On Wed, Apr 21, 2010 at 09:41:47AM +0200, Joakim Tjernlund wrote: > I am using Quagga ATM but I had a quick look at BIRD and I got a few > observations.
Hello. Thank you for your tips and notes. > The LSA/checksum code seem very inefficient. > LSAs are built allocating/reallocing bits > of memory. This is slow and will case memory fragmentation. You mean lsab_alloc() in originate_rt_lsa_body()? This allocation is just a sequential allocation in a persistent memory buffer, therefore it is very efficient (in most cases just increase of lsab_used counter) and there si no memory fragmentation (all is done inside a persistent memory buffer). > The fletcher checksum is very slow as it has extra tests in the hot path and > also > flips endian in the LSA back and forth. Do you have some suggestions for a better algorithm, or just a better implementation? Yes, the problem with flipping endianity is known. I do not studied this part of the code yet (the checksum algorithm). > I can't work out how the SPF next hop works(calc_next_hop). I tried to > compare it with > Quagga's ospf_nexthop_calculation() but the structure is too different. The > reason > for me looking into this was to see how much work it would be to add > unnumbered ppp links > but as I can't work out how nexthop is working I didn't get very far. The current code is different from what RFC says. For direct neighbors (on both ptp and non-ptp networks), we just use IP address taken from the source address of the HELLO packet of the neighbor (stored in neighbor structure returned by find_neigh_noifa()). This works well [*] for both broadcast and ptp links (numbered or unnumbered), but is broken on NBMA networks. I have some not-yet-commited changes to calc_next_hop() that on broadcast and NBMA networks uses the standard way (taking IP address from the router LSA) and the source address from HELLO packet as a nexthop is used just for PTP links. Such behavior is also suggested by RFC 5340 (for OSFPv3). [*] Regardless of how the other side is implemented. > I have impl. unnumbered ppp link for Quagga that works really well but this > work > hasn't been accepted into Quagga yet since Quagga development has stalled. > I could show you how I did it Quagga though. The development state of Quagga is sad. Do you implement it in a different way than in BIRD? I wonder whether there is any other possible way to get next hop address for unnumbered ptp links than from source address of HELLO packet. -- Elen sila lumenn' omentielvo Ondrej 'SanTiago' Zajicek (email: santi...@crfreenet.org) OpenPGP encrypted e-mails preferred (KeyID 0x11DEADC3, wwwkeys.pgp.net) "To err is human -- to blame it on a computer is even more so."
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