git: efb381caf102 - stable/13 - EC2: Turn off IPv6 DAD

The branch stable/13 has been updated by cperciva:

URL: https://cgit.FreeBSD.org/src/commit/?id=efb381caf102938d24149f38e98881d282ded11a

commit efb381caf102938d24149f38e98881d282ded11a
Author:     Colin Percival <cperciva@FreeBSD.org>
AuthorDate: 2021-11-23 04:16:34 +0000
Commit:     Colin Percival <cperciva@FreeBSD.org>
CommitDate: 2021-12-11 01:34:23 +0000

    EC2: Turn off IPv6 DAD
    
    Disable Duplicate Address Detection in EC2 instances.  The networking
    configuration in EC2, with IPv6 addresses assigned by DHCPv6 and
    host egress filtering, makes "duplicate addresses" impossible.
    
    This speeds up the boot process in EC2 by 2 seconds.
    
    Sponsored by:   https://www.patreon.com/cperciva
    Differential Revision:  https://reviews.freebsd.org/D33091
    
    (cherry picked from commit 81075203a057c9ba3467a7f90ea1e9469d7f7723)
---
 release/tools/ec2.conf | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/release/tools/ec2.conf b/release/tools/ec2.conf
index 888a446659a5..bb972c456fbc 100644
--- a/release/tools/ec2.conf
+++ b/release/tools/ec2.conf
@@ -68,6 +68,10 @@ vm_extra_pre_umount() {
 	echo 'rtsold_enable="YES"' >> ${DESTDIR}/etc/rc.conf
 	echo 'rtsold_flags="-M /usr/local/libexec/rtsold-M -a"' >> ${DESTDIR}/etc/rc.conf
 
+	# Turn off IPv6 Duplicate Address Detection; the EC2 networking
+	# configuration makes it unnecessary.
+	echo 'net.inet6.ip6.dad_count=0' >> ${DESTDIR}/etc/sysctl.conf
+
 	# Provide a script which rtsold can use to launch DHCPv6
 	mkdir -p ${DESTDIR}/usr/local/libexec
 	cat > ${DESTDIR}/usr/local/libexec/rtsold-M <<'EOF'