[PATCH v2 2/2] iproute2: ip addr: Add support for setting 'optimistic'

["Ian K. Coolidge" <icoolidge@google.com>]

optimistic DAD is controllable via sysctl for an interface
or all interfaces on the system. This would affect addresses
added by the kernel only.

Recent kernels, however, have enabled support for adding optimistic
address via userspace. This plumbs that support.
---
 ip/ipaddress.c           | 2 +-
 man/man8/ip-address.8.in | 7 ++++++-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/ip/ipaddress.c b/ip/ipaddress.c
index 403f7010..3b53933f 100644
--- a/ip/ipaddress.c
+++ b/ip/ipaddress.c
@@ -1243,7 +1243,7 @@ static const struct ifa_flag_data_t {
 	{ .name = "secondary",		.mask = IFA_F_SECONDARY,	.readonly = true,	.v6only = false},
 	{ .name = "temporary",		.mask = IFA_F_SECONDARY,	.readonly = true,	.v6only = false},
 	{ .name = "nodad",		.mask = IFA_F_NODAD,	 	.readonly = false,	.v6only = true},
-	{ .name = "optimistic",		.mask = IFA_F_OPTIMISTIC,	.readonly = true,	.v6only = true},
+	{ .name = "optimistic",		.mask = IFA_F_OPTIMISTIC,	.readonly = false,	.v6only = true},
 	{ .name = "dadfailed",		.mask = IFA_F_DADFAILED,	.readonly = true,	.v6only = true},
 	{ .name = "home",		.mask = IFA_F_HOMEADDRESS,	.readonly = false,	.v6only = true},
 	{ .name = "deprecated",		.mask = IFA_F_DEPRECATED,	.readonly = true,	.v6only = true},
diff --git a/man/man8/ip-address.8.in b/man/man8/ip-address.8.in
index 2a553190..fe773c91 100644
--- a/man/man8/ip-address.8.in
+++ b/man/man8/ip-address.8.in
@@ -92,7 +92,7 @@ ip-address \- protocol address management
 
 .ti -8
 .IR CONFFLAG " := "
-.RB "[ " home " | " mngtmpaddr " | " nodad " | " noprefixroute " | " autojoin " ]"
+.RB "[ " home " | " mngtmpaddr " | " nodad " | " optimstic " | " noprefixroute " | " autojoin " ]"
 
 .ti -8
 .IR LIFETIME " := [ "
@@ -258,6 +258,11 @@ stateless auto-configuration was active.
 (IPv6 only) do not perform Duplicate Address Detection (RFC 4862) when
 adding this address.
 
+.TP
+.B optimistic
+(IPv6 only) When performing Duplicate Address Detection, use the RFC 4429
+optimistic variant.
+
 .TP
 .B noprefixroute
 Do not automatically create a route for the network prefix of the added
-- 
2.27.0.rc0.183.gde8f92d652-goog