[Pkg-utopia-maintainers] Bug#892854: Hostname resolution getting stuck for many seconds

[Eduard Bloch]

Package: libnss-mdns
Version: 0.10-8
Severity: normal

Hi,

a few days ago I realized that something wrong is going on. The route
started freezing for no apparent reason, also ssh logins (which probably
include reverse hostname resolution) were stuck and even could timeout.

I figure that this might have to do something with unconventional
network interfaces being registered here.
Example with route:

Kernel-IP-Routentabelle
Ziel            Router          Genmask         Flags Metric Ref    Use Iface
default         _gateway        0.0.0.0         UG    0      0        0 eth0
192.168.0.0     0.0.0.0         255.255.255.0   U     0      0        0 eth0
<stuck for a while>
192.168.10.6    0.0.0.0         255.255.255.255 UH    0      0        0 tap4

I checked the process with strace and saw something weird. My DNS was
accessed, was queried, it returned data, then the connection was closed
and then it started doing something with your library and THAT is where
it didn't continue anymore. So I removed your lib and it's all fine
again.

Details:

recvfrom(4, "3W\205\3\0\1\0\0\0\1\0\0\0016\00210\003168\003192\7in-add"..., 1024, 0, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("8.8.8.8")}, [28->16]) = 93
close(4)                                = 0
openat(AT_FDCWD, "/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 4
fstat(4, {st_mode=S_IFREG|0644, st_size=291488, ...}) = 0
mmap(NULL, 291488, PROT_READ, MAP_PRIVATE, 4, 0) = 0x7f59aec84000
close(4)                                = 0
access("/etc/ld.so.nohwcap", F_OK)      = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/lib/x86_64-linux-gnu/libnss_mdns4.so.2", O_RDONLY|O_CLOEXEC) = 4
read(4, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\20\f\0\0\0\0\0\0"..., 832) = 832
fstat(4, {st_mode=S_IFREG|0644, st_size=10160, ...}) = 0
mmap(NULL, 2105360, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 4, 0) = 0x7f59ad724000
mprotect(0x7f59ad726000, 2093056, PROT_NONE) = 0
mmap(0x7f59ad925000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 4, 0x1000) = 0x7f59ad925000
close(4)                                = 0
mprotect(0x7f59ad925000, 4096, PROT_READ) = 0
munmap(0x7f59aec84000, 291488)          = 0
socket(AF_UNIX, SOCK_STREAM, 0)         = 4
fcntl(4, F_GETFD)                       = 0
fcntl(4, F_SETFD, FD_CLOEXEC)           = 0
connect(4, {sa_family=AF_UNIX, sun_path="/var/run/avahi-daemon/socket"}, 110) = 0
fcntl(4, F_GETFL)                       = 0x2 (flags O_RDWR)
fstat(4, {st_mode=S_IFSOCK|0777, st_size=0, ...}) = 0
write(4, "RESOLVE-ADDRESS 192.168.10.6\n", 29) = 29
read(4, ^C0x557ea9f505b0, 4096)           = ? ERESTARTSYS (To be restarted if SA_RESTART is set)

-- System Information:
Debian Release: buster/sid
  APT prefers unstable-debug
  APT policy: (500, 'unstable-debug'), (500, 'unstable'), (1, 'experimental-debug'), (1, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.15.0-1-amd64 (SMP w/4 CPU cores)
Locale: LANG=de_DE.UTF-8, LC_CTYPE=de_DE.UTF-8 (charmap=UTF-8), LANGUAGE=de_DE.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/bash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

-- 
Eine Rechtsprechung, die an der grundsätzlichen Kriminalisierung von
Cannabis festhält, geht an medizinischen Erkenntnissen vorbei.
		-- Ellis Huber