getpeername() returns 0 instead of failing with ENOTCONN on an unconnected socket

[lukkrusz]

Description

When getpeername() is called on a socket that is not connected and has no pre-specified peer, it returns 0 instead of
failing with -1 and setting errno to ENOTCONN.

Expected behavior

getpeername() shall fail with ENOTCONN when the socket is not connected or otherwise has not had the peer pre-specified.

Actual behavior

getpeername() returns 0 and does not set errno.

Observed output:

getpeername(unconnected): ret=0 errno=0 (EOK)

POSIX requirement (if applicable)

POSIX.1-2017 (IEEE Std 1003.1-2017), getpeername(3p), section ERRORS:

"[ENOTCONN] The socket is not connected or otherwise has not had the peer pre-specified."

Minimal reproduction code

#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <sys/socket.h>
#include <sys/un.h>

int main(void)
{
    int fd, ret;
    struct sockaddr_un peer;
    socklen_t len = sizeof(peer);

    fd = socket(AF_UNIX, SOCK_STREAM, 0);
    errno = 0;
    ret = getpeername(fd, (struct sockaddr *)&peer, &len);
    printf("getpeername(unconnected): ret=%d errno=%d (%s)\n", ret, errno, strerror(errno));
    close(fd);
    return 0;
}

Host behavior

getpeername(unconnected): ret=-1 errno=107 (Transport endpoint is not connected)

Revision

Discovered on 62b46f9

Target

Reproduced on ia32-generic-qemu, not tested on other targets yet.

Related tests

• phoenix-rtos-tests/libc/socket/getpeername.c

These tests are currently skipped on the affected target. After applying a fix, re-enable them and re-run the suite to
verify the fix.