On Wed, Mar 28, 2012 at 4:05 PM, Maxim Wexler maxim.wex...@gmail.com wrote:
with ppp connections you are not using a dhcp client, pppd gets the
nameserver ip addressess as part of the connection negotiation (if
peerdns is set) and the aforemetioned script in
/etc/ppp/ip-up.d/40-dns.sh writes those to /etc/resolv.conf
This is at the top of /etc/resolv.conf
# Generated by dhcpcd
# /etc/resolv.conf.head can replace this line
# /etc/resolv.conf.tail can replace this line
But according to /var/log/messages:
Mar 28 13:24:01 lumby pppd[16825]: primary DNS address 75.153.176.1
Mar 28 13:24:01 lumby pppd[16825]: secondary DNS address 75.153.176.9
But whatever is in resolv.conf is overwritten with blanks AFTER I
connect. Which creates this odd situation where I can ping numbers,
ie, 8.8.8.8 but not com, net, org etc.
Once I connect I have to echo the DNS addresses into resolv.conf
before I can reach anything.
Also, I notice whenever I set up a route to my router those numbers
get wiped. Is that the default behavio(u)r?. NB, I have nothing in the
way of services other than ppp configured at all. Maybe later after I
sort it all out I'll rig up something automatic.
Thanks for everybody's hlp
MW
ps: according to /etc/ppp/ip-up.d/40-dns.sh:
---
#!/bin/sh
# Handle resolv.conf generation when usepeerdns pppd option is being used.
# Used parameters and environment variables:
# $1 - interface name (e.g. ppp0)
# $USEPEERDNS - set if user specified usepeerdns
# $DNS1 and $DNS2 - DNS servers reported by peer
if [ $USEPEERDNS ]; then
if [ -x /sbin/resolvconf ]; then
{
echo # Generated by ppp for $1
[ -n $DNS1 ] echo nameserver $DNS1
[ -n $DNS2 ] echo nameserver $DNS2
} | /sbin/resolvconf -a $1
else
# add the server supplied DNS entries to /etc/resolv.conf
# (taken from debian's usepeerdns)
# follow any symlink to find the real file
REALRESOLVCONF=$(readlink -f /etc/resolv.conf)
if [ $REALRESOLVCONF != /etc/ppp/resolv.conf ]; then
# merge the new nameservers with the other options
from the old configuration
{
grep --invert-match '^nameserver[[:space:]]'
$REALRESOLVCONF
cat /etc/ppp/resolv.conf
} $REALRESOLVCONF.tmp
# backup the old configuration and install the new one
cp -dpP $REALRESOLVCONF $REALRESOLVCONF.pppd-backup
mv $REALRESOLVCONF.tmp $REALRESOLVCONF
# correct permissions
chmod 0644 /etc/resolv.conf
chown root:root /etc/resolv.conf
fi
fi
fi
the software is aware of two resolv.confs, one under /etc/, one under
/etc/ppp. /etc/ppp/resolv.conf is correctly filled in, but the other
is wiped. Can anyone see why?
MW
If I recall, this was my guess as the real problem you were running
into. As for what's making the last change to /etc/resolv.conf...
aside from kernel-level auditing, there's nothing I'm aware of that
can tell you. Since /etc/ppp/resolv.conf is correct but
/etc/resolv.conf isn't, one of three things is happening:
a) 40-dns.sh is running, making the changes it needs to, and they're
being promptly overwritten by something else... unlikely and
excessively hard to diagnose,
b) 40-dns.sh is running but isn't actually updating /etc/resolv.conf
properly... it looks fine, matches the default I have here (which
works on my pppoe setup at least), but could happen if one of the
assumptions it makes is wrong (or if, say, if [ $USEPEERDNS ]; is
coming up false), or...
c) 40-dns.sh is not even running, meaning /etc/resolv.conf never gets
updated by pppd... this would have been my first guess, except for the
fact that /etc/ppp/ip-up just outright sources all *.sh in
/etc/ppp/ip-up.d/ so... shouldn't be that (and I saved myself from
looking a bit silly, checking that beforehand).
The first step to tracking it down would probably be stepping through
that script and comparing it to your situation. Does
/etc/resolv.conf.pppd-backup exist? If so, it *is* at least making
changes to the original. I recall usepeerdns is set, so is
/sbin/resolvconf an existing, executable, file? If not, and since they
differ, I suspect it's failing somewhere in merging them. You might
add some echo calls writing out to a file in /tmp to 40-dns.sh so you
can track what, if anything, it does (and what values it's using in
the process).
