git: 81075203a057 - main - EC2: Turn off IPv6 DAD

The branch main has been updated by cperciva:

URL: https://cgit.FreeBSD.org/src/commit/?id=81075203a057c9ba3467a7f90ea1e9469d7f7723

commit 81075203a057c9ba3467a7f90ea1e9469d7f7723
Author:     Colin Percival <cperciva@FreeBSD.org>
AuthorDate: 2021-11-23 04:16:34 +0000
Commit:     Colin Percival <cperciva@FreeBSD.org>
CommitDate: 2021-11-26 03:08:48 +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.
    
    Reviewed by:    kp, imp, bz
    MFC after:      2 weeks
    Sponsored by:   https://www.patreon.com/cperciva
    Differential Revision:  https://reviews.freebsd.org/D33091
---
 release/tools/ec2.conf | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/release/tools/ec2.conf b/release/tools/ec2.conf
index 2bf47b01077d..f0665646088b 100644
--- a/release/tools/ec2.conf
+++ b/release/tools/ec2.conf
@@ -70,6 +70,10 @@ 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'