Thread: getsockopt: Error EFAULT

Here's the code:

Code:

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <errno.h>

int main()
{
	int sock = socket(AF_LOCAL, SOCK_STREAM, 0);
	if(sock == -1)
	   printf("Error\n");
	
	char *s[100];
	socklen_t *x;
	int ret = getsockopt(sock, SOL_SOCKET, 1, s, x);
	if(ret==0)
       printf("Sucess!\n");
	else
	{
		if(errno==EBADF)
            printf("The argument sockfd is not a valid file descriptor.\n");
		else if(errno==EFAULT)
		    printf("The address pointed to by optval is not in a valid part of.the process address space.  For getsockopt(), this error may also be returned if optlen is not in a valid part of the process address space.\n");
		else if(errno==EINVAL)
		    printf("optlen invalid in setsockopt().  In some cases this error.can also occur for an invalid value in optval (e.g., for the IP_ADD_MEMBERSHIP option described in ip(7)).\n");
		else if(errno==ENOPROTOOPT)
		    printf("The option is unknown at the level indicated.\n");
		else if(errno==ENOTSOCK)
		    printf("The file descriptor sockfd does not refer to a socket.\n");
	}
}

When executed, it displays the text of the EFAULT error. I did everything according to the instructions and still can not understand what the problem is! Who can tell?

Do you know the difference between

Code:

    socklen_t *x;
    int ret = getsockopt(sock, SOL_SOCKET, 1, s, x);

and

Code:

    char s[100];
    socklen_t x = sizeof(s);
    int ret = getsockopt(sock, SOL_SOCKET, 1, s, &x);

Also, replace 1 with some suitable numeric constant.

For getsockopt(), optlen is a value-result argument, initially containing the size
of the buffer pointed to by optval, and modified on return to indicate
the actual size of the value returned. If no option value is to be
supplied or returned, optval may be NULL.

You can replace lines 19 to 28 with a call to perror().