|
- SOCKS 4A: A Simple Extension to SOCKS 4 Protocol
-
- Ying-Da Lee
- yingda@best.com or yingda@esd.sgi.com
-
- Please read SOCKS4.protocol first for an description of the version 4
- protocol. This extension is intended to allow the use of SOCKS on hosts
- which are not capable of resolving all domain names.
-
- In version 4, the client sends the following packet to the SOCKS server
- to request a CONNECT or a BIND operation:
-
- +----+----+----+----+----+----+----+----+----+----+....+----+
- | VN | CD | DSTPORT | DSTIP | USERID |NULL|
- +----+----+----+----+----+----+----+----+----+----+....+----+
- # of bytes: 1 1 2 4 variable 1
-
- VN is the SOCKS protocol version number and should be 4. CD is the
- SOCKS command code and should be 1 for CONNECT or 2 for BIND. NULL
- is a byte of all zero bits.
-
- For version 4A, if the client cannot resolve the destination host's
- domain name to find its IP address, it should set the first three bytes
- of DSTIP to NULL and the last byte to a non-zero value. (This corresponds
- to IP address 0.0.0.x, with x nonzero. As decreed by IANA -- The
- Internet Assigned Numbers Authority -- such an address is inadmissible
- as a destination IP address and thus should never occur if the client
- can resolve the domain name.) Following the NULL byte terminating
- USERID, the client must sends the destination domain name and termiantes
- it with another NULL byte. This is used for both CONNECT and BIND requests.
-
- A server using protocol 4A must check the DSTIP in the request packet.
- If it represent address 0.0.0.x with nonzero x, the server must read
- in the domain name that the client sends in the packet. The server
- should resolve the domain name and make connection to the destination
- host if it can.
-
- SOCKSified sockd may pass domain names that it cannot resolve to
- the next-hop SOCKS server.
|
