It looks like when http request comes from ipv6 address, the module inserts Via header without [] around the address:
Feb 20 14:26:17 east /usr/local/sbin/kamailio[30965]: ERROR: <core> [parser/parse_via.c:2193]: parse_via(): ERROR:parse_via: bad port Feb 20 14:26:17 east /usr/local/sbin/kamailio[30965]: ERROR: <core> [parser/parse_via.c:2708]: parse_via(): ERROR: parse_via on: <SIP/2.0/TCP 2601:3:8840:A:172E:9CAD:6BB2:3F69:45306 Host: sip1.callwithus.com:5060 Connection: Upgrade Pragma: no-cache Cache-Control: no-cache Upgrade: websocket Origin: http://www.callwithus.com Sec-WebSocket-Version: 13 User-Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/40.0.2214.93 Safari/537.36 Accept-Encoding: gzip, deflate, sdch Accept-Language: en-US,en;q=0.8 Sec-WebSocket-Key: nyAUyArASVRXTI+Nvx82/Q== Sec-WebSocket-Extensions: permessage-deflate; client_max_window_bits Sec-WebSocket-Protocol: sip
Feb 20 14:26:17 east /usr/local/sbin/kamailio[30965]: ERROR: <core> [parser/parse_via.c:2712]: parse_via(): ERROR: parse_via parse error, parsed so far:<SIP/2.0/TCP 2601:3> Feb 20 14:26:17 east /usr/local/sbin/kamailio[30965]: ERROR: <core> [parser/msg_parser.c:125]: get_hdr_field(): ERROR: get_hdr_field: bad via Feb 20 14:26:17 east /usr/local/sbin/kamailio[30965]: INFO: <core> [parser/msg_parser.c:338]: parse_headers(): ERROR: bad header field [Via: SIP/2.0/TCP 260] Feb 20 14:26:17 east /usr/local/sbin/kamailio[30965]: ERROR: <core> [parser/msg_parser.c:688]: parse_msg(): ERROR: parse_msg: message=<GET / HTTP/1.1 *Via: SIP/2.0/TCP 2601:3:8840:A:172E:9CAD:6BB2:3F69:45306* Host: sip1.callwithus.com:5060 Connection: Upgrade Pragma: no-cache Cache-Control: no-cache Upgrade: websocket Origin: http://www.callwithus.com Sec-WebSocket-Version: 13 User-Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/40.0.2214.93 Safari/537.36 Accept-Encoding: gzip, deflate, sdch Accept-Language: en-US,en;q=0.8 Sec-WebSocket-Key: nyAUyArASVRXTI+Nvx82/Q== Sec-WebSocket-Extensions: permessage-deflate; client_max_window_bits Sec-WebSocket-Protocol: sip
Feb 20 14:26:17 east /usr/local/sbin/kamailio[30965]: ERROR: xhttp [xhttp_mod.c:264]: xhttp_process_request(): parse_msg failed