From 00bf4eda2ad056d273af668462536d26c86afe3e Mon Sep 17 00:00:00 2001
From: Simon Rettberg
Date: Tue, 3 Dec 2024 15:07:47 +0100
Subject: [download] Refine download_retry timeout logic to stay in bounds

The old implementation would overshoot the set --slx-time by up to 15
seconds. Fix this.
---
 modules/download.inc | 22 ++++++++++++++--------
 1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/modules/download.inc b/modules/download.inc
index 8c717eb..46f4f14 100644
--- a/modules/download.inc
+++ b/modules/download.inc
@@ -1,25 +1,31 @@
 #!/bin/ash
 
 download() {
-	curl --location --max-redirs 5 --max-time 15 --connect-timeout 2 "$@"
+	curl --location --max-redirs 5 --max-time 15 --connect-timeout 3 "$@"
 }
 
 download_retry() {
-	local delay max_time start end ret
-	max_time=8
+	local delay total_time start end ret timeout
+	total_time=10
 	ret=100
 	if [ "$1" = "--slx-time" ]; then
-		max_time="$2"
+		total_time="$2"
 		shift 2
 	fi
+	if ! [ "$total_time" -gt 0 ]; then
+		echo "download_retry: passed timeout is not > 0" >&2
+		return 1
+	fi
 	start="$( date +%s )"
-	for delay in 1 2 2 3 3 3 4 4 4 5 5 5 5 5 5 5 5 5 ""; do
-		download "$@"
+	end="$start"
+	for delay in 0 1 1 2 2 3 3 3 4 4 4 5 5 5 5 5 5 5 5 5; do
+		timeout=$(( total_time - delay - (end - start) ))
+		[ "$timeout" -gt 0 ] || break
+		sleep "$delay"
+		download --max-time "$timeout" "$@"
 		ret="$?"
 		[ "$ret" = 0 ] && return 0
 		end="$( date +%s )"
-		[ "$(( end - start ))" -ge "$max_time" ] && break
-		[ -n "$delay" ] && sleep "$delay"
 	done
 	return "$ret"
 }
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