[PATCH] examples/udhcp/simple.script: fix IPv6 support when using udhcpc

Quentin Schulz quentin.schulz at streamunlimited.com
Tue Jun 16 08:06:27 UTC 2020

From: Stefan Agner <stefan.agner at toradex.com>

The udhcpc script calls ip addr flush .. which flushes addresses
of any address family, including IPv6. However, busybox udhcpc is
IPv4 only and should not influence IPv6 addressing. Hence use ip
addr flush with family constraint.

The script particularly broke IPv6 SLAAC: Typically when udhcpc
calls the script the kernel already assigned the IPv6 link-local
address. The flush removes the link-local IPv6 address again and
prohibits proper IPv6 operation such as SLAAC since neighbor
discovery protocol relies on IPv6 link-local addressing.

Signed-off-by: Stefan Agner <stefan.agner at toradex.com>
[Taken from https://git.openembedded.org/openembedded-core/commit/meta/recipes-core/busybox/files/simple.script?id=b77541dbb2f442e51842f9d24c8745a6df2d1478]
Signed-off-by: Quentin Schulz <quentin.schulz at streamunlimited.com>
 examples/udhcp/simple.script | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/examples/udhcp/simple.script b/examples/udhcp/simple.script
index 6658fbeef..f079ec8b8 100755
--- a/examples/udhcp/simple.script
+++ b/examples/udhcp/simple.script
@@ -18,7 +18,7 @@ case "$1" in
 		echo "Clearing IP addresses on $interface, upping it"
 		if command -v ip >/dev/null; then
-			ip addr flush dev $interface
+			ip -4 addr flush dev $interface
 			ip link set dev $interface up
 			ifconfig $interface

More information about the busybox mailing list