vn_sndrcv — Send to or receive from a socket

Function

The vn_sndrcv operation sends datagrams to or receives datagrams from a socket. The socket must be connected.

Environment on entry and exit

Input parameter format

vn_sndrcv   (Token_structure,
             OSI_structure,
             Audit_structure,
             Open_flags,
             User_IO_structure,
             Flags,
             Return_value,
             Return_code,
             Reason_code)

Parameters

Token_structure

Supplied parameter

Type:: TOKSTR
Length:: Specified by TOKSTR.ts_hdr.cblen.

The Token_structure represents the file (vnode) that is being operated on. It contains the PFS's initialization token, mount token, and the file token. Refer to LFS/PFS control block structure for a discussion of this structure, and to the TOKSTR typedef in BPXYPFSI in Interface structures for C language servers and clients for its mapping.

OSI_structure

Supplied and returned parameter

Type:: OSI
Length:: Specified by OSI.osi_hdr.cblen.

The OSI_structure contains information that is used by the OSI operations that may be called by the PFS. See OSI services for more information.

It also contains MVS-specific information that needs to be passed to the PFS, including SMF accounting fields, a work area, a recovery area, and an optional pointer to an output ATTR structure. For more details on the OSI structure, see The OSI structure.

This area is mapped by the OSI typedef in BPXYPFSI in Interface structures for C language servers and clients.

Audit_structure

Supplied parameter

Type:: CRED
Length:: Specified by CRED.cred_hdr.cblen.

The Audit_structure contains information that is used by the security product for access checks and auditing. It is passed to most SAF routines that are invoked by the PFS.

Refer to Security responsibilities and considerations for a discussion of security processing, and to the CRED typedef in BPXYPFSI in Interface structures for C language servers and clients for the mapping of this structure.

Open_flags

Supplied parameter

Type:: Structure
Length:: Fullword

A fullword that contains the bits that are associated with the socket. The defined values for this field are mapped by fcntl.h.

User_IO_structure

Supplied and returned parameter

Type:: UIO
Length:: Specified by UIO.u_hdr.cblen.

An area that contains the parameters for the I/O that is to be performed. This area is mapped by the UIO typedef in the BPXYVFSI header file (see Interface structures for C language servers and clients). See "Specific processing notes" for details on how the fields in this structure are processed.

Flags

Supplied parameter

Type:: Structure
Length:: Fullword

A fullword that indicates special processing requests. The defined values for this field are mapped by socket.h.

Return_value

Returned parameter

Type:: Integer
Length:: Fullword

A fullword in which the vn_sndrcv operation returns the results of the operation, as one of the following:

Return_value: Meaning
-1: The operation was not successful. The Return_code and Reason_Code values must be filled in by the PFS when Return_value is -1.
0 or greater: The operation was successful. The value represents the number of bytes that were transferred.

Return_code

Returned parameter

Type:: Integer
Length:: Fullword

A fullword in which the vn_sndrcv operation stores the return code. The vn_sndrcv operation returns Return_code only if Return_value is -1. For a complete list of supported return code values, see z/OS UNIX System Services Messages and Codes.

The vn_sndrcv operation should support at least the following error values:

Return_code	Explanation
EFAULT	A buffer address that was specified is not in addressable storage.
EINVAL	An incorrect parameter was specified.
EWOULDBLOCK	The operation would have required a blocking wait, and this socket was marked as nonblocking.

Reason_code

Returned parameter

Type:: Integer
Length:: Fullword

A fullword in which the vn_sndrcv operation stores the reason code. The vn_sndrcv operation returns Reason_code only if Return_value is -1. Reason_code further qualifies the Return_code value. These reason codes are documented by the PFS.

Implementation notes

Overview of vn_sndrcv processing

For more information about the semantics of this operation for a POSIX-conforming PFS, refer to the publications that are mentioned in Finding more information about sockets for the recv and send functions.

Specific processing notes

The following UIO fields are provided by the LFS:

UIO.u_hdr.cbid: Contains UIO_ID (from the BPXYVFSI header file)
UIO.u_hdr.cblen: Specifies the length of the user_IO_structure
UIO.u_buffaddr: Specifies the address of the caller's buffer
UIO.u_buffalet: Specifies the ALET of the caller's buffer
UIO.u_count: Specifies the maximum number of bytes that can be written to or read from the caller's buffer
UIO.u_asid: Specifies the ASID of the caller
UIO.u_rw: Specifies whether the request is a read (0) or a write (1)
UIO.u_key: Specifies the storage key of the caller's buffer

The UIO contains fields that may point to a 64-bit addressable user buffer. When FuioAddr64 is on (and FuioRealPage is off), FuioBuff64Vaddr points to a buffer, an IOV64, or an MSGH64.

Serialization provided by the LFS

The vn_sndrcv operation is invoked with an exclusive latch held on the vnode of the socket.

Security calls to be made by the PFS

None.