Where is a UNIX socket on the filesystem? - c

Question

I am using Unix domain sockets. Want to know about its location in the system.
If I am creating a socketpair using a system call
socketpair(AF_UNIX,SOCK_STREAM,0,fd) ;
I have read it is unnamed socket (a socket that is not been bound to pathname using bind).
On the other hand, named socket or better a socket bound to file system path name using bind call get stored in some directory we specify.
for example
struct sockaddr_un {
sa_family_t sun_family; /* AF_UNIX */
char sun_path[UNIX_PATH_MAX]; /* pathname */
};
here sun_path can be /tmp/sock file.
So, similarly , I want to know does unnamed socket have any location in the system or anywhere in the memory or kernel ?
Thanks in advance.

Answer 1

I'm no kernel expert, so take this as an (educated?) guess.
#include <sys/un.h>
#include <sys/socket.h>
#include <stdio.h>
#include <string.h>
int main()
{
struct sockaddr_un sun;
socklen_t socklen;
int fd[2];
if(socketpair(AF_UNIX,SOCK_STREAM,0,fd) < 0) {
perror("socketpair");
return 111;
}
socklen = sizeof(sun);
memset(&sun, 0, sizeof sun);
sun.sun_path[0] = '!'; /* replace with any character */
if(getsockname(fd[0], (struct sockaddr *)&sun, &socklen) < 0) {
perror("getsockname");
return 111;
}
printf("sunpath(%s)\n", sun.sun_path);
return 0;
}
This program says the socket doesn't have a corresponding path, so my guess is that a unix socketpair is never associated with a filename -- it only stays alive as a data structure inside the kernel until all references are closed.
A better answer is welcome of course :)