71 lines
1.4 KiB
Go
71 lines
1.4 KiB
Go
package ssdp
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import (
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"net"
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"sync"
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)
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// Interfaces specify target interfaces to multicast. If no interfaces are
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// specified, all interfaces will be used.
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var Interfaces []net.Interface
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var ifLock sync.Mutex
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var ifList []net.Interface
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// interfaces gets list of net.Interface to multicast UDP packet.
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func interfaces() ([]net.Interface, error) {
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ifLock.Lock()
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defer ifLock.Unlock()
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if len(Interfaces) > 0 {
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return Interfaces, nil
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}
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if len(ifList) > 0 {
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return ifList, nil
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}
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l, err := interfacesIPv4()
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if err != nil {
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return nil, err
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}
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ifList = l
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return ifList, nil
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}
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// interfacesIPv4 lists net.Interface on IPv4.
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func interfacesIPv4() ([]net.Interface, error) {
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iflist, err := net.Interfaces()
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if err != nil {
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return nil, err
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}
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list := make([]net.Interface, 0, len(iflist))
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for _, ifi := range iflist {
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if !hasLinkUp(&ifi) || !hasIPv4Address(&ifi) {
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continue
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}
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list = append(list, ifi)
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}
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return list, nil
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}
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// hasLinkUp checks an I/F have link-up or not.
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func hasLinkUp(ifi *net.Interface) bool {
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return ifi.Flags&net.FlagUp != 0
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}
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// hasIPv4Address checks an I/F have IPv4 address.
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func hasIPv4Address(ifi *net.Interface) bool {
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addrs, err := ifi.Addrs()
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if err != nil {
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return false
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}
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for _, a := range addrs {
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ip, _, err := net.ParseCIDR(a.String())
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if err != nil {
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continue
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}
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if len(ip.To4()) == net.IPv4len && !ip.IsUnspecified() {
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return true
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}
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}
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return false
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}
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