Yeahlink registers with the wrong local IP

[gregdel]

If a Yealink (SIP phone) registers behind an OTB, the local IP of the phone is the IP of the xtun0 device.
The OTB is NATing the sip register with the nf_nat_sip kernel module.

Removing this module fixes the issue:

root@OverTheBox:~# diff nf-nathelper-extra /etc/modules.d/nf-nathelper-extra
--- nf-nathelper-extra
+++ /etc/modules.d/nf-nathelper-extra
@@ -7,8 +7,6 @@
 nf_nat_h323
 nf_conntrack_pptp
 nf_nat_pptp
-nf_conntrack_sip
-nf_nat_sip
 nf_conntrack_snmp
 nf_nat_snmp_basic
 nf_conntrack_tftp