On Apr 6, 2009, at 11:21 AM, Jeff Layton wrote:
On Mon, 6 Apr 2009 11:03:11 -0400
Chuck Lever <chuck.lever@xxxxxxxxxx> wrote:
On Apr 3, 2009, at 3:04 PM, Jeff Layton wrote:
On Wed, 1 Apr 2009 14:01:30 -0400
Chuck Lever <chuck.lever@xxxxxxxxxx> wrote:
As far as I understand it, the ai_socktype and ai_protocol fields
are
used to return the values needed for subsequent socket(2)/bind(2)
system calls. In this case you are not using these fields from the
results...
If ai_protocol is zero, then getaddrinfo(3) assumes you want one
copy
of the address for each supported protocol type, so it returns
three
structures (one for IPPROTO_UDP, one for IPPROTO_TCP, and one
with a
zero protocol number). The contents, except for the socktype and
protocol fields, are the same for each.
Hypothetical situation...
Suppose there is a service in /etc/services that has a different
port
number for tcp than for udp:
fooserv 50001/tcp
fooserv 50002/udp
You're saying that getaddrinfo will return the same port number in
all
of the returned structures? Won't that mean that one of the port
numbers
is wrong? That seems broken if so...
I was trying to describe observed behavior here -- it's pretty
unlikely that there will be different port numbers in these returned
structures. It's difficult to say precisely how this is supposed to
behave based on the man page or even browsing the glibc source code
for a few minutes.
It's certainly possible to set up /etc/services as you suggest, but
there is an IANA policy to assign the same port for both transports.
As near as I can tell the reason we have the transport listed in /
etc/
services at all is because some protocols support only one transport.
So IMO it would be quite unlikely to encounter such a case where the
port number depended on the transport.
If that's not the case, then I think we need to at least set the
ai_protocol in the hints.
Perhaps that's true. What are the expected values of @service ?
I've only ever seen "nfs" here, but I guess you could use this with
others. Maybe "nfsacl" too?
What's even stranger is that one is supposed to use rpcbind to figure
out what NFS port to use, not /etc/services.
IANA might not set different port like this, but there's nothing
that stops someone from doing this at their site.
True, but one might expect that setting the NFS service port via
rpc.nfsd on the server would make gssd use that port too. I guess
that's why the port number is now passed up from the kernel.
I agree that it's an unlikely (and somewhat pathological) situation,
but it's easy to deal with -- just set the protocol in the hints. I've
confirmed that it makes getaddrinfo do the right thing.
That's good. I think we need to understand exactly what this is
supposed to do, though. Should we use an rpcbind call here instead?
This is _rpc_ gssd, after all. If it's OK as it stands, then I think
some comments about why this works this way are in order :-)
Kevin, can you enlighten us?
--
Chuck Lever
chuck[dot]lever[at]oracle[dot]com
--
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
