[OpenSIPS-Users] opensips 2.4.6 crash dns_cache module with CNAME record

[William Jin]

Hi,

We are using Opensips 2.4.6(apt repo) on Debian stretch

opensips -V
version: opensips 2.4.6 (x86_64/linux)
flags: STATS: On, DISABLE_NAGLE, USE_MCAST, SHM_MMAP, PKG_MALLOC, F_MALLOC, FAST_LOCK-ADAPTIVE_WAIT
ADAPTIVE_WAIT_LOOPS=1024, MAX_RECV_BUFFER_SIZE 262144, MAX_LISTEN 16, MAX_URI_SIZE 1024, BUF_SIZE 65535
poll method support: poll, epoll, sigio_rt, select.
main.c compiled on  with gcc 6.3.0

We started to use dns_cache module recently.

However, after we add the module, opensips crashes when it stores a particular dns_cache and we noticed below error
Dec  4 03:53:17 /usr/sbin/opensips[10788]: INFO:dns_cache:put_dnscache_value: putting key [dnscache_xxxx_naptr] with value [|] ttl = 7200
Dec  4 03:53:17 /usr/sbin/opensips[10788]: INFO:dns_cache:put_dnscache_value: putting key [dnscache__sip._udp.xxxx_srv] with value [|] ttl = 7200
Dec  4 03:53:17 /usr/sbin/opensips[10788]: INFO:dns_cache:put_dnscache_value: putting key [dnscache_xxxx_aaaa] with value [|] ttl = 7200
Dec  4 03:53:17 /usr/sbin/opensips[10788]: INFO:dns_cache:put_dnscache_value: putting key [dnscache_xxxx_a] with value [#002] ttl = 1769
Dec  4 03:53:17 /usr/sbin/opensips[10788]: INFO:dns_cache:put_dnscache_value: putting key [dnscache_yyyy_naptr] with value [|] ttl = 7200
Dec  4 03:53:17 /usr/sbin/opensips[10788]: INFO:dns_cache:put_dnscache_value: putting key [dnscache__sip._udp.yyyy_srv] with value [|] ttl = 7200
Dec  4 03:53:17 /usr/sbin/opensips[10788]: INFO:dns_cache:put_dnscache_value: putting key [dnscache_yyyy_aaaa] with value [|] ttl = 7200
Dec  4 03:53:17 /usr/sbin/opensips[10788]: INFO:dns_cache:put_dnscache_value: putting key [dnscache_yyyy_a] with value [#002] ttl = 60
Dec  4 03:53:24 /usr/sbin/opensips[10789]: INFO:dns_cache:put_dnscache_value: putting key [dnscache_[CNAME_hostname]_aaaa] with value [#012] ttl = 20062
Dec  4 03:53:24 /usr/sbin/opensips[10789]: CRITICAL:core:sig_usr: segfault in process pid: 10789, id: 6
Dec  4 03:53:24 /usr/sbin/opensips[10854]: CRITICAL:core:handle_worker: dead child 6 (EOF received), pid 10789
Dec  4 03:53:24 /usr/sbin/opensips[10773]: INFO:core:handle_sigs: child process 10789 exited by a signal 11

To replicate:
======================
dns_try_ipv6=yes
...
loadmodule "cachedb_local.so"
loadmodule "dns_cache.so"
...
modparam("dns_cache", "cachedb_url","local://")
modparam("dns_cache", "blacklist_timeout",7200)

Create a hostname with AAAA record points to a CNAME without any records (E.g www.example.com<http://www.example.com>     60     IN     CNAME    www.example.net<http://www.example.net>., but do not give any AAAA record to www.example.net<http://www.example.net>)

modparam("proto_hep", "hep_id", "[hep_dst] www.example.com;transport=udp;version=3<http://www.example.com;transport=udp;version=3>")    #we are using the hostname here in proto_hep, I think it can be triggered anywhere.
======================


>From the log, I believe if the dns query fail, it will store it for {blacklist_timeout} seconds.
However, in my case, it can get a CNAME answer, but there is no actual IPv6 IP associate with it, and it is where opensips crash happens.  The ttl = 20062 also looks weird in the log, because I set it up for 60 only.

We also tried to use the cachedb_memcached by setting up a memcache server, same crash. However, when we tried to use the same settings on a server without this particular CNAME record, then the issue is gone.

--
Regards,
William Jin

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