xjasonlyu/tun2socks

package dialer

import (
    "net"
    "syscall"

    "golang.org/x/sys/unix"
)

func setSocketOptions(network, address string, c syscall.RawConn, opts *Options) (err error) {
    if opts == nil || !isTCPSocket(network) && !isUDPSocket(network) {
        return
    }

    var innerErr error
    err = c.Control(func(fd uintptr) {
        host, _, _ := net.SplitHostPort(address)
        if ip := net.ParseIP(host); ip != nil && !ip.IsGlobalUnicast() {
            return
        }

        if opts.InterfaceIndex == 0 && opts.InterfaceName != "" {
            if iface, err := net.InterfaceByName(opts.InterfaceName); err == nil {
                opts.InterfaceIndex = iface.Index
            }
        }

        if opts.InterfaceIndex != 0 {
            switch network {
            case "tcp4", "udp4":
                innerErr = unix.SetsockoptInt(int(fd), syscall.IPPROTO_IP, syscall.IP_BOUND_IF, opts.InterfaceIndex)
            case "tcp6", "udp6":
                innerErr = unix.SetsockoptInt(int(fd), syscall.IPPROTO_IPV6, syscall.IPV6_BOUND_IF, opts.InterfaceIndex)
            }
            if innerErr != nil {
                return
            }
        }
    })

    if innerErr != nil {
        err = innerErr
    }
    return
}