Re: getsockopt(2)

[christos%astron.com@localhost (Christos Zoulas)]

In article <x7wp3xi6py.fsf%ren.fdy2.co.uk@localhost>,
Robert Swindells  <rjs%fdy2.co.uk@localhost> wrote:
>
>I wrote:
>>Does anyone know why we don't use the input 'optlen' parameter to the
>>getsockopt(2) syscall, we do write back to it on return.
>>
>>In ip_output() there is this, which suggests that someone had come
>>across this before.
>>
>>#if 0   /* defined(IPSEC) */
>>                case IP_IPSEC_POLICY:
>>                {
>>                        struct mbuf *m = NULL;
>>
>>                        /* XXX this will return EINVAL as sopt is empty */
>>                        error = ipsec4_get_policy(inp, sopt->sopt_data,
>>                            sopt->sopt_size, &m);
>>                        if (error == 0)
>>                                error = sockopt_setmbuf(sopt, m);
>>                        break;
>>                }       
>>#endif /*IPSEC*/  
>>
>>There are also lots of places in sctp_usrreq that want to use it.
>>
>>I can set it with the following patch (line numbers will be slightly
>>out), but wondered if there was a reason for the current behaviour.
>
>Version 2 of the patch is below, the uses of getsockopt(2) by IPSEC and
>SCTP expect that the optval data is copied into the kernel and back out
>again by the syscall.
>
>It looks like it was broken by this commit:
>
><http://mail-index.netbsd.org/source-changes/2008/08/06/msg208868.html>
>
>Index: uipc_syscalls.c
>===================================================================
>RCS file: /cvsroot/src/sys/kern/uipc_syscalls.c,v
>retrieving revision 1.187
>diff -u -r1.187 uipc_syscalls.c
>--- uipc_syscalls.c	20 Jun 2017 20:34:49 -0000	1.187
>+++ uipc_syscalls.c	14 Oct 2017 22:24:15 -0000
>@@ -1235,7 +1240,13 @@
> 	if ((error = fd_getsock1(SCARG(uap, s), &so, &fp)) != 0)
> 		return (error);
> 
>-	sockopt_init(&sopt, SCARG(uap, level), SCARG(uap, name), 0);
>+	sockopt_init(&sopt, SCARG(uap, level), SCARG(uap, name), valsize);
>+
>+	if (valsize > 0) {
>+		error = copyin(SCARG(uap, val), sopt.sopt_data, valsize);
>+		if (error)
>+			goto out;
>+	}
> 
> 	if (fp->f_flag & FNOSIGPIPE)
> 		so->so_options |= SO_NOSIGPIPE;

Neither FreeBSD or OpenBSD copyin the value, but I think it is ok to
do so if it is useful to read the input to deduce the output. But that
would make the call asymetric, so let's examine the examples where this
is useful first.

christos