commit 3d39bd4: [Minor] lua_scanners - icap - use Allow 204 again

[Carsten Rosenberg]

Author: Carsten Rosenberg
Date: 2021-11-02 21:13:07 +0100
URL: https://github.com/rspamd/rspamd/commit/3d39bd4c3f9703094fc288826f5b3d64f2483b30

[Minor] lua_scanners - icap - use Allow 204 again

---
 lualib/lua_scanners/icap.lua | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/lualib/lua_scanners/icap.lua b/lualib/lua_scanners/icap.lua
index 899855059..0eb5f8583 100644
--- a/lualib/lua_scanners/icap.lua
+++ b/lualib/lua_scanners/icap.lua
@@ -556,10 +556,11 @@ local function icap_check(task, content, digest, rule, maybe_part)
 
           if icap_headers.icap and string.find(icap_headers.icap, 'ICAP%/1%.. 2%d%d') then
             if icap_headers['Methods'] and string.find(icap_headers['Methods'], 'RESPMOD') then
-              --Preview is currently ununsed
-              --if icap_headers['Allow'] and string.find(icap_headers['Allow'], '204') then
-              -- add_respond_header('Allow', '204')
-              --end
+              -- Allow "204 No Content" responses 
+              -- https://datatracker.ietf.org/doc/html/rfc3507#section-4.6
+              if icap_headers['Allow'] and string.find(icap_headers['Allow'], '204') then
+                add_respond_header('Allow', '204')
+              end
 
               if rule.x_client_header then
                 local client = task:get_from_ip()