BIND2ADDRSEL

The BIND2ADDRSEL call binds a socket to the local IP address that would be selected by the stack to communicate with the input destination IP address.

Use the BIND2ADDRSEL call when the application must verify that the local IP address assigned by the stack meets its address selection criteria as specified by the IPV6_ADDR_PREFERENCES socket option before the stack sends any packets to the remote host. In a TCP or UDP application, the BIND2ADDRSEL call usually follows the SETSOCKOPT call with option IPV6_ADDR_PREFERENCES and precedes any communication with a remote host.

Result: The stack attempts to select a local IP address according to your application preferences. However, a successful BIND2ADDRSEL call does not guarantee that all of your source IP address selection preferences were met.

Guidelines:

Use the SETSOCKOPT call to set the IPV6_ADDR_PREFERENCES option to indicate your selection preferences of source IP address before binding the socket and before allowing an implicit bind of the socket to occur.
Result: If a socket has not been explicitly bound to a local IP address with a BIND or BIND2ADDRSEL call when a CONNECT, SENDTO, or SENDMSG call is issued, an implicit bind occurs. The stack chooses the local IP address used for outbound packets.

Requirement: When your application is using stream sockets, and must prevent the stack from sending any packets whatsoever (such as SYN) to the remote host before it can verify that the local IP address meets the values specified for the IPV6_ADDR_PREFERENCES option, do not allow the CONNECT call to implicitly bind the socket to a local IP address. Instead, bind the socket with the BIND2ADDRSEL call and test the local IP address assigned with the INET6_IS_SRCADDR call. If the assigned local IP address is satisfactory, you can then use the CONNECT call to establish communication with the remote host.
After you successfully issue the BIND2ADDRSEL call, use the GETSOCKNAME call to obtain the local IP address that is bound to the socket. When the local IP address is obtained, use the INET6_IS_SRCADDR call to verify that the local IP address meets your address selection criteria.

The following requirements apply to this call:

Authorization:

Supervisor state or problem state, any PSW key.

Dispatchable unit mode:

Task.

Cross memory mode:

PASN = HASN.

Amode:

31-bit or 24-bit.

Note: See "Addressability mode (Amode) considerations" under CALL instruction API environmental restrictions and programming requirements.

ASC mode:

Primary address space control (ASC) mode.

Interrupt status:

Enabled for interrupts.

Locks:

Unlocked.

Control parameters:

All parameters must be addressable by the caller and in the primary address space.

Figure 1 shows an example of BIND2ADDRSEL call instructions.

Figure 1. BIND2ADDRSEL call instruction example

    WORKING-STORAGE SECTION.
             01  SOC-FUNCTION    PIC X(16)  VALUE IS 'BIND2ADDRSEL'.
             01  S               PIC 9(4) BINARY.
          * IPv6 socket address structure.
             01  NAME.
                 03  FAMILY      PIC 9(4) BINARY.
                 03  PORT        PIC 9(4) BINARY.
                 03  FLOWINFO    PIC 9(8) BINARY.
                 03  IP-ADDRESS.
                     10 FILLER   PIC 9(16) BINARY.
                     10 FILLER   PIC 9(16) BINARY.
                 03  SCOPE-ID    PIC 9(8) BINARY.
             01  ERRNO           PIC 9(8) BINARY.
             01  RETCODE         PIC S9(8) BINARY.

         PROCEDURE DIVISION.
              CALL 'EZASOKET' USING SOC-FUNCTION S NAME ERRNO RETCODE.

For equivalent PL/I and assembler language declarations, see Converting parameter descriptions.