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Add resolv_conf_mv=auto option #24

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Add resolv_conf_mv=auto option #24

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a4179ca
Add resolv_conf_mv=auto option
pemensik Jul 9, 2023
a8bb65b
Detect stat parameter on build time
pemensik Jul 10, 2023
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4 changes: 4 additions & 0 deletions Makefile
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Original file line number Diff line number Diff line change
Expand Up @@ -38,6 +38,7 @@ SED_RCDIR= -e 's:@RCDIR@:${RCDIR}:g'
SED_RESTARTCMD= -e 's:@RESTARTCMD@:${RESTARTCMD}:g'
SED_RCDIR= -e 's:@RCDIR@:${RCDIR}:g'
SED_STATUSARG= -e 's:@STATUSARG@:${STATUSARG}:g'
SED_STAT_FMT= -e 's:@STAT_FMT@:${STAT_FMT}:g'

DISTPREFIX?= ${PKG}-${VERSION}
DISTFILE?= ${DISTPREFIX}.tar.xz
Expand All @@ -46,6 +47,8 @@ DISTINFOMD= ${DISTINFO}.md
DISTSIGN= ${DISTFILE}.asc
SHA256?= sha256
PGP?= gpg
STAT_FMT?= stat -c


GITREF?= HEAD

Expand All @@ -57,6 +60,7 @@ all: ${TARGET}
${SED} ${SED_SBINDIR} ${SED_SYSCONFDIR} ${SED_LIBEXECDIR} \
${SED_VARDIR} \
${SED_RCDIR} ${SED_RESTARTCMD} ${SED_RCDIR} ${SED_STATUSARG} \
${SED_STAT_FMT} \
$< > $@

clean:
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6 changes: 6 additions & 0 deletions configure
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Expand Up @@ -95,6 +95,7 @@ linux*)
# cksum doesn't support -a and netpgp is rare
echo "CKSUM= sha256sum --tag" >>$CONFIG_MK
echo "PGP= gpg2" >>$CONFIG_MK
echo "STAT_FMT= stat -c" >>$CONFIG_MK
;;
esac

Expand All @@ -106,6 +107,10 @@ dragonfly*|freebsd*)
if [ -z "$STATUSARG" ]; then
STATUSARG="onestatus"
fi
echo "STAT_FMT= stat -f" >>$CONFIG_MK
;;
*bsd*)
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I think the whole stat check needs to be in it's own section.
I'm tempted to suggest that we assume BSD style by default and add an exception for Linux.

The only potential issue I think is kFreeBSD which may use the coreutils stat rather than the FreeBSD one.
Also some stat's just don't offer the functionality we need such as Plan9 or disabled as in the case for busybox.

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Those unusual cases should be able to handle by make STAT_FMT=. I am not sure how often is crossbuilding done for such systems. I think configure could test the output by actually checking stat -c %d . and that it does report a number. Not sure if such check would work on busybox systems. At least stat from alpine docker image and BusyBox v1.36.1 has -c %d support.

I expect Linux systems are dominant today. But if the BSD variant is likely to work on different systems, which may use openresolv, it would be okay. It should have own case "$OS" just for stat check, is that what you mean?

echo "STAT_FMT= stat -f" >>$CONFIG_MK
;;
esac

Expand Down Expand Up @@ -164,4 +169,5 @@ echo
echo " RESTARTCMD = $RESTARTCMD"
echo " RCDIR = $RCDIR"
echo " STATUSARG = $STATUSARG"
echo " STAT_FMT = $STAT_FMT"
echo
44 changes: 37 additions & 7 deletions libc.in
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Expand Up @@ -227,23 +227,53 @@ if $backup; then
fi
fi

# There are pros and cons for writing directly to resolv.conf
# instead of a temporary file and then moving it over.
# The default is to write to resolv.conf as it has the least
# issues and has been the long standing default behaviour.
case "${resolv_conf_mv:-NO}" in
[Yy][Ee][Ss]|[Tt][Rr][Uu][Ee]|[Oo][Nn]|1)
resolv_conf_mk_tmp()
{
# Protect against symlink attack, ensure new file does not exist
rm -f "$resolv_conf_tmp"
# Keep original file owner, group and mode
[ -r "$resolv_conf" ] && cp -p "$resolv_conf" "$resolv_conf_tmp"
}

resolv_conf_do_mv()
{
# Create our resolv.conf now
if (umask 022; printf %s "$newconf" >"$resolv_conf_tmp"); then
mv "$resolv_conf_tmp" "$resolv_conf"
fi
}

resolv_conf_do_print()
{
(umask 022; printf %s "$newconf" >"$resolv_conf")
}

# There are pros and cons for writing directly to resolv.conf
# instead of a temporary file and then moving it over.
# The default is to write to resolv.conf as it has the least
# issues and has been the long standing default behaviour.
case "${resolv_conf_mv:-NO}" in
[Yy][Ee][Ss]|[Tt][Rr][Uu][Ee]|[Oo][Nn]|1)
resolv_conf_mk_tmp
resolv_conf_do_mv
;;
# Do mv only if resolv_conf_tmp and resolv_conf are on
# the same filesystem. Use print method for bind-mounted file
[Aa][Uu][Tt][Oo])
if [ -r "$resolv_conf" ] && [ -n "@STAT_FMT@" ]; then
resolv_conf_mk_tmp
if [ "$(@STAT_FMT@ %d "$resolv_conf_tmp")" = "$(@STAT_FMT@ %d "$resolv_conf")" ]; then
resolv_conf_do_mv
else
rm -f "$resolv_conf_tmp"
resolv_conf_do_print
fi
else
resolv_conf_do_print
fi
;;
*)
(umask 022; printf %s "$newconf" >"$resolv_conf")
resolv_conf_do_print
;;
esac

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