feat: expand device networking and management

internal/exportproxy/bind_linux.go

@@ -0,0 +1,80 @@
+//go:build linux
+
+package exportproxy
+
+import (
+	"bufio"
+	"context"
+	"hash/fnv"
+	"net"
+	"os"
+	"path/filepath"
+	"strings"
+	"syscall"
+)
+
+func platformSupported() error { return nil }
+
+func boundDialer(networkInterface string) net.Dialer {
+	return net.Dialer{Control: func(_, _ string, raw syscall.RawConn) error {
+		var bindError error
+		err := raw.Control(func(fd uintptr) {
+			if err := syscall.SetsockoptInt(int(fd), syscall.SOL_SOCKET, syscall.SO_MARK, int(exportRouteMark(networkInterface))); err != nil {
+				bindError = err
+				return
+			}
+			bindError = syscall.SetsockoptString(int(fd), syscall.SOL_SOCKET, syscall.SO_BINDTODEVICE, networkInterface)
+		})
+		if err != nil {
+			return err
+		}
+		return bindError
+	}}
+}
+
+func exportRouteMark(networkInterface string) uint32 {
+	hash := fnv.New32a()
+	_, _ = hash.Write([]byte(networkInterface))
+	return 0x56000000 | (hash.Sum32() & 0x00ffffff)
+}
+
+func boundResolver(networkInterface string) *net.Resolver {
+	dialer := boundDialer(networkInterface)
+	return &net.Resolver{PreferGo: true, Dial: func(ctx context.Context, network, _ string) (net.Conn, error) {
+		var lastError error
+		for _, server := range exportRouteDNSServers(networkInterface) {
+			connection, err := dialer.DialContext(ctx, network, net.JoinHostPort(server, "53"))
+			if err == nil {
+				return connection, nil
+			}
+			lastError = err
+		}
+		return nil, lastError
+	}}
+}
+
+func exportRouteDNSServers(networkInterface string) []string {
+	safeName := strings.Map(func(character rune) rune {
+		if character >= 'a' && character <= 'z' || character >= 'A' && character <= 'Z' ||
+			character >= '0' && character <= '9' || character == '-' || character == '_' || character == '.' {
+			return character
+		}
+		return '_'
+	}, networkInterface)
+	file, err := os.Open(filepath.Join("/run/vocat", "cellular-"+safeName+".dns"))
+	if err != nil {
+		return []string{"1.1.1.1", "8.8.8.8"}
+	}
+	defer file.Close()
+	servers := make([]string, 0, 2)
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		if value := strings.TrimSpace(scanner.Text()); net.ParseIP(value) != nil {
+			servers = append(servers, value)
+		}
+	}
+	if len(servers) == 0 {
+		return []string{"1.1.1.1", "8.8.8.8"}
+	}
+	return servers
+}