Re: VNET jail and dhclient
Oleg Ginzburg
https://lists.freebsd.org/pipermail/freebsd-jail/2017-October/003444.html
comment: it looks like it's a regression in FreeBSD 12/Current,
because in FreeBSD 11 dhclient works fine:
--
jail1:/root@[15:16] # dhclient eth0
DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 3
DHCPOFFER from 192.168.10.1
DHCPREQUEST on eth0 to 255.255.255.255 port 67
DHCPACK from 192.168.10.1
bound to 192.168.8.8 -- renewal in 900 seconds.
jail1:/root@[15:16] # uname -a
FreeBSD jail1.my.domain 11.0-RELEASE-p12 FreeBSD 11.0-RELEASE-p12 #0
r324489: Tue Oct 10 14:57:58 MSK 2017
ro...@f10.my.domain:/usr/obj/usr/jails/src/src_11.0/src/sys/VIMAGE
amd64
--
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Kristof Provost
> What is your FreeBSD version? This problem reproduced on FreeBSD 12
> only.
> /var/empty is exist and trivial test:
>
I’m running r324317 on CURRENT, yes.
What arguments are you calling dhclient with?
Clearly there’s a difference between what you’re doing and what
I’m doing.
> I'm not sure if this fd leak (due to pidfile_remove at the end of
> dhclient), nevertheless closing pid fd in my jail/FreeBSD12 before
> chroot
> solve dhclient issue.
I would not expect an open file descriptor to be a problem, unless
perhaps you’ve got an open directory and
kern.chroot_allow_open_directories is unset.
Regards,
Kristof
Oleg Ginzburg
On Tue, Oct 10, 2017 at 8:24 PM, Kristof Provost <kri...@sigsegv.be> wrote:
> On 9 Oct 2017, at 9:25, Goran Mekić wrote:
> > Hello,
> >
> > TLDR: I can setup static IP or use dhcpcd to get address, but not
> dhclient.
> >
> > Let me elaborate. I run 12-CURRENT on my laptop and use CBSD as jail
> manager (I don't think it matters).
> >
> What version of CURRENT are you using?
>
> > # dhclient eth0
> > chroot
> > exiting.
> >
> > This is what I found with truss: https://gist.github.com/anonymous/
> 36a4e2bf1760198971934ff609a7d0de#file-gistfile1-txt-L227-L228. Selected
> lines are what I think is the problem. Offending line in the code is
> probably https://svnweb.freebsd.org/base/head/sbin/dhclient/
> dhclient.c?revision=317915&view=markup#l507. With that asumption, Oleg,
> CBSD author, noticed that the following "patch" works:
> >
> Is there any chance you don’t have /var/empty in your jail?
>
> I do this to create a simple vnet jail:
> sudo jail -c name=alcatraz persist vnet vnet.interface=epair0b
> (in the jail) dhclient epair0b
>
> And see:
> …
> fsync(0x9) = 0 (0x0)
> close(8) = 0 (0x0)
> socket(PF_ROUTE,SOCK_RAW,0) = 8 (0x8)
> shutdown(8,SHUT_WR) = 0 (0x0)
> cap_rights_limit(8,{ CAP_READ,CAP_EVENT }) = 0 (0x0)
> chroot("/var/empty") = 0 (0x0)
> chdir("/") = 0 (0x0)
> setgroups(0x1,0x800e2c1e4) = 0 (0x0)
> …
>
> I also see the DCHP request packets on the other end of the epair
> interface.
>
> Regards,
> Kristof
>
What is your FreeBSD version? This problem reproduced on FreeBSD 12 only.
/var/empty is exist and trivial test:
#include <stdio.h>
#include <stdlib.h>
int main()
{
printf("%d\n",chroot("/var/empty");
}
works successfully.
I think I found something, but I do not understand why this is only
observed in jail and with commit change this.
The problem about which the Goran wrote can be fixed with:
# diff -ruN dhclient.c-orig dhclient.c
--- dhclient.c-orig 2017-10-10 23:51:52.451361000 +0000
+++ dhclient.c 2017-10-10 23:54:55.803404000 +0000
@@ -479,6 +479,7 @@
fork_privchld(pipe_fd[0], pipe_fd[1]);
+ pidfile_close(pidfile);
close(ifi->ufdesc);
ifi->ufdesc = -1;
close(ifi->wfdesc);
From pidfile(3) man page:
The pidfile_close() function closes a pidfile. It should be used after
daemon fork()s to start a child process.
chroot(2) in dhclient return NOPERM (via global errno). it seems to be
related to open descriptor outside the chroot.
I'm not sure if this fd leak (due to pidfile_remove at the end of
dhclient), nevertheless closing pid fd in my jail/FreeBSD12 before chroot
solve dhclient issue.
Goran Mekić
> I think I found something, but I do not understand why this is only
> observed in jail and with commit change this.
> The problem about which the Goran wrote can be fixed with:
>
> # diff -ruN dhclient.c-orig dhclient.c
> --- dhclient.c-orig 2017-10-10 23:51:52.451361000 +0000
> +++ dhclient.c 2017-10-10 23:54:55.803404000 +0000
> @@ -479,6 +479,7 @@
>
> fork_privchld(pipe_fd[0], pipe_fd[1]);
>
> + pidfile_close(pidfile);
> close(ifi->ufdesc);
> ifi->ufdesc = -1;
> close(ifi->wfdesc);
>
>
>
>
> From pidfile(3) man page:
>
> The pidfile_close() function closes a pidfile. It should be used after
> daemon fork()s to start a child process.
>
>
> chroot(2) in dhclient return NOPERM (via global errno). it seems to be
> related to open descriptor outside the chroot.
>
> I'm not sure if this fd leak (due to pidfile_remove at the end of
> dhclient), nevertheless closing pid fd in my jail/FreeBSD12 before chroot
> solve dhclient issue.
KOT MATPOCKuH
I'm got same problem...
Did someone open an PR for this issue?
--
MATPOCKuH
Kristof Provost
> Hello, all!
>
> I'm got same problem...
>
What’s the output of `sysctl kern.chroot_allow_open_directories`?
Regards,
Kristof
Goran Mekić
> Hello, all!
>
> I'm got same problem...
> Did someone open an PR for this issue?
KOT MATPOCKuH
jail# dhclient epair71b.71
chroot
exiting.
jail# echo $?
1
I'm running 12.0-CURRENT r325051 and:
# sysctl kern.chroot_allow_open_directories
kern.chroot_allow_open_directories: 1
And I found some another workaround:
# dhclient -p /var/empty/pid epair71b.71
Cannot open or create pidfile: Operation not permitted
DHCPDISCOVER on epair71b.71 to 255.255.255.255 port 67 interval 6
2017-11-16 16:07 GMT+03:00 Kristof Provost <kri...@sigsegv.be>:
> On 16 Nov 2017, at 14:04, KOT MATPOCKuH wrote:
>
> Hello, all!
>
> I'm got same problem...
>
> Can you show how you call dhclient? What FreeBSD version are you running?
>
> What’s the output of sysctl kern.chroot_allow_open_directories?
>
> Regards,
> Kristof
>
--
MATPOCKuH