add header into http-request redirect

[lukastribus]

(user hat on)

Output of haproxy -vv

HA-Proxy version 2.0-dev0-4afdd1-27 2019/01/01 - https://haproxy.org/
Build options :
  TARGET  = linux2628
  CPU     = generic
  CC      = gcc
  CFLAGS  = -O2 -g -fno-strict-aliasing -Wdeclaration-after-statement -fwrapv -Wno-unused-label -Wno-sign-compare -Wno-unused-parameter -Wno-old-style-declaration -Wno-ignored-qualifiers -Wno-clobbered -Wno-missing-field-initializers -Wtype-limits
  OPTIONS = USE_GETADDRINFO=1

Default settings :
  maxconn = 2000, bufsize = 16384, maxrewrite = 1024, maxpollevents = 200

Built with transparent proxy support using: IP_TRANSPARENT IPV6_TRANSPARENT IP_FREEBIND
Built without compression support (neither USE_ZLIB nor USE_SLZ are set).
Compression algorithms supported : identity("identity")
Built without PCRE or PCRE2 support (using libc's regex instead)
Encrypted password support via crypt(3): yes
Built with multi-threading support.

Available polling systems :
      epoll : pref=300,  test result OK
       poll : pref=200,  test result OK
     select : pref=150,  test result OK
Total: 3 (3 usable), will use epoll.

Available multiplexer protocols :
(protocols marked as <default> cannot be specified using 'proto' keyword)
              h2 : mode=HTX        side=FE|BE
              h2 : mode=HTTP       side=FE
       <default> : mode=HTX        side=FE|BE
       <default> : mode=TCP|HTTP   side=FE|BE

Available filters :
        [SPOE] spoe
        [COMP] compression
        [CACHE] cache
        [TRACE] trace

What should haproxy do differently? Which functionality do you think we should add?

Haproxy can't add header to a redirect because redirect is a final
directive. After executing the redirect no more action are executed.

Also see:
https://www.mail-archive.com/haproxy@formilux.org/msg29294.html

What are you trying to do?

Adding HSTS headers to all responses, including redirects and errors.