FreeBSD src
24c42ee823
- yp_dblookup.c: Create non-DB specific database access functions. Using these allows access to the underlying database functions without needing explicit knowledge of Berkeley DB. (These are used only when DB_CACHE is #defined. Other programs that use the non-caching functions (yp_mkdb, ypxfr, yppush, rpc.yppasswdd) shouldn't notice the difference.) - yp_dnslookup: Implement async DNS lookups. We send our own DNS requests using UDP and put the request in a queue. When the response arrives, we use the ID in the header to find the corresponsing queue entry and then send the response to the client. We can go about our business and handle other YP requests in the meantime. This way, we can deal with time consuming DNS requests without blocking and without forking. - yp_server.c: Convert to using new non-DB-specific database access functions. This simplifies the code a bit and removes the need for this module to know anything about Berkeley DB. Also convert the ypproc_match_2_svc() function to use the async DNS lookup routines. - yp_main.c: tweak yp_svc_run() to add the resolver socket to the set of descriptors monitored in the select() loop. Also add a timeout to select(); we may get stale DNS requests stuck in the queue which we want to invalidate after a while. If the timeout hits, we decrement the ttl on all pending DNS requests and nuke those requests that aren't handled before ttl hits zero. - yp_extern.h: Add prototypes for new stuff. - yp_svc_udp.c (new file): The async resolver code needs to be able to rummage around inside the RPC UDP transport handle in order to work correcty. There's basically one transport handle, and each time a request comes in, the transaction ID in the handle is changed. This means that if we queue a DNS request, then we handle some other unrelated requests, we will be unable to send the DNS response because the transaction ID and remote address of the client that made the DNS request will have been lost. What we need to do is save the client address and transaction ID in the queue entry for the DNS request, then put the transaction ID and address back in the transport handle when we're ready to reply. (And then we have to undo the change so as not to confuse any other part of the server.) The trouble is that the transaction ID is hidden in an opaque part of the transport handle, and only the code in the svc_udp module in the RPC library knows how to handle it. This file contains a couple of functions that let us read and set the transaction ID in spite of this. This is really a dirty trick and I should be taken out and shot for even thinking about it, but there's no other way to get this stuff to work. - Makefile: add yp_svc_udp.c to SRCS. |
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