7 Jul
2020
7 Jul
'20
6:13 p.m.
This bug report concerns a Kamailio instance that's functioning as an edge proxy,
accepting requests from clients over TLS and forwarding them to internal components over
UDP.
I've observed occasional "deadlocks" that all take place after there were
connectivity issues between Kamailio and one or more of the clients (logging messages such
as "tcp_send failed", "handle_tcpconn_ev(): connect x failed",
"tcp_read_data(): error reading: Connection reset by peer").
Environment:
* Ubuntu 16.04
* Kamailio 5.2.7 (5.2.7+ubuntu16.04)
Relevant config:
```
# for TLS clients
socket_workers=10
listen=tls:wan.ip:TLS_PORT
# to be able to forward incoming TCP requests to UDP destinations
socket_workers=10
listen=udp:wan.ip:TLS_PORT
# for RPC commands
socket_workers=2
listen=tcp:127.0.0.1:HTTP_PORT
```
## Reproduction
After a lot of trial and error, I've found a way to somewhat reproducibly trigger the
problem using sipp. It involves setting up a large amount of simultaneous calls dialing
into the edge proxy using TLS, to a destination UA that will answer the call and keep it
open for a few seconds, then using `ctrl-c` to suddenly quit sipp which will ungracefully
terminate the TCP/TLS connections.
It takes me a couple of iterations to trigger the problem, e.g repeat until Kamailio
starts failing:
* start sipp
* terminate sipp with ctrl-c
* (quickly) restart sipp
* terminate sipp
* etc
The amount of simultaneous calls has to be sufficiently large. In my environment I'm
unable to reproduce the problem at all with 10-20 calls, while 50 calls always triggers
the problem after a couple of iterations.
Example sipp commandline: `sipp -nd -sf caller.xml -d 2000 -r 50 -l 500 -m 5000
-max_socket 1000 -t ln -tls_cert cert.crt -tls_key key.key kamailio.edge.proxy:5061`
## Failure mode 1
In one of the failure modes, it appears that all available TCP/TLS workers are permanently
bricked; sipp's calls will simply timeout and not trigger any dialplan handling.
Interestingly, even though I have dedicated workers for TLS (SIP client) and TCP (RPC
commands), and my reproduction scenario doesn't connect to the HTTP_PORT at all, this
failure scenario bricks the TCP (RPC) listeners as well; any curl requests to it will
simply timeout as well.
Kamailio will hang for a while on (systemd) restart.
## Failure mode 2
In another failure mode, it looks like the TCP workers are unaffected but the UDP perform
forwarding to UDP destinations are broken. Sipp's calls will enter Kamailio, but
forwarding (`relay()`) to the next hop will timeout even though the destination is
functioning just fine. Since this failure mode doesn't break RPC I was able to enable
debug logging:
```
2020-07-07T17:26:58.770411+02:00 kamailio[24056]: INFO: From Customer
2020-07-07T17:26:58.770697+02:00 kamailio[24056]: DEBUG: pv [pv_trans.c:590]:
tr_eval_string(): i=0 j=2
2020-07-07T17:26:58.770971+02:00 kamailio[24056]: DEBUG: dispatcher [dispatch.c:2055]:
ds_manage_routes(): set [4]
2020-07-07T17:26:58.771248+02:00 kamailio[24056]: DEBUG: dispatcher [dispatch.c:2161]:
ds_manage_routes(): using alg [0] hash [250849449]
2020-07-07T17:26:58.771535+02:00 kamailio[24056]: DEBUG: dispatcher [dispatch.c:2205]:
ds_manage_routes(): selected [0-4-0/1] <sip:wan.ip:8065>
2020-07-07T17:26:58.771817+02:00 kamailio[24056]: DEBUG: dispatcher [dispatch.c:2226]:
ds_manage_routes(): using first entry [4/1]
2020-07-07T17:26:58.772090+02:00 kamailio[24056]: DEBUG: dispatcher [dispatch.c:2269]:
ds_manage_routes(): using entry [4/0]
2020-07-07T17:26:58.772362+02:00 kamailio[24056]: DEBUG: dispatcher [dispatch.c:2016]:
ds_select_dst_limit(): selected target destinations: 2
2020-07-07T17:26:58.773001+02:00 kamailio[24056]: DEBUG: pv [pv_core.c:2611]:
pv_set_force_sock(): trying to set send-socket to [udp:wan.ip:5061]
2020-07-07T17:26:58.773353+02:00 kamailio[24056]: DEBUG: <core>
[core/socket_info.c:559]: grep_sock_info(): checking if host==us: 13==13 &&
[wan.ip] == [wan.ip]
2020-07-07T17:26:58.773829+02:00 kamailio[24056]: DEBUG: <core>
[core/socket_info.c:566]: grep_sock_info(): checking if port 5061 (advertise 0) matches
port 5061
2020-07-07T17:26:58.774122+02:00 kamailio[24056]: NOTICE: Relaying (cid:
1-9151(a)sipp.ip).
2020-07-07T17:26:58.774417+02:00 kamailio[24056]: DEBUG: siputils [checks.c:120]:
has_totag(): no totag
2020-07-07T17:26:58.774708+02:00 kamailio[24056]: DEBUG: tm [t_lookup.c:1344]:
t_newtran(): msg (0x7f69d1cc4980) id=1265/24056 global id=1265/24056 T start=(nil)
2020-07-07T17:26:58.774989+02:00 kamailio[24056]: DEBUG: tm [t_lookup.c:499]:
t_lookup_request(): start searching: hash=43232, isACK=0
2020-07-07T17:26:58.775315+02:00 kamailio[24056]: DEBUG: tm [t_lookup.c:457]:
matching_3261(): RFC3261 transaction matching failed - via branch [z9hG4bK-9151-1-1]
2020-07-07T17:26:58.775612+02:00 kamailio[24056]: DEBUG: tm [t_lookup.c:682]:
t_lookup_request(): no transaction found
2020-07-07T17:26:58.775908+02:00 kamailio[24056]: DEBUG: <core>
[core/md5utils.c:67]: MD5StringArray(): MD5 calculated: 0a5d4a8d13f9606523da9c4d193b2261
2020-07-07T17:26:58.776270+02:00 kamailio[24056]: DEBUG: <core>
[core/dns_cache.c:3197]: dns_srv_sip_resolve(): (wan.ip, 0, 0), ip, ret=0
2020-07-07T17:26:58.776701+02:00 kamailio[24056]: DEBUG: <core>
[core/msg_translator.c:1765]: check_boundaries(): no multi-part body
2020-07-07T17:26:58.777012+02:00 kamailio[24056]: DEBUG: <core>
[core/msg_translator.c:2935]: create_via_hf(): id added: <;i=a701>, rcv proto=3
2020-07-07T17:26:58.777596+02:00 kamailio[24056]: DEBUG: tm [t_funcs.c:375]:
t_relay_to(): new transaction forwarded
2020-07-07T17:26:58.777948+02:00 kamailio[24056]: DEBUG: <core>
[core/receive.c:354]: receive_msg(): request-route executed in: 1927 usec
2020-07-07T17:26:58.778243+02:00 kamailio[24056]: DEBUG: <core>
[core/usr_avp.c:636]: destroy_avp_list(): destroying list (nil)
2020-07-07T17:26:58.779265+02:00 kamailio[24056]: message repeated 5 times: [ DEBUG:
<core> [core/usr_avp.c:636]: destroy_avp_list(): destroying list (nil)]
2020-07-07T17:26:58.779431+02:00 kamailio[24056]: DEBUG: <core> [core/xavp.c:507]:
xavp_destroy_list(): destroying xavp list (nil)
2020-07-07T17:26:58.779753+02:00 kamailio[24056]: DEBUG: <core>
[core/receive.c:458]: receive_msg(): cleaning up
2020-07-07T17:27:00.705303+02:00 kamailio[24053]: DEBUG: tm [t_reply.c:1266]:
t_should_relay_response(): ->>>>>>>>> T_code=0, new_code=408
2020-07-07T17:27:00.705917+02:00 kamailio[24053]: DEBUG: tm [t_lookup.c:1041]:
t_check_msg(): msg (0x7f69b1017e80) id=1264/24056 global id=1264/24056 T
start=0x7f69b10167c0
2020-07-07T17:27:00.706187+02:00 kamailio[24053]: DEBUG: tm [t_lookup.c:1116]:
t_check_msg(): T (0x7f69b10167c0) already found for msg (0x7f69b1017e80)!
2020-07-07T17:27:00.706533+02:00 kamailio[24053]: DEBUG: tmx [t_var.c:539]:
pv_get_tm_reply_code(): reply code is <408>
2020-07-07T17:27:00.706879+02:00 kamailio[24053]: DEBUG: tm [t_lookup.c:1041]:
t_check_msg(): msg (0x7f69b1017e80) id=1264/24056 global id=1264/24056 T
start=0x7f69b10167c0
2020-07-07T17:27:00.707198+02:00 kamailio[24053]: DEBUG: tm [t_lookup.c:1116]:
t_check_msg(): T (0x7f69b10167c0) already found for msg (0x7f69b1017e80)!
2020-07-07T17:27:00.707522+02:00 kamailio[24053]: DEBUG: tmx [t_var.c:594]:
pv_get_tm_reply_reason(): reply reason is [Request Timeout]
{
"DSC": "tcp receiver (tls:wan.ip:5061) child=0",
"IDX": 14,
"PID": 24056
},
{
"DSC": "slow timer",
"IDX": 11,
"PID": 24053
},
```
Kamailio will restart (systemd) normally and everything will function normally again
afterwards.
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7 Jul
7 Jul
6:33 p.m.
If the RPC worker is not blocked, can you get the output of `kamctl trap`? It is written
in a text file, path being printed at the end of command execution.
Is the Ubuntu 16.04 with latest security fixes? Iirc, on another deployment I had access
to, it somehow messed up the use of libssl, because it ships normally with libssl 1.0, but
I think libmysqlclient-dev enforced the installation of libssl 1.1.
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6:54 p.m.
All libssl packages are `1.0.2g-1ubuntu4.16`. Attached is a trap file for both failure
modes (with some manual hacking to retrieve pids for failure mode 1). Although I suspect
(but didn't verify yet as I don't normally use plaintext SIP over TCP) the issue
is with the TCP handling rather than anything SSL specific.
[trap_failuremode1.txt](https://github.com/kamailio/kamailio/files/4886100/t…
[trap_failuremode2.txt](https://github.com/kamailio/kamailio/files/4886103/t…
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7:12 p.m.
I looked at one trace and the blocking leads to the libmysqlclient:
```
#0 0x00007fa250dd3730 in futex_wait (private=<optimized out>, expected=0,
futex_word=0x7fa2523a2d1c) at ../sysdeps/unix/sysv/linux/futex-internal.h:61
__ret = -512
err = <optimized out>
#1 futex_wait_simple (private=<optimized out>, expected=0,
futex_word=0x7fa2523a2d1c) at ../sysdeps/nptl/futex-internal.h:135
No locals.
#2 __pthread_rwlock_wrlock_slow (rwlock=0x7fa2523a2d10) at pthread_rwlock_wrlock.c:67
waitval = 0
result = 0
#3 0x00007fa251b11d30 in ?? () from /usr/lib/x86_64-linux-gnu/libmysqlclient.so.20
No symbol table info available.
#4 0x00007fa2510468e7 in CRYPTO_add_lock () from
/lib/x86_64-linux-gnu/libcrypto.so.1.0.0
No symbol table info available.
#5 0x00007fa251466cfc in SSL_CTX_free () from /lib/x86_64-linux-gnu/libssl.so.1.0.0
No symbol table info available.
#6 0x00007fa251468ff0 in SSL_free () from /lib/x86_64-linux-gnu/libssl.so.1.0.0
No symbol table info available.
#7 0x00007fa24ef6a38a in tls_h_tcpconn_clean (c=0x7fa2535b8998) at tls_server.c:655
extra = 0x7fa2535ca9c8
__func__ = "tls_h_tcpconn_clean"
#8 0x00000000004ed791 in _tcpconn_free (c=0x7fa2535b8998) at core/tcp_main.c:1352
__func__ = "_tcpconn_free"
#9 0x00000000004ff708 in tcpconn_put_destroy (tcpconn=0x7fa2535b8998) at
core/tcp_main.c:3030
__func__ = "tcpconn_put_destroy"
```
Can you get the output for:
```
ldd /usr/lib/x86_64-linux-gnu/libmysqlclient.so.20
```
There were couple of similar reports for ubuntu 16.04 with security updates, having issues
when connecting to mysql server via IP sockets. You can check the latest commits to
db_mysql module done in master branch (backported to 5.3, iirc), among them leading to
addition of opt_ssl_mode parameter. You can try to connect to mysql via unix socket file,
if you have the mysql server on the same system as kamailio (use `localhost` instead of
`127.0.0.1` in db url). I spent quite some time analyzing such a similar issue on ubuntu
16.04 with security updates, trying to track changes in libssl/libcrypto and
libmysqlclient, but at the end the solution was to upgrade ubuntu not to have a mixture of
libraries built with libssl1.0 and couple of them with 1.1.
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7:20 p.m.
Thanks so far!
```
$ ldd /usr/lib/x86_64-linux-gnu/libmysqlclient.so.20
linux-vdso.so.1 => (0x00007ffdb0fc4000)
libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007ff76e52c000)
libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007ff76e312000)
libssl.so.1.0.0 => /lib/x86_64-linux-gnu/libssl.so.1.0.0 (0x00007ff76e0a9000)
libcrypto.so.1.0.0 => /lib/x86_64-linux-gnu/libcrypto.so.1.0.0 (0x00007ff76dc64000)
libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007ff76da47000)
libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007ff76d6c5000)
libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007ff76d3bc000)
libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007ff76d1a6000)
libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007ff76cddc000)
/lib64/ld-linux-x86-64.so.2 (0x00007ff76ece7000)
```
In failure mode 1, I see only 1 process stuck in libmysqlclient, in failure mode 2 only 3.
Could that explain Kamailio to be deadlocked completely (on either TLS or UDP level) even
though there are more workers available?
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7:28 p.m.
Do those commits in the db_mysql module have any chance of being backported to 5.2 as
well?
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7:40 p.m.
I see that libmysqlclient is linked against libssl 1.0, so doesn't seem to be mixed
libs.
A blocked process can block the instance, if they acquired other mutexes (e.g., a mutex
used to protect other tcp/tls connections). In the traces, only one process seems to be
blocked, so for some cases it should still work, but not easy to say which should work and
what is locked.
Probably the db_mysql commits will be backported before the next 5.2.x release.
In master branch I also aded `kamctl pstrap` command to use ps for getting the list of
pids for kamailio and write the gdb backtrace file.
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7:43 p.m.
You can also try installing the packages with debugging symbols for libssl and
libmysqlclient, then get the trap again to see more details about what happens inside
libssl and libmysqlclient. Now it seems that some function is overwritten from inside
libmysqlclient.
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8:40 p.m.
Looks like there's actually no libmysqlclient-dbg package :-/ I'll see what I can
do to try and reproduce/pinpoint this further and report back.
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9 Jul
9 Jul
4:10 p.m.
OK, this turns out to be a lot more complicated. I'll try to describe as accurately as
possible.
Turns out SSL support was already disabled on the server-side, so in all above examples
there was no SSL used for the database connection. Although that doesn't rule out
libssl still being involved in the db code, to _try_ to negotiate a SSL connection.
I was able to upgrade to Kamailio 5.3 without any problems, with exactly the same behavior
as before; able to reproduce both failure modes.
With `modparam("db_mysql", "opt_ssl_mode", 1)` I can still easily
reproduce failure mode 1.
I'm struggling to generate "accurate" backtraces for that, because either
I'm crazy, or Kamailio keeps on "fixing itself" at _exactly_ the moment I
decide to run `pstrap`. It can be frozen for minutes, not responding to any TCP socket at
all, then suddenly in the middle of the gdb process print a bunch of messages like
"tcpconn_1st_send(): connect 157.245.69.206:40573 failed (RST) Connection
refused" then continue to function again.
Nonetheless, even with `modparam("db_mysql", "opt_ssl_mode", 1)` I see
libmysqlclient in the backtrace coming from various ssl functions, e.g.
```
#3 0x00007fe9a9c87d30 in ?? () from /usr/lib/x86_64-linux-gnu/libmysqlclient.so.20
#4 0x00007fe9a9275c63 in ssleay_rand_add (buf=0x7ffcf0a04b18, num=8, add=0) at
md_rand.c:230
```
Finally, so far I'm completely unable to reproduce the issue when `db_mysql.so` is not
loaded! Looks like having both db_mysql.so and tls.so loaded causes some kind of
conflict..
That's a lot of input - does this help and/or is there any avenue you'd like me to
debug further?
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5:22 p.m.
Nonetheless, even with `modparam("db_mysql",
"opt_ssl_mode", 1)` I see libmysqlclient in the backtrace coming from various
ssl functions, e.g.
Note that libmysqlclient is somehow intertwining itself with a SIP-TLS connection here.
This Kamailio instance only uses db_mysql for the dispatcher module, so it only actually
queries the database once on startup. All subsequent TCP/TLS connections, as seen in my
backtraces, are SIP clients.
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6:20 p.m.
To be sure: are you using mysql-client or maridb-client library?
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6:20 p.m.
MySQL client.
ii libmysqlclient20:amd64 5.7.30-0ubuntu0.16.04.1 amd64
MySQL database client library
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20 Jul
20 Jul
2:09 p.m.
Something seems to be strange with libmysqlclient and libssl on ubuntu 16.04, especially
after latest security updates. I spent a bit of time and could track it down, not being
familiar with its code. At the end, the system I troubleshooted was upgraded to a newer
Ubuntu. Libssl was in a rather fluid state during past few years, between 1.0 and 1.1
releases, then libmysqlclient also was sometimes compiled with another ssl lib. New
versions of distros shifted to mariadb, which doesn't seem to expose any similar
issue.
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30 Jul
30 Jul
11:25 a.m.
I think I figured out why all these issues are popping up all of a sudden.
A couple of months ago, Xenial's libmysqlclient 5.7.28-0ubuntu0.16.04.2 made the
following change:
```
* debian/rules: removed -DWITH_SSL=bundled, option no longer works.
* debian/control: add libssl-dev to Build-Depends.
```
Before that, the `WITH_SSL=bundled` option was the default, and "bundled"
didn't actually use OpenSSL but yaSSL (see
https://mysqlserverteam.com/mysql-is-openssl-only-now/)!
So in the past, the db_mysql module would use YaSSL and the tls module would use OpenSSL
and everyone was happy. But now suddenly both modules use OpenSSL (1.0.2, in Xenial) and
there's a conflict with how both of them handle locking callbacks.
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12:07 p.m.
Thanks fo digging further on this one and updating here
Does it depend on libssl 1.0.2? Because, iirc, I noticed dependency on libssl 1.1.x where
the most of the other packages were using libssl 1.0.x, but maybe that was on Ubuntu
18.04
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12:48 p.m.
I guess that was Ubuntu 18 indeed, on Ubuntu 16 I've never seen anything other than
1.0.2. See
https://packages.ubuntu.com/search?keywords=libssl&searchon=names&s…
I can confirm that after downgrading libmysqlclient20 to `5.7.26-0ubuntu0.16.04.1` the
problem seems to be gone - at the very least my sipp stress test no longer manages to
cause any deadlocks.
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23 Nov
23 Nov
4:25 p.m.
New subject: [kamailio/kamailio] Deadlocks with libmysqlclient and TLS connections on Ubuntu 16.04 (#2395)
Related to report:
https://lists.kamailio.org/pipermail/sr-users/2020-August/110179.html
Around Aug 24 2020, we've upgraded to Ubuntu 18 + mysql + all updates + kamailio 5.3.
and the issue is gone.
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9 Dec
9 Dec
12:34 p.m.
New subject: [kamailio/kamailio] Deadlocks with libmysqlclient and TLS connections on Ubuntu 16.04 (#2395)
Closing, based on @arkadiam comment, there were updates of dependency packages that seem
to get rid of this behaviour.
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12:34 p.m.
New subject: [kamailio/kamailio] Deadlocks with libmysqlclient and TLS connections on Ubuntu 16.04 (#2395)
Closed #2395.
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1234
days inactive
1389
days old
19 comments
3 participants
participants (3)
-
arkadiam -
Daniel-Constantin Mierla
-
Laszlo