flaky mDNS test

[marten-seemann]

It looks like packing the DNS message is the problem here. Maybe we're violating some kind of length limit?

2021/09/27 21:33:52 [ERR] zeroconf: failed to send probe: failed to pack msg ;; opcode: QUERY, status: NOERROR, id: 4344
  ;; flags:; QUERY: 1, ANSWER: 0, AUTHORITY: 2, ADDITIONAL: 0
  
  ;; QUESTION SECTION:
  ;\018\ *\198*\229\139\238e\188..\002K?\172#\'\000\249LY\248<\177\131\ \246<\2081\154\009._p2p._udp.local.	IN	 PTR
  
  ;; AUTHORITY SECTION:
  \018\ *\198*\229\139\238e\188..\002K?\172#\'\000\249LY\248<\177\131\ \246<\2081\154\009._p2p._udp.local.	3200	IN	SRV	0 0 4001 QmRDdGEXksiR4mHSCUBFPGi7oUWkvJg1ZjkTgXps4WyeQp.local.
  \018\ *\198*\229\139\238e\188..\002K?\172#\'\000\249LY\248<\177\131\ \246<\2081\154\009._p2p._udp.local.	3200	IN	TXT	"dnsaddr=/ip4/127.0.0.1/tcp/49492/p2p/QmRDdGEXksiR4mHSCUBFPGi7oUWkvJg1ZjkTgXps4WyeQp"
  : dns: bad rdata
  2021/09/27 21:33:52 [ERR] zeroconf: failed to send probe: failed to pack msg ;; opcode: QUERY, status: NOERROR, id: 4344
  ;; flags:; QUERY: 1, ANSWER: 0, AUTHORITY: 2, ADDITIONAL: 0
  
  ;; QUESTION SECTION:
  ;\018\ *\198*\229\139\238e\188..\002K?\172#\'\000\249LY\248<\177\131\ \246<\2081\154\009._p2p._udp.local.	IN	 PTR
  
  ;; AUTHORITY SECTION:
  \018\ *\198*\229\139\238e\188..\002K?\172#\'\000\249LY\248<\177\131\ \246<\2081\154\009._p2p._udp.local.	3200	IN	SRV	0 0 4001 QmRDdGEXksiR4mHSCUBFPGi7oUWkvJg1ZjkTgXps4WyeQp.local.
  \018\ *\198*\229\139\238e\188..\002K?\172#\'\000\249LY\248<\177\131\ \246<\2081\154\009._p2p._udp.local.	3200	IN	TXT	"dnsaddr=/ip4/127.0.0.1/tcp/49492/p2p/QmRDdGEXksiR4mHSCUBFPGi7oUWkvJg1ZjkTgXps4WyeQp"

[marten-seemann]

The problem seems to be the .., triggering this error check:
https://github.com/miekg/dns/blob/1630ffe2ca114df2491e320f7aa488abb209b271/msg.go#L267-L271

[marten-seemann]

two dots back to back
sprintName  ׇ��\�f�cD��x..�}��T�Z.{�I���._p2p._udp.local.
sprintName QmcqzLMatusgFduNJibEnaLyMKYYyPG2qcBWCkjfY4nQ2K.local.
sprintName  ׇ��\�f�cD��x..�}��T�Z.{�I���._p2p._udp.local.
sprintName _p2p._udp.local.
sprintName  ׇ��\�f�cD��x..�}��T�Z.{�I���._p2p._udp.local.
sprintName _services._dns-sd._udp.local.
sprintName _p2p._udp.local.
sprintName QmcqzLMatusgFduNJibEnaLyMKYYyPG2qcBWCkjfY4nQ2K.local.
2021/09/30 02:05:43 [ERR] zeroconf: failed to send announcement: failed to pack msg ;; opcode: QUERY, status: NOERROR, id: 0
;; flags: qr; QUERY: 0, ANSWER: 5, AUTHORITY: 0, ADDITIONAL: 0

;; ANSWER SECTION:
\018\ \215\135\166\133\020\135f\212cD\250\177\024x..\206}\142\016\153T\130Z.{\136I\160\176\160._p2p._udp.local.	3200	CLASS32769	SRV	0 0 4001 QmcqzLMatusgFduNJibEnaLyMKYYyPG2qcBWCkjfY4nQ2K.local.
\018\ \215\135\166\133\020\135f\212cD\250\177\024x..\206}\142\016\153T\130Z.{\136I\160\176\160._p2p._udp.local.	3200	CLASS32769	TXT	"dnsaddr=/ip4/127.0.0.1/tcp/36301/p2p/QmcqzLMatusgFduNJibEnaLyMKYYyPG2qcBWCkjfY4nQ2K"
_p2p._udp.local.	3200	IN	PTR	\018\ \215\135\166\133\020\135f\212cD\250\177\024x..\206}\142\016\153T\130Z.{\136I\160\176\160._p2p._udp.local.
_services._dns-sd._udp.local.	3200	IN	PTR	_p2p._udp.local.
QmcqzLMatusgFduNJibEnaLyMKYYyPG2qcBWCkjfY4nQ2K.local.	120	CLASS32769	A	127.0.0.1
: dns: bad rdata