explain_getsockopt(3)

NAME
explain_getsockopt - explain getsockopt(2) errors

SYNOPSIS
#include <libexplain/getsockopt.h>

const char *explain_getsockopt(int fildes, int level, int name, void *data, socklen_t *data_size);
const char *explain_errno_getsockopt(int errnum, int fildes, int level, int name, void *data, socklen_t *data_size);
void explain_message_getsockopt(char *message, int message_size, int fildes, int level, int name, void *data, socklen_t *data_size);
void explain_message_errno_getsockopt(char *message, int message_size, int errnum, int fildes, int level, int name, void *data, socklen_t *data_size);

DESCRIPTION
These functions may be used to obtain explanations for errors returned by the getsockopt(2) system call.

  explain_getsockopt
const char *explain_getsockopt(int fildes, int level, int name, void *data, socklen_t *data_size);

The explain_getsockopt function is used to obtain an explanation of an error returned by the getsockopt(2) system call. The least the message will contain is the value of strerror(errno), but usually it will do much better, and indicate the underlying cause in more detail.

The errno global variable will be used to obtain the error value to be decoded.

This function is intended to be used in a fashion similar to the following example:
    if (getsockopt(fildes, level, name, data, data_size) < 0)
    {
        fprintf(stderr, "%s\n", explain_getsockopt(fildes,
            level, name, data, data_size));
        exit(EXIT_FAILURE);
    }

The above code example is available pre-packaged as the explain_getsockopt_or_die(3) function.

fildes
    The original fildes, exactly as passed to the getsockopt(2) system call.

level
    The original level, exactly as passed to the getsockopt(2) system call.

name
    The original name, exactly as passed to the getsockopt(2) system call.

data
    The original data, exactly as passed to the getsockopt(2) system call.

data_size
    The original data_size, exactly as passed to the getsockopt(2) system call.

Returns:
    The message explaining the error. This message buffer is shared by all libexplain functions which do not supply a buffer in their argument list. This will be overwritten by the next call to any libexplain function which shares this buffer, including other threads.

Note: This function is not thread safe, because it shares a return buffer across all threads, and many other functions in this library.

  explain_errno_getsockopt
const char *explain_errno_getsockopt(int errnum, int fildes, int level, int name, void *data, socklen_t *data_size);

The explain_errno_getsockopt function is used to obtain an explanation of an error returned by the getsockopt(2) system call. The least the message will contain is the value of strerror(errnum), but usually it will do much better, and indicate the underlying cause in more detail.

This function is intended to be used in a fashion similar to the following example:
    if (getsockopt(fildes, level, name, data, data_size) < 0)
    {
        int err = errno;
        fprintf(stderr, "%s\n", explain_errno_getsockopt(err,
            fildes, level, name, data, data_size));
        exit(EXIT_FAILURE);
    }

The above code example is available pre-packaged as the explain_getsockopt_or_die(3) function.

errnum
    The error value to be decoded, usually obtained from the errno global variable just before this function is called. This is necessary if you need to call any code between the system call to be explained and this function, because many libc functions will alter the value of errno.

fildes
    The original fildes, exactly as passed to the getsockopt(2) system call.

level
    The original level, exactly as passed to the getsockopt(2) system call.

name
    The original name, exactly as passed to the getsockopt(2) system call.

data
    The original data, exactly as passed to the getsockopt(2) system call.

data_size
    The original data_size, exactly as passed to the getsockopt(2) system call.

Returns:
    The message explaining the error. This message buffer is shared by all libexplain functions which do not supply a buffer in their argument list. This will be overwritten by the next call to any libexplain function which shares this buffer, including other threads.

Note: This function is not thread safe, because it shares a return buffer across all threads, and many other functions in this library.

  explain_message_getsockopt
void explain_message_getsockopt(char *message, int message_size, int fildes, int level, int name, void *data, socklen_t *data_size);

The explain_message_getsockopt function may be used to obtain an explanation of an error returned by the getsockopt(2) system call. The least the message will contain is the value of strerror(errno), but usually it will do much better, and indicate the underlying cause in more detail.

The errno global variable will be used to obtain the error value to be decoded.

This function is intended to be used in a fashion similar to the following example:
    if (getsockopt(fildes, level, name, data, data_size) < 0)
    {
        char message[3000];
        explain_message_getsockopt(message, sizeof(message),
            fildes, level, name, data, data_size);
        fprintf(stderr, "%s\n", message);
        exit(EXIT_FAILURE);
    }

The above code example is available pre-packaged as the explain_getsockopt_or_die(3) function.

message
    The location in which to store the returned message. If a suitable message return buffer is supplied, this function is thread safe.

message_size
    The size in bytes of the location in which to store the returned message.

fildes
    The original fildes, exactly as passed to the getsockopt(2) system call.

level
    The original level, exactly as passed to the getsockopt(2) system call.

name
    The original name, exactly as passed to the getsockopt(2) system call.

data
    The original data, exactly as passed to the getsockopt(2) system call.

data_size
    The original data_size, exactly as passed to the getsockopt(2) system call.

  explain_message_errno_getsockopt
void explain_message_errno_getsockopt(char *message, int message_size, int errnum, int fildes, int level, int name, void *data, socklen_t *data_size);

The explain_message_errno_getsockopt function may be used to obtain an explanation of an error returned by the getsockopt(2) system call. The least the message will contain is the value of strerror(errnum), but usually it will do much better, and indicate the underlying cause in more detail.

This function is intended to be used in a fashion similar to the following example:
    if (getsockopt(fildes, level, name, data, data_size) < 0)
    {
        int err = errno;
        char message[3000];
        explain_message_errno_getsockopt(message, sizeof(message),
            err, fildes, level, name, data, data_size);
        fprintf(stderr, "%s\n", message);
        exit(EXIT_FAILURE);
    }

The above code example is available pre-packaged as the explain_getsockopt_or_die(3) function.

message
    The location in which to store the returned message. If a suitable message return buffer is supplied, this function is thread safe.

message_size
    The size in bytes of the location in which to store the returned message.

errnum
    The error value to be decoded, usually obtained from the errno global variable just before this function is called. This is necessary if you need to call any code between the system call to be explained and this function, because many libc functions will alter the value of errno.

fildes
    The original fildes, exactly as passed to the getsockopt(2) system call.

level
    The original level, exactly as passed to the getsockopt(2) system call.

name
    The original name, exactly as passed to the getsockopt(2) system call.

data
    The original data, exactly as passed to the getsockopt(2) system call.

data_size
    The original data_size, exactly as passed to the getsockopt(2) system call.

SEE ALSO

getsockopt(2)
    get and set options on sockets

explain_getsockopt_or_die(3)
    get and set options on sockets and report errors

COPYRIGHT
libexplain version
Copyright (C) 2009 Peter Miller