This patch solves some problems in wget and Firefox, when doing a partial
request (Range:) on a file on a Plan 9 httpd. The Plan 9 httpd does not
send out a Content-Length: when doing so, but these applications expect to
have one and show it directly to the user.

One clause in the HTTP 1.1 RFC says in section 4.4 Message Length:
"For compatibility with HTTP/1.0 applications, HTTP/1.1 requests contain-
ing a message-body MUST include a valid Content-Length header field unless
the server is known to be HTTP/1.1 compliant."

Compliant or not complianet - here is the patch.

Notes:
Thu Oct 13 07:24:23 EDT 2005 rsc
    Installed and running on the plan9.bell-labs.com web server.
    Please be more careful about spacing issues -- make the
    spacing on changed code look like the spacing around it.
    
    Thanks.


Reference: /n/sources/patch/applied/httpd-range-compliance
Date: Thu Oct 13 09:40:19 CES 2005
Reviewed-by: rsc

--- /sys/src/cmd/ip/httpd/sendfd.c	Thu Oct 13 09:40:10 2005
+++ /sys/src/cmd/ip/httpd/sendfd.c	Thu Oct 13 09:40:07 2005
@@ -125,9 +125,10 @@
 		r = c->head.range;
 		if(r == nil)
 			hprint(hout, "Content-Length: %lld\r\n", length);
-		else if(r->next == nil)
+		else if(r->next == nil) {
 			hprint(hout, "Content-Range: bytes %ld-%ld/%lld\r\n", r->start, r->stop, length);
-		else{
+			hprint(hout, "Content-Length: %ld\r\n", r->stop - r->start);
+		} else{
 			multir = 1;
 			boundary = hmkmimeboundary(c);
 			hprint(hout, "Content-Type: multipart/byteranges; boundary=%s\r\n", boundary);
@@ -195,6 +196,7 @@
 			hprint(hout, "\r\n--%s\r\n", boundary);
 			printtype(hout, type, enc);
 			hprint(hout, "Content-Range: bytes %ld-%ld/%lld\r\n", r->start, r->stop, length);
+			hprint(hout, "Content-Length: %ld\r\n", r->stop - r->start);
 			hprint(hout, "\r\n");
 		}
 		hflush(hout);