Kamailio not receiving packets on high CPS - sr-users

19 Dec 2024

Hello!

for this ST/SH project, we are using Kamailio 5.8.4 in stateless mode,
making HTTP requests to a REST API (Java Spring) that will reply with a
JSON object, and then Kamailio replaces the Contact header and sends a SIP
300 Multiple Choice reply to the SBC that sent the initial INVITE.

Kamailio is running on a VM with 4vCPUs and 4GB RAM and 2 NICs.
On NIC ens224 there is a Virtual IP managed by Keepalived.
Kamailio is listening on port 5060 on ens224 and set with 32 children
process (tried with 8, 16, 24 and also 64, but with this value it was a lot
worst).

We are doing load performance tests on our PreProd environment. With the
SBC we are sending 450 to 600 CAPS to Kamailio, and what we noticed is that
above 450 CAPS, and after less than 1 minute, Kamailio only replies SIP 100
to some INVITEs. We also could figure out that Kamailio is not receiving
all the INVITES, despite having proved that ALL invites are sent to the
server.
It seems to me that, for some reason, the OS is somehow not able to deliver
*all* SIP packets to Kamailio, because:
- sngrep does capture all the SIP packets and shows the flows
- though the flow shows SIP invite coming from SBC to Kamailio Server,
there is no SIP 100 replied back to SBC, even though this is the 1st thing
kamailio does, so, for me, Kamailio did not received the SIP Invite
- picking a call with reinvites, which after some seconds, SBC cancels, if
I copy the Call-ID value and grep on kamailio's logs, I just do not find
any content!

I have read some "network tuning" articles, including Linux Tune Network
Stack (Buffers Size) To Increase Networking Performance - nixCraft
<https://www.cyberciti.biz/faq/linux-tcp-tuning/> and Tuning Kamailio for
high throughput and performance | Evariste Systems Blog
<https://blog.evaristesys.com/2016/02/15/tuning-kamailio-for-high-throughput-and-performance/>
and
when running the following command I get:

$  ss -4 -n -l | grep 5060
udp   UNCONN 0        0          10.242.17.125:5060       0.0.0.0:*
udp   UNCONN 324224   0          10.242.17.146:5060       0.0.0.0:*

According to the article, the 3rd column should be as near 0 as possible,
ideally 0.

While I am waiting for some sysadmin with root permissions to be available
and modify some of the network parameters on this VM, I wonder if anyone
has some tips to share on how to solve this behaviour. I'm not sure,
either, what parameters to change or if they should be changed! The goal is
to have a minimum 750 CAPS.

Lastly, some parts of the code:

Kamailio.cfg:

...
  ### LOG Levels: 3=DBG, 2=INFO, 1=NOTICE, 0=WARN,
-1=ERR
 debug=1
 log_stderror=no
 rundir="/tmp"
 memdbg=5
 memlog=5
 log_facility=LOG_LOCAL0
 # configure the prefix for all log messages
 log_prefix_mode = 1
 log_prefix="{$mt $hdr(CSeq) $ci} "
 /* number of SIP routing processes */
 children=32 # ------------- ALREADY TRIED WITH 8,16,24... no results.....
 /* uncomment the next line to disable TCP (default on) */
 disable_tcp=no
 /* uncomment the next line to disable the auto discovery of local aliases
  * based on reverse DNS on IPs (default on) */
 # auto_aliases=no
 /* add local domain aliases */
 # alias="sip.mydomain.com"

####### Custom Parameters #########

/* These parameters can be modified runtime via RPC interface
 * - see the documentation of 'cfg_rpc' module.
 *
 * Format: group.id = value 'desc' description
 * Access: $sel(cfg_get.group.id) or @cfg_get.group.id */

####### Modules Section ########

/* set paths to location of modules */
loadmodule "db_mysql.so"
loadmodule "db_cluster.so"
loadmodule "http_client.so"
loadmodule "jsonrpcs.so"
loadmodule "kex.so"
loadmodule "corex.so"
loadmodule "sl.so"
loadmodule "pv.so"
loadmodule "maxfwd.so"
loadmodule "textops.so"
loadmodule "xlog.so"
loadmodule "sanity.so"
loadmodule "jansson.so"
loadmodule "snmpstats.so"
loadmodule "file_out.so"
loadmodule "ctl.so"
loadmodule "permissions.so"
loadmodule "xhttp.so"
loadmodule "xhttp_rpc.so"

####### Other Args and Env Vars #########

/* listen addresses */
include_file "listen.cfg"
include_file "db_conn.cfg"

# ----------------- setting module-specific parameters --------------
# --- DB Cluster params ---
# minimum requirement is to have DBURL1 defined
#!ifdef DBURL1
modparam("db_cluster", "connection" , DBURL1)
#!endif
#!ifdef DBURL2
modparam("db_cluster", "connection" , DBURL2)
#!endif
#!ifdef DBURL3
modparam("db_cluster", "connection" , DBURL3)
#!endif
#!ifdef DBURL4
modparam("db_cluster", "connection" , DBURL4)
#!endif
#!ifdef DBURL5
modparam("db_cluster", "connection" , DBURL5)
#!endif
modparam("db_cluster", "cluster", DBCLUSTER)

# --- Permissions params ---
modparam("permissions", "db_url", "cluster://k1")
modparam("permissions", "db_mode", 1)
#modparam("permissions", "reload_delta", 30)

# ----- jsonrpcs params -----
modparam("jsonrpcs", "pretty_format", 1)
/* set the path to RPC fifo control file */
modparam("jsonrpcs", "fifo_name", "/tmp/kamailio_rpc.fifo")
/* set the path to RPC unix socket control file */
modparam("jsonrpcs", "dgram_socket",
"/tmp/kamailio_rpc.sock")

modparam("jsonrpcs", "transport", 0)
# ----- ctl params -----
/* set the path to RPC unix socket control file */
modparam("ctl", "binrpc", "unix:/tmp/kamailio_ctl")

# ----- http_async_client params -----
modparam("http_client", "query_result", 0)
modparam("http_client", "keep_connections", 0)
modparam("http_client", "connection_timeout",2)
modparam("http_client", "timeout_mode",2)
modparam("http_client", "config_file",
"/usr/local/etc/kamailio/http_client.cfg")
# ---- SNMP Stats params ----
modparam("snmpstats", "sipEntityType", "proxyServer")
modparam("snmpstats", "sipEntityType", "redirectServer")
modparam("snmpstats", "sipEntityType", "other")
modparam("snmpstats", "snmpgetPath", "/usr/bin/")
modparam("snmpstats", "MsgQueueMinorThreshold", 20)
modparam("snmpstats", "MsgQueueMajorThreshold", 100)
modparam("snmpstats", "dlg_minor_threshold", 20)
modparam("snmpstats", "dlg_major_threshold", 100)
modparam("snmpstats", "snmpCommunity", "kamailio")

# ---- File_Out params ----
modparam("file_out", "base_folder",
"/data/sabire002/log/kamailio/")
modparam("file_out", "file",
"name=stsh_requests;interval=1440;extension=.log")
modparam("file_out", "file",
"name=cdr;interval=1440;extension=.log")
modparam("file_out", "file",
"name=http;interval=1440;extension=.log")
####### Routing Logic ########

include_file "includes/reqinit.cfg"
include_file "includes/handle_options.cfg"
include_file "includes/handle_cancel.cfg"
include_file "includes/handle_stir_shaken_stateless.cfg"
include_file "includes/handle_http_rpc.cfg"

request_route {
  $avp(START_TIME)=$utimef(%Y-%m-%d %H:%M:%S);
  $avp(GROUPID) = allow_address_group($si, $sp);

  if ( $avp(GROUPID) == 100 || !allow_address_group($si, $sp) ) {
          xlog("L_INFO", "INIT - $si:$sp is not in the allowed ACL Group
ID
!\n");
          #sl_reply("401", "Address not allowed");
          exit;
  };

  if (is_method("ACK") ) { #&& t_check_trans() ){
    exit;
  }

  if (is_method("INVITE")) {

file_out("cdr","$rm|$ft|$tt|$ci|$rs|$rr|$Ts|$avp(START_TIME)|$fU|$fd|$si|$tU|$rU|$rd|$utimef(%Y-%m-%d
%H:%M:%S)");
          send_reply("100","Trying");
  }

  route(HANDLE_OPTIONS);

  route(REQINIT);

  xlog("L_INFO"," ********** Route START ***********");
  # log the basic info regarding this call
  xlog("L_INFO","===================================================
\n");
  xlog("L_INFO","New SIP message $rm with call-ID $ci received $pr request
$rm $ou source $si:$sp from $fu to $tu \n");
  xlog("L_INFO","===================================================
\n");

  route(HANDLE_STIRSHAKEN);

  route(HANDLE_CANCEL);

  if (method == "INVITE"){
        route(RELAY);
  }
}

route[RELAY] {
  # Sends a 300 Multiple Choices back to the proxy that requested the
routing lookup
  xlog("L_INFO","RELAY - send reply     \n");

file_out("cdr","RELAY|$ft|$tt|$ci|$rs|$rr|$Ts|$avp(START_TIME)|$fU|$fd|$si|$tU|$rU|$rd|$utimef(%Y-%m-%d
%H:%M:%S)");
  send_reply("300", "Multiple Choices");
  exit;
}

As for the HANDLE_STIRSHAKEN route, where the main process is:

route[HANDLE_STIRSHAKEN]
{

    if (!is_method("INVITE")) {
        return;
    }

    $xavp(requestTime)   = $utimef(%s);
    $var(post) = $null; // resets and makes sure the $var(post) variable is
null before usage

  [.... get some header values ...]

  $var(res) = http_connect("api1", "/stsh",
"application/json",
"$var(post)", "$var(result)");
  jansson_xdecode($var(result), "json");
    if ( $xavp(json=>sip-response-code) == 300 )
    {
         remove_hf("Contact");
         append_to_reply("Contact: $xavp(json=>contact)\r\n");
    }
    else
    {
        # add error message to reply

sl_reply("$xavp(json=>sip-response-code)","$xavp(json=>sip-response-text)");
        exit;
    }
}

Atenciosamente / Kind Regards / Cordialement / Un saludo,

*Sérgio Charrua*