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. 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.
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?
+
+ 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.
+ 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
--
Chuck Lever
chuck[dot]lever[at]oracle[dot]com
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