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//go:build linux
package linux
import (
"fmt"
"net"
"syscall"
"unsafe"
)
// NetlinkInterface returns a net.Interface extended to also contain its addresses.
type NetlinkInterface struct {
net.Interface
Addresses []net.Addr
}
// NetlinkInterfaces performs a RTM_GETADDR call to get both.
func NetlinkInterfaces() ([]NetlinkInterface, error) {
// Grab the interface list.
ifaces, err := net.Interfaces()
if err != nil {
return nil, err
}
// Initialize result slice.
netlinkIfaces := make([]NetlinkInterface, 0, len(ifaces))
for _, iface := range ifaces {
netlinkIfaces = append(netlinkIfaces, NetlinkInterface{iface, make([]net.Addr, 0)})
}
// Turn it into a map.
ifaceMap := make(map[int]*NetlinkInterface, len(ifaces))
for k, v := range netlinkIfaces {
ifaceMap[v.Index] = &netlinkIfaces[k] //nolint:typecheck
}
// Make the netlink call.
rib, err := syscall.NetlinkRIB(syscall.RTM_GETADDR, syscall.AF_UNSPEC)
if err != nil {
return nil, fmt.Errorf("Failed to query RTM_GETADDR: %v", err)
}
messages, err := syscall.ParseNetlinkMessage(rib)
if err != nil {
return nil, fmt.Errorf("Failed to parse RTM_GETADDR: %v", err)
}
for _, m := range messages {
if m.Header.Type == syscall.RTM_NEWADDR {
addrMessage := (*syscall.IfAddrmsg)(unsafe.Pointer(&m.Data[0]))
addrAttrs, err := syscall.ParseNetlinkRouteAttr(&m)
if err != nil {
return nil, fmt.Errorf("Failed to parse route attribute: %v", err)
}
ifi, ok := ifaceMap[int(addrMessage.Index)]
if ok {
ifi.Addresses = append(ifi.Addresses, newAddr(addrMessage, addrAttrs))
}
}
}
return netlinkIfaces, nil
}
// Variation of function of the same name from within Go source.
func newAddr(ifam *syscall.IfAddrmsg, attrs []syscall.NetlinkRouteAttr) net.Addr {
var ipPointToPoint bool
// Seems like we need to make sure whether the IP interface
// stack consists of IP point-to-point numbered or unnumbered
// addressing.
for _, a := range attrs {
if a.Attr.Type == syscall.IFA_LOCAL {
ipPointToPoint = true
break
}
}
for _, a := range attrs {
if ipPointToPoint && a.Attr.Type == syscall.IFA_ADDRESS {
continue
}
switch ifam.Family {
case syscall.AF_INET:
return &net.IPNet{IP: net.IPv4(a.Value[0], a.Value[1], a.Value[2], a.Value[3]), Mask: net.CIDRMask(int(ifam.Prefixlen), 8*net.IPv4len)}
case syscall.AF_INET6:
ifa := &net.IPNet{IP: make(net.IP, net.IPv6len), Mask: net.CIDRMask(int(ifam.Prefixlen), 8*net.IPv6len)}
copy(ifa.IP, a.Value[:])
return ifa
}
}
return nil
}
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