On Monday 29 Nov 2021, at 20:38, Robert Elz wrote: > | In addition, I just noticed that res_nquery(3) in > | libc/resolv/res_query.c uses a similar buffer but of size > | min(PACKETSZ, 1024). PACKETSZ seems to be 512 bytes only. > > That is as it shoukd be. > PR tge huge stack array if yiu want, but not the different sizes. > > DNS queries (via UDP) are limited to max 512, as that is what the > protocol always required, so can be handled by everything (or should be). > Further, that's big enough fro almost every query, in which the only > large object is thd domain name to lookup which is limited to 256 bytes. > > Replies however can be any size (allowed by UDP) as the query can inform > tge server what max size reply csn be received.
OK. But then I don't see why the res_queryN() function in net/getaddrinfo.c ( https://anonhg.netbsd.org/src/file/tip/lib/libc/net/getaddrinfo.c#l2550 ) would need more than PACKETSZ bytes to send a query. It seems to me (but I might be wrong) that the function is doing the same as res_nquery() in resolv/res_query.c, and the answers are stored in the input buffer passed in "target" as a parameter, not in the buffer on the stack. Am I missing something? It seems to me that rev. 1.63 of net/getaddrinfo.c ( http://cvsweb.netbsd.org/bsdweb.cgi/src/lib/libc/net/getaddrinfo.c.diff?r1=1.62&r2=1.63 ) correctly updated the buffer size for the function _dns_query, but as an unwanted side effect also increased the req_queryN() that uses the same MAXPACKET definition.
