nl_recvmsgs() does not inform caller when other end closes connection about libnl HOT 1 CLOSED

1.) yes, the documentation is wrong. It's fixed now: 3dd2a0f

The behavior was changed with version 3.2.22: 375a629

See for example how NetworkManager handles this.

2.)

In case where socket is non-blocking and recvmsg() returns 0 (this happens when we get EPOLLERR on that soket), do libnl APIs inform caller when other end closes connection i.e when recvmsg() inside nl_recv return 0 ?
libnl does not seem to have a way to let app know about this case.

How do you mean "inform"? No, nl_recv() is only a wrapper around recv. epoll tells you about the state of the file descriptor and whether you can read from it. See the manual for recv().

3.)

Why am i getting EPOLLERR in epoll_wait() on netlink socket ? is this because other side of netlink ie kernel side closed connection ?
even if kernel side closed connection why non-stop repeated EPOLLERR s on netlink sockets ?

It is a question about how epoll works with netlink sockets. I don't know the details.

from libnl.