Hi,
it looks to me that Kamailio detects NAT without NAT being there, when used in IPv6 scenarios.
I have a register, which comes in like this:
U 2015/01/23 11:42:31.013284 2a01:1234:123:1234::2:16732 -> 2001:9876:98:9876::aa01:5060
REGISTER sip:domain SIP/2.0
Via: SIP/2.0/UDP [2a01:1234:123:1234::2]:16732;branch=z9hG4bK45528eba
After it has run through Kamailio, the packet is sent out like this:
U 2015/01/23 11:42:31.015126
1.2.3.4:5060 ->
9.8.7.6:5060REGISTER sip:domain SIP/2.0
Via: SIP/2.0/UDP 1.2.3.4;branch=z9hG4bK8d21.7fa5fb060c2acc9583f05a93b93f9873.0
Via: SIP/2.0/UDP [2a01:1234:123:1234::2]:16732;received=2A01:1234:123:1234:0:0:0:2;branch=z9hG4bK45528eba
As far as I know, the received part should only get appended, if the source IP of the packet differs from the IP advertised in the topmost Via header. But to me it looks like it always gets appended. In just IPv4 scenarios, the received parameter only gets appended if a difference is detected.
And if it gets appended, shouldn't the received parameter IP be in square brackets, too?
Later on, we have something like this in our code:
if(method=="REGISTER") {
if (nat_uac_test("23")) {
append_hf("X-nathint: nat\r\n");
force_rport();
if (!add_path_received()) {
sl_send_reply("503", "Internal Path Error");
};
} else {
if (!add_path()) {
sl_send_reply("503", "Internal Path Error");
};
};
}
In our code, Kamailio always jumps into the add_path_received() part, so I guess, NAT detection triggers. But why?