Copy socks5.trunnel from trunnel examples dir

// Example: here's a quickie implementation of the messages in the

// socks5 protocol.

struct socks5_client_version {

   u8 version IN [5];

   u8 n_methods;

   u8 methods[n_methods];

}

struct socks5_server_method {

   u8 version IN [5];

   u8 method;

}

const CMD_CONNECT = 1;

const CMD_BIND = 2;

const CMD_UDP_ASSOCIATE = 3;

// This is a tor extension

const CMD_RESOLVE_PTR = 0xF1;

const ATYPE_IPV4 = 1;

const ATYPE_IPV6 = 4;

const ATYPE_DOMAINNAME = 3;

struct domainname {

   u8 len;

   char name[len];

}

struct socks5_client_request {

   u8 version IN [5];

   u8 command IN [CMD_CONNECT, CMD_BIND, CMD_UDP_ASSOCIATE, CMD_RESOLVE_PTR];

   u8 reserved IN [0];

   u8 atype;

   union dest_addr[atype] {

     ATYPE_IPV4: u32 ipv4;

     ATYPE_IPV6: u8 ipv6[16];

     ATYPE_DOMAINNAME: struct domainname domainname;

     default: fail;

   };

   u16 dest_port;

}

struct socks5_server_reply {

   u8 version IN [5];

   u8 reply;

   u8 reserved IN [0];

   u8 atype;

   union bind_addr[atype] {

     ATYPE_IPV4: u32 ipv4;

     ATYPE_IPV6: u8 ipv6[16];

     ATYPE_DOMAINNAME: struct domainname domainname;

     default: fail;

   };

   u16 bind_port;

}

struct socks5_client_userpass_auth {

   u8 version IN [1];

   u8 username_len;

   char username[username_len];

   u8 passwd_len;

   char passwd[passwd_len];

}

struct socks5_server_userpath_auth {

   u8 version IN [1];

   u8 status;

}

// Oh why not.  Here's socks4 and socks4a.

struct socks4_client_request {

   u8 version IN [4];

   u8 command IN [CMD_CONNECT,CMD_BIND,CMD_RESOLVE_PTR];

   u16 port;

   u32 addr;

   nulterm username;

   union socks4a_addr[addr] {

      1..255:

               nulterm hostname;

      default:

               ;

   };

}

struct socks4_server_reply {

   u8 version IN [4];

   u8 status;

   u16 port;

   u32 addr;

}

// And here's the extended stuff from proposal 229

struct tor_socksauth_keyval {

  u16 keylen;

  char key[keylen];

  u16 vallen;

  char val[vallen];

}

struct tor_extended_socks_auth_request {

  u8 version IN [1];

  u16 npairs;

  struct tor_socksauth_keyval pairs[npairs];

}

struct tor_extended_socks_auth_response {

  u8 version IN [1];

  u8 status;

  u16 npairs;

  struct tor_socksauth_keyval pairs[npairs];

}