From: Martin KaFai Lau

Sent: 27 July 2022 07:09

A latter patch refactors bpf_setsockopt(SOL_SOCKET) with the
sock_setsockopt() to avoid code duplication and code
drift between the two duplicates.

The current sock_setsockopt() takes sock ptr as the argument.
The very first thing of this function is to get back the sk ptr
by 'sk = sock->sk'.

bpf_setsockopt() could be called when the sk does not have
a userspace owner.  Meaning sk->sk_socket is NULL.  For example,
when a passive tcp connection has just been established.  Thus,
it cannot use the sock_setsockopt(sk->sk_socket) or else it will
pass a NULL sock ptr.

I'm intrigued, I've some code that uses sock_create_kern() to create
sockets without a userspace owner - I'd have though bpf is doing
much the same.

I end up doing:
        if (level == SOL_SOCKET)
                err = sock_setsockopt(sock, level, optname, koptval, optlen);
        else
                err = sock->ops->setsockopt(sock, level, optname, koptval,
                                            optlen);
to set options.
(This code used to use kern_setsockopt() - but that got removed.)

I'd have though bpf would need similar code??

	David

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