BUG/MINOR: cache: Correctly handle existing-but-empty 'accept-encoding' header
RFC 7231#5.3.4 makes a difference between a completely missing
'accept-encoding' header and an 'accept-encoding' header without any values.
This case was already correctly handled by accident, because an empty accept
encoding does not match any known encoding. However this resulted in the
'other' encoding being added to the bitmap. Usually this also succeeds in
serving cached responses, because the cached response likely has no
'content-encoding', thus matching the identity case instead of not serving the
response, due to the 'other' encoding. But it's technically not 100% correct.
Fix this by special-casing 'accept-encoding' values with a length of zero and
extend the test to check that an empty accept-encoding is correctly handled.
Due to the reasons given above the test also passes without the change in
cache.c.
Vary support was added in HAProxy 2.4. This fix should be backported to 2.4+.
(cherry picked from commit 3bc6af417d10e0f5c46f2997be919e14c689ab9c)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
diff --git a/src/cache.c b/src/cache.c
index bdb8258..feab63f 100644
--- a/src/cache.c
+++ b/src/cache.c
@@ -2280,6 +2280,19 @@
/* Iterate over all the ACCEPT_ENCODING_MAX_ENTRIES first accept-encoding
* values that might span acrosse multiple accept-encoding headers. */
while (http_find_header(htx, hdr_name, &ctx, 0) && count < ACCEPT_ENCODING_MAX_ENTRIES) {
+ count++;
+
+ /* As per RFC7231#5.3.4, "An Accept-Encoding header field with a
+ * combined field-value that is empty implies that the user agent
+ * does not want any content-coding in response."
+ *
+ * We must (and did) count the existence of this empty header to not
+ * hit the `count == 0` case below, but must ignore the value to not
+ * include VARY_ENCODING_OTHER into the final bitmap.
+ */
+ if (istlen(ctx.value) == 0)
+ continue;
+
/* Turn accept-encoding value to lower case */
ist2bin_lc(istptr(ctx.value), ctx.value);
@@ -2294,8 +2307,6 @@
/* Unknown encoding */
encoding_bitmap |= VARY_ENCODING_OTHER;
}
-
- count++;
}
/* If a "*" was found in the accepted encodings (without a null weight),