wip: migrate to mono-repo. SPN has already been moved to spn/

service/nameserver/conflict.go

@@ -0,0 +1,75 @@
+package nameserver
+
+import (
+	"net"
+	"os"
+
+	processInfo "github.com/shirou/gopsutil/process"
+
+	"github.com/safing/portbase/log"
+	"github.com/safing/portmaster/service/network/packet"
+	"github.com/safing/portmaster/service/network/state"
+)
+
+var commonResolverIPs = []net.IP{
+	net.IPv4zero,
+	net.IPv4(127, 0, 0, 1),  // default
+	net.IPv4(127, 0, 0, 53), // some resolvers on Linux
+	net.IPv6zero,
+	net.IPv6loopback,
+}
+
+func findConflictingProcess(ip net.IP, port uint16) (conflictingProcess *processInfo.Process) {
+	// Evaluate which IPs to check.
+	var ipsToCheck []net.IP
+	if ip.Equal(net.IPv4zero) || ip.Equal(net.IPv6zero) {
+		ipsToCheck = commonResolverIPs
+	} else {
+		ipsToCheck = []net.IP{ip}
+	}
+
+	// Find the conflicting process.
+	var err error
+	for _, resolverIP := range ipsToCheck {
+		conflictingProcess, err = getListeningProcess(resolverIP, port)
+		switch {
+		case err != nil:
+			// Log the error and let the worker try again.
+			log.Warningf("nameserver: failed to find conflicting service: %s", err)
+		case conflictingProcess != nil:
+			// Conflicting service found.
+			return conflictingProcess
+		}
+	}
+
+	return nil
+}
+
+func getListeningProcess(resolverIP net.IP, resolverPort uint16) (*processInfo.Process, error) {
+	pid, _, err := state.Lookup(&packet.Info{
+		Inbound:  true,
+		Version:  0, // auto-detect
+		Protocol: packet.UDP,
+		Src:      nil, // do not record direction
+		SrcPort:  0,   // do not record direction
+		Dst:      resolverIP,
+		DstPort:  resolverPort,
+	}, true)
+	if err != nil {
+		// there may be nothing listening on :53
+		return nil, nil //nolint:nilerr // Treat lookup error as "not found".
+	}
+
+	// Ignore if it's us for some reason.
+	if pid == os.Getpid() {
+		return nil, nil
+	}
+
+	proc, err := processInfo.NewProcess(int32(pid))
+	if err != nil {
+		// Process may have disappeared already.
+		return nil, err
+	}
+
+	return proc, nil
+}