code review 174030043: x/net/ipv4: add support for source-specific multicast

ipv4/dgramopt_posix.go

 // Copyright 2012 The Go Authors.  All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
 // +build darwin dragonfly freebsd linux netbsd openbsd windows
 
 package ipv4
 
 import (
         "net"
@@ skipping 75 matching lines @@
         if !c.ok() {
                 return syscall.EINVAL
         }
         fd, err := c.sysfd()
         if err != nil {
                 return err
         }
         return setInt(fd, &sockOpts[ssoMulticastLoopback], boolint(on))
 }
 
-// JoinGroup joins the group address group on the interface ifi.
+// JoinGroup joins the group address group on the interface ifi. By
+// default all sources that can cast data to group are accepted. It's
+// possible to mute and unmute data transmission from a specific
+// source by using ExcludeSourceSpecificGroup and
+// IncludeSourceSpecificGroup.
 // It uses the system assigned multicast interface when ifi is nil,
 // although this is not recommended because the assignment depends on
 // platforms and sometimes it might require routing configuration.
 func (c *dgramOpt) JoinGroup(ifi *net.Interface, group net.Addr) error {
         if !c.ok() {
                 return syscall.EINVAL
         }
         fd, err := c.sysfd()
         if err != nil {
                 return err
         }
         grp := netAddrToIP4(group)
         if grp == nil {
                 return errMissingAddress
         }
         return setGroup(fd, &sockOpts[ssoJoinGroup], ifi, grp)
 }
 
 // LeaveGroup leaves the group address group on the interface ifi.
+// It's allowed to leave the group which is formed by
+// JoinSourceSpecificGroup for convenience.
 func (c *dgramOpt) LeaveGroup(ifi *net.Interface, group net.Addr) error {
         if !c.ok() {
                 return syscall.EINVAL
         }
         fd, err := c.sysfd()
         if err != nil {
                 return err
         }
         grp := netAddrToIP4(group)
         if grp == nil {
                 return errMissingAddress
         }
         return setGroup(fd, &sockOpts[ssoLeaveGroup], ifi, grp)
 }
+
+// JoinSourceSpecificGroup joins the source-specific group consisting
+// group and source on the interface ifi. It uses the system assigned
+// multicast interface when ifi is nil, although this is not
+// recommended because the assignment depends on platforms and
+// sometimes it might require routing configuration.
+func (c *dgramOpt) JoinSourceSpecificGroup(ifi *net.Interface, group, source net.Addr) error {
+        if !c.ok() {
+                return syscall.EINVAL
+        }
+        fd, err := c.sysfd()
+        if err != nil {
+                return err
+        }
+        grp := netAddrToIP4(group)
+        if grp == nil {
+                return errMissingAddress
+        }
+        src := netAddrToIP4(source)
+        if src == nil {
+                return errMissingAddress
+        }
+        return setSourceGroup(fd, &sockOpts[ssoJoinSourceGroup], ifi, grp, src)
+}
+
+// LeaveSourceSpecificGroup leaves the source-specific group on the
+// interface ifi.
+func (c *dgramOpt) LeaveSourceSpecificGroup(ifi *net.Interface, group, source net.Addr) error {
+        if !c.ok() {
+                return syscall.EINVAL
+        }
+        fd, err := c.sysfd()
+        if err != nil {
+                return err
+        }
+        grp := netAddrToIP4(group)
+        if grp == nil {
+                return errMissingAddress
+        }
+        src := netAddrToIP4(source)
+        if src == nil {
+                return errMissingAddress
+        }
+        return setSourceGroup(fd, &sockOpts[ssoLeaveSourceGroup], ifi, grp, src)
+}
+
+// ExcludeSourceSpecificGroup excludes the source-specific group from
+// the already joined groups by either JoinGroup or
+// JoinSourceSpecificGroup on the interface ifi.
+func (c *dgramOpt) ExcludeSourceSpecificGroup(ifi *net.Interface, group, source net.Addr) error {
+        if !c.ok() {
+                return syscall.EINVAL
+        }
+        fd, err := c.sysfd()
+        if err != nil {
+                return err
+        }
+        grp := netAddrToIP4(group)
+        if grp == nil {
+                return errMissingAddress
+        }
+        src := netAddrToIP4(source)
+        if src == nil {
+                return errMissingAddress
+        }
+        return setSourceGroup(fd, &sockOpts[ssoBlockSourceGroup], ifi, grp, src)
+}
+
+// IncludeSourceSpecificGroup includes the excluded source-specific
+// group by ExcludeSourceSpecificGroup again on the interface ifi.
+func (c *dgramOpt) IncludeSourceSpecificGroup(ifi *net.Interface, group, source net.Addr) error {
+        if !c.ok() {
+                return syscall.EINVAL
+        }
+        fd, err := c.sysfd()
+        if err != nil {
+                return err
+        }
+        grp := netAddrToIP4(group)
+        if grp == nil {
+                return errMissingAddress
+        }
+        src := netAddrToIP4(source)
+        if src == nil {
+                return errMissingAddress
+        }
+        return setSourceGroup(fd, &sockOpts[ssoUnblockSourceGroup], ifi, grp, src)
+}