Re: [Dnsmasq-discuss] dnsmasq drops CNAME cache entries when CNAMEs collide
Hi Simon, > Answered here: > > http://lists.thekelleys.org.uk/pipermail/dnsmasq-discuss/2017q1/011068.h > tml Thanks for the pointer. Is there any chance I can convince you to revisit this? I work in a high-latency office for a big company with lots of internal apps. each on its own domain. They all point at the same CNAME (a proxy service), so this is causing me and my coworkers considerable pain in the form of extra latency. In my totally uneducated intuition, it seems like a cache for CNAMES should be a simple name -> name mapping, with the result feeding into a recursive cache lookup process. In other words, maybe it should be separate from a cache of names to records. Thanks again, Aaron ___ Dnsmasq-discuss mailing list Dnsmasq-discuss@lists.thekelleys.org.uk http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss
Re: [Dnsmasq-discuss] dnsmasq drops CNAME cache entries when CNAMEs collide
-BEGIN PGP SIGNED MESSAGE- Hash: SHA256 Answered here: http://lists.thekelleys.org.uk/pipermail/dnsmasq-discuss/2017q1/011068.h tml Cheers, Simon. On 02/02/17 11:23, Aaron Jacobs wrote: > Hi all, > > I've found what seems to me an odd behavior in dnsmasq related to > CNAME caching, and am wondering if it's a bug, or just a subtlety > of the DNS standard that I don't understand. > > I'm using dnsmasq 2.76, invoking in a way that should enable > caching: > > % ./src/dnsmasq -v Dnsmasq version 2.76 > > % sudo ./src/dnsmasq --no-resolv --server= --keep-in-foreground > --no-hosts --bind-interfaces --listen-address=127.0.2.1 > --cache-size=400 -dq > > Normally it caches fine. The first query for a domain takes awhile, > and the second takes no time at all: > > % dig @127.0.2.1 photos.yahoo.com ; sudo killall -USR1 dnsmasq > [...] ;; ANSWER SECTION: photos.yahoo.com. 299 IN > CNAME rc.yahoo.com. rc.yahoo.com. 299 IN CNAME > src.g03.yahoodns.net. src.g03.yahoodns.net. 155 IN A > 98.137.236.150 > > ;; Query time: 144 msec ;; SERVER: 127.0.2.1#53(127.0.2.1) > > % dig @127.0.2.1 photos.yahoo.com ; sudo killall -USR1 dnsmasq > [...] ;; ANSWER SECTION: photos.yahoo.com. 289 IN > CNAME rc.yahoo.com. rc.yahoo.com. 289 IN CNAME > src.g03.yahoodns.net. src.g03.yahoodns.net. 145 IN A > 98.137.236.150 > > ;; Query time: 0 msec ;; SERVER: 127.0.2.1#53(127.0.2.1) > > Note that photos.yahoo.com has a CNAME of rc.yahoo.com, which in > turn has a CNAME of src.g03.yahoodns.net. When I query another > domain with that CNAME, it appears to kill the cache entries for > those CNAMES; the next query for photos.yahoo.com is slow again, > clearly not hitting cache: > > % dig @127.0.2.1 www.flicker.com ; sudo killall -USR1 dnsmasq > [...] ;; ANSWER SECTION: www.flicker.com.1799IN > CNAME rc.yahoo.com. rc.yahoo.com. 299 IN CNAME > src.g03.yahoodns.net. src.g03.yahoodns.net. 264 IN A > 124.108.105.150 > > ;; Query time: 143 msec ;; SERVER: 127.0.2.1#53(127.0.2.1) > > % dig @127.0.2.1 photos.yahoo.com ; sudo killall -USR1 dnsmasq > [...] ;; ANSWER SECTION: photos.yahoo.com. 299 IN > CNAME rc.yahoo.com. rc.yahoo.com. 299 IN CNAME > src.g03.yahoodns.net. src.g03.yahoodns.net. 299 IN A > 124.108.105.150 > > ;; Query time: 147 msec ;; SERVER: 127.0.2.1#53(127.0.2.1) > > Here are the cache dumps after each query above: > > === dnsmasq: Host Address > Flags Expires dnsmasq: photos.yahoo.com > rc.yahoo.com CF Thu Feb 2 22:13:43 2017 dnsmasq: > src.g03.yahoodns.net 98.137.236.150 4F Thu Feb 2 > 22:11:19 2017 dnsmasq: rc.yahoo.com > src.g03.yahoodns.net CF Thu Feb 2 22:13:43 2017 === > dnsmasq: Host Address Flags > Expires dnsmasq: photos.yahoo.com rc.yahoo.com CF > Thu Feb 2 22:13:43 2017 dnsmasq: src.g03.yahoodns.net > 98.137.236.150 4F Thu Feb 2 22:11:19 2017 dnsmasq: > rc.yahoo.com src.g03.yahoodns.net CF Thu > Feb 2 22:13:43 2017 === dnsmasq: Host > Address Flags Expires dnsmasq: photos.yahoo.com CF Thu > Feb 2 22:13:43 2017 dnsmasq: src.g03.yahoodns.net > 124.108.105.150 4F Thu Feb 2 22:13:22 2017 dnsmasq: > rc.yahoo.com src.g03.yahoodns.net CF Thu > Feb 2 22:13:57 2017 dnsmasq: www.flicker.com > rc.yahoo.com CF Thu Feb 2 22:38:57 2017 === dnsmasq: > Host Address Flags > Expires dnsmasq: photos.yahoo.com rc.yahoo.com CF > Thu Feb 2 22:14:00 2017 dnsmasq: src.g03.yahoodns.net > 124.108.105.150 4F Thu Feb 2 22:14:00 2017 dnsmasq: > rc.yahoo.com src.g03.yahoodns.net CF Thu > Feb 2 22:14:00 2017 dnsmasq: www.flicker.com CF Thu Feb 2 > 22:38:57 2017 > > It appears that when dnsmasq discovers the CNAME for > www.flicker.come, it knocks the CNAME for photos.yahoo.com out of > the cache (and vice versa). Is this intended behavior? > > Thanks, Aaron > > ___ Dnsmasq-discuss > mailing list Dnsmasq-discuss@lists.thekelleys.org.uk > http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss > -BEGIN PGP SIGNATURE- Version: GnuPG v2.0.22 (GNU/Linux) iQIcBAEBCAAGBQJYkzVeAAoJEBXN2mrhkTWirzgP/RtsUl84PxNrQImJaD3VRUgR HHwdHEDrpb7wNUgMNDzoBABqjAyn0eJH/amzoz7/5ZBPegioTJ4jiOpKenQgCZA5 XVmgyX7EoFf/sOB6H1vjxuSvt25TZbTNE6WaL9LhuE/RD+xuEX31M0HGvlUHC1J3 zW5zT1tA9O2A3n6ZtaVsuS7YDYLqXvlblAIJzEb+emFq8dm1kz4it6JniWvRcL67 nIrkwBG7K/uFvevq0VVVI74YpFJIsi/epUAK3uY5xgPXukRW7d7dV8dmGg03L8Tc TmE/rZEQnYACzUl+VlA/TSB8dPlJUJmbkizApfI6kEON/HXtB9rNJPSyjp5zqdjR NRxdspoi+bB9KyMI4cngnfEMMxEieViaarv62tbIlX+2BN0QD7y4eB3ukiM3S1W5 /XRb/fEKbDM+ym8bAcc6EdBN57w7l3I+K/urxmi7bOegLdipUh3vaiGhGSX64JGA 4U
[Dnsmasq-discuss] dnsmasq drops CNAME cache entries when CNAMEs collide
Hi all, I've found what seems to me an odd behavior in dnsmasq related to CNAME caching, and am wondering if it's a bug, or just a subtlety of the DNS standard that I don't understand. I'm using dnsmasq 2.76, invoking in a way that should enable caching: % ./src/dnsmasq -v Dnsmasq version 2.76 % sudo ./src/dnsmasq --no-resolv --server= --keep-in-foreground --no-hosts --bind-interfaces --listen-address=127.0.2.1 --cache-size=400 -dq Normally it caches fine. The first query for a domain takes awhile, and the second takes no time at all: % dig @127.0.2.1 photos.yahoo.com ; sudo killall -USR1 dnsmasq [...] ;; ANSWER SECTION: photos.yahoo.com. 299 IN CNAME rc.yahoo.com. rc.yahoo.com. 299 IN CNAME src.g03.yahoodns.net. src.g03.yahoodns.net. 155 IN A 98.137.236.150 ;; Query time: 144 msec ;; SERVER: 127.0.2.1#53(127.0.2.1) % dig @127.0.2.1 photos.yahoo.com ; sudo killall -USR1 dnsmasq [...] ;; ANSWER SECTION: photos.yahoo.com. 289 IN CNAME rc.yahoo.com. rc.yahoo.com. 289 IN CNAME src.g03.yahoodns.net. src.g03.yahoodns.net. 145 IN A 98.137.236.150 ;; Query time: 0 msec ;; SERVER: 127.0.2.1#53(127.0.2.1) Note that photos.yahoo.com has a CNAME of rc.yahoo.com, which in turn has a CNAME of src.g03.yahoodns.net. When I query another domain with that CNAME, it appears to kill the cache entries for those CNAMES; the next query for photos.yahoo.com is slow again, clearly not hitting cache: % dig @127.0.2.1 www.flicker.com ; sudo killall -USR1 dnsmasq [...] ;; ANSWER SECTION: www.flicker.com.1799IN CNAME rc.yahoo.com. rc.yahoo.com. 299 IN CNAME src.g03.yahoodns.net. src.g03.yahoodns.net. 264 IN A 124.108.105.150 ;; Query time: 143 msec ;; SERVER: 127.0.2.1#53(127.0.2.1) % dig @127.0.2.1 photos.yahoo.com ; sudo killall -USR1 dnsmasq [...] ;; ANSWER SECTION: photos.yahoo.com. 299 IN CNAME rc.yahoo.com. rc.yahoo.com. 299 IN CNAME src.g03.yahoodns.net. src.g03.yahoodns.net. 299 IN A 124.108.105.150 ;; Query time: 147 msec ;; SERVER: 127.0.2.1#53(127.0.2.1) Here are the cache dumps after each query above: === dnsmasq: Host Address Flags Expires dnsmasq: photos.yahoo.com rc.yahoo.com CF Thu Feb 2 22:13:43 2017 dnsmasq: src.g03.yahoodns.net 98.137.236.150 4F Thu Feb 2 22:11:19 2017 dnsmasq: rc.yahoo.com src.g03.yahoodns.net CF Thu Feb 2 22:13:43 2017 === dnsmasq: Host Address Flags Expires dnsmasq: photos.yahoo.com rc.yahoo.com CF Thu Feb 2 22:13:43 2017 dnsmasq: src.g03.yahoodns.net 98.137.236.150 4F Thu Feb 2 22:11:19 2017 dnsmasq: rc.yahoo.com src.g03.yahoodns.net CF Thu Feb 2 22:13:43 2017 === dnsmasq: Host Address Flags Expires dnsmasq: photos.yahoo.com CF Thu Feb 2 22:13:43 2017 dnsmasq: src.g03.yahoodns.net 124.108.105.150 4F Thu Feb 2 22:13:22 2017 dnsmasq: rc.yahoo.com src.g03.yahoodns.net CF Thu Feb 2 22:13:57 2017 dnsmasq: www.flicker.comrc.yahoo.com CF Thu Feb 2 22:38:57 2017 === dnsmasq: Host Address Flags Expires dnsmasq: photos.yahoo.com rc.yahoo.com CF Thu Feb 2 22:14:00 2017 dnsmasq: src.g03.yahoodns.net 124.108.105.150 4F Thu Feb 2 22:14:00 2017 dnsmasq: rc.yahoo.com src.g03.yahoodns.net CF Thu Feb 2 22:14:00 2017 dnsmasq: www.flicker.com CF Thu Feb 2 22:38:57 2017 It appears that when dnsmasq discovers the CNAME for www.flicker.come, it knocks the CNAME for photos.yahoo.com out of the cache (and vice versa). Is this intended behavior? Thanks, Aaron ___ Dnsmasq-discuss mailing list Dnsmasq-discuss@lists.thekelleys.org.uk http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss
