// GetNetlinkSocketAt opens a netlink socket in the network namespace newNs
// and positions the thread back into the network namespace specified by curNs,
// when done. If curNs is close, the function derives the current namespace and
// moves back into it when done. If newNs is close, the socket will be opened
// in the current network namespace.
func GetNetlinkSocketAt(newNs, curNs netns.NsHandle, protocol int) (*NetlinkSocket, error) {
var err error
if newNs.IsOpen() {
runtime.LockOSThread()
defer runtime.UnlockOSThread()
if !curNs.IsOpen() {
if curNs, err = netns.Get(); err != nil {
return nil, fmt.Errorf("could not get current namespace while creating netlink socket: %v", err)
}
defer curNs.Close()
}
if err := netns.Set(newNs); err != nil {
return nil, fmt.Errorf("failed to set into network namespace %d while creating netlink socket: %v", newNs, err)
}
defer netns.Set(curNs)
}
return getNetlinkSocket(protocol)
}
// executeInNetns sets execution of the code following this call to the
// network namespace newNs, then moves the thread back to curNs if open,
// otherwise to the current netns at the time the function was invoked
// In case of success, the caller is expected to execute the returned function
// at the end of the code that needs to be executed in the network namespace.
// Example:
// func jobAt(...) error {
// d, err := executeInNetns(...)
// if err != nil { return err}
// defer d()
// < code which needs to be executed in specific netns>
// }
// TODO: his function probably belongs to netns pkg.
func executeInNetns(newNs, curNs netns.NsHandle) (func(), error) {
var (
err error
moveBack func(netns.NsHandle) error
closeNs func() error
unlockThd func()
)
restore := func() {
// order matters
if moveBack != nil {
moveBack(curNs)
}
if closeNs != nil {
closeNs()
}
if unlockThd != nil {
unlockThd()
}
}
if newNs.IsOpen() {
runtime.LockOSThread()
unlockThd = runtime.UnlockOSThread
if !curNs.IsOpen() {
if curNs, err = netns.Get(); err != nil {
restore()
return nil, fmt.Errorf("could not get current namespace while creating netlink socket: %v", err)
}
closeNs = curNs.Close
}
if err := netns.Set(newNs); err != nil {
restore()
return nil, fmt.Errorf("failed to set into network namespace %d while creating netlink socket: %v", newNs, err)
}
moveBack = netns.Set
}
return restore, nil
}
func conditionalClose(ns *netns.NsHandle) {
if ns != nil && ns.IsOpen() {
ns.Close()
}
}