Date: Thu, 31 Jan 2008 17:01:49 +0100 From: "Heiko Wundram (Beenic)" <wundram@beenic.net> To: Dag-Erling =?utf-8?q?Sm=C3=B8rgrav?= <des@des.no>, freebsd-hackers@freebsd.org Subject: Re: OT: getting the protocol family of a file descriptor Message-ID: <200801311701.49792.wundram@beenic.net> In-Reply-To: <86zlumvwob.fsf@ds4.des.no> References: <200801310923.16029.wundram@beenic.net> <86zlumvwob.fsf@ds4.des.no>
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Am Donnerstag, 31. Januar 2008 16:31:32 schrieben Sie: > "Heiko Wundram (Beenic)" <wundram@beenic.net> writes: > > I'm currently in the need to get the protocol family that was used to > > create a socket (and passed via a unix domain socket to another > > program), and I've not really come up with a proper scheme other than > > to use getsockname and retrieve sa_family from the resulting socket > > (which currently matches the socket domain and historically has, but > > why take the chances ;-)). > > This is the correct way to do it, I don't understand why you think it > might not work in the future. > > > Is there any other "better" way to get at the domain (protocol family) > > of a socket? > > Why should there be a better way? Just like there is getsockopt(fd,SOL_SOCKET,SO_TYPE), I'd (somehow) assume that there's a getsockopt(fd,SOL_SOCKET,SO_DOMAIN/SO_FAMILY). I can understand that the actual protocol used to create a socket is irrelevant in most of the applications which get sockets from "outside" (as long as the type they want matches the type of the passed socket), and I've not found any (general [!], of course there's specific ways depending on the PF) way to get at that yet from a file-descriptor, but I can't understand why this also applies to the domain, as for example in case you're trying to format the address a socket is bound/connected to in a user-readable manner, you will have different code depending on the actual address type. Currently, you're basically required to do a getsockname to a struct sockaddr_storage and typecast that to the actual socket addres type based on the ss_family member (to be able to pass it to one of the *_ntop-functions, for example), but generally, I don't find this too beautiful. But, maybe, that's just my (horribly broken) taste. ;-) -- Heiko Wundram Product & Application Development
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