engine: mac: more ipv6 gm

engine/mac_resolver.go

@@ -4,10 +4,12 @@ import (
 	"bufio"
 	"net"
 	"os"
-	"os/exec"
 	"strings"
 	"sync"
 	"time"
+
+	"github.com/mdlayher/netlink"
+	"golang.org/x/sys/unix"
 )
 
 const (
@@ -166,7 +168,7 @@ func (r *sourceMACResolver) refreshNDPCache(now time.Time) {
 	m, ok := readNeighborCacheFile("/proc/net/ndisc_cache")
 	if !ok || len(m) == 0 {
 		// Fallback for environments without /proc/net/ndisc_cache.
-		m = readIPv6NeighCommand()
+		m = readIPv6NeighNetlink()
 	}
 	r.mu.Lock()
 	r.ndpByIP = m
@@ -196,19 +198,63 @@ func readNeighborCacheFile(path string) (map[string]net.HardwareAddr, bool) {
 	return m, true
 }
 
-func readIPv6NeighCommand() map[string]net.HardwareAddr {
+func readIPv6NeighNetlink() map[string]net.HardwareAddr {
+	const (
+		ndMsgLen  = 12
+		ndaDst    = 1
+		ndaLLAddr = 2
+	)
+
 	m := make(map[string]net.HardwareAddr)
-	out, err := exec.Command("ip", "-6", "neigh", "show").Output()
+	conn, err := netlink.Dial(unix.NETLINK_ROUTE, nil)
 	if err != nil {
 		return m
 	}
-	for _, line := range strings.Split(string(out), "\n") {
-		ip, mac, ok := parseNeighborLine(line)
-		if !ok {
+	defer conn.Close()
+
+	req := make([]byte, ndMsgLen)
+	req[0] = unix.AF_INET6
+	msgs, err := conn.Execute(netlink.Message{
+		Header: netlink.Header{
+			Type:  unix.RTM_GETNEIGH,
+			Flags: netlink.Request | netlink.Dump,
+		},
+		Data: req,
+	})
+	if err != nil {
+		return m
+	}
+
+	for _, msg := range msgs {
+		if msg.Header.Type != unix.RTM_NEWNEIGH || len(msg.Data) < ndMsgLen || msg.Data[0] != unix.AF_INET6 {
 			continue
 		}
-		m[ip] = mac
+		attrs, err := netlink.UnmarshalAttributes(msg.Data[ndMsgLen:])
+		if err != nil {
+			continue
+		}
+		var ipStr string
+		var mac net.HardwareAddr
+		for _, a := range attrs {
+			switch a.Type {
+			case ndaDst:
+				if len(a.Data) == net.IPv6len {
+					ipStr = net.IP(append([]byte(nil), a.Data...)).String()
+				}
+			case ndaLLAddr:
+				if len(a.Data) >= 6 {
+					candidate := append(net.HardwareAddr(nil), a.Data...)
+					if candidate.String() != "00:00:00:00:00:00" {
+						mac = candidate
+					}
+				}
+			}
+		}
+		if ipStr != "" && len(mac) != 0 {
+			m[ipStr] = mac
+		}
 	}
+
 	return m
 }