Kevin Ryde <[EMAIL PROTECTED]> writes: > There's a note in "Network Address Conversion" where ipv4 addrs are > described. Hopefully a cross reference to it is enough, unless > there's something especially zany happening.
Sounds good. These calls aren't odd from the htonl viewpoint. > About IP_ADD_MEMBERSHIP: In linux I see there's a separate imr_ifindex > in struct ip_mreqn for an interface index. Do you need/want to do > anything with that? (I've never used this stuff, so I've got no idea > if it's good for anything or what it should look like.) It is useful, but complex. Here's the full story: When joining a multicast group, you have to specify the group (straightforward), and some way to specify the interface. The struct ip_mreq dates from BSD long long ago (multicast patches to 4.3 in late 80s I think). The second IP address is INADDR_ANY for "use the default interface (found by looking up the group in the routing table, almost always hitting the default route)", or an address used to find an interface, usually by it being an address of some interface. At some point the BSDs added the convention that 0.0.0.x would refer to the interface with ifindex x, and this follows RFC1724, which provides for this method of referring to unnumered interfaces in the RIPv2 MIB. This was added to NetBSD in early 2001: http://mail-index.netbsd.org/tech-net/2001/01/13/0003.html Specifying by ifindex is useful for unnumbered interfaces, for example joining the ospf all routers group on a ppp link with no IPv4 addresses, or addresses reused from some other interface. Normal programs don't do this - it's typically a routing protocol implementation issue. My understanding is that Linux has an additional field to specify by ifindex (the imr_ifindex you mention). So, the right thing to do for guile is to either follow the BSD way, and translate 0.0.0.x/8 in the second arg into setting imr_ifindex on Linux. follow the Linux way, and make it a vector of 3 and translate back into the 0.0.0.x/8 on BSD. I prefer the first way, since this is orginally a BSD interface and because it's less burdensome to those who are blissfully unaware of this complexity, as I suspect you wish you still were. The code I submitted just puts the two addresses in the two fields; someone could spiff it up for ifindex support on Linux if they were so inclined. I suspect the need will not arise, given how long guile went without being able to join groups at all. -- Greg Troxel <[EMAIL PROTECTED]> _______________________________________________ Guile-devel mailing list Guile-devel@gnu.org http://lists.gnu.org/mailman/listinfo/guile-devel
