51 lines
1.2 KiB
Go
51 lines
1.2 KiB
Go
package redir
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import (
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"errors"
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"net"
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"syscall"
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"unsafe"
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"github.com/Dreamacro/go-shadowsocks2/socks"
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)
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const (
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SO_ORIGINAL_DST = 80 // from linux/include/uapi/linux/netfilter_ipv4.h
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IP6T_SO_ORIGINAL_DST = 80 // from linux/include/uapi/linux/netfilter_ipv6/ip6_tables.h
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)
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func parserPacket(conn net.Conn) (socks.Addr, error) {
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c, ok := conn.(*net.TCPConn)
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if !ok {
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return nil, errors.New("only work with TCP connection")
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}
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rc, err := c.SyscallConn()
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if err != nil {
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return nil, err
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}
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var addr socks.Addr
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rc.Control(func(fd uintptr) {
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addr, err = getorigdst(fd)
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})
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return addr, err
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}
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// Call getorigdst() from linux/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c
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func getorigdst(fd uintptr) (socks.Addr, error) {
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raw := syscall.RawSockaddrInet4{}
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siz := unsafe.Sizeof(raw)
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if err := socketcall(GETSOCKOPT, fd, syscall.IPPROTO_IP, SO_ORIGINAL_DST, uintptr(unsafe.Pointer(&raw)), uintptr(unsafe.Pointer(&siz)), 0); err != nil {
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return nil, err
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}
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addr := make([]byte, 1+net.IPv4len+2)
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addr[0] = socks.AtypIPv4
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copy(addr[1:1+net.IPv4len], raw.Addr[:])
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port := (*[2]byte)(unsafe.Pointer(&raw.Port)) // big-endian
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addr[1+net.IPv4len], addr[1+net.IPv4len+1] = port[0], port[1]
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return addr, nil
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}
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