dockerd-rootless: default MTU 65520 for slirp4netns

robmry · robmry · commit a6206f2da9b0 · 2025-10-10T10:13:50.000+01:00
When DOCKERD_ROOTLESS_ROOTLESSKIT_MTU is not set, and ...
- DOCKERD_ROOTLESS_ROOTLESSKIT_NET is not set and slirp4netns
  is selected, MTU defaults to 65520.
- DOCKERD_ROOTLESS_ROOTLESSKIT_NET=slirp4netns, MTU defaults
  to 1500.

Change the logic so that, however slirp4netns is selected, MTU
defaults to 65520.

Signed-off-by: Rob Murray &lt;rob.murray@docker.com&gt;
diff --git a/contrib/dockerd-rootless.sh b/contrib/dockerd-rootless.sh
@@ -112,9 +112,6 @@ if [ -z "$net" ]; then
 		# If --netns-type is present in --help, slirp4netns is >= v0.4.0.
 		if slirp4netns --help | grep -qw -- --netns-type; then
 			net=slirp4netns
-			if [ -z "$mtu" ]; then
-				mtu=65520
-			fi
 		else
 			echo "slirp4netns found but seems older than v0.4.0. Checking for other network drivers."
 		fi
@@ -134,7 +131,7 @@ if [ -z "$net" ]; then
 	fi
 fi
 if [ -z "$mtu" ]; then
-	if [ "$net" = pasta ]; then
+	if [ "$net" = slirp4netns -o "$net" = pasta ]; then
 		mtu=65520
 	else
 		mtu=1500
