[git commit] examples: make udhcpc script handle /32 netmasks

Denys Vlasenko vda.linux at googlemail.com
Wed Apr 5 22:53:43 UTC 2017


commit: https://git.busybox.net/busybox/commit/?id=9c192e7f946a351c811e2278bbf56b4dc6a4b663
branch: https://git.busybox.net/busybox/commit/?id=refs/heads/master

Signed-off-by: Denys Vlasenko <vda.linux at googlemail.com>
---
 examples/udhcp/sample.bound  |  9 ++++++++-
 examples/udhcp/sample.renew  | 11 +++++++++--
 examples/udhcp/simple.script | 10 ++++++++--
 3 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/examples/udhcp/sample.bound b/examples/udhcp/sample.bound
index 7c9d857..efd98cf 100755
--- a/examples/udhcp/sample.bound
+++ b/examples/udhcp/sample.bound
@@ -18,11 +18,18 @@ then
 	metric=0
 	for i in $router
 	do
+		if [ "$subnet" = "255.255.255.255" ]; then
+			# special case for /32 subnets:
+			# /32 instructs kernel to always use routing for all outgoing packets
+			# (they can never be sent to local subnet - there is no local subnet for /32).
+			# Used in datacenters, avoids the need for private ip-addresses between two hops.
+			/sbin/ip route add $i dev $interface
+		fi
 		/sbin/route add default gw $i dev $interface metric $((metric++))
 	done
 fi
 
-# Only replace resolv.conf is we have at least one DNS server
+# Only replace resolv.conf if we have at least one DNS server
 if [ -n "$dns" ]
 then
 	echo -n > $RESOLV_CONF
diff --git a/examples/udhcp/sample.renew b/examples/udhcp/sample.renew
index 4dce848..efd98cf 100755
--- a/examples/udhcp/sample.renew
+++ b/examples/udhcp/sample.renew
@@ -1,5 +1,5 @@
 #!/bin/sh
-# Sample udhcpc bound script
+# Sample udhcpc renew script
 
 RESOLV_CONF="/etc/udhcpc/resolv.conf"
 
@@ -18,11 +18,18 @@ then
 	metric=0
 	for i in $router
 	do
+		if [ "$subnet" = "255.255.255.255" ]; then
+			# special case for /32 subnets:
+			# /32 instructs kernel to always use routing for all outgoing packets
+			# (they can never be sent to local subnet - there is no local subnet for /32).
+			# Used in datacenters, avoids the need for private ip-addresses between two hops.
+			/sbin/ip route add $i dev $interface
+		fi
 		/sbin/route add default gw $i dev $interface metric $((metric++))
 	done
 fi
 
-# Only replace resolv.conf is we have at least one DNS server
+# Only replace resolv.conf if we have at least one DNS server
 if [ -n "$dns" ]
 then
 	echo -n > $RESOLV_CONF
diff --git a/examples/udhcp/simple.script b/examples/udhcp/simple.script
index 2a917eb..e4c1f2d 100755
--- a/examples/udhcp/simple.script
+++ b/examples/udhcp/simple.script
@@ -29,8 +29,14 @@ case "$1" in
 			metric=0
 			for i in $router ; do
 				echo "Adding router $i"
-				route add default gw $i dev $interface metric $metric
-				: $(( metric += 1 ))
+				if [ "$subnet" = "255.255.255.255" ]; then
+	# special case for /32 subnets:
+	# /32 instructs kernel to always use routing for all outgoing packets
+	# (they can never be sent to local subnet - there is no local subnet for /32).
+	# Used in datacenters, avoids the need for private ip-addresses between two hops.
+					ip route add $i dev $interface
+				fi
+				route add default gw $i dev $interface metric $((metric++))
 			done
 		fi
 


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