One
of the unit tests[3] does this:

1. The test framework forks the test (s2n_fork_generation_number_test)
2. The test process forks a child and calls waitpid()
3. The child creates 2 threads (pthread_create()), waits for the
threads to finish (pthread_join()), forks a grandchild, and calls
waitpid()
4. The grandchild is supposed to create 2 threads, wait for the
threads, fork a great grandchild, and call waitpid()
5. The great grandchild is supposed to create 2 threads, wait for the
threads, and exit
6. The processes exit in reverse order, and the test is finished.

During #3, the great grandchild never starts to execute and the
grandchild doesn't return from fork(). The test fails after a timeout.

ktrace[4] shows the grandchild (pid 91188) getting to the point where
it calls fork() (line 23862), but then it spins on sched_yield():

  23860  91188 s2n_fork_generation_num CALL  write(2,0x7f7d4f80,0x33)
  23861  69848 ctestCALL
kevent(4,0x7f7e3d40,0,0x7f7e3d40,1024,0x7f7ebd48)
  23862  91188 s2n_fork_generation_num GIO   fd 2 wrote 51 bytes
  23863"s2n_unit_test_fork: calling fork(); fork_level = 1
  23864"
  23865  69848 ctestSTRU  struct timespec { 9.91400 }
  23866  91188 s2n_fork_generation_num RET   write 51/0x33
  23867  69848 ctestSTRU  struct kevent { ident=12,
filter=EVFILT_READ, flags=0x1, fflags=0<>, data=51, udata=0x0
}
  23868  91188 s2n_fork_generation_num CALL  sched_yield()
  23869  69848 ctestRET   kevent 1
  23870  69848 ctestCALL  read(12,0x6eb25d1f000,0x1)
  23871  91188 s2n_fork_generation_num CALL  __threxit(0xc296ca59e30)
  23872  69848 ctestGIO   fd 12 read 51 bytes
  23873"s2n_unit_test_fork: calling fork(); fork_level = 1
  23874"
  23875  69848 ctestRET   read 51/0x33
  23876  91188 s2n_fork_generation_num CALL  __threxit(0xc296ca59230)
  23877  91188 s2n_fork_generation_num RET   sched_yield 0
  23878  91188 s2n_fork_generation_num CALL  sched_yield()
  23879  91188 s2n_fork_generation_num RET   sched_yield 0
[...]

btrace also doesn't show that the grandchild enters fork()

1668777953577037810 ctest (69848/127562) syscall:fork:entry (0)
1668777953577858328 ctest (69848/127562) syscall:fork:return (87140)
 # test process is pid 87140
1668777953577876672 ctest (87140/115691) syscall:fork:return (0)
1668777953586430021 s2n_fork_generation_num (87140/115691)
syscall:fork:entry (0)
1668777953586746921 s2n_fork_generation_num (87140/115691)
syscall:fork:return (62504)# child pid 62504
1668777953586831091 s2n_fork_generation_num (62504/463506)
syscall:fork:return (0)
1668777953587202790 s2n_fork_generation_num (87140/115691)
syscall:wait4:entry (62504)
1668777953658413274 s2n_fork_generation_num (62504/463506)
syscall:fork:entry (0)
1668777953658911264 s2n_fork_generation_num (62504/463506)
syscall:fork:return (91188)# grandchild pid 91188
1668777953658967606 s2n_fork_generation_num (91188/186182)
syscall:fork:return (0)
1668777953660934467 s2n_fork_generation_num (62504/463506)
syscall:wait4:entry (91188)
# no entry showing 91188 entering fork()

If I comment out the part of the test which creates the threads, the
test completes successfully. So some sort of locking/contention issue
in the threading code?

[1] https://github.com/aws/s2n-tls
[2] https://github.com/knightjoel/s2n-tls/tree/fix/build-on-openbsd
[3] 
https://github.com/knightjoel/s2n-tls/blob/fix/build-on-openbsd/tests/unit/s2n_fork_generation_number_test.c
[4] https://www.packetmischief.ca/files/fork_test2.txt.gz



.joel

less prints superfluous characters with --no-init

[Richard Ulmer]

Hi all,
I find this behaviour unexpected:

$ printf foo | less --no-init | xxd
: 666f 6f1b 5b41 1b5b 4b   foo.[A.[K

less prints ANSI escape codes for 'cursor up' and 'erase in line' at the
end of my message. Interestingly, when doing the same within tmux, the
result is different:

$ printf foo | less --no-init | xxd
: 666f 6f1b 4d1b 5b4b  foo.M.[K

Is this intended behaviour? If so, is there any flag to disable this?

Greetings,
Richard

IPV6 ND and non-local prefixes

[Martijn van Duren]

Hello misc,

I'm starting to play around with IPv6 and rad(8). I've noticed that I
can broadcast arbitrary prefixes via "no auto prefix" combined with
"prefix ". These get assigned properly via slaac and can be
used to forward packets, but if I don't assign an IP in the prefix on
the broadcasting interface the return packets won't get delivered,
because that interface doesn't participate in the ND process for that
prefix.

>From what I gathered RA (and thus the default gateway on the slaac nodes
using them) is always the link-local address. If I don't have a need for
a public IPv6 address on my router:
1) Is there a requirement I overlooked to have the public IP on the
   interface?
2) If there is no such requirement, is there a requirement to not do ND
   for not locally assigned prefixes?
3) If there is no such requirement, did I miss a switch to enable ND
   for a non-local assigned prefix? Or is there a reason to not have
   one?

martijn@