[openwrt/openwrt] base-files: ipcalc.sh: fail when network is too small

[LEDE Commits]

ansuel pushed a commit to openwrt/openwrt.git, branch master:
https://git.openwrt.org/a40a96e54b0d047d14d99bb715ee2dd94458acb6

commit a40a96e54b0d047d14d99bb715ee2dd94458acb6
Author: Leon M. George <leon at georgemail.eu>
AuthorDate: Fri May 6 00:02:52 2022 +0200

    base-files: ipcalc.sh: fail when network is too small
    
    It's possible to move range boundaries in a way that the start address
    lies behind the end address.
    Detect this condition and exit with an error message.
    
    Signed-off-by: Leon M. George <leon at georgemail.eu>
---
 package/base-files/files/bin/ipcalc.sh | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/package/base-files/files/bin/ipcalc.sh b/package/base-files/files/bin/ipcalc.sh
index 66d37952de..b21b6e28dc 100755
--- a/package/base-files/files/bin/ipcalc.sh
+++ b/package/base-files/files/bin/ipcalc.sh
@@ -44,13 +44,14 @@ BEGIN {
 	}
 
 	network=and(ipaddr,netmask)
+	prefix=32-bitcount(compl32(netmask))
 	broadcast=or(network,compl32(netmask))
 
 	print "IP="int2ip(ipaddr)
 	print "NETMASK="int2ip(netmask)
 	print "BROADCAST="int2ip(broadcast)
 	print "NETWORK="int2ip(network)
-	print "PREFIX="32-bitcount(compl32(netmask))
+	print "PREFIX="prefix
 
 	# range calculations:
 	# ipcalc <ip> <netmask> <start> <num>
@@ -68,6 +69,11 @@ BEGIN {
 	if (end>limit) end=limit
 	if (end==ipaddr) end=ipaddr-1
 
+	if (start>end) {
+		print "network ("int2ip(network)"/"prefix") too small" > "/dev/stderr"
+		exit(1)
+	}
+
 	if (ipaddr > start && ipaddr < end) {
 		print "ipaddr inside range" > "/dev/stderr"
 		exit(1)