EFS mount fails on dual-stack/NAT64 hosts: IPv6 address selected over IPv4, causing NFS timeout

[guessi]

Problem

On hosts where the DNS resolver returns both IPv4-mapped IPv6 (NAT64) and IPv4 addresses, efs-utils connects using the IPv6 address, which either times out or is unreachable on port 2049. The mount fails with mount.nfs4: Connection timed out.

Reproduction

# DNS returns IPv6 (NAT64-mapped) address first
$ getent ahosts fs-07aa54b903aedf48c.efs.us-east-1.amazonaws.com
64:ff9b::c0a8:6188 STREAM fs-07aa54b903aedf48c.efs.us-east-1.amazonaws.com
64:ff9b::c0a8:6188 DGRAM
64:ff9b::c0a8:6188 RAW
192.168.97.136  STREAM
192.168.97.136  DGRAM
192.168.97.136  RAW

# EFS CSI node pod logs
E0617 10:26:40.650836 mount_linux.go:272] Mount failed: exit status 32
Mounting command: mount
Mounting arguments: -t efs -o accesspoint=fsap-...,tls fs-07aa54b903aedf48c:/ /var/lib/kubelet/...
Output: Could not start amazon-efs-mount-watchdog, unrecognized init system "aws-efs-csi-dri"
Mount attempt 1/3 failed due to timeout after 15 sec, wait 0 sec before next attempt.
Mount attempt 2/3 failed due to timeout after 15 sec, wait 0 sec before next attempt.
b'mount.nfs4: Connection timed out'

Root cause

efs-utils uses AF_UNSPEC for DNS resolution, so the OS picks the first address returned — which on NAT64/dual-stack hosts is an IPv6 address. The EFS mount target is only reachable over IPv4 (port 2049), so the connection times out.

Workaround

None currently. A DNS-level workaround (suppressing AAAA records via CoreDNS) is possible but requires cluster-level config changes.

Expected behaviour

1. A config option (e.g. prefer_ipv4 = true in efs-utils.conf) to force AF_INET resolution and connect over IPv4.
2. Dynamically detect/discover whether IPv4 should be used or IPv6 should be used at the time.

[YangjinanHu]

Amazon EFS supports IPv6 and dual-stack mount targets. You can create a IPv6 or dual-stack mount target following the instructions below.

https://docs.aws.amazon.com/efs/latest/ug/manage-fs-access-create-delete-mount-targets.html
https://docs.aws.amazon.com/efs/latest/APIReference/API_CreateMountTarget.html