Hi,
I can see an issue in assigning the port_start and port_end members of ngx_http_request_t inside ngx_http_parse_request_line().
If the request line has a absolute URI with explicit port specified, then port_end is set correctly inside ngx_http_parse_request_line():
...
case sw_port:
if (ch >= '0' && ch <= '9') {
break;
}

switch (ch) {
case '/':
r->port_end = p;
r->uri_start = p;
state = sw_after_slash_in_uri;
break;
...

However, r->port_start is still 0.
I think the following code should be modified:
...
case sw_host_end:

r->host_end = p;

switch (ch) {
case ':':
+ r->port_start = (p + 1);
state = sw_port;
break;
...

Let me know if it sounds OK.
Regards,
-anirudh