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Bug#618920: debootstrap: needs more robust download error handling



package: debootstrap
version: 1.0.28
severity: important
tags: patch

debootstrap's current download error handling isn't very robust.  It
declares success just for the presence of a downloaded file, which may
be a partial download, or one for which the checksum doesn't match.
Eventually those conditions will lead to unhandled failures elsewhere
within debootstrap.

This can make d-i very rocky on certain mirrors since one bad package
download ultimately lead to a complete failure of the debootstrap
process, and thus a failed install.  An expert can recover from this,
but an average user will get rather frustrated (especially since the
dialogs for debootstrap errors are rather confusing).  

It may also be useful to expand a bit on these d-i debootstrap error
messages: when an error happens, the right answer that the user wants is
to hit 'go back' twice in a row to start the debootstrap all over again,
but the dialogs are confusing, and 'continue' seems to be the obvious
choice, but that will lead to the broken debootstrap continuing to
completion with various brokenness. Anyway, that maybe should be
submitted as another bug.

So, back to the original issue, I've created a patch that will retry
downloads whenever anything in the "get" routine fails, which I
believe is much more robust than the current situation.  Please see
attached patch.

Best wishes,
Mike
--- newhd/source/debootstrap-1.0.28/functions	2011-02-21 19:25:08.000000000 -0500
+++ /usr/share/debootstrap/functions	2011-03-19 10:58:57.000000000 -0400
@@ -1,3 +1,5 @@
+MAXATTEMPTS="10"
+
 ############################################################### smallutils
 
 smallyes() {
@@ -241,6 +243,13 @@
 }
 
 get () {
+	for iters in $(seq 1 $MAXATTEMPTS); do
+		if single_get "$@"; then break; fi
+		warning RETRYING "Retrying failed download."
+	done
+}
+
+single_get () {
 	# args: from dest 'nocache'
 	# args: from dest [checksum size] [alt {checksum size type}]
 	local displayname
@@ -331,13 +340,6 @@
 		# http/ftp mirror
 		if wgetprogress -O "$dest" "$from"; then
 			return 0
-		elif [ -s "$dest" ]; then
-			local iters=0
-			while [ "$iters" -lt 3 ]; do
-				warning RETRYING "Retrying failed download of %s" "$from"
-				if wgetprogress -c -O "$dest" "$from"; then break; fi
-				iters="$(($iters + 1))"
-			done
 		else
 			rm -f "$dest"
 			return 1
@@ -346,13 +348,6 @@
 		# http/ftp mirror
 		if wgetprogress $CHECKCERTIF $CERTIFICATE $PRIVATEKEY -O "$dest" "$from"; then
 			return 0
-		elif [ -s "$dest" ]; then
-			local iters=0
-			while [ "$iters" -lt 3 ]; do
-				warning RETRYING "Retrying failed download of %s" "$from"
-				if wgetprogress $CHECKCERTIF $CERTIFICATE $PRIVATEKEY -c -O "$dest" "$from"; then break; fi
-				iters="$(($iters + 1))"
-			done
 		else
 			rm -f "$dest"
 			return 1

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