On Dec 12, 2003, at 1:15 AM, Jun-ichiro itojun Hagino wrote:
now we have couple of new transport protocols coming, such as SCTP and
DCCP. how can we support service name lookup for those? i.e.
how can we tell getnameinfo(3) to use "sctp" or "dccp" for the 2nd
argument of getservbyport(3)?
my proposal:
define NI_UDP as replacement of NI_DGRAM. deprecate NI_DGRAM (keep
it as an alias to NI_UDP is okay). define NI_SCTP, NI_DCCP and such.
these three are mutually exclusive, and if more than one is specified
it would cause EAI_FAIL.
Since getnameinfo in theory should apply to non-Inet protocols
I think it would be useful to try to abstract from NI_SCTP and NI_DCCP
to something which captures the flavors/attributes of those transports.
I don't know if NI_SEQPACKET is descriptive for SCTP and protocols
of that flavor.
I have no idea what a more abstract name would be descriptive for DCCP.
SCTP supports both SOCK_DGRAM, SOCK_STREAM as well as SOCK_SEQPACKET. DCCP should be SOCK_DGRAM only, if i understand correctly.
therefore, there's no 1-by-1 mapping from SOCK_xx to IPPROTO_xx.
to clarify, i agree there should be some way to support non-inet
protocols, however i'm not sure how service lookup works for non-inet
protocols. do people have any examples (such as appletalk or whatever)?
AppleTalk is dead. Well, it's not quite dead yet, but it's getting there.
AppleTalk used something called NBP (Name Binding Protocol?). There were no host names, only service names. Services were discovered by type and a service name (an instance of a service) was resolved to an AppleTalk address and port. AppleTalk didn't have the notion of different sets of port lists for different protocols. The port came right after the address. It would be sort of like layering TCP, ICMP, and all other IP protocols on top of UDP.
It is unlikely anyone would ever work to support AppleTalk service name resolution through the getnameinfo API.
I don't think it is useful to abstract NI_SCTP and friends to support non-inet protocols. No matter what you do with getnameinfo, writing code to try and abstract out the protocol family with the socket APIs is nearly impossible. If someone wants to support some non-inet protocol, then they can probably handle an additional lookup or use some new vendor specific value that means SCTP or ApplesSCTPLikeAppleTalkBasedProtocol. What is there other than IP/IPv6? NetBIOS...IPX...AppleTalk...OSI? They're all dying (or should be).
-josh
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