On Thu, Jan 21, 2010 at 03:28:46PM -0500, Chuck Lever wrote: > On 01/21/2010 02:57 PM, J. Bruce Fields wrote: >> On Thu, Jan 21, 2010 at 02:37:58PM -0500, Chuck Lever wrote: >>> rpcb_getaddr(3t) is designed to use the rpcbind protocol to determine >>> the address and transport to use when contacting a remote service. Our >>> mount command has its own negotiation mechanism that is a superset of >>> rpcbind calls, in addition to having a faster timeout than >>> rpcb_getaddr(3t). >> >> What does "is a superset of rpcbind calls" mean? > > rpcb_getaddr(3t) performs a single specific rpcbind query with a long > fixed timeout. mount.nfs uses several rpcbind queries, in a particular > order, to identify which NFS-related services are available. mount.nfs > uses individual queries rather than a single DUMPALL in order to enable > firewalls to detect which ports should be opened. > >> I still don't >> understand what the proper protocol family negotiation is: what actually >> happens on the wire? > > If a particular RPC service (including rpcbind) cannot be contacted via > "inet6," and the server has an "inet" address listed in DNS, then > mount.nfs should be smart enough to try the mount request via the "inet" > address too. This is in addition to support for rpcbind queries that > can return a netid, which would include information about which protocol > family to use). > > Currently our mount.nfs command fails if the target server has at least > one IPv6 address listed in DNS in addition to an IPv4 address, but does > not support NFS/IPv6. > > For NFSv4, a server that has an IPv6 address but does not support > NFS/IPv6 will refuse connection to port 2049 over IPv6. In that case, > mount.nfs should tell the kernel to retry the mount with the server's > IPv4 address, if it has one. > > For NFSv3, a server that has an IPv6 address, but does not support > NFS/IPv6, will not register any inet6 netids in its rpcbind database. > Thus the mount.nfs command has to be smart enough to retry > PROGNOTREGISTERED results with the server's IPv4 address, if it has one. > > If the server has an IPv6 address, but is running portmap instead of > rpcbind, the initial rpcbind query connection will be refused (portmap > does not set up an IPv6 listener). In that case, the mount request > should be retried with the server's IPv4 address, if it has one. > > Note that in any of these cases, if an NFS server does not have any IPv6 > addresses listed in DNS, then behavior should be the same as before. OK, got it. (I think.) Thanks! --b. -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
