Listen ipv4 to ipv6 backend server

Hi, I am using haproxy to send traffic/requests to multiple backend server IPs but my problem is that i
cant send traffic/requests to an ipv6 backend server. (but ipv4 works fine)

I tried the following as backend servers but they didnt work:

server s1 resolvers mydns resolve-prefer ipv6
server s1
server s1 appIPv6:443
server s1 appIPv6:::443
server s1 appIPv6::1:443
server s1 [appIPv6::1]:443
server s1 [appIPv6]:443

what is the problem?
on the backend server i also run haproxy and i done like this:

listen front
mode tcp
bind :::443 v4v6

use_backend app …
backend app
mode tcp
server sr1

backend server IPv6 is ok and has connection, but does not work in haproxy to send traffic/requests from front end to ipv6 backend server.
HAProxy version 2.4.22-0ubuntu0.22.04.3 2023/12/04

It’s probably the backend app… It’s going to see headers with IPv4 addresses which can confuse it…

I assume it works IPv6 to IPv6…?

have a look at the headers, try an experiment like rewriting the headers such as the client ip…

This is the sort of issue I’m referring to: azure - How to configure IIS 8.5 to accept translated IPv4->IPv6 address in host header - Server Fault