там есть вот такое для инвайтов
/* Loop through the unknown headers */
for (un = sip->sip_unknown; un; un = un->un_next) {
if (!zstr(un->un_name) && !zstr(un->un_value)) {
char *parsed_name;
if ((parsed_name = switch_mprintf("sip_i_%s", un->un_name))) {
char *p, *x = parsed_name;
switch_tolower_max(x);
while ((p = strchr(x, '-'))) {
*p = '_';
x = ++p;
}
switch_channel_add_variable_var_check(channel, parsed_name, un->un_value, SWITCH_FALSE, SWITCH_STACK_PUSH);
free(parsed_name);
}
}
}