I don't think it exists. It might be possible to add one and we would probably review that patch, but why wouldn't you just use rfc2833 instead and/or report this error to the vendors? On Thursday, October 22, 2015, Chris B. Ware <chrisbware@yahoo.it> wrote:

Hi guys,

I've discovered that Gigatset and Yealink IP cordless send SIP INFO in a wrong way, according to SDP RFC. If I press 4, I get on SDP

Signal=4\r\n Duration=100

While should be

Signal=4\r\n Duration=100\r\n

Freeswitch (1.4.23) answers with 400 Bad Request. I wonder if there's something like a NDLB params to accept this format, based on SDP Content Length.

Thank you