From c5fd097e5cce8b461c6443af02b3448baef2491d Mon Sep 17 00:00:00 2001
From: Martin Blix Grydeland <martin@varnish-software.com>
Date: Thu, 4 Aug 2022 10:59:33 +0200
Subject: [PATCH] Do not call http_hdr_flags() on pseudo-headers

In http_EstimateWS(), all headers are passed to the http_isfiltered()
function to calculate how many bytes is needed to serialize the entire
struct http. http_isfiltered() will check the headers for whether they are
going to be filtered out later and if so skip them.

However http_isfiltered() would attempt to treat all elements of struct
http as regular headers with an implicit structure. That does not hold for
the first three pseudo-header entries, which would lead to asserts in
later steps.

This patch skips the filter step for pseudo-headers.

Fixes: #3830
---
 bin/varnishd/cache/cache_http.c  |  2 ++
 bin/varnishtest/tests/r03830.vtc | 29 +++++++++++++++++++++++++++++
 2 files changed, 31 insertions(+)
 create mode 100644 bin/varnishtest/tests/r03830.vtc

diff --git a/bin/varnishd/cache/cache_http.c b/bin/varnishd/cache/cache_http.c
index ed15e07f9e..d48c0bb366 100644
--- a/bin/varnishd/cache/cache_http.c
+++ b/bin/varnishd/cache/cache_http.c
@@ -1147,6 +1147,8 @@ http_isfiltered(const struct http *fm, unsigned u, unsigned how)
 
 	if (fm->hdf[u] & HDF_FILTER)
 		return (1);
+	if (u < HTTP_HDR_FIRST)
+		return (0);
 	e = strchr(fm->hd[u].b, ':');
 	if (e == NULL)
 		return (0);
diff --git a/bin/varnishtest/tests/r03830.vtc b/bin/varnishtest/tests/r03830.vtc
new file mode 100644
index 0000000000..5155981923
--- /dev/null
+++ b/bin/varnishtest/tests/r03830.vtc
@@ -0,0 +1,29 @@
+varnishtest "3830: Do not call http_hdr_flags() on pseudo-headers"
+
+server s1 {
+	rxreq
+	txresp -reason ":x"
+
+	rxreq
+	txresp
+} -start
+
+varnish v1 -vcl+backend {
+	sub vcl_recv {
+		return (hash);
+	}
+} -start
+
+client c1 {
+	txreq
+	rxresp
+	expect resp.status == 200
+} -run
+
+client c2 {
+	txreq -url :x -method :x
+	rxresp
+	expect resp.status == 200
+} -run
+
+varnish v1 -vsl_catchup
