default_expires (integer)
min_expires (integer)
max_expires (integer)
default_q (integer)
append_branches (integer)
case_sensitive (integer)
desc_time_order (integer)
received_avp (integer)
received_param (integer)
max_contacts (integer)
retry_after (integer)
save_nat_flag (flagname or integer)
load_nat_flag (flagname or integer)
trust_received_flag (flagname or integer)
received_to_uri (boolean)
reply_code_attr (avp name)
reply_reason_attr (avp name)
contact_attr (avp name)
aor_attr (avp name)
server_id_attr (avp name)
Registrar and usrloc modules implement NAT extensions that ensure that SIP messages beging sent to registered contacts would use the same socket (with the same IP address and port) on which the REGISTER that registered the contact had been received. REGISTER messages generated by user agents behind NAT ofter open a pinhole in the NAT because REGISTER is usually the first message sent from the user agent to the SIP server. A small example follows.
Let's suppose that we have a single SER instance listening on two ports -- 5060 and 5090. Using a different port seems to be often necessary because of broken SIP ALGs (Application Level Gateways) that are often built into DSL routers or other devices. Such ALGs would mangle SIP requests and responses coming to and from port 5060 and the only option how to avoid such mangling is using a different port number.
Let's suppose that we have two UAs beind NAT, one of them is configured to reach SER on port 5060, the other one is configured to use port 5090 (due to the reasons described above):
SER
+---------+
UA1 ---- NAT1 ----| 5060 |
| |
UA2 ---- NAT2 ----| 5090 |
+---------+
Registrar and usrloc would store the public IP of NAT with each registered contact, thus it would know how to reach both user agents.
In addition to the public IP and port of the NAT device, registrar would also remember the destination IP and port of the REGISTER request (the IP and port used in SER). If registrar did not store this information, it would not know what outbound socket it should use when sending SIP messages to the registered contact. It would use the default port number (often 5060) for such outgoing requests.
When an INVITE for UA1 comes, everything would work because UA1 used port 5060 when registering and that is also the destination port in the pinhole being kept open in NAT1:
SER
INVITE UA1 +--------+ INVITE UA1
UA1 ---- NAT1 <------------- | 5060 | <----------------
| |
UA2 ---- NAT2 | 5090 |
+--------+
When an INVITE for UA2 comes, SER would again use port 5060 as the default outgoing source port number, but this time the message will be dropped by NAT2, because the pinhole opened during the registration has 5060 as the destination port number:
SER
INVITE UA2 +--------+ INVITE UA2
UA1 ---- NAT1 +------ | 5060 | <---------------
| | |
UA2 ---- NAT2 X <----+ | 5090 |
+--------+
That is the reason why registrar and usrloc also need to remember the IP and port used on the server side, that information would be used later when forwarding INVITEs:
SER
+--------+ INVITE UA2
UA1 ---- NAT1 | 5060 | <---------------
INVITE UA2 | |
UA2 ---- NAT2 <------------- | 5090 |
+--------+
The X next to NAT2 has disappeared in this picture which means that the message will be lucky enough to make it through.
SER would encode this information into a SIP URI when saving contacts in database and later, after restart of SER, this information will be restored. The URI looks like:
sip:1.2.3.4:5060;dstip=5.6.7.8;dstport=5090
Where the hostname part is the public IP of the NAT, the port (5060) is the port allocated by the NAT, "dstip" parameter is the IP used on SER side and "dstport" parameter is the port number used on SER side during registration. This information is later used to find the correct outgoing socket in SER. If no such socket can be found (it can happen if you reconfigure SER to use different ports or IPs), it will use the default IP/port again.
Many existing user agents support date and time synchronization from the registrar. Registrar can append "Date" header field to the 200 OK to REGISTER message received from the user agent. User agents that support time synchronization would read the current date and time from the header field and set internal clock to it. For example:
SIP/2.0 200 OK
Via: SIP/2.0/UDP 62.240.165.98;branch=z9hG4bK3E66B9EB
CSeq: 1469 REGISTER
To: "1 1" <sip:jan@charon.ok2rab.cz>;tag=2bd21cbe8bf183397d829c66d62463e6.0aea
From: "1 1" <sip:jan@charon.ok2rab.cz>
Call-ID: 1767561454@62.240.165.98
Date: Fri, 02 Sep 2005 11:20:12 GMT
You can use append_time function from textops
module to append the header field to the reply. Put the function
before save("location"); in the configuration file.
Example 1. Adding Date header to Replies
if (uri == myself) {
if (method == "REGISTER") {
append_time();
save("location");
break;
};
};
The GRUU extension for SIP (draft-ietf-sip-gruu-04) adds a new parameter to the URI of the Contact header in the REGISTER request to identify a UA instance globaly unique in the world. This is reached by adding a globaly unqiue identifier, the so called sip instace, as a parameter to the Contact URI within all REGISTER requests.
Example 2. A Contact header with sip instance parameter
Contact: <sip:nils@192.168.0.122:2532>;q=1.0;+sip.instance="<urn:uuid:6a66f3bd-5b1f-448a-a8be-e29572ea3bee>"
By looking at this sip instance parameter the registrar can decide if the incoming request is just an update of an existing Contact URI or if a new Contact URI has to be added to the AOR of this account. Thus even after a reboot of the UA the new REGISTER can be determined the request as an update of an old, already existing entry.
The registrar module now looks for the sip instance parameter in the Contact URI:
If the sip instance parameter is not present in the URI of the Contact header the algorithm stays the same as like before the GRUU extension. Which means the registrar only compares the SIP URI from the Contact header with the existing URIs for the AOR (account). If exactly the same URI already exists the existing entry will be updated, otherwise the URI will be added to the list.
If the sip instace parameter is present in the URI of the Contact header it will be first searched for an existing Contact with exactly the same sip instance value. If an URI with exactly the same sip instance value exists already in the database, the existing entry will be replaced with the new value, no matter if they differ or not. If no Contact with this sip instance value exists a new entry for it will be added.
For example the following Contact would replace the Contact value from the example above in the usrloc database because the sip instance value is the same, although the Contact URI differs. Without the sip instance this would have created two entries in the usrloc database.
Example 3. Different Contact with the same sip.instance
Contact: <sip:lando@192.168.0.2:2500>;q=1.0;+sip.instance="<urn:uuid:6a66f3bd-5b1f-448a-a8be-e29572ea3bee>"
Registrar module depends on the following SER modules:
usrloc - User Location Module.
sl - Stateless Replies.
If the processed message contains neither Expires HFs nor expires contact parameters, this value will be used for newly created usrloc records. The parameter contains number of second to expire (for example use 3600 for one hour).
Default value is 3600.
The minimum expires value of a Contact, values lower than this minimum will be automatically set to the minimum. Value 0 disables the checking.
Default value is 60.
The maximum expires value of a Contact, values higher than this maximum will be automatically set to the maximum. Value 0 disables the checking.
Default value is 0.
The parameter represents default q value for new contacts. Because ser doesn't support float parameter types, the value in the parameter is divided by 100 and stored as float. For example, if you want default_q to be 0.38, use value 38 here.
Default value is 0.
The parameter controls how lookup function processes multiple contacts. If there are multiple contacts for the given username in usrloc and this parameter is set to 1, Request-URI will be overwritten with the highest-q rated contact and the rest will be appended to sip_msg structure and can be later used by tm for forking. If the parameter is set to 0, only Request-URI will be overwritten with the highest-q rated contact and the rest will be left unprocessed.
Default value is 1.
This parameter was removed (obsolete since ser 2.0).
If set to 1 then AOR comparison will be case sensitive, if set to 0 then AOR comparison will be case insensitive--This is recommended.
Default value is 0.
This parameter was removed (obsolete since ser 2.0).
If set to 1 then all contacts will be ordered in descending modification time order. In this case the most recently updated/created contact will be used.
Default value is 0.
Registrar will store the value of the AVP configured by this parameter in the received column in the user location database. It will leave the column empty if the AVP is empty. The AVP should contain a SIP URI consisting of the source IP, port, and protocol of the REGISTER message being processed.
The value of this parameter should be the same as the value of corresponding parameter of nathelper module.
Default value is 42.
The name of the parameter that will be appended to Contacts of 200 OK when the received URI was set by nathelper module.
Default value is "received".
The parameter can be used to limit the number of contacts per AOR (Address of Record) in the user location database. Value 0 disables the check.
Default value is 0.
Example 13. Set max_contacts parameter
...
# Allow no more than 10 contacts per AOR
modparam("registrar", "max_contacts", 10)
...
The registrar can generate 5xx reply to REGISTER in various
situations. It can, for example, happen when the
max_contacts parameter is set and the processing
of REGISTER request would exceed the limit. In this case the
registrar would generate "503 Service Unavailable" response.
If you want to add the Retry-After header field in 5xx replies, set this parameter to a value grater than zero (0 means do not add the header field). See section 20.33 of RFC3261 for more details.
Default value is 0 (disabled).
The contact will be marked as behind the NAT if this flag is set before calling one of registrar save*() functions.
See also load_nat_flag.
The default value is 4 (flag number 4).
Example 15. Set save_nat_flag parameter
flags FLAG_NAT;
...
modparam("registrar", "save_nat_flag", "FLAG_NAT")
...
route{
...
if (nat_uac_test("19"))
setflag(FLAG_NAT);
...
}
This flag will be set by the registrar lookup*() functions if the contact was marked as behind the NAT during its registration.
See also save_nat_flag.
The default value is 4 (flag number 4).
Example 16. Set load_nat_flag parameter
flags FLAG_NAT;
...
modparam("registrar", "load_nat_flag", "FLAG_NAT")
...
route{
...
if (lookup_contacts("location")) {
if (isflagset(FLAG_NAT)){
log(1, "natted contact");
# use rtpproxy a.s.o
}
...
}
...
}
If this flag is set, the received information added to the REGISTER
contacts on another machine (e.g. upstream proxy or replication
peer) by the fix_nated_register() function
from the nathelper module (ser version,
under modules_s/) is trusted. If it is not set, it will be
ignored.
It is especially useful in REGISTER replication scenarios of
registrars behind a transparent load balancer (one IP) or a proxy /
load balancer that can make use of the original received
information (in this case combined with
received_to_uri).
A contact with received information looks like: <sip:foo@10.0.0.3:5060>;received="sip:1.2.3.4:3412;transport=TCP;dstip=4.5.6.7;dstport=5060".
Besides the normal flags values (flag names or positive integers),
there are 2 special integer values: -1 and -2.
If trust_received_flag is set to
-1 it is equivalent with disabling it
globally (no contact "received" parameter will be trusted, they
will be all ignored). If set to -2 all the
contact "received" parameters will be trusted.
See also fix_nated_register() in
ser nathelper version (modules_s/nathelper).
The default value is -2 (always trust received), due to config compatibility reasons with older ser versions.
Example 17. Set trust_received_flag parameter
flags FLAG_REPLICATED;
...
modparam("registrar", "trust_received_flag", "FLAG_REPLICATED")
...
route{
...
if (dst_ip==224.0.1.75 && method == "REGISTER") {
# REGISTER replicated on multicast (trusted)
setflag(FLAG_REPLICATED);
save_mem_nr("location");
...
}
...
}
If set the lookup*() functions will add a contact received information to the uri, instead of using the contact received information as a destination for the message.
The resulting message uri will look like: <sip:contact>;received="sip:src_ip:src_port;transport=proto;dstip=iface_ip;dstport=iface_port".
Is is useful when the registrar is behind some other proxy (e.g. load balancer) and using Path is not desired. In this case the outer proxy would have to look at the message uri, remove the "received" parameter from the uri and use it as destination for the message.
The default value is 0 (off).
Example 18. Set received_to_uri parameter
...
modparam("registrar", "received_to_uri", 1)
# example uri for a message received on 1.2.3.4:5060 from 192.168.1.1:5060:
# <sip:foo@10.0.0.3>;received="sip:192.168.1.1:5060;dstip=1.2.3.4;dstport=5060"
If one of the save*() functions that do not send a reply is
used (save_contacts_no_reply(),
save_noreply() or
save_mem_nr()), an AVP with the given
name will be set to the code of the reply that should be send
by other means.
See also reply_reason_attr and
contact_attr.
The default value is "$code".
Example 19. Set reply_code_attr,
reply_reason_attr parameters and
contact_attr
modparam("registrar", "reply_code_attr", "$repl_code")
modparam("registrar", "reply_reason_attr", "$repl_reason")
modparam("registrar", "contact_attr", "$contact")
...
route{
...
if (!save_noreply("location")) {
append_to_reply("$contact");
sl_send_reply($reply_code, $repl_reason);
}
...
}
If set to an AVP name, the AOR will be taken from this AVP, instead of the message "To:" header (when using one of the save*() functions).
The default value is "$aor".
Example 20. Set aor_attr
modparam("registrar", "aor_attr", "$my_aor")
...
route{
...
if (src_ip==1.2.3.4)
$my_aor=@msg.header["From"];
save("location");
...
}
If set to an AVP name, the server ID associated to the contact
will be set to the AVP value. If not set or the AVP is not found,
the server ID will be set to the server_id of
the current server.
The default value is "$server_id".
See also server_id (core parameter).
Example 21. Set server_id_attr
...
modparam("registrar", "server_id_attr", "$remote_server_id")
...
route{
...
if (dst_ip==224.0.1.75 && method == "REGISTER") {
# REGISTER replicated on multicast, use the originator server_id
# (saved in the custom SER-Server-ID header)
$remote_server_id = @msg.header["SER-Server-ID"];
setflag(FLAG_REPLICATED);
save_mem_nr("location");
...
}
...
}
The function processes a REGISTER message. It can add, remove or modify usrloc records depending on Contact and Expires HFs in the REGISTER message. On success, 200 OK will be returned listing all contacts that are currently in usrloc. On an error, error message will be send with a short description in reason phrase.
Meaning of the parameters is as follows:
domain - Logical domain within registrar. If database is used then this must be name of the table which stores the contacts.
Same as save() but it doesn't send a reply.
Meaning of the parameters is as follows:
domain - Logical domain within registrar. If database is used then this must be na e of the table which stores the contacts.
The functions extracts username from Request-URI and tries to find all contacts for the username in usrloc. If there are no such contacts, -1 will be returned. If there are such contacts, Request-URI will be overwritten with the contact that has the highest q value and optionally the rest will be appended to the message (depending on append_branches parameter value).
Meaning of the parameters is as follows:
domain - Name of table that should be used for the lookup.
The function returns true if the AOR in the Request-URI is registered, false otherwise. The function does not modify the message being process, it neither rewrites the Request-URI if a contact is found not append branches.
Meaning of the parameters is as follows:
domain - Name of table that should be used for the lookup.
Example 25. registered usage
...
if (registered("location")) {
sl_send_reply("100", "Trying");
...
};
...