[master] 158ca120b cache_range: Bring back VCL control over backend range Requests

[Nils Goroll]

commit 158ca120ba05361adba73f2f8239916957893e7a
Author: Nils Goroll <nils.goroll at uplex.de>
Date:   Wed May 21 19:27:07 2025 +0200

    cache_range: Bring back VCL control over backend range Requests
    
    The added VTC contains a test case for a (crude) partial caching pattern in VCL,
    which stopped working with 4ab110047130e3a89936104d74f4729b650676f9 because the
    Range header to check is taken from bereq0, rather than bereq, which VCL has
    under control and is also the request sent to the backend.
    
    Ref #3246

diff --git a/bin/varnishd/cache/cache_range.c b/bin/varnishd/cache/cache_range.c
index 73e7cc1a4..48d28ee35 100644
--- a/bin/varnishd/cache/cache_range.c
+++ b/bin/varnishd/cache/cache_range.c
@@ -353,7 +353,7 @@ VRG_CheckBo(struct busyobj *bo)
 	if (!cache_param->http_range_support)
 		return (0);
 
-	err = http_GetRange(bo->bereq0, &rlo, &rhi, -1);
+	err = http_GetRange(bo->bereq, &rlo, &rhi, -1);
 	clen = http_GetContentLength(bo->beresp);
 	crlen = http_GetContentRange(bo->beresp, &crlo, &crhi);
 
diff --git a/bin/varnishtest/tests/r04336.vtc b/bin/varnishtest/tests/r04336.vtc
new file mode 100644
index 000000000..5e1fc3e0c
--- /dev/null
+++ b/bin/varnishtest/tests/r04336.vtc
@@ -0,0 +1,57 @@
+varnishtest "Range headers"
+
+server s1 {
+	rxreq
+	expect req.http.Range == "bytes=0-"
+	txresp -status 206 -hdr "Content-Range: bytes 0-99/100" -bodylen 100
+} -start
+
+varnish v1 -vcl+backend {
+	sub vcl_recv {
+		if (req.http.Range ~ "^bytes=") {
+			set req.http.X-Range = req.http.Range;
+		} else {
+			unset req.http.X-Range;
+		}
+		unset req.http.Range;
+	}
+
+	sub vcl_hash {
+		hash_data(req.http.X-Range);
+	}
+
+	sub vcl_backend_fetch {
+		if (bereq.http.X-Range) {
+			set bereq.http.Range = bereq.http.X-Range;
+		}
+	}
+
+	sub vcl_backend_response {
+		if (beresp.status != 206 && beresp.status != 416) {
+			unset beresp.http.Content-Range;
+		}
+		if (beresp.status == 206) {
+			if (! bereq.http.X-Range) {
+				return (abandon);
+			}
+			set beresp.http.X-Content-Range = beresp.http.Content-Range;
+		}
+	}
+
+	sub vcl_deliver {
+		if (resp.status == 206) {
+			if (! resp.http.X-Content-Range) {
+				return (synth(500, "206 but no X-Content-Range"));
+			}
+			set resp.http.Content-Range = resp.http.X-Content-Range;
+		}
+		unset resp.http.X-Content-Range;
+	}
+} -start
+
+client c1 {
+	txreq -hdr "Range: bytes=0-"
+	rxresp
+	expect resp.status == 206
+	expect resp.bodylen == 100
+} -run