[9fans] continued dns problems

[9fans] continued dns problems

[erik quanstrom]

disclaimer: dns works great at 2 of the 3 plan 9 sites i maintain.
unfortunately, one squeeky mouse gets the exterminator fired.

dns under heavy use is continuing to be problematic.  before
the recent locking changes, i was seeing several crashes a month.
after the locking changes, i am seeing many bad rrs that appear
to cause lookups to fail.  the changes all looked good to me, so
i'm uncertain what's going on.  regardless, there were 6-7 *reported*
lookup failures on friday.  i don't know if the crashes were masking
the old problem. google.com, for example,  tends to get a number
of wierd rrs. pages don't load.

bowing to pressure over failed lookups, i'm trying a downgrade to
the server as of 20100305.  i'm hoping i can more easily detect a
broken server than one with bad rrs.

sorry for the crappy bug report.  there has been zero time in the
schedule to debug this problem.  (and people don't generally
even report a problem.)  i'm also sorry that there's no code, but
it's not clear to me that change is welcome.

despite russ' objections, i still think ndb/dns needs a restructuring.
if the rr db were a single thread that communicated with the
query threads via channels, it would be much easier to debug.

after at least 10 years of the current setup, we've proven that
the current structure is at a minimum hard to debug.

- erik

Re: [9fans] continued dns problems

[erik quanstrom]

further information.  it appears that plan 9 dns is vulnerable to
cache poisoning.  i just caught a second machine with these entries

	 ns	localhost UN 1269483730/1269483730
	 ns	B.ROOT-SERVERS.NET UN 1273157904/1273157904
	 ns	C.ROOT-SERVERS.NET UN 1273157904/1273157904
	 ns	D.ROOT-SERVERS.NET UN 1273157904/1273157904
	 ns	E.ROOT-SERVERS.NET UN 1273157904/1273157904
	 ns	F.ROOT-SERVERS.NET UN 1273157904/1273157904
	 ns	G.ROOT-SERVERS.NET UN 1273157904/1273157904
	 ns	H.ROOT-SERVERS.NET UN 1273157904/1273157904
	 ns	I.ROOT-SERVERS.NET UN 1273157904/1273157904
	 ns	J.ROOT-SERVERS.NET UN 1273157904/1273157904
	 ns	K.ROOT-SERVERS.NET UN 1273157904/1273157904
	 ns	L.ROOT-SERVERS.NET UN 1273157904/1273157904
	 ns	M.ROOT-SERVERS.NET UN 1273157904/1273157904
	 ns	A.ROOT-SERVERS.NET UN 1273157904/1273157904
>>	 ns	ns1.parked.com UN 1269855557/1269855557
>>	 ns	ns2.parked.com UN 1269855557/1269855557
	 ns	A.ROOT-SERVERS.NET UD 1303335771/0
	 ns	B.ROOT-SERVERS.NET UD 1303335771/0
	 ns	C.ROOT-SERVERS.NET UD 1303335771/0
	 ns	D.ROOT-SERVERS.NET UD 1303335771/0
	 ns	E.ROOT-SERVERS.NET UD 1303335771/0
	 ns	F.ROOT-SERVERS.NET UD 1303335771/0
	 ns	G.ROOT-SERVERS.NET UD 1303335771/0
	 ns	H.ROOT-SERVERS.NET UD 1303335771/0
	 ns	I.ROOT-SERVERS.NET UD 1303335771/0
	 ns	J.ROOT-SERVERS.NET UD 1303335771/0
	 ns	K.ROOT-SERVERS.NET UD 1303335771/0
	 ns	L.ROOT-SERVERS.NET UD 1303335771/0
	 ns	M.ROOT-SERVERS.NET UD 1303335771/0
>>	 ns	ns1.trafficz.com UN 1272210527/1272210527
>>	 ns	ns2.trafficz.com UN 1272210527/1272210527
	 soa	ns1.parked.com admin.parked.com 2006032101 7200 1800 1209600 10800 AN 1269743556/1269743556
	 soa	ns01.cashparking.com dns.jomax.net 2010021700 28800 7200 604800 86400 AN 1271491124/1271491124
	 soa	ns1.gunas.net hostmaster 2008092011 3600 900 604800 14400 AN 1271839986/1271839986
	 soa	A.ROOT-SERVERS.NET nstld.verisign-grs.com 2010042200 1800 900 604800 86400 AN 1272015686/1272015686
	 soa	ns1.trafficz.com hostmaster 1271791802 16384 2048 1048576 2560 AN 1271945458/1271945458
[etc]


- erik