schoberw left a comment (kamailio/kamailio#3982)
FTR: I did this (for debug reasons):
``` xlog("L_INFO", "XXX: $sdp(c:ip)"); $var(cFound) = 0; sdp_iterator_start("s1"); while(sdp_iterator_next("s1")) { xlog("L_INFO", "XXX: ($var(cFound)) body line: $sdpitval(s1)"); if ($sdpitval(s1) =~ "^c=IN IP4 ") { xlog("L_INFO", "XXX: c-line found before m-line!"); $var(cFound) = 1; break; } if ($sdpitval(s1) =~ "^m=audio [0-9]+ RTP" && $var(cFound) == 0) { xlog("L_INFO", "XXX: no session level c-line, insert one"); sdp_iterator_insert("s1", "c=IN IP4 $sdp(c:ip)\r\n"); break; } } sdp_iterator_end("s1"); ```