x/net/ipv6: update package documentation
LGTM=iant
R=iant
CC=golang-codereviews
https://golang.org/cl/177840043
diff --git a/ipv6/doc.go b/ipv6/doc.go
index e524627..3f91fa3 100644
--- a/ipv6/doc.go
+++ b/ipv6/doc.go
@@ -34,7 +34,7 @@
// defer c.Close()
//
// The outgoing packets will be labeled DiffServ assured forwarding
-// class 1 low drop precedence, as known as AF11 packets.
+// class 1 low drop precedence, known as AF11 packets.
//
// if err := ipv6.NewConn(c).SetTrafficClass(DiffServAF11); err != nil {
// // error handling
@@ -191,4 +191,44 @@
// if err := p.JoinGroup(en0, &net.UDPAddr{IP: net.ParseIP("ff01::114")}); err != nil {
// // error handling
// }
+//
+//
+// Source-specific multicasting
+//
+// An application that uses PacketConn on MLDv2 supported platform is
+// able to join source-specific multicast groups as described in RFC
+// 3678. The application may use JoinSourceSpecificGroup and
+// LeaveSourceSpecificGroup for the operation known as "include" mode,
+//
+// ssmgroup := net.UDPAddr{IP: net.ParseIP("ff32::8000:9")}
+// ssmsource := net.UDPAddr{IP: net.ParseIP("fe80::cafe")}
+// if err := p.JoinSourceSpecificGroup(en0, &ssmgroup, &ssmsource); err != nil {
+// // error handling
+// }
+// if err := p.LeaveSourceSpecificGroup(en0, &ssmgroup, &ssmsource); err != nil {
+// // error handling
+// }
+//
+// or JoinGroup, ExcludeSourceSpecificGroup,
+// IncludeSourceSpecificGroup and LeaveGroup for the operation known
+// as "exclude" mode.
+//
+// exclsource := net.UDPAddr{IP: net.ParseIP("fe80::dead")}
+// if err := p.JoinGroup(en0, &ssmgroup); err != nil {
+// // error handling
+// }
+// if err := p.ExcludeSourceSpecificGroup(en0, &ssmgroup, &exclsource); err != nil {
+// // error handling
+// }
+// if err := p.LeaveGroup(en0, &ssmgroup); err != nil {
+// // error handling
+// }
+//
+// Note that it depends on each platform implementation what happens
+// when an application which runs on MLDv2 unsupported platform uses
+// JoinSourceSpecificGroup and LeaveSourceSpecificGroup.
+// In general the platform tries to fall back to conversations using
+// MLDv1 and starts to listen to multicast traffic.
+// In the fallback case, ExcludeSourceSpecificGroup and
+// IncludeSourceSpecificGroup may return an error.
package ipv6
