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? IANA might not set different port like this, but there's nothing that stops someone from doing this at their site. 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. -- Jeff Layton <jlayton@xxxxxxxxxx> -- 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
