On Tue, 19 Jan 2010 10:43:34 -0500
Chuck Lever <chuck.lever@xxxxxxxxxx> wrote:
>
> On Jan 19, 2010, at 8:27 AM, Jeff Layton wrote:
>
> > We're poised to enable IPv6 in nfs-utils in distros. There is a
> > potential problem however. mount.nfs will prefer IPv6 addrs.
> >
> > If someone has a working IPv4 server today that has an IPv6 address,
> > then clients may start trying to mount over that address. If the
> > server
> > doesn't support NFS serving over IPv6 (and virtually no linux servers
> > currently do), then the mount will start failing.
> >
> > Avoid this problem by making the mount code prefer IPv4 addresses
> > when they are available and an address family isn't specified.
> >
> > This is the second attempt at this patch. This moves the changes
> > into nfs_validate_options. Chuck also mentioned parameterizing this
> > behavior too. This patch doesn't include that, as I wasn't exactly
> > clear on what he had in mind.
> >
> > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
> > ---
> > utils/mount/stropts.c | 32 +++++++++++++++++++++++++-------
> > 1 files changed, 25 insertions(+), 7 deletions(-)
> >
> > diff --git a/utils/mount/stropts.c b/utils/mount/stropts.c
> > index 57a4b32..f0937a2 100644
> > --- a/utils/mount/stropts.c
> > +++ b/utils/mount/stropts.c
> > @@ -326,6 +326,29 @@ static int nfs_set_version(struct nfsmount_info
> > *mi)
> > return 1;
> > }
> >
> > +static int nfs_addr_option_lookup(struct nfsmount_info *mi)
> > +{
> > + struct sockaddr *sap = &mi->address.sa;
> > + sa_family_t family;
> > +
> > + if (!nfs_nfs_proto_family(mi->options, &family))
> > + return 0;
>
> The real problem is that nfs_nfs_proto_family() returns AF_UNSPEC if
> "proto=" was not specified.
...and if it was built with libtirpc support.
> The negotiation logic here in this file
> can't handle that return properly.
>
> We could change nfs_nfs_proto_family(), or we could decide that
> returning AF_UNSPEC is the right thing to do when "proto=" isn't
> specified. If the latter, then nfs_nfs_proto_family() (and
> nfs_mount_proto_family) should get a documenting comment that
> describes the meaning of the AF_UNSPEC return.
>
Yep, and we also will need to fix it up for the non-libtirpc case.
> Also, do you need to look at how nfs_mount_proto_family is used in
> other nearby routines? It has the same problem. What do you do when
> "mountproto=udp6" is specified?
>
That is a problem we'll have to deal with, yes...
> > +
> > + mi->salen = sizeof(mi->address);
> > +
> > +#ifdef IPV6_SUPPORTED
> > + /*
> > + * A lot of servers don't support NFS over IPv6 yet. For now,
> > + * IPv4 addresses are preferred.
> > + */
>
> I think that doesn't describe this workaround adequately. This is a
> temporary crutch that prevents us from using IPv6 if "proto=" isn't
> specified. The underlying problem here is that nfs_lookup() returns
> just one address.
>
Yes. The best solution would be to somehow try all addresses in the
list until one works. That's a larger project however and we'll
probably need some significant kernel changes to handle that anyway.
> > + if (family == AF_UNSPEC &&
> > + nfs_lookup(mi->hostname, AF_INET, sap, &mi->salen))
> > + return 1;
> > +#endif /* IPV6_SUPPORTED */
> > +
> > + return nfs_lookup(mi->hostname, family, sap, &mi->salen);
> > +}
> > +
> > /*
> > * Set up mandatory non-version specific NFS mount options.
> > *
> > @@ -333,16 +356,11 @@ static int nfs_set_version(struct
> > nfsmount_info *mi)
> > */
> > static int nfs_validate_options(struct nfsmount_info *mi)
> > {
> > - struct sockaddr *sap = &mi->address.sa;
> > - sa_family_t family;
> >
> > if (!nfs_parse_devname(mi->spec, &mi->hostname, NULL))
> > return 0;
> >
> > - if (!nfs_nfs_proto_family(mi->options, &family))
> > - return 0;
> > - mi->salen = sizeof(mi->address);
> > - if (!nfs_lookup(mi->hostname, family, sap, &mi->salen))
> > + if (!nfs_addr_option_lookup(mi))
> > return 0;
> >
> > if (!nfs_set_version(mi))
> > @@ -351,7 +369,7 @@ static int nfs_validate_options(struct
> > nfsmount_info *mi)
> > if (!nfs_append_sloppy_option(mi->options))
> > return 0;
> >
> > - if (!nfs_append_addr_option(sap, mi->salen, mi->options))
> > + if (!nfs_append_addr_option(&mi->address.sa, mi->salen, mi-
> > >options))
> > return 0;
> >
> > return 1;
> > --
> > 1.6.5.2
> >
>
--
Jeff Layton <jlayton@xxxxxxxxxx>
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